In-situ monitoring of droplet jetting formed resin cure quality and apparatus

Abstract

The application relates to a micro-droplet jetting forming resin curing quality in-situ monitoring method and device, the micro-droplet jetting forming resin curing quality in-situ monitoring method comprising: jetting and depositing a light-curing resin on a forming platform layer by layer to form a target forming layer; applying a curing energy to the target forming layer; collecting a physical quantity signal of the target forming layer, and obtaining a signal distribution of the target forming layer based on the physical quantity signal; mapping pixel coordinates in the signal distribution to physical coordinates of the forming platform; converting the physical quantity signal of each physical coordinate into a chemical curing degree value according to a preset conversion relationship to obtain a chemical curing degree distribution of the target forming layer; calculating an error between the chemical curing degree distribution and a preset target chemical curing degree, and adjusting the curing energy of the target forming layer according to the error; and repeatedly executing the above steps until the deposition and curing of all forming layers of a three-dimensional object are completed. According to the closed-loop regulation and control of the chemical curing degree distribution, the curing uniformity and consistency of each forming layer are improved.

Description

Technical Field

[0001] This application relates to the field of microdroplet jetting resin curing additive manufacturing technology, and in particular to a method and apparatus for in-situ monitoring of the curing quality of microdroplet jetting resin. Background Technology

[0002] Microdroplet jetting is an additive manufacturing technology. Its basic principle involves depositing photocurable resin as micron-sized droplets layer by layer onto a forming platform through a jetting head. After each layer is deposited, ultraviolet light is applied to polymerize and cure the resin. This process is repeated layer by layer to ultimately form a three-dimensional solid component. To ensure curing quality during the layer-by-layer curing process, an in-situ curing quality monitoring method is proposed. This method utilizes non-contact sensing to acquire real-time information on the curing reaction process of each resin layer, thus providing a basis for resin curing quality assessment and control.

[0003] Currently, existing in-situ monitoring technologies for curing quality mainly rely on visual inspection methods to monitor the geometry of the deposited layers and adjust the spraying parameters of subsequent layers accordingly. However, relying on visual inspection methods only focuses on whether the "shape" of the formed part meets expectations and cannot directly reflect whether the curing reaction inside the resin is sufficient and uniform. Existing technologies are affected by factors such as oxygen inhibition effect, differences in light penetration between layers, and inconsistent curing processes in the microdroplet spraying layer-by-layer forming process, resulting in problems such as uneven curing, weak interlayer bonding, and untraceable curing quality.

[0004] There are currently no effective solutions to the problems of uneven curing, weak interlayer bonding, and lack of traceability of curing quality in related technologies. Summary of the Invention

[0005] This embodiment provides a method and apparatus for in-situ monitoring of the curing quality of microdroplet jet molding resin, in order to solve the problems of uneven curing, weak interlayer bonding, and untraceable curing quality in related technologies.

[0006] In a first aspect, this embodiment provides a method for in-situ monitoring of the curing quality of microdroplet jet molding resin, including:

[0007] The photocurable resin is sprayed and deposited layer by layer onto the molding platform to form the target molding layer;

[0008] Curing energy is applied to the target molding layer to cause the resin in the target molding layer to polymerize and cure;

[0009] During the curing process of the target forming layer, and / or after the target forming layer has been cured, physical quantity signals of the target forming layer are acquired by a non-contact optical sensing unit, and the signal distribution of the target forming layer is obtained based on the physical quantity signals; the physical quantity signals are used to characterize the degree of consumption or crosslinking of polymerizable groups of resin in the target forming layer;

[0010] Based on the pre-defined transformation relationship between pixel coordinates and physical coordinates of the forming surface, the pixel coordinates in the signal distribution are mapped to the physical coordinates of the forming platform;

[0011] The physical quantity signals of each physical coordinate are converted into chemical curing degree values ​​according to a preset conversion relationship to obtain the chemical curing degree distribution of the target forming layer;

[0012] Calculate the error between the chemical curing degree distribution and the preset target chemical curing degree. When the error exceeds a preset first threshold, adjust the curing energy of the target forming layer and / or adjust the spraying parameters of the subsequent forming layer in the region where there is a chemical curing degree error between the forming platform and the target forming layer. The subsequent forming layer is a forming layer that is deposited layer by layer after the target forming layer.

[0013] The target forming layer is subjected to at least one of the following curing compensations:

[0014] The surface chemical curing degree and the bottom chemical curing degree of the target forming layer are obtained. When the surface chemical curing degree is lower than the bottom chemical curing degree by a preset second threshold, the curing energy of the surface of the target forming layer is increased.

[0015] Predict the additional curing amount that adjacent formed layers will produce on the target formed layer due to curing light penetration, and reduce the curing energy supply to the target formed layer according to the additional curing amount when applying curing energy to the target formed layer;

[0016] Repeat the above steps layer by layer on the three-dimensional object until the deposition and solidification of all the forming layers of the three-dimensional object are completed.

[0017] In some embodiments, when the physical quantity signal is a fluorescence intensity signal, the step of converting the physical quantity signals of each physical coordinate into chemical curing degree values ​​according to a preset conversion relationship to obtain the chemical curing degree distribution of the target forming layer includes:

[0018] The fluorescence intensity of the uncured liquid resin was measured as the lower limit reference value;

[0019] The fluorescence intensity of the fully cured sample was measured as the upper limit reference value;

[0020] A calibration curve between fluorescence intensity and chemical curing degree was established based on multiple standard samples to obtain a preset conversion relationship between fluorescence intensity and chemical curing degree.

[0021] The collected physical quantity signals are substituted into the preset conversion relationship to obtain the chemical curing degree value of each physical coordinate.

[0022] In some embodiments, when the physical quantity signal is a characteristic absorption peak signal of a polymerizable group, the step of converting the physical quantity signals of each physical coordinate into chemical curing degree values ​​according to a preset conversion relationship to obtain the chemical curing degree distribution of the target forming layer includes:

[0023] The ratio of the area of ​​the polymerizable unsaturated bond characteristic absorption peak of the target forming layer to the area of ​​the reference peak is used as a calculation parameter;

[0024] The calculated parameters at the initial moment when the target forming layer is not cured are used as the initial reference values;

[0025] During the curing process of the target forming layer, and / or after the target forming layer has been cured, the calculated parameters obtained in real time are used as real-time measurement values;

[0026] Calculate the ratio of the real-time measured value to the initial reference value to obtain the remaining ratio;

[0027] Subtracting the remaining ratio from 1 yields the chemical curing degree value for each of the physical coordinates.

[0028] In some embodiments, mapping the pixel coordinates in the signal distribution to the physical coordinates of the forming platform based on a pre-defined transformation relationship between pixel coordinates and forming surface physical coordinates includes:

[0029] A calibration pattern containing multiple preset control points is projected onto the forming platform. Based on the imaging of the calibration pattern on the forming platform, the pixel coordinates of each control point in the pixel coordinate system are extracted.

[0030] Based on the correspondence between the pixel coordinates of the control points and the physical coordinates of the control points on the forming platform, a homography transformation matrix between the pixel coordinate system and the physical coordinate system of the forming platform is established.

[0031] Lens distortion correction is performed on the captured calibration pattern image to eliminate the spatial position deviation introduced by imaging distortion, and the distortion-corrected image is obtained.

[0032] A mapping lookup table is constructed based on the homography transformation matrix and the distortion-corrected image. The coordinates of each pixel in the signal distribution are mapped to the physical coordinates of the forming platform through the mapping lookup table. The mapping lookup table includes the correspondence between the coordinates of each pixel in the signal distribution and the physical coordinates of the forming platform.

[0033] In some embodiments, the projection of a calibration pattern containing multiple preset control points onto the forming platform, and the extraction of the pixel coordinates of each control point in the pixel coordinate system based on the imaging of the calibration pattern on the forming platform, includes:

[0034] Project a calibration pattern containing multiple feature points onto the forming platform;

[0035] The calibration pattern is imaged on the forming platform by an area array detector to obtain the captured calibration image;

[0036] Based on the captured calibration image, the pixel coordinates of each feature point in the pixel coordinate system are extracted using sub-pixel edge detection and centroid extraction algorithms.

[0037] In some embodiments, when the surface chemical curing degree is lower than the underlying chemical curing degree by a preset second threshold, the method further includes:

[0038] The region in the target forming layer where the surface chemical curing degree is lower than that of the bottom chemical curing degree is identified as an oxygen-inhibited polymerization region.

[0039] A pulsed inert gas jet is injected into the oxygen inhibition region to form a local inert gas coating layer on the surface of the oxygen inhibition region.

[0040] And / or, aspirate the oxygen-containing boundary layer above the region in the target forming layer where the surface chemical curing degree is lower than that of the bottom layer, and form an inert gas curtain above the oxygen-inhibiting region;

[0041] And / or, apply short-wavelength ultraviolet overload exposure to the area of ​​the target forming layer where the surface chemical curing degree is lower than that of the underlying chemical curing degree, and consume the dissolved oxygen on the surface of the oxygen inhibition region in situ through the photochemical reaction of the resin; the penetration depth of the short-wavelength ultraviolet overload exposure is less than the thickness of the target forming layer.

[0042] In some embodiments, predicting the additional curing amount of the target formed layer caused by the curing light penetration of adjacent formed layers, and reducing the curing energy supply to the target formed layer based on the additional curing amount when applying curing energy to the target formed layer, includes:

[0043] Obtain the interlayer spacing between the target forming layer and the adjacent formed layer;

[0044] The permeation coupling coefficient is determined based on the interlayer spacing using an exponential decay model.

[0045] The additional curing amount generated by the curing light of the target forming layer on the adjacent formed layer is determined based on the penetration coupling coefficient.

[0046] The curing energy compensation amount of the target forming layer is determined based on the additional curing amount;

[0047] When applying curing energy to the target forming layer, the curing energy supply to the target forming layer is reduced according to the curing energy compensation amount.

[0048] Secondly, this embodiment provides an in-situ monitoring device for the curing quality of microdroplet jet molding resin, comprising: a jet curing module, a curing sensing module, and a curing control module; wherein:

[0049] The spray curing module sprays and deposits photocurable resin layer by layer onto the forming platform to form a target forming layer; and applies curing energy to the target forming layer to cause the resin in the target forming layer to polymerize and cure.

[0050] The curing sensing module is used to acquire physical quantity signals of the target forming layer through a non-contact optical sensing unit during and / or after the curing of the target forming layer, and to obtain the signal distribution of the target forming layer based on the physical quantity signals; the physical quantity signals are used to characterize the degree of consumption or crosslinking of polymerizable groups of resin in the target forming layer; according to a preset transformation relationship between pixel coordinates and physical coordinates of the forming surface, the pixel coordinates in the signal distribution are mapped to the physical coordinates of the forming platform; the physical quantity signals of each physical coordinate are converted into chemical curing degree values ​​according to a preset conversion relationship to obtain the chemical curing degree distribution of the target forming layer;

[0051] The curing control module is used to calculate the error between the chemical curing degree distribution and the preset target chemical curing degree. When the error exceeds a preset first threshold, the curing energy of the target forming layer is adjusted, and / or the spraying parameters of the subsequent forming layers in the region corresponding to the chemical curing degree error between the forming platform and the target forming layer are adjusted. The subsequent forming layers are forming layers deposited layer by layer after the target forming layer. The target forming layer is cured by at least one of the following: obtaining the surface chemical curing degree and the bottom chemical curing degree of the target forming layer; when the surface chemical curing degree is lower than the bottom chemical curing degree by a value reaching a preset second threshold, the curing energy of the surface of the target forming layer is increased; predicting the additional curing amount generated by the curing light penetration of adjacent formed layers on the target forming layer, and reducing the curing energy supply of the target forming layer according to the additional curing amount when applying the curing energy of the target forming layer; repeating the above steps layer by layer on the three-dimensional object until the deposition and curing of all forming layers of the three-dimensional object are completed.

[0052] Thirdly, this embodiment provides an electronic device including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the in-situ monitoring method for the curing quality of microdroplet jet molding resin described in the first aspect above.

[0053] Fourthly, this embodiment provides a storage medium storing a computer program that, when executed by a processor, implements the steps of the in-situ monitoring method for the curing quality of microdroplet jet molding resin described in the first aspect.

[0054] Compared with related technologies, the method and apparatus for in-situ monitoring of the curing quality of microdroplet jet molding resin provided in this embodiment are as follows: First, photocurable resin is jetted and deposited layer by layer onto a molding platform to form a target molding layer. Second, curing energy is applied to the target molding layer to cause the resin in the target molding layer to polymerize and cure. Then, during and / or after the curing process of the target molding layer, physical quantity signals of the target molding layer are collected by a non-contact optical sensing unit, and the signal distribution of the target molding layer is obtained based on the physical quantity signals. The physical quantity signals are used to characterize the degree of consumption or cross-linking of polymerizable groups of the resin in the target molding layer. Further, according to a pre-set transformation relationship between pixel coordinates and the physical coordinates of the molding surface, the pixel coordinates in the signal distribution are mapped to the physical coordinates of the molding platform. Subsequently, the physical quantity signals of each physical coordinate are converted into chemical curing degree values ​​according to a preset conversion relationship to obtain the chemical curing degree distribution of the target molding layer. Then, the chemical curing degree distribution and the preset target chemical curing degree are calculated. The error between the chemical curing degrees is addressed by adjusting the curing energy of the target forming layer and / or adjusting the spraying parameters of subsequent forming layers in the region corresponding to the chemical curing degree error between the forming platform and the target forming layer when the error exceeds a preset first threshold. Subsequent forming layers are formed layers deposited layer by layer after the target forming layer. Furthermore, at least one of the following curing compensations is applied to the target forming layer: obtaining the surface chemical curing degree and the bottom chemical curing degree of the target forming layer; when the surface chemical curing degree is lower than the bottom chemical curing degree by a value reaching a preset second threshold, increasing the curing energy of the surface layer of the target forming layer; predicting the additional curing amount generated by the light penetration of adjacent formed layers on the target forming layer; and reducing the curing energy supply of the target forming layer based on the additional curing amount when applying the curing energy to the target forming layer. Finally, the above steps are repeated layer by layer on the three-dimensional object until the deposition and curing of all forming layers of the three-dimensional object are completed. By acquiring physical quantity signals characterizing the degree of consumption or cross-linking of polymerizable groups in resin in situ through a non-contact optical sensing unit, the chemical curing degree distribution is obtained based on the distribution of physical quantity signals, and the curing energy and spraying parameters are controlled in a closed loop accordingly. This improves the curing uniformity and consistency of each forming layer, effectively solving the problems of uneven surface curing and weak interlayer bonding in microdroplet spraying. Furthermore, by recording the chemical curing degree data layer by layer, curing quality traceability is achieved, providing technical support for highly reliable mass production.

[0055] Details of one or more embodiments of this application are set forth in the following drawings and description to make other features, objects and advantages of this application more readily apparent. Attached Figure Description

[0056] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0057] Figure 1 This is a hardware structure block diagram of a terminal for an embodiment of the microdroplet jet molding resin curing quality in-situ monitoring method according to this application.

[0058] Figure 2 This is a flowchart of an embodiment of a method for in-situ monitoring of the curing quality of microdroplet jet molding resin according to this application;

[0059] Figure 3 This is a schematic diagram of the structure of an in-situ monitoring device for the curing quality of microdroplet jet molding resin according to an embodiment of this application;

[0060] Figure 4 This is a flowchart of a closed-loop control method for in-situ monitoring of the curing quality of microdroplet jet molding resin, according to an embodiment of this application.

[0061] Figure 5 This is a structural block diagram of an in-situ monitoring device for the curing quality of microdroplet jet molding resin according to an embodiment of this application. Detailed Implementation

[0062] To better understand the purpose, technical solution, and advantages of this application, the application is described and illustrated below in conjunction with the accompanying drawings and embodiments.

[0063] Unless otherwise defined, the technical or scientific terms used in this application shall have the general meaning understood by one of ordinary skill in the art to which this application pertains. Words such as “a,” “an,” “an,” “the,” “the,” and “these” used in this application do not indicate quantitative limitation and may be singular or plural. The terms “comprising,” “including,” “having,” and any variations thereof used in this application are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or device that comprises a series of steps or modules (units) is not limited to the listed steps or modules (units) but may include steps or modules (units) not listed, or may include other steps or modules (units) inherent to these processes, methods, products, or devices. Words such as “connected,” “linked,” and “coupled” used in this application are not limited to physical or mechanical connections but may include electrical connections, whether direct or indirect. “Multiple” used in this application refers to two or more. “And / or” describes the relationship between related objects, indicating that three relationships may exist; for example, “A and / or B” can represent: A alone, A and B simultaneously, and B alone. Normally, the character " / " indicates that the objects before and after it are in an "or" relationship. The terms "first," "second," "third," etc., used in this application are merely to distinguish similar objects and do not represent a specific order of objects.

[0064] The method embodiments provided in this example can be executed in a terminal, computer, or similar electronic device with a certain computing power. For example, it can run on a terminal. Figure 1 This is a hardware structure block diagram of a terminal for an embodiment of the in-situ monitoring method for the curing quality of microdroplet jet molding resin according to this application. Figure 1 As shown, a terminal may include one or more ( Figure 1 Only one is shown in the diagram. A processor 102 and a memory 104 for storing data are also included. The processor 102 may be, but is not limited to, a microprocessor (MCU) or a programmable logic device (FPGA). The terminal may also include a transmission device 106 for communication functions and an input / output device 108. Those skilled in the art will understand that… Figure 1 The structure shown is for illustrative purposes only and does not limit the structure of the terminal described above. For example, the terminal may also include components that are larger than... Figure 1 The more or fewer components shown, or having the same Figure 1 The different configurations shown are illustrated.

[0065] The memory 104 can be used to store computer programs, such as application software programs and modules, like the computer program corresponding to the in-situ monitoring method for the curing quality of microdroplet jet molding resin in this embodiment. The processor 102 executes various functional applications and data processing by running the computer program stored in the memory 104, thereby implementing the above-described method. The memory 104 may include high-speed random access memory, and may also include non-volatile memory, such as one or more magnetic storage devices, flash memory, or other non-volatile solid-state memory. In some instances, the memory 104 may further include memory remotely located relative to the processor 102, and these remote memories can be connected to the terminal via a network. Examples of such networks include, but are not limited to, the Internet, corporate intranets, local area networks, mobile communication networks, and combinations thereof.

[0066] The transmission device 106 is used to receive or send data via a network. This network includes a wireless network provided by the terminal's communication provider. In one example, the transmission device 106 includes a Network Interface Controller (NIC), which can connect to other network devices via a base station to communicate with the Internet. In another example, the transmission device 106 can be a Radio Frequency (RF) module used for wireless communication with the Internet.

[0067] This embodiment provides a method for in-situ monitoring of the curing quality of microdroplet jet molding resin. Figure 2 This is a flowchart of an embodiment of the in-situ monitoring method for the curing quality of microdroplet jet molding resin, as shown below. Figure 2 As shown, the process includes the following steps:

[0068] Step S210: Photocurable resin is sprayed and deposited layer by layer onto the molding platform to form the target molding layer.

[0069] In the microdroplet jetting process, photocurable resin is deposited layer by layer onto the forming platform in the form of micron-sized droplets by a jetting head following a preset path. The jetting head can eject liquid photocurable resin in droplet form through piezoelectric or thermal foaming methods, and scan and deposit it line by line in the XY coordinate plane of the forming platform according to the preset printing path. After each layer of resin is deposited, the forming platform provides space for the jetting of the next layer of resin. Finally, through multi-layer jetting, a target three-dimensional object (formed part) is formed by stacking multiple layers of resin films. The thickness of each resin layer can be determined by jetting parameters (such as droplet volume, jetting frequency, scanning speed, etc.) and the physical properties of the resin material. After deposition, each target forming layer is immediately irradiated with curing energy, causing the photocurable resin to change from a liquid state to a solid state, and finally, the layers are accumulated to form a three-dimensional solid. The forming platform provides a supporting substrate for the target forming layers and controls the relative positional accuracy and layer thickness consistency between the layers throughout the printing process.

[0070] Step S220: Apply curing energy to the target molding layer to cause the resin in the target molding layer to polymerize and cure.

[0071] Specifically, the curing energy is provided by a curing unit, which can employ an ultraviolet light-emitting diode array, an ultraviolet laser scanning system, or a digital light processing projection system to emit ultraviolet light of appropriate wavelength and intensity according to the resin system and curing requirements. The curing unit irradiates the target forming layer according to a preset exposure time and light intensity, causing the photoinitiator in the curing unit to absorb photon energy and generate active free radicals or cations, thereby initiating a chain polymerization reaction in the polymerizable groups of the resin, transforming the resin from a liquid monomer into a solid polymer. To ensure that each resin layer receives sufficient curing energy, the curing energy can be applied uniformly across the entire layer based on the resin type, layer thickness, and target chemical degree of cure, or adjusted independently for different areas to achieve differentiated curing by region.

[0072] After curing, the target forming layer forms a solid thin layer with predetermined chemical curing degree and mechanical properties on the forming platform, providing a curing support foundation for the spray deposition of the next layer of resin. The timing of applying curing energy can be performed after each layer of resin is sprayed, or it can be implemented in parallel with the spraying process. In addition, the specific curing parameters of the curing unit, including light intensity, wavelength, exposure time, and irradiation angle, can be adjusted according to the resin system, layer thickness, and target chemical curing degree to flexibly match the curing requirements of different materials and printing processes.

[0073] Step S230: During the curing process of the target forming layer and / or after the target forming layer is cured, the physical quantity signal of the target forming layer is collected by a non-contact optical sensing unit, and the signal distribution of the target forming layer is obtained based on the physical quantity signal; the physical quantity signal is used to characterize the degree of consumption or crosslinking of the polymerizable groups of the resin in the target forming layer.

[0074] Specifically, the physical quantity signal is the optical signal output by the non-contact optical sensing unit in response to changes in the chemical state of the resin in the target forming layer. The magnitude of the physical quantity signal changes systematically with the progress of the resin polymerization reaction. Resin polymerizable groups refer to the active functional groups in the resin molecule structure that can participate in the polymerization reaction and form a cross-linked network. During photocuring, the resin polymerizable groups open under the initiation of free radicals or cationic active species, undergoing chain polymerization reactions to form a three-dimensional cross-linked network structure. As the curing reaction proceeds, the number of polymerizable groups in the resin gradually decreases, while the density of the cross-linked network gradually increases. Therefore, the degree of consumption of polymerizable groups reflects the proportion of polymerization that has occurred, while the degree of cross-linking directly reflects the density of intermolecular chemical bonds and the integrity of the network structure.

[0075] Based on the degree of consumption or cross-linking of polymerizable groups in the target molding layer, a non-contact optical sensing unit can be used to acquire signals of the target molding layer in real time during curing energy irradiation to capture dynamic information on the change in the concentration of polymerizable groups of the resin with irradiation time during the curing reaction. Alternatively, acquisition can be performed within a preset time window after the curing energy irradiation ends (e.g., within 100 milliseconds after curing) to avoid stray light interference from the curing light source and ensure signal stability. The non-contact optical sensing unit can employ fluorescence sensing mode or near-infrared / infrared spectral sensing mode.

[0076] Specifically, when using the fluorescence sensing mode, the non-contact optical sensing unit emits excitation light towards the target molding layer through an excitation source, causing the environmentally sensitive fluorescent probes doped in the resin to emit fluorescence, which is then received by an area array detector. The fluorescence intensity increases with the crosslinking density of the polymerizable groups in the resin; therefore, changes in fluorescence intensity reflect the degree of consumption of polymerizable groups and the degree of crosslinking network formation in the target molding layer. The acquired raw fluorescence signal is converted by the photoelectric conversion of the non-contact optical sensing unit, forming two-dimensional fluorescence intensity distribution data in pixels, i.e., the signal distribution of the target molding layer.

[0077] When using near-infrared / infrared spectral sensing mode, the non-contact optical sensing unit emits broadband infrared light towards the target forming layer through an infrared light source and collects the spectral signal after reflection or transmission from the target forming layer. The degree of polymerization conversion of the resin can be quantitatively characterized by directly measuring the concentration of remaining polymerizable groups in the target forming layer. The collected raw spectral signal is converted into two-dimensional spectral characteristic distribution data in spatial units by the non-contact optical sensing unit, i.e., the signal distribution of the target forming layer.

[0078] During the signal distribution generation process of the target forming layer, the physical quantity signals acquired by the non-contact optical sensing unit are area array data containing spatial location information. Each pixel corresponds to a tiny physical region on the target forming layer, and each pixel value represents the magnitude of the physical quantity signal at that location. The signal distribution is stored in the form of a pixel matrix, the spatial resolution of which is determined by the number of pixels in the area array detector of the non-contact optical sensing unit and the optical magnification. The data format of the signal distribution is consistent with the pixel coordinate system used in the subsequent coordinate mapping step to ensure accurate registration of the spatial distribution of chemical curing degree and reliable execution of region-by-region control.

[0079] Step S240: Based on the pre-set transformation relationship between pixel coordinates and physical coordinates of the forming surface, the pixel coordinates in the signal distribution are mapped to the physical coordinates of the forming platform.

[0080] The signal distribution acquired by the non-contact optical sensing unit is a two-dimensional matrix data in pixels, where each pixel value represents the signal intensity of a physical quantity at the corresponding spatial location, and the physical coordinates of the forming platform are the actual spatial coordinates in millimeters or micrometers. For example, the area array detector of the non-contact optical sensing unit and the target forming layer can be installed at a certain angle (e.g., an oblique angle of 15° to 45°) to obtain a larger field of view coverage within the compact space of the printing equipment.

[0081] Because the non-contact optical sensing unit is not perfectly perpendicular to the forming platform during installation, but rather has a certain installation tilt angle and spatial offset, and the optical lens itself also has radial and tangential distortion, the relationship between the sensor pixel coordinates and the physical coordinates of the forming platform is not a simple linear scaling relationship. Therefore, it is necessary to pre-establish the corresponding transformation relationship between the pixel coordinates in the signal distribution and the physical coordinates on the forming platform through a calibration process, i.e., the transformation relationship between the pixel coordinates and the physical coordinates of the forming surface. Specifically, this pre-defined transformation relationship can be achieved by projecting a calibration pattern containing multiple feature points onto the forming platform through a curing unit. The non-contact optical sensing unit then acquires the image of this calibration pattern on the forming platform. Distortion correction is performed on the acquired calibration pattern image, and image processing algorithms are used to extract the corresponding pixel coordinates of each feature point in the sensor pixel coordinate system. Simultaneously, based on the known geometric dimensions of the calibration pattern, the physical coordinates of each feature point on the forming platform are determined. Finally, a projection transformation matrix is ​​established using the matching point pairs between the pixel coordinates and physical coordinates of each feature point. This projection transformation matrix can be a perspective transformation matrix or an affine transformation matrix.

[0082] For example, when it is necessary to consider perspective distortion caused by the oblique mounting of the non-contact optical sensing unit and nonlinear lens distortion, a perspective transformation matrix (homography matrix) is used to establish the transformation relationship. This perspective transformation matrix is ​​a 3×3 matrix that can describe the complete projection mapping relationship between the pixel coordinate system and the physical coordinate system, and can be solved iteratively by a nonlinear least squares algorithm for multiple extracted matching point pairs.

[0083] After obtaining the transformation relationship between pixel coordinates and physical coordinates, for any pixel coordinate in the signal distribution, the corresponding physical coordinate on the forming platform can be calculated using this transformation relationship. Furthermore, to further improve the real-time response speed of coordinate mapping to meet the needs of layer-by-layer online monitoring, a two-dimensional mapping lookup table can be constructed after the transformation relationship calibration. This table records the corresponding mapping relationship between each pixel coordinate in the signal distribution and the physical coordinates of the forming platform. In actual monitoring, this mapping lookup table replaces real-time matrix operations. Through the mapping lookup table, a spatial correspondence is established between the physical quantity signal value carried by each pixel in the signal distribution and the actual physical position of each pixel on the forming platform. This ensures that the chemical curing degree values ​​of each region subsequently calculated based on the physical quantity signal can accurately correspond to the actual physical regions on the forming platform.

[0084] Step S250: Convert the physical quantity signals of each physical coordinate into chemical curing degree values ​​according to a preset conversion relationship to obtain the chemical curing degree distribution of the target forming layer.

[0085] After obtaining the physical quantity signals of the physical coordinates, the signals can be converted into chemical curing degree values ​​according to a preset conversion relationship. Chemical curing degree is defined as the proportion of reacted polymerizable groups to the initial polymerizable groups at spatial position r and time t.

[0086] ;

[0087] Where C0 is the initial concentration of polymerizable groups (such as C=C double bonds in acrylate), C(r,t) is the concentration at time t, and α(r,t) ranges from 0 to 1.

[0088] Specifically, the preset conversion relationship is used to establish a quantitative correspondence between the physical quantity signals collected by the non-contact optical sensing unit and the chemical curing degree of the resin in the target molding layer, so that the original physical quantity signals can be converted into chemical curing degree values ​​with clear physical meaning. The preset conversion relationship is determined according to the sensing mode type selected by the non-contact optical sensing unit, and different types of sensing modes correspond to different conversion methods.

[0089] When the non-contact optical sensing unit uses the fluorescence sensing mode, the physical quantity signal is the fluorescence intensity signal, and the preset conversion relationship is the correspondence between the pre-calibrated fluorescence intensity and the degree of chemical curing. When the non-contact optical sensing unit uses the near-infrared / infrared spectral sensing mode, the physical quantity signal is the characteristic absorption peak signal of polymerizable unsaturated bonds, and the preset conversion relationship is established based on the Lambert-Beer law. Furthermore, when the non-contact optical sensing unit simultaneously uses multiple modes such as fluorescence sensing and near-infrared / infrared spectral sensing, for the same physical coordinate position in the target forming layer, the corresponding estimated value of the degree of chemical curing is calculated according to the preset conversion relationship of each sensing mode. Then, the estimated values ​​of each mode are weighted and fused to obtain the fused chemical curing value at that physical coordinate.

[0090] ;

[0091] Where, α fused (r,t) is the final chemical solidification value obtained after multimodal weighted fusion at spatial location r and time t; N represents the total number of sensing modes participating in the fusion; i represents the mode number; α i (r,t) represents the chemical curing degree value independently measured at spatial location r and time t for the i-th sensing mode; w i The weighting coefficients for different sensing modes are determined by the signal-to-noise ratio and calibration accuracy of each mode in the corresponding chemical curing degree range.

[0092] Before performing conversion based on a preset conversion relationship for multimodal fusion, temperature drift correction can be applied to the physical quantity signal. Temperature drift correction includes: monitoring the temperature change of the target forming layer during the curing process; and performing first-order temperature drift compensation on the physical quantity signal based on a pre-calibrated temperature sensitivity coefficient to eliminate the influence of exothermic curing reaction and / or ambient temperature fluctuations on the measurement accuracy of the physical quantity signal. This ensures that the converted chemical cure degree value accurately reflects the actual curing state of the resin. The specific formula is as follows:

[0093] ;

[0094] Where κ is the temperature sensitivity coefficient, and T(r,t) is the real-time temperature value at spatial location r and time t. ref To calibrate the reference temperature, This represents the chemical degree of curing after temperature drift correction, indicating the true chemical degree of curing value after deducting the effect of temperature.

[0095] After the above processing, the physical quantity signals at each physical coordinate on the target molding layer are converted into corresponding chemical curing degree values, thus forming a chemical curing degree distribution covering the entire surface of the target molding layer. This chemical curing degree distribution is a two-dimensional matrix indexed by the physical coordinates of the molding platform. Each element value in the matrix represents the chemical curing degree of the resin at the corresponding physical location, ranging from 0 to 1 (or 0% to 100%), where 0 represents completely uncured and 1 represents completely cured. This chemical curing degree distribution directly reflects the differences in the curing reaction process in different regions of the target molding layer, providing a quantitative data basis for subsequent curing quality judgment and closed-loop control. Simultaneously, each element in this chemical curing degree distribution maintains a precise correspondence with the physical coordinates on the molding platform, enabling accurate location of specific areas when calculating chemical curing degree errors.

[0096] Step S260: Calculate the error between the chemical curing degree distribution and the preset target chemical curing degree. When the error exceeds the preset first threshold, adjust the curing energy of the target forming layer and / or adjust the spraying parameters of the subsequent forming layer in the region where there is a chemical curing degree error between the forming platform and the target forming layer. The subsequent forming layer is a forming layer that is deposited layer by layer after the target forming layer.

[0097] The chemical cure degree values ​​at each physical coordinate of the target molding layer are received and compared with the preset target chemical cure degree. The preset target chemical cure degree is a pre-set expected value of chemical cure degree based on the final performance requirements of the molded part. The value of the preset target chemical cure degree is determined based on the resin system and the end application scenario. For each physical coordinate position on the target molding layer, the difference between the chemical cure degree value at that position and the preset target chemical cure degree is calculated. This difference is defined as the chemical cure degree error at that position. The specific formula for the chemical cure degree error is as follows:

[0098] ;

[0099] Where e(r,t) is the chemical solidification error value at spatial location r and time t, and α target (r) is the preset target chemical curing degree value at spatial location r, and α(r,t) is the actual chemical curing degree value measured at spatial location r and time t.

[0100] Chemical curing degree error is a signed numerical value: a positive error indicates that the actual chemical curing degree at that location is higher than the target value (risk of over-curing); a negative error indicates that the actual chemical curing degree at that location is lower than the target value (risk of under-curing). Therefore, each physical coordinate position on the target forming layer corresponds to a chemical curing degree error value, forming a chemical curing degree error distribution covering the target forming layer. This distribution directly identifies which areas on the target forming layer have curing quality deviations, the direction of these deviations, and the magnitude of the deviations.

[0101] When the absolute value of the chemical curing degree error at a certain physical coordinate location exceeds a preset first threshold, it is determined that there is an abnormality in the curing quality at that physical coordinate location, requiring further adjustment. The preset first threshold is an upper limit of the allowable error, set based on a comprehensive consideration of measurement noise, resin system curing kinetic fluctuations, and the quality tolerance of the molded part. Areas where the absolute value of the chemical curing degree error does not exceed this threshold are considered to have acceptable curing quality and require no intervention.

[0102] When an abnormal curing quality is detected in a certain area, corresponding control commands are generated based on the direction and magnitude of the error. If the error is negative, the curing energy output corresponding to that area is increased, for example, by extending the exposure time or increasing the light intensity, to promote further curing of the resin in that area. The curing energy is defined by the cumulative exposure dose, and the formula is:

[0103] ;

[0104] Where D(r) is the cumulative exposure dose applied at spatial position r; I(r,t) is the curing light intensity at spatial position r and time t; and dt is the integral element of the exposure time.

[0105] If the error is positive, reduce the curing energy output for that area, or reduce the curing energy supply for that area during subsequent layer printing to avoid over-curing accumulation. The amount of curing energy adjustment is determined proportionally based on the error amplitude to ensure a smooth control process without generating new overshoot.

[0106] For example, when the error exceeds a preset first threshold e th At the same time, apply additional curing agents to the corresponding areas in a controlled manner according to the specified ratio: Where ΔD(r) is the amount of curing agent that needs to be applied at spatial location r; The proportional gain is used to convert the chemical curing degree error into an adjustment amount for the curing dose; e(r,t) is the chemical curing degree error at spatial position r and time t. Iterative learning control can be used for layer-by-layer forming, and the formula for correcting the curing dose of subsequent regions at the same location based on the error of the current layer is:

[0107] ;

[0108] Where k is the layer number; D k (r) is the actual curing dose applied to the k-th layer at spatial location r; D k+1 (r) is the curing dose required for the (k+1)th layer at the same spatial location r; e k (r) is the chemical curing error detected at spatial location r for the k-th layer; K p This is a proportional gain. By using the chemical curing degree error at the same location in the previous layer as a correction basis, the curing dosage of subsequent layers can be adjusted in a feedforward manner.

[0109] Furthermore, based on the chemical curing degree error distribution detected in the current layer, the spraying parameters of subsequent forming layers at the same physical coordinate position can be feedforward corrected. Since subsequent forming layers are deposited layer by layer after the target forming layer, they share the same physical coordinate reference system in space. Therefore, the physical coordinate position corresponding to the chemical curing degree error detected in the current layer is the spatial position where the spraying parameters need to be adjusted in subsequent layers. Spraying parameters include spray droplet volume, spraying frequency, scanning speed, and single-layer resin deposition thickness.

[0110] Step S270, perform curing compensation on the target forming layer using at least one of the following methods:

[0111] Step S271: Obtain the surface chemical curing degree and the bottom chemical curing degree of the target forming layer. When the surface chemical curing degree is lower than the bottom chemical curing degree by a preset second threshold, increase the curing energy of the surface of the target forming layer.

[0112] During the oxygen inhibition compensation process, the surface chemical curing degree and the bottom chemical curing degree of the target forming layer are first obtained. Specifically, the surface chemical curing degree is the chemical curing degree value of the side of the target forming layer closest to the upper surface (i.e., the side exposed to the printing environment atmosphere), which reflects the actual curing degree of this surface area under the influence of the oxygen inhibition effect. The bottom chemical curing degree is the chemical curing degree value of the side of the target forming layer closest to the lower surface (i.e., the side in contact with the previous formed layer or forming platform). The bottom chemical curing degree is not affected by the inhibition of oxygen in the atmosphere of the current layer and can be used as a reference benchmark to determine whether oxygen inhibition has occurred in the target forming layer. The surface chemical curing degree and the bottom chemical curing degree are extracted separately along the depth direction from the chemical curing degree distribution collected and converted by the in-situ chemical curing degree sensing unit.

[0113] The surface chemical curing degree is then compared with the underlying chemical curing degree. If the surface chemical curing degree is lower than the underlying chemical curing degree, it indicates that the surface of the target forming layer is not fully cured due to oxygen inhibition. When the difference between the surface and underlying chemical curing degrees reaches a preset second threshold, oxygen inhibition is determined to have occurred on the surface of the target forming layer, requiring compensation intervention. The preset second threshold is a threshold for judging the severity of oxygen inhibition, and its specific value can be determined based on the resin system, layer thickness, and printing process conditions.

[0114] When oxygen inhibition compensation is deemed necessary, it can be achieved by increasing the curing energy of the target forming layer surface. Specifically, based on the difference between the surface chemical curing degree and a preset target chemical curing degree, or based on the difference between the surface chemical curing degree and the underlying chemical curing degree, the additional curing energy dose to be applied to the target forming layer surface is determined, and the additional curing energy is applied to the target forming layer surface through the curing unit. Methods for applying the additional curing energy include extending the exposure time of the target forming layer surface, increasing the output light intensity of the curing unit, and performing a second exposure on the target forming layer surface.

[0115] Step S272: Predict the additional curing amount of the target formed layer caused by the penetration of curing light in the adjacent formed layer, and reduce the curing energy supply of the target formed layer according to the additional curing amount when applying curing energy to the target formed layer.

[0116] In the interlayer secondary curing compensation process, the additional curing amount of the target formed layer caused by the light penetration of adjacent formed layers is first predicted. Specifically, in the microdroplet jetting layer-by-layer forming process, when the curing unit applies curing energy to the target formed layer, part of the curing light energy is absorbed by the resin in the target formed layer and used to initiate a polymerization reaction; another part of the curing light energy penetrates the target formed layer and reaches the cured adjacent formed layers (such as the layer above or even earlier than the target formed layer), and initiates the continued polymerization reaction of unreacted polymerizable groups in the adjacent formed layer, i.e., post-curing occurs. This post-curing phenomenon causes the final chemical degree of curing of the adjacent formed layer to be higher than the chemical degree of curing it achieved during initial curing. The adjacent formed layers include one or more formed layers that have been cured before the target formed layer. Among the adjacent formed layers, the layer directly adjacent to the target formed layer is most affected by light penetration, and the layer farther away is less affected.

[0117] To predict the additional curing amount, the interlayer spacing between the target forming layer and adjacent formed layers needs to be obtained, and the penetration coupling coefficient is determined based on the interlayer spacing using an exponential decay model. The penetration coupling coefficient characterizes the degree to which adjacent formed layers are affected by light penetration during the curing process of the target forming layer; a smaller interlayer spacing results in a larger penetration coupling coefficient, and vice versa. Based on this, the penetration coupling coefficient is multiplied by the current chemical curing degree of the adjacent formed layer to obtain the additional curing amount due to light penetration. When multiple adjacent formed layers exist, the additional curing amount of each layer is calculated separately and then summed to obtain the total additional curing amount generated by the curing light of the target forming layer on the formed layers. The total additional curing amount reflects the additional increase in chemical curing degree of adjacent formed layers due to the penetration effect of the curing light of the target forming layer, without compensation.

[0118] Then, when applying the curing energy to the target forming layer, the curing energy supply to the target forming layer is reduced according to the additional curing amount. Specifically, since the curing light of the target forming layer inevitably penetrates into adjacent formed layers and causes them to cure additionally, the curing energy supply to the target forming layer is actively reduced during curing, so that the target forming layer itself is not completely cured to the target value, but rather a certain amount of under-curing space is reserved. The degree of under-curing corresponds to the additional curing amount, so that after receiving the penetrated light from the target forming layer, the final chemical curing degree of the adjacent formed layers exactly reaches the preset target value, without over-curing due to the accumulation of post-curing. The amount of reduction in the curing energy of the target forming layer can be determined by back-calculating the corresponding amount of reduction in curing energy (compensation amount) based on the total additional curing amount and the curing kinetics characteristics of the resin. When applying the curing energy to the target forming layer, the curing energy of the target forming layer is reduced by subtracting the compensation amount, thereby reducing the actual curing energy supply of the target forming layer and reducing the energy of curing light penetrating into the adjacent formed layers at the source.

[0119] Step S280: Repeat the above steps layer by layer on the three-dimensional object until the deposition and solidification of all the forming layers of the three-dimensional object are completed.

[0120] In the overall printing process of a 3D object, the target forming layer is used as the basic unit. Steps such as spraying, curing, signal acquisition, coordinate mapping, chemical curing degree conversion, error calculation, closed-loop control, and curing compensation are performed layer by layer. The same sequence of operations is repeated for the next forming layer until all forming layers of the 3D object are deposited and cured. After each forming layer completes curing and corresponding compensation operations, its chemical curing degree distribution data and the control record for that layer are recorded and stored using the physical coordinates of the forming platform as an index, along with the layer number, printing timestamp, and corresponding process parameters, forming a layer-by-layer, region-by-region 3D chemical curing quality archive. The 3D chemical curing quality archive records the final chemical curing degree information of each forming layer at every location in space for the 3D object. It includes chemical curing degree data and process parameter adjustment records for all regions of all forming layers from the first to the last layer, forming a 3D data matrix with physical coordinates, layer number, and chemical curing degree as core data. This supports backtracking and querying of curing quality for any layer and any region after forming. After layer-by-layer accumulation, all forming layers of the 3D object are stacked layer by layer in the thickness direction to obtain the target 3D object.

[0121] Because each layer undergoes in-situ monitoring and closed-loop control during the printing process, the chemical curing degree of each region within the 3D object is controlled within the preset target range. Simultaneously, since the chemical curing degree data of each layer is recorded, the overall curing quality of the 3D object can be determined based on the recorded data to determine whether it meets the design requirements. For areas with substandard curing quality, the specific layer and physical coordinates can be directly traced, providing data for quality analysis and process improvement. After the deposition and curing of all forming layers are completed, the overall curing quality of the 3D object is traceable and verifiable, allowing it to directly proceed to subsequent post-processing steps such as cleaning and post-curing.

[0122] Compared to related technologies that rely on visual inspection to monitor the geometry of deposited layers and adjust spraying parameters accordingly, this approach only focuses on whether the formed part's shape meets expectations and cannot address the chemical essence of whether the internal curing reaction of the resin is sufficient and uniform. Visual inspection can only perceive physical geometric quantities such as layer thickness, width, and surface smoothness. However, it cannot provide any effective monitoring information for chemical-level quality defects such as insufficient surface curing caused by oxygen inhibition, inconsistent chemical curing degrees between layers due to differences in interlayer light penetration, and weak interfacial bonding caused by insufficient chemical bonding between layers. These defects accumulate and couple with each other during the layer-by-layer stacking process, leading to problems such as uneven curing, weak interlayer bonding, and untraceable curing quality.

[0123] In steps S210 to S280 above, firstly, photocurable resin is sprayed and deposited layer by layer onto a forming platform to form a target forming layer; secondly, curing energy is applied to the target forming layer to cause the resin in the target forming layer to polymerize and cure; then, during and / or after the target forming layer has cured, physical quantity signals of the target forming layer are collected by a non-contact optical sensing unit, and the signal distribution of the target forming layer is obtained based on the physical quantity signals; the physical quantity signals are used to characterize the degree of consumption or crosslinking of polymerizable groups of the resin in the target forming layer; further, according to a pre-set transformation relationship between pixel coordinates and physical coordinates of the forming surface, the pixel coordinates in the signal distribution are mapped to the physical coordinates of the forming platform; subsequently, the physical quantity signals of each physical coordinate are converted into chemical curing degree values ​​according to a preset conversion relationship to obtain the chemical curing degree distribution of the target forming layer; then, the chemical curing degree distribution is calculated and... The error between the preset target chemical curing degree and the target layer is considered. When the error exceeds a preset first threshold, the curing energy of the target forming layer is adjusted, and / or the spraying parameters of the subsequent forming layers in the region corresponding to the chemical curing degree error between the forming platform and the target forming layer are adjusted. The subsequent forming layers are formed layers that are stacked and deposited layer by layer after the target forming layer. Furthermore, at least one of the following curing compensations is performed on the target forming layer: the surface chemical curing degree and the bottom chemical curing degree of the target forming layer are obtained. When the value of the surface chemical curing degree being lower than that of the bottom chemical curing degree reaches a preset second threshold, the curing energy of the surface of the target forming layer is increased. The additional curing amount generated by the light penetration of adjacent formed layers on the target forming layer is predicted. When applying the curing energy of the target forming layer, the curing energy supply of the target forming layer is reduced according to the additional curing amount. Finally, the above steps are repeated layer by layer on the three-dimensional object until the deposition and curing of all forming layers of the three-dimensional object are completed. By acquiring physical quantity signals characterizing the degree of consumption or cross-linking of polymerizable groups in resin in situ through a non-contact optical sensing unit, the chemical curing degree distribution is obtained based on the distribution of physical quantity signals, and the curing energy and spraying parameters are controlled in a closed loop accordingly. This improves the curing uniformity and consistency of each forming layer, effectively solving the problems of uneven surface curing and weak interlayer bonding in microdroplet spraying. Furthermore, by recording the chemical curing degree data layer by layer, curing quality traceability is achieved, providing technical support for highly reliable mass production.

[0124] Optionally, in one embodiment, when the physical quantity signal is a fluorescence intensity signal, the physical quantity signals of each physical coordinate are converted into chemical curing degree values ​​according to a preset conversion relationship to obtain the chemical curing degree distribution of the target forming layer, including:

[0125] The fluorescence intensity of the uncured liquid resin is measured as the lower limit benchmark value; the fluorescence intensity of the fully cured sample is measured as the upper limit benchmark value; a calibration curve between fluorescence intensity and chemical curing degree is established based on multiple standard samples to obtain a preset conversion relationship between fluorescence intensity and chemical curing degree; the collected physical quantity signals are substituted into the preset conversion relationship to obtain the chemical curing degree value of each physical coordinate.

[0126] When the non-contact optical sensing unit adopts the fluorescence sensing mode, the obtained physical quantity signal is a fluorescence intensity signal. The non-contact optical sensing unit emits excitation light towards the target forming layer through an excitation source, causing the environmentally sensitive fluorescent probes doped in the resin to emit fluorescence, which is then received by an area array detector. This fluorescence intensity signal increases with the rigidity of the resin cross-linking microenvironment and has a definite correlation with the degree of chemical curing of the resin. To quantitatively convert the acquired fluorescence intensity signal into a chemical curing degree value, a calibration curve between fluorescence intensity and chemical curing degree needs to be established beforehand as a preset conversion relationship.

[0127] Specifically, the fluorescence intensity of the uncured liquid resin was first measured as the lower limit reference value. By taking an uncured liquid resin sample and, under an inert atmosphere (such as a nitrogen atmosphere) to eliminate oxygen inhibition, using the same excitation source and area array detector parameters as in real-time monitoring, the fluorescence intensity of the uncured liquid resin sample was measured as the lower limit reference value. Lower limit benchmark value This corresponds to the state where the chemical curing degree is 0, that is, the fluorescence intensity benchmark point when the resin has not undergone any polymerization reaction.

[0128] Secondly, the fluorescence intensity of the fully cured sample was measured as the upper limit benchmark value. Specifically, resin samples from the same batch are taken and subjected to full exposure under the same light source conditions as the real-time monitoring (e.g., full UV exposure until the double bond conversion rate is greater than 95%) to allow the resin to reach a fully cured state. The fluorescence intensity of the fully cured sample is then measured as the upper limit benchmark value. Upper limit benchmark value This corresponds to the state where the chemical curing degree approaches 100%, that is, the fluorescence intensity benchmark point when the resin is fully cured.

[0129] Next, a calibration curve between fluorescence intensity and chemical curing degree is established based on multiple standard samples. Multiple (e.g., 5) standard samples are prepared at different exposure doses, covering the entire chemical curing degree range from uncured to fully cured, ensuring a uniform distribution of chemical curing degree between 0% and 100%. The fluorescence intensity of each standard sample is measured using the same excitation source and area array detector parameters as the real-time monitoring, and the true chemical curing degree of each standard sample is determined, establishing a correspondence between fluorescence intensity and chemical curing degree. This allows for fitting of the calibration data points, using either linear or nonlinear fitting, to obtain the calibration curve between fluorescence intensity and chemical curing degree. The calibration curve represents the preset conversion relationship between fluorescence intensity and chemical curing degree, with a coefficient of determination of not less than 0.98, ensuring that the fitting accuracy of the calibration curve meets the requirements of subsequent quantitative conversion.

[0130] Finally, by substituting the fluorescence intensity signals collected at each physical coordinate point into the calibration curve, the corresponding chemical curing degree value at each physical coordinate point can be calculated. For the fluorescence sensing mode using a linear calibration curve, the normalization formula for the chemical curing degree value is:

[0131] ;

[0132] Where α(r,t) represents the real-time chemical curing degree value, and F(r,t) represents the real-time fluorescence intensity signal. For fluorescence sensing modes using nonlinear calibration curves, the chemical curing degree value can be determined through a lookup table or fitting function. This forms the chemical curing degree distribution of the target forming layer.

[0133] Furthermore, in one embodiment, when the physical quantity signal is a characteristic absorption peak signal of a polymerizable group, the physical quantity signals of each physical coordinate are converted into chemical curing degree values ​​according to a preset conversion relationship to obtain the chemical curing degree distribution of the target forming layer, including:

[0134] The ratio of the area of ​​the polymerizable unsaturated bond characteristic absorption peak of the target forming layer to the area of ​​the reference peak is used as a calculation parameter; the calculation parameter at the initial moment when the target forming layer is not cured is used as the initial reference value; during the curing process of the target forming layer and / or after the target forming layer is cured, the calculation parameter obtained by real-time measurement is used as the real-time measurement value; the ratio of the real-time measurement value to the initial reference value is calculated to obtain the remaining ratio; the remaining ratio is subtracted from one to obtain the chemical curing degree value of each physical coordinate.

[0135] When the non-contact optical sensing unit adopts the near-infrared / infrared spectral sensing mode, the obtained physical quantity signal is the characteristic absorption peak signal of polymerizable groups. The non-contact optical sensing unit emits broadband infrared light to the target molding layer through an infrared light source and collects the spectral signal after reflection or transmission from the target molding layer. Since polymerizable unsaturated bonds have characteristic absorption peaks in the near-infrared band, and the area of ​​these absorption peaks gradually decreases as the curing reaction proceeds, the concentration of remaining polymerizable groups in the target molding layer can be directly determined by analyzing the change in the area of ​​these characteristic absorption peaks, thereby quantitatively characterizing the degree of polymerization conversion of the resin. The collected characteristic absorption peak signal is quantitatively converted into a chemical degree of curing value using the following formula:

[0136] ;

[0137] Where α(r,t) is the degree of chemical curing; A C=C The absorption peak area characteristic of polymerizable unsaturated bonds (carbon-carbon double bonds), A ref The area of ​​the reference peak. The normalized calculation parameters are used for the current moment; This is a normalized calculation parameter for the initial moment. As can be seen from the formula, in this embodiment, the ratio of the characteristic absorption peak area of ​​the polymerizable unsaturated bond in the target forming layer to the reference peak area is used as the calculation parameter. Specifically, in the acquired spectral signal, the characteristic absorption peak area of ​​the polymerizable unsaturated bond (C=C) is selected as the activity parameter (denoted as A). C=C The peak area gradually decreases as the curing reaction proceeds; simultaneously, the characteristic absorption peak area of ​​stable chemical groups in the resin system that do not participate in the curing reaction is selected as the reference peak (denoted as A). ref The area of ​​the reference peak remains constant during the curing process and does not change with the polymerization reaction. Dividing the area of ​​the characteristic absorption peak by the area of ​​the reference peak yields the normalized calculation parameter at the current moment, which is the real-time measurement value. Additionally, the normalized calculation parameter at the initial moment before the target formed layer has cured is used as the initial reference value.

[0138] The ratio of the real-time measured value to the initial baseline value is calculated to obtain the remaining ratio. The remaining ratio represents the proportion of remaining polymerizable groups to the initial polymerizable groups at the current moment. The value ranges from 0 to 1. The closer the value is to 1, the more remaining polymerizable groups there are and the lower the degree of curing reaction. The closer the value is to 0, the fewer remaining polymerizable groups there are and the higher the degree of curing reaction.

[0139] Finally, subtracting the remaining proportion from the initial value yields the chemical degree of curing at each physical coordinate. The initial value represents the initial state, where all polymerizable groups are unreacted. Subtracting the current proportion of remaining polymerizable groups from the initial value gives the proportion of polymerizable groups that have undergone polymerization, i.e., the chemical degree of curing. This chemical degree of curing value ranges from 0 to 1, where 0 represents completely uncured and 1 represents completely cured. Repeating the above calculation at each physical coordinate location of the target forming layer yields the chemical degree of curing value at each physical coordinate, thus forming the chemical degree of curing distribution of the target forming layer.

[0140] In one embodiment, mapping the pixel coordinates in the signal distribution to the physical coordinates of the forming platform according to a pre-defined transformation relationship between pixel coordinates and the physical coordinates of the forming surface includes:

[0141] A calibration pattern containing multiple preset control points is projected onto the forming platform. Based on the image of the calibration pattern on the forming platform, the pixel coordinates of each control point in the pixel coordinate system are extracted. Based on the correspondence between the pixel coordinates of the control points and their physical coordinates on the forming platform, a homography transformation matrix is ​​established between the pixel coordinate system and the physical coordinate system of the forming platform. Lens distortion correction is performed on the image of the captured calibration pattern to eliminate the spatial position deviation introduced by imaging distortion, resulting in a distortion-corrected image. A mapping lookup table is constructed based on the homography transformation matrix and the distortion-corrected image, mapping the pixel coordinates in the signal distribution to the physical coordinates of the forming platform. The mapping lookup table includes the correspondence between the pixel coordinates in the signal distribution and the physical coordinates of the forming platform.

[0142] First, a calibration pattern containing multiple preset control points is projected onto the forming platform. The calibration pattern is a standard checkerboard pattern or a calibration target pattern containing regularly distributed feature points, projected by the curing unit onto the forming platform. The preset control points are locatable feature points in the calibration pattern, such as the corners of the checkerboard or the center of the target. The area array detector of the non-contact optical sensing unit captures an image of the calibration pattern on the forming platform at a preset oblique angle, obtaining a calibration image. Image processing is performed on the calibration image to determine the pixel coordinates of each control point in the pixel coordinate system. For example, the sensor pixel coordinate system Σ... S (u,v), the physical coordinate system of the solidification unit Σ C (x c ,y c ) and the physical coordinate system of the forming platform Σ P (X p ,Y p Spatial registration and coordinate transformation model between ) and , calibrating the graphic in the solidified unit physical coordinate system Σ C The center coordinates of each control point in the diagram are (x... ci ,yci ), where i = 1, 2, ..., M×N.

[0143] Secondly, because the area array detector of the non-contact optical sensing unit has a preset oblique angle (i.e., tilt angle θ) with the forming platform during installation, the calibration pattern undergoes perspective distortion during imaging. Simultaneously, the optical lens itself also exhibits radial and tangential distortion, resulting in a relationship between the sensor pixel coordinates and the physical coordinates of the forming platform that is not a simple linear scaling relationship, but rather satisfies a homography perspective transformation relationship. For example, the homography transformation matrix is ​​a 3×3 matrix, with the following form:

[0144] ;

[0145] Wherein, the pixel coordinates are (u, v), and the control point center coordinates are (x, v). ci ,y ci ), where s is an arbitrary scale factor. It is a 3×3 homography calibration matrix.

[0146] Next, due to unavoidable manufacturing and assembly errors in the optical lens of the non-contact optical sensing unit, the actual imaging position of each pixel in the image deviates from its ideal projection position. A comprehensive correction model incorporating first-order radial distortion, second-order radial distortion, and tangential distortion can be used to correct the distortion of the captured calibration pattern image. The distortion correction model establishes a mathematical relationship between the measured distorted image coordinates and the coordinates of the distortion-free ideal image, with the specific formula as follows:

[0147] ;

[0148] ;

[0149] Among them, (x p ,y p (x) represents the ideal projection coordinates without distortion. pd ,y pd ) represents the measured coordinates of the distorted projection image, r 2 =x pd 2 +y pd 2 Let k1 and k2 be the radial distortion coefficients, and k3, k4, k5, and k6 be the combined tangential and thin prism distortion coefficients. The above distortion parameters are obtained by jointly fitting and solving calibration plate images with known geometric dimensions under multiple spatial attitudes, thus achieving pixel-level resampling and distortion elimination of the raw data acquired by the sensor.

[0150] Finally, after calibrating the homography transformation matrix and distortion correction parameters, a two-dimensional mapping lookup table is constructed. This table records the correspondence between pixel coordinates in the signal distribution and the physical coordinates of the forming platform. It is an index table generated based on the homography transformation matrix and distortion correction results after homography transformation matrix calibration and lens distortion correction. During actual monitoring, when the sensing unit detects an abnormality in local chemical curing degree at a pixel location, resulting in a chemical curing degree error, the pixel coordinates can be quickly mapped to the corresponding physical coordinates of the forming platform by querying the two-dimensional mapping lookup table; or the actual physical position of the pixel coordinates in the physical coordinate system of the forming platform can be determined by using the inverse of the homography transformation matrix, thus identifying the spatial location of the abnormal area. Based on this spatial location information, the curing unit can be driven to accurately adjust the curing energy of the area corresponding to the physical coordinates, ensuring that energy compensation only applies to the specific area with chemical curing degree error, without affecting other areas with normal curing quality. This achieves high-precision closed-loop control of spatially partitioned modulation of curing energy.

[0151] In one embodiment, a calibration pattern containing multiple preset control points is projected onto a forming platform, and the pixel coordinates of each control point in the pixel coordinate system are extracted based on the image of the calibration pattern on the forming platform, including:

[0152] A calibration pattern containing multiple feature points is projected onto the forming platform; the calibration pattern is imaged on the forming platform using an area array detector to obtain a captured calibration image; based on the captured calibration image, the pixel coordinates of each feature point in the pixel coordinate system are extracted using sub-pixel edge detection and centroid extraction algorithms.

[0153] The calibration pattern is a standard checkerboard pattern or a calibration circular target pattern containing M×N regularly distributed feature points, projected from the curing unit onto the forming platform. Feature points are locatable markers within the calibration pattern; when using a checkerboard pattern, the feature points are the corner points of the checkerboard; when using a calibration circular target pattern, the feature points are the centers of the circular markers. The area array detector of the non-contact optical sensing unit captures an image of the calibration pattern on the forming platform at a preset oblique angle, obtaining a calibration image. After obtaining the calibration image, image preprocessing is performed, including image denoising, contrast enhancement, and brightness normalization, to improve the robustness and positioning accuracy of feature point detection. Then, a sub-pixel edge detection algorithm accurately extracts the edge positions of each feature point, improving edge positioning accuracy to the sub-pixel level. Finally, a centroid extraction algorithm calculates the centroid position of each feature point as its accurate pixel coordinates in the pixel coordinate system.

[0154] In one embodiment, when the degree of chemical curing of the surface layer is lower than the degree of chemical curing of the underlying layer by a preset second threshold, the method further includes:

[0155] The region in the target forming layer where the surface chemical curing degree is lower than that of the underlying chemical curing degree is identified as the oxygen inhibition region; a pulsed inert gas jet is injected into the oxygen inhibition region to form a local inert gas covering layer on the surface of the oxygen inhibition region; and / or, the oxygen-containing boundary layer above the region in the target forming layer where the surface chemical curing degree is lower than that of the underlying chemical curing degree is aspirated to form an inert gas curtain above the oxygen inhibition region; and / or, short-wavelength ultraviolet overload exposure is applied to the region in the target forming layer where the surface chemical curing degree is lower than that of the underlying chemical curing degree, and the dissolved oxygen on the surface of the oxygen inhibition region is consumed in situ through the photochemical reaction of the resin; the penetration depth of the short-wavelength ultraviolet overload exposure is less than the thickness of the target forming layer.

[0156] While increasing the curing energy of the target forming layer surface, an auxiliary deoxidation operation can also be performed to enhance the oxygen inhibition compensation effect. Specific auxiliary deoxidation operations include:

[0157] (1) Local inert gas replacement: A pulsed inert gas jet is injected into the oxygen inhibition region to form a local inert gas coating layer on the surface of the oxygen inhibition region. Specifically, a pulsed nitrogen jet is injected into the surface of the oxygen inhibition region through an annular micro-nozzle array (nozzle orifice diameter of 50μm to 200μm, array inner diameter of 1mm to 3mm, coaxial with the injection head) set on the side of the injection head. The nozzle outlet is at a slight inclination angle of 15° to 30° with the forming platform to form a momentary local inert gas coating layer on the surface of the oxygen inhibition region. The pulse width of the pulsed nitrogen jet is 0.1 seconds to 1 second, the pulse interval is 0.5 seconds to 2 seconds, and the peak flow velocity is 5m / s to 20m / s. The pulsed nitrogen jet moves synchronously with the movement of the injection head, and only performs local atmosphere replacement at fixed points and times in the oxygen inhibition region. The replacement time is much less than 1 second, which is less than the overall gas washing time of the sealed chamber, thus avoiding continuous airflow disturbance to the surface morphology of the uncured resin in adjacent areas. Through the above operations, the oxygen on the surface of the oxygen-inhibited region is temporarily replaced by an inert gas, and the oxygen concentration on the surface is significantly reduced. This effectively inhibits the continuous consumption of free radicals on the surface by the oxygen inhibition effect, allowing the surface resin to fully react during the subsequent curing process.

[0158] (2) Combined use of negative pressure suction and inert gas curtain: The oxygen-containing boundary layer above the area where the surface chemical curing degree of the target forming layer is lower than that of the bottom layer is suctioned, and an inert gas curtain is formed above the oxygen inhibition area. Specifically, the oxygen-containing boundary layer above the surface of the oxygen inhibition area (e.g., within 2 mm above) is suctioned through a negative pressure suction tank (vacuum degree of -5 kPa to -20 kPa) set around the forming platform, and the oxygen in the surface of this area is actively removed. At the same time as or after the start of negative pressure suction (delay of less than 0.5 seconds), an inert gas curtain device set above the spraying / curing station is used to form an inert gas curtain above the oxygen inhibition area (nitrogen flow rate of 2 L / min to 10 L / min, curtain thickness of 2 mm to 5 mm). This method can first suction and remove the oxygen-containing boundary layer, and then use an inert gas curtain to prevent the re-intrusion of the surrounding oxygen-containing atmosphere, so as to achieve a more thorough local deoxygenation effect, which is suitable for scenarios where oxygen inhibition is more serious.

[0159] (3) Combined Short-Wavelength UV Overload Exposure and Chemical Deoxygenation: Short-wavelength UV overload exposure is applied to areas in the target molded layer where the surface chemical curing degree is lower than that of the underlying layer. Dissolved oxygen in the surface of the oxygen-inhibiting region is consumed in situ through photochemical reactions within the resin. The penetration depth of the short-wavelength UV overload exposure is less than the thickness of the target molded layer. Specifically, short-wavelength UV light (e.g., the 280nm to 320nm mid-wave ultraviolet band, with a penetration depth less than 5μm) with a shorter penetration depth is used to overload expose the surface of the oxygen-inhibiting region, ensuring that the short-wavelength UV overload exposure only affects the thin surface layer of the target molded layer without affecting the underlying layer or the already molded layer. Simultaneously, the photosensitizer doped in the resin consumes dissolved oxygen in situ through photochemical reactions under short-wavelength UV irradiation, enabling rapid curing of the surface layer without relying on atmosphere replacement. This method does not rely on inert gas supply and is suitable for applications where inert gases cannot be used.

[0160] When performing assisted deoxygenation, one or more of the above methods can be flexibly selected and combined according to the severity of oxygen inhibition and equipment configuration. Through the synergistic effect of assisted deoxygenation and the main path of increasing surface curing energy, the oxygen inhibition effect is compensated from two dimensions: reducing oxygen concentration and increasing curing energy supply. Efficient surface curing compensation is achieved with lower energy input without replacing the entire printing cavity with an inert atmosphere.

[0161] Furthermore, in one embodiment, predicting the additional curing amount of the target formed layer caused by the curing light penetration of adjacent formed layers, and reducing the curing energy supply to the target formed layer based on the additional curing amount when applying curing energy to the target formed layer, includes:

[0162] Obtain the interlayer spacing between the target forming layer and the adjacent formed layers; determine the penetration coupling coefficient based on the interlayer spacing using an exponential decay model; determine the additional curing amount generated by the curing light of the target forming layer on the adjacent formed layers based on the penetration coupling coefficient; determine the curing energy compensation amount of the target forming layer based on the additional curing amount; reduce the curing energy supply of the target forming layer based on the curing energy compensation amount when applying curing energy to the target forming layer.

[0163] In microdroplet jetting layer-by-layer molding, when the curing unit applies curing energy to the target layer (current layer), a portion of the curing light penetrates the target layer and reaches the adjacent cured layer, initiating further polymerization of unreacted polymerizable groups in that adjacent layer—a phenomenon known as post-curing. The final chemical degree of curing of the nth layer is the sum of the primary chemical degree of curing achieved during the curing of that layer itself and the post-curing contributions from subsequent layers.

[0164] ;

[0165] in, It is the final chemical curing degree of the nth layer at position r; β is the primary chemical degree of curing of the nth layer at position r, that is, the chemical degree of curing achieved by the polymerization reaction of the layer itself when the curing energy of the target forming layer is applied; m It is the permeation coupling coefficient of the m-th layer; It is the additional chemical curing degree contribution caused by the penetration of curing light into the nth layer when the n+mth layer is cured; This represents the sum of the post-curing contributions of all subsequent layers to the nth layer. Interlayer secondary curing compensation ensures that the chemical cure degree of each layer falls within the allowable error range of the preset target chemical cure degree. The specific formula is:

[0166] ;

[0167] in, α represents the final chemical degree of curing of the nth layer, i.e., the final chemical degree of curing value reached by this layer after its own curing and the curing of all subsequent layers; target To preset the target chemical curing degree; ε tol This indicates the allowable tolerance for chemical curing degree error; This means that it holds true for all n.

[0168] Therefore, in order to calculate the additional curing amount for compensation and ensure that the chemical curing degree of each layer falls within the allowable error range of the preset target chemical curing degree, the interlayer spacing between the target forming layer and the adjacent formed layers is first obtained. The interlayer spacing is equal to the single-layer cured thickness, which is determined by the set value of the printed slice layer thickness.

[0169] Then, the penetration coupling coefficient is determined based on the interlayer spacing using an exponential decay model. The penetration coupling coefficient characterizes the degree to which adjacent formed layers are affected by light penetration during the curing process of the target formed layer; its value ranges from 0 to 1, with a larger value indicating a more significant influence. The exponential decay model is as follows: ,in γ is the coupling coefficient of the formed layer directly adjacent to the target formed layer, with a value ranging from 0.05 to 0.20; γ is the attenuation coefficient, with a value ranging from... to ; Let be the interlayer spacing between the target forming layer and the adjacent formed layers. According to this model, the smaller the interlayer spacing, the larger the penetration coupling coefficient, indicating that the influence of light penetration on the adjacent formed layers is more significant; conversely, the larger the interlayer spacing, the smaller the penetration coupling coefficient, indicating that the influence of light penetration decays rapidly with increasing distance. The exponential decay model can quantitatively describe the attenuation characteristics of curing light as it penetrates the cured resin layer.

[0170] Next, the additional curing amount generated by the curing light of the target forming layer on adjacent formed layers is determined based on the penetration coupling coefficient. Specifically, the penetration coupling coefficient is multiplied by the chemical degree of curing achieved by the adjacent formed layers during initial curing (i.e., the chemical degree of curing before the penetration of the curing light from the target forming layer) to obtain the additional curing amount generated by the curing light of the target forming layer on adjacent formed layers. When there are multiple adjacent formed layers, the additional curing amount for each layer is calculated separately, and the additional curing amounts for each layer are added together to obtain the total additional curing amount generated by the curing light of the target forming layer on all adjacent formed layers. The additional curing amount reflects the additional increase in chemical degree of curing of adjacent formed layers due to the penetration of the curing light from the target forming layer without compensation.

[0171] Then, the curing energy compensation amount for the target molded layer is determined based on the additional curing amount. Based on the additional curing amount and the curing kinetics of the resin used in the target molded layer, the compensation amount that needs to be deducted from the curing energy of the target molded layer is calculated. The curing energy compensation amount is positively correlated with the additional curing amount; that is, the larger the additional curing amount, the larger the compensation amount that needs to be deducted in advance. This compensation amount can be determined by multiplying the additional curing amount by a preset proportional coefficient, which is pre-calibrated based on the curing kinetics of the resin system.

[0172] Finally, when applying curing energy to the target forming layer, the curing energy supply to the target forming layer is reduced according to the curing energy compensation amount. The preset curing energy of the target forming layer is subtracted from the curing energy compensation amount to obtain the actual applied curing energy value, and the curing unit is driven to irradiate the target forming layer with the actual applied curing energy value.

[0173] In one embodiment, taking the fluorescence sensing mode as an example, a 0.05 wt% 7-diethylamino-3-formylcoumarin fluorescent probe is pre-doped uniformly into the photocurable resin. The main peak of the excitation spectrum of this probe is located near 405 nm, and the main peak of the fluorescence emission spectrum is located in the range of 480 nm to 530 nm. Before the photocuring reaction begins, the control unit places the liquid resin sample doped with the probe in a calibration test stage, and uses phenylphosphine oxide to initiate free radical polymerization, inducing different degrees of curing under different exposure doses. Simultaneously, the absolute chemical degree of curing is measured using a real-time infrared spectrometer and an ultraviolet differential scanning calorimeter, and the corresponding local normalized fluorescence intensity F collected by the area array detector is read. norm This allows us to plot the calibration curve and fit it to obtain its corresponding mathematical equation:

[0174] ;

[0175] Where g is a preset calibration mapping function, F norm The normalized fluorescence intensity is calculated as follows:

[0176] ;

[0177] Where F0 is the initial fluorescence intensity value of the completely uncured liquid resin, F ∞ The value represents the saturated fluorescence intensity under the fully cross-linked limiting state, and F represents the measured fluorescence intensity.

[0178] In one embodiment, the non-contact optical sensing unit employs a near-infrared spectral sensing mode. This mode includes a near-infrared active excitation source, a reflective focusing optical path, a mid-narrow band near-infrared filter, an area array indium gallium arsenide (IGaAs) near-infrared detector camera, and spectral absorption integration processing. The near-infrared active excitation source is a high-power near-infrared LED array with a wavelength coverage of 1500 nm to 1700 nm. The area array IGaAs near-infrared detector camera has an effective pixel count of no less than 640 × 512, a spectral response range of 900 nm to 1700 nm, and readout noise controlled within a specified range. The following is an example of a narrow-band near-infrared filter positioned in front of an indium gallium arsenide (IGaAs) near-infrared detector. Its center transmission wavelength is precisely aligned with the first-order overtone absorption peak of the double bond at 1620 nm, with a full width at half maximum (FWHM) of no more than 15 nm, serving as the measurement channel. A separate reference filter is also configured with its center transmission wavelength aligned with 1530 nm, a wavelength at which there is no resin absorption characteristic, serving as the reference channel. The reference channel is the reference detection channel used in near-infrared spectroscopy sensing modes to eliminate interference from non-curing factors on the measurement signal.

[0179] When near-infrared excitation light shines on the resin thin layer on the forming platform, the near-infrared light penetrates the resin layer and is reflected from the forming platform. It then passes through the resin again and is received by the area array indium gallium arsenide near-infrared detector camera. The reflected light intensity field of the measurement channel images is read separately. Reference Channel The reflected light intensity field is used to calculate the absorbance, followed by first-order spectral smoothing filtering. According to the Lambert-Beer law, the monomer-double bond conversion rate at physical coordinates (x, y), i.e., the degree of chemical solidification, is calculated using the normalized absorption peak integral ratio:

[0180] ;

[0181] in, This represents the ratio of absorbance of the resin in its initial, uncured liquid state. This represents the absorbance ratio at a specific moment during the curing process. The introduction of a 1530nm reference channel effectively suppresses interference from factors such as layer thickness variations caused by jetting volume fluctuations, diffuse reflection due to surface unevenness, and light source intensity fluctuations in the calculation of chemical curing degree.

[0182] After obtaining the chemical curing degree distribution α(x,y), the absolute deviation between the chemical curing degree distribution and the target chemical curing degree is calculated and substituted into the closed-loop control formula. Spatial partition adjustment control commands are issued to the digital micromirror device, and closed-loop adjustment is achieved by adjusting the next exposure time or increasing the spray volume.

[0183] In one embodiment, the non-contact optical sensing unit simultaneously employs both fluorescence sensing and near-infrared spectroscopy sensing modes. The control unit performs dynamic weighted fusion of the chemical curing degree estimates measured by the two modes at the same physical coordinate location. Specifically, at the same physical location (x, y), the control unit acquires the temperature-compensated fluorescence chemical curing degree estimate. and the absolute estimate of chemical curing degree α obtained from near-infrared spectroscopy inversion. nir (x,y), and dynamically determine the fusion weight of each mode based on the current thickness h of the printed layer, and perform weighted fusion according to the following formula:

[0184] ;

[0185] Among them, w fl (h) is the weighting factor for the fluorescence mode, w nir (h) is the weighting factor for the near-infrared mode, and both satisfy w fl (h)+w nir (h)=1. Weighting factor w fl and w nirThis is a function that dynamically adjusts with the current printed layer thickness h. Because the near-infrared signal-to-noise ratio degrades significantly in extremely thin layers (h < 20 μm), while the fluorescence signal is extremely strong, the weighting function is set as follows: if h is less than or equal to 20 μm, then w... fl =0.9, w nir =0.1; If h is greater than or equal to 50 μm, due to the advantages of near-infrared penetration and direct quantification of chemical bonds, the weighting function is adjusted to: w fl =0.3, w nir =0.7.

[0186] By employing the aforementioned multimodal dynamic weighted fusion strategy, the high sensitivity of the fluorescence mode can be fully utilized during thin-layer printing, while the strong penetration and direct quantitative analysis of chemical bonds of the near-infrared mode can be fully utilized during thick-layer printing. This overcomes the problem of single sensor failure caused by significant variations in the thickness of the forming layer, thereby improving the absolute accuracy of in-situ monitoring of chemical curing degree and the stability of the closed-loop system throughout the entire process window.

[0187] Figure 3 This is a schematic diagram of the structure of an in-situ monitoring device for the curing quality of microdroplet jet molding resin according to an embodiment of this application, as shown below. Figure 3 As shown, the system comprises a spraying unit, a curing unit, a cure degree in-situ sensing unit, a control unit, a quality archive, and a forming platform (including the target forming layer and the formed layer). The spraying unit, positioned above the forming platform, sprays and deposits photocurable resin layer by layer onto the platform in a micro-droplet manner to form the target forming layer. The curing unit, also positioned above the forming platform, applies curing light to the target forming layer, causing the resin in the target forming layer to polymerize and cure. The cure degree in-situ sensing unit, also positioned above the forming platform, collects physical quantity signals of the target forming layer during and / or after curing to obtain the chemical cure degree distribution of the target forming layer. The control unit is connected to the spraying unit, the curing unit, and the cure degree in-situ sensing unit, respectively, to receive the collected physical quantity signals, calculate the error between the chemical cure degree distribution of the target forming layer and the preset target chemical cure degree, and generate control commands based on the error to adjust the curing energy of the curing unit and / or the spraying parameters of the spraying unit in a closed loop. The quality archive, connected to the control unit, stores the layer-by-layer and region-by-region chemical cure degree data and control records generated by the control unit. The forming platform is used to support the layer-by-layer deposition and curing of each forming layer, so as to form a three-dimensional object after all forming layers have been deposited and cured.

[0188] Figure 4 This is a flowchart of a closed-loop control method for in-situ monitoring of the curing quality of microdroplet jet molding resin, according to an embodiment of this application. Figure 4 As shown, the in-situ monitoring and closed-loop control method for the curing quality of microdroplet jet molding resin includes the following steps:

[0189] Step S401, spray deposition; the control unit drives the spraying unit to precisely deposit photocurable resin containing fluorescent probes onto the forming platform in the form of microdroplets according to the slice geometry information of the current layer, forming a layer to be cured with a specified thickness (e.g., 20 micrometers).

[0190] Step S402: Initial energy is applied; the curing unit projects a preset reference light power distribution onto the layer to be cured for rapid photocuring.

[0191] Step S403: In-situ signal acquisition and spatial registration; within a preset time window (e.g., 100 milliseconds) after the curing unit irradiation ends, the excitation light source is turned on, and the area array detector synchronously acquires the emitted fluorescence image to obtain the full-field fluorescence intensity distribution F(u,v). Lens distortion is corrected using the distortion correction formula, and then coordinate mapping is performed according to the calibrated projection transformation matrix to transform and map the pixel position (u,v) to the physical coordinates (x,y) of the forming platform. Finally, the true two-dimensional spatial physicochemical curing degree distribution α(x,y) of the target forming layer is calculated by substituting it into the calibration function.

[0192] Step S404, Error Calculation and Zoned Closed-Loop Adjustment; The control unit calculates the chemical curing degree error at each coordinate point: , where α target Assuming a preset target chemical curing degree, if the chemical curing degree error e(x,y) of a certain spatial region is greater than 0.05, the region is considered to have an under-curing defect. The curing energy compensation difference at this coordinate is calculated as: ΔE(x,y) = K p ·e(x,y);K p The gain is proportional. The difference in curing energy is converted into a driving pulse width signal, which drives the digital micromirror device to independently apply secondary supplementary light exposure to the undercured region (x,y).

[0193] Step S405, oxygen inhibition compensation and interlayer post-curing compensation: For free radical photocuring systems, while collecting the surface chemical curing degree, the control unit reads the bottom layer chemical curing degree recorded after the previous layer was formed. Because the surface layer is directly exposed to air, there is a significant oxygen inhibition effect, resulting in a lower actual chemical curing degree for the outermost layer of the formed layer. When the calculated difference between the surface and bottom layer chemical curing degrees is greater than 0.1, the control unit drives the curing unit to multiply the curing energy of the oxygen-inhibited area by a compensation coefficient (e.g., 1.25) for overload compensation, or locally purges nitrogen into that area. Furthermore, to avoid oxygen inhibition, a synergistic system of eosin photosensitive dye and triethanolamine tertiary amine co-initiator can be introduced into the resin system to efficiently consume dissolved oxygen through hydrogen abstraction. Simultaneously, since microdroplet jetting is a layer-by-layer stacking process, the curing ultraviolet light of the (n+1)th layer will penetrate downwards and cause light scattering and light penetration into the nth layer and even the (n-1)th layer, resulting in secondary post-curing of the formed layer. To avoid over-curing of the formed layer, the control unit estimates the final chemical curing degree of the adjacent nth layer during the exposure design of the (n+1)th layer based on the following post-curing stacking model: α n final =α n cur +β m ·E n+1 ; where α n final α represents the final estimated chemical curing degree of the nth layer. n cur β represents the intrinsic chemical curing degree of the nth layer produced by the target layer chemical curing light source; m E is the pre-calibrated dimensionless coefficient for optical penetration coupling. n+1 The exposure energy for the (n+1)th layer is set. This is achieved by predicting the post-curing increment in advance and setting E... n+1 When the actual exposure dose is applied, the penetration contribution is subtracted in reverse to ensure that the final chemical curing degree after the nth layer is stacked does not exceed the target threshold.

[0194] Step S406, Quality Archive Archiving: Write the final closed-loop chemical curing degree data of each region of the target layer into the quality archive as the interlayer chemical curing quality archive of the three-dimensional component.

[0195] Step S407: Determine if the target layer is the last layer. If so, the forming is complete; otherwise, the forming platform moves down by one layer thickness and returns to step S401 until the forming is complete.

[0196] Step S408, forming is complete.

[0197] Steps S401 to S408 above, through a complete closed-loop control process, realize in-situ real-time monitoring and precise regional control of the chemical curing degree of each region of each forming layer during the microdroplet jet forming process, which can significantly improve the overall curing uniformity and consistency of the formed part.

[0198] Figure 5 This is a structural block diagram of an in-situ monitoring device 50 for the curing quality of microdroplet jet molding resin according to an embodiment of this application, as shown below. Figure 5 As shown, the in-situ monitoring device 50 for the curing quality of microdroplet jet molding resin includes: a jet curing module 52, a curing sensing module 54, and a curing control module 56; wherein:

[0199] The spray curing module 52 sprays and deposits photocurable resin layer by layer onto the forming platform to form a target forming layer; it applies curing energy to the target forming layer to cause the resin in the target forming layer to polymerize and cure; the curing sensing module 54 is used to collect physical quantity signals of the target forming layer through a non-contact optical sensing unit during and / or after the target forming layer is cured, and obtain the signal distribution of the target forming layer based on the physical quantity signals; the physical quantity signals are used to characterize the degree of consumption or crosslinking of polymerizable groups of resin in the target forming layer; according to the preset transformation relationship between pixel coordinates and physical coordinates of the forming surface, the pixel coordinates in the signal distribution are mapped to the physical coordinates of the forming platform; the physical quantity signals of each physical coordinate are converted into chemical curing degree values ​​according to a preset conversion relationship to obtain the chemical curing degree distribution of the target forming layer; the curing control module 56 is used to calculate the chemical curing degree distribution. The error between the fabric and the preset target chemical curing degree is considered. When the error exceeds a preset first threshold, the curing energy of the target forming layer is adjusted, and / or the spraying parameters of the subsequent forming layers in the region corresponding to the chemical curing degree error between the forming platform and the target forming layer are adjusted. The subsequent forming layers are forming layers deposited layer by layer after the target forming layer. At least one of the following curing compensations is performed on the target forming layer: the surface chemical curing degree and the bottom chemical curing degree of the target forming layer are obtained. When the value of the surface chemical curing degree being lower than that of the bottom chemical curing degree reaches a preset second threshold, the curing energy of the surface of the target forming layer is increased. The additional curing amount generated by the curing light penetration of adjacent formed layers on the target forming layer is predicted. When applying the curing energy of the target forming layer, the curing energy supply of the target forming layer is reduced according to the additional curing amount. The above steps are repeated layer by layer on the three-dimensional object until the deposition and curing of all forming layers of the three-dimensional object are completed.

[0200] It should be noted that the above modules can be functional modules or program modules, and can be implemented through software or hardware. For modules implemented through hardware, the above modules can reside in the same processor; or the above modules can be located in different processors in any combination.

[0201] This embodiment also provides an electronic device including a memory and a processor, the memory storing a computer program and the processor being configured to run the computer program to perform the steps in any of the above method embodiments.

[0202] Optionally, the electronic device may further include a transmission device and an input / output device, wherein the transmission device is connected to the processor and the input / output device is connected to the processor.

[0203] Optionally, in this embodiment, the processor can be configured to perform the following steps via a computer program:

[0204] S1, Photocurable resin is sprayed and deposited layer by layer onto the molding platform to form the target molding layer;

[0205] S2, apply curing energy to the target molding layer to cause the resin in the target molding layer to polymerize and cure;

[0206] S3, during the curing process of the target forming layer and / or after the target forming layer is cured, the physical quantity signals of the target forming layer are collected by a non-contact optical sensing unit, and the signal distribution of the target forming layer is obtained based on the physical quantity signals; the physical quantity signals are used to characterize the degree of consumption or crosslinking of the polymerizable groups of the resin in the target forming layer.

[0207] S4, based on the pre-set transformation relationship between pixel coordinates and physical coordinates of the forming surface, maps the pixel coordinates in the signal distribution to the physical coordinates of the forming platform;

[0208] S5, convert the physical quantity signals of each physical coordinate into chemical curing degree values ​​according to a preset conversion relationship to obtain the chemical curing degree distribution of the target forming layer;

[0209] S6, calculate the error between the chemical curing degree distribution and the preset target chemical curing degree. When the error exceeds the preset first threshold, adjust the curing energy of the target forming layer and / or adjust the spraying parameters of the subsequent forming layer in the region where there is a chemical curing degree error between the forming platform and the target forming layer. The subsequent forming layer is a forming layer that is stacked and deposited layer by layer after the target forming layer.

[0210] S7, perform curing compensation on the target forming layer using at least one of the following methods:

[0211] S701, obtain the surface chemical curing degree and the bottom chemical curing degree of the target forming layer. When the surface chemical curing degree is lower than the bottom chemical curing degree by a preset second threshold, increase the curing energy of the surface of the target forming layer.

[0212] S702, predicts the additional curing amount of the target forming layer caused by the curing light penetration of the adjacent formed layer, and reduces the curing energy supply of the target forming layer according to the additional curing amount when applying the curing energy of the target forming layer.

[0213] S8. Repeat the above steps layer by layer on the three-dimensional object until the deposition and solidification of all the forming layers of the three-dimensional object are completed.

[0214] It should be noted that the specific examples in this embodiment can refer to the examples described in the above embodiments and optional implementations, and will not be repeated in this embodiment.

[0215] Furthermore, in conjunction with the in-situ monitoring method for the curing quality of microdroplet jet molding resin provided in the above embodiments, this embodiment can also provide a storage medium for implementation. This storage medium stores a computer program; when executed by a processor, the computer program implements any one of the in-situ monitoring methods for the curing quality of microdroplet jet molding resin in the above embodiments.

[0216] It should be understood that the specific embodiments described herein are merely illustrative of the application and not intended to limit it. All other embodiments derived by those skilled in the art based on the embodiments provided in this application without inventive effort are within the scope of protection of this application.

[0217] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties.

[0218] Obviously, the accompanying drawings are merely some examples or embodiments of this application. Those skilled in the art can apply this application to other similar situations based on these drawings without any creative effort. Furthermore, it is understood that although the work done in this development process may be complex and lengthy, for those skilled in the art, certain design, manufacturing, or production modifications made based on the technical content disclosed in this application are merely conventional technical means and should not be considered as insufficient disclosure of this application.

[0219] The term "embodiment" in this application refers to a specific feature, structure, or characteristic described in connection with an embodiment that may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily imply the same embodiment, nor does it imply that it is mutually exclusive with or independent of other embodiments. It will be clearly or implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments without conflict.

[0220] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of patent protection. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the appended claims.

Claims

1. A method for in-situ monitoring of the curing quality of microdroplet jet molding resin, characterized in that, include: The photocurable resin is sprayed and deposited layer by layer onto the molding platform to form the target molding layer; Curing energy is applied to the target molding layer to cause the resin in the target molding layer to polymerize and cure; During the curing process of the target forming layer, and / or after the target forming layer has been cured, physical quantity signals of the target forming layer are acquired by a non-contact optical sensing unit, and the signal distribution of the target forming layer is obtained based on the physical quantity signals; the physical quantity signals are used to characterize the degree of consumption or crosslinking of polymerizable groups of resin in the target forming layer; Based on the pre-defined transformation relationship between pixel coordinates and physical coordinates of the forming surface, the pixel coordinates in the signal distribution are mapped to the physical coordinates of the forming platform; The physical quantity signals of each physical coordinate are converted into chemical curing degree values ​​according to a preset conversion relationship to obtain the chemical curing degree distribution of the target forming layer; Calculate the error between the chemical curing degree distribution and the preset target chemical curing degree. When the error exceeds a preset first threshold, adjust the curing energy of the target forming layer and / or adjust the spraying parameters of the subsequent forming layer in the region where there is a chemical curing degree error between the forming platform and the target forming layer. The subsequent forming layer is a forming layer that is deposited layer by layer after the target forming layer. The target forming layer is subjected to at least one of the following curing compensations: The surface chemical curing degree and the bottom chemical curing degree of the target forming layer are obtained. When the surface chemical curing degree is lower than the bottom chemical curing degree by a preset second threshold, the curing energy of the surface of the target forming layer is increased. Predict the additional curing amount that adjacent formed layers will produce on the target formed layer due to curing light penetration, and reduce the curing energy supply to the target formed layer according to the additional curing amount when applying curing energy to the target formed layer; Repeat the above steps layer by layer on the three-dimensional object until the deposition and solidification of all the forming layers of the three-dimensional object are completed.

2. The method for in-situ monitoring of the curing quality of microdroplet jet molding resin according to claim 1, characterized in that, When the physical quantity signal is a fluorescence intensity signal, the step of converting the physical quantity signals of each physical coordinate into chemical curing degree values ​​according to a preset conversion relationship to obtain the chemical curing degree distribution of the target forming layer includes: The fluorescence intensity of the uncured liquid resin was measured as the lower limit reference value; The fluorescence intensity of the fully cured sample was measured as the upper limit reference value; A calibration curve between fluorescence intensity and chemical curing degree was established based on multiple standard samples to obtain a preset conversion relationship between fluorescence intensity and chemical curing degree. The collected physical quantity signals are substituted into the preset conversion relationship to obtain the chemical curing degree value of each physical coordinate.

3. The method for in-situ monitoring of the curing quality of microdroplet jet molding resin according to claim 1, characterized in that, When the physical quantity signal is a characteristic absorption peak signal of a polymerizable group, the step of converting the physical quantity signals of each physical coordinate into chemical curing degree values ​​according to a preset conversion relationship to obtain the chemical curing degree distribution of the target forming layer includes: The ratio of the area of ​​the polymerizable unsaturated bond characteristic absorption peak of the target forming layer to the area of ​​the reference peak is used as a calculation parameter; The calculated parameters at the initial moment when the target forming layer is not cured are used as the initial reference values; During the curing process of the target forming layer, and / or after the target forming layer has been cured, the calculated parameters obtained in real time are used as real-time measurement values; Calculate the ratio of the real-time measured value to the initial reference value to obtain the remaining ratio; Subtracting the remaining ratio from 1 yields the chemical curing degree value for each of the physical coordinates.

4. The method for in-situ monitoring of the curing quality of microdroplet jet molding resin according to claim 1, characterized in that, The step of mapping the pixel coordinates in the signal distribution to the physical coordinates of the forming platform based on a pre-defined transformation relationship between pixel coordinates and physical coordinates of the forming surface includes: A calibration pattern containing multiple preset control points is projected onto the forming platform. Based on the imaging of the calibration pattern on the forming platform, the pixel coordinates of each control point in the pixel coordinate system are extracted. Based on the correspondence between the pixel coordinates of the control points and the physical coordinates of the control points on the forming platform, a homography transformation matrix between the pixel coordinate system and the physical coordinate system of the forming platform is established. Lens distortion correction is performed on the captured calibration pattern image to eliminate the spatial position deviation introduced by imaging distortion, and the distortion-corrected image is obtained. A mapping lookup table is constructed based on the homography transformation matrix and the distortion-corrected image. The coordinates of each pixel in the signal distribution are mapped to the physical coordinates of the forming platform through the mapping lookup table. The mapping lookup table includes the correspondence between the coordinates of each pixel in the signal distribution and the physical coordinates of the forming platform.

5. The method for in-situ monitoring of the cured quality of microdroplet jet molding resin according to claim 4, characterized in that, The process involves projecting a calibration pattern containing multiple preset control points onto the forming platform, and extracting the pixel coordinates of each control point in the pixel coordinate system based on the image of the calibration pattern on the forming platform. This includes: Project a calibration pattern containing multiple feature points onto the forming platform; The calibration pattern is imaged on the forming platform by an area array detector to obtain the captured calibration image; Based on the captured calibration image, the pixel coordinates of each feature point in the pixel coordinate system are extracted using sub-pixel edge detection and centroid extraction algorithms.

6. The method for in-situ monitoring of the curing quality of microdroplet jet molding resin according to claim 1, characterized in that, When the surface chemical curing degree is lower than the underlying chemical curing degree by a preset second threshold, the method further includes: The region in the target forming layer where the surface chemical curing degree is lower than that of the bottom chemical curing degree is identified as an oxygen-inhibited polymerization region. A pulsed inert gas jet is injected into the oxygen inhibition region to form a local inert gas coating layer on the surface of the oxygen inhibition region. And / or, aspirate the oxygen-containing boundary layer above the region in the target forming layer where the surface chemical curing degree is lower than that of the bottom layer, and form an inert gas curtain above the oxygen-inhibiting region; And / or, apply short-wavelength ultraviolet overload exposure to the area of ​​the target forming layer where the surface chemical curing degree is lower than that of the underlying chemical curing degree, and consume the dissolved oxygen on the surface of the oxygen inhibition region in situ through the photochemical reaction of the resin; the penetration depth of the short-wavelength ultraviolet overload exposure is less than the thickness of the target forming layer.

7. The method for in-situ monitoring of the curing quality of microdroplet jet molding resin according to claim 1, characterized in that, The method of predicting the additional curing amount caused by the light penetration of adjacent already formed layers to the target formed layer, and reducing the curing energy supply to the target formed layer based on the additional curing amount when applying curing energy to the target formed layer, includes: Obtain the interlayer spacing between the target forming layer and the adjacent formed layer; The permeation coupling coefficient is determined based on the interlayer spacing using an exponential decay model. The additional curing amount generated by the curing light of the target forming layer on the adjacent formed layer is determined based on the penetration coupling coefficient. The curing energy compensation amount of the target forming layer is determined based on the additional curing amount; When applying curing energy to the target forming layer, the curing energy supply to the target forming layer is reduced according to the curing energy compensation amount.

8. A device for in-situ monitoring of the curing quality of microdroplet jet molding resin, characterized in that, include: The module comprises a spray curing module, a curing sensing module, and a curing control module; among which: The spray curing module sprays and deposits photocurable resin layer by layer onto the forming platform to form a target forming layer; and applies curing energy to the target forming layer to cause the resin in the target forming layer to polymerize and cure. The curing sensing module is used to acquire physical quantity signals of the target forming layer through a non-contact optical sensing unit during and / or after the curing of the target forming layer, and to obtain the signal distribution of the target forming layer based on the physical quantity signals; the physical quantity signals are used to characterize the degree of consumption or crosslinking of polymerizable groups of resin in the target forming layer; according to a preset transformation relationship between pixel coordinates and physical coordinates of the forming surface, the pixel coordinates in the signal distribution are mapped to the physical coordinates of the forming platform; the physical quantity signals of each physical coordinate are converted into chemical curing degree values ​​according to a preset conversion relationship to obtain the chemical curing degree distribution of the target forming layer; The curing control module is used to calculate the error between the chemical curing degree distribution and the preset target chemical curing degree. When the error exceeds a preset first threshold, the curing energy of the target forming layer is adjusted, and / or the spraying parameters of the subsequent forming layers in the region corresponding to the chemical curing degree error between the forming platform and the target forming layer are adjusted. The subsequent forming layers are forming layers deposited layer by layer after the target forming layer. The target forming layer is cured by at least one of the following: obtaining the surface chemical curing degree and the bottom chemical curing degree of the target forming layer; when the surface chemical curing degree is lower than the bottom chemical curing degree by a value reaching a preset second threshold, the curing energy of the surface of the target forming layer is increased; predicting the additional curing amount generated by the curing light penetration of adjacent formed layers on the target forming layer, and reducing the curing energy supply of the target forming layer according to the additional curing amount when applying the curing energy of the target forming layer; repeating the above steps layer by layer on the three-dimensional object until the deposition and curing of all forming layers of the three-dimensional object are completed.

9. An electronic device comprising a memory and a processor, characterized in that, The memory stores a computer program, and the processor is configured to run the computer program to perform the in-situ monitoring method for the curing quality of microdroplet jet molding resin as described in any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the in-situ monitoring method for the curing quality of microdroplet jet molding resin as described in any one of claims 1 to 7.

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