Variable focus 3D printing device and working method thereof

Abstract

The application relates to the technical field of optical focusing, and discloses a 3D printing device with variable focal points and a working method thereof, which comprises a laser generator for generating laser, a collimating mirror and a galvanometer mirror arranged in sequence on a light path of the laser generator; and further comprises a focusing control system for adjusting the collimating mirror according to a target spot size of a scanning area on a working plane, so that an actual spot size meets the target spot size. The position of the collimating mirror is adjusted by the focusing control system according to different scanning areas on the working plane, the focal length is adjusted, different scanning areas on the working plane adopt different target spot sizes for processing, and the processing precision and efficiency of plastic materials are improved; in addition, when printing is performed in the same scanning area, the actual spot size can be adjusted in real time by the focusing control system, so that the processing precision of a fine processing scanning area is ensured, and the processing efficiency of a filling processing scanning area is ensured.

Description

Technical Field

[0001] This invention relates to the field of optical focusing technology, and more specifically, to a variable focus 3D printing apparatus and its operating method. Background Technology

[0002] When processing plastic materials using laser 3D printing equipment, it is usually necessary to print layer by layer. The printing process is generally divided into two types of processing areas: the processing of fine parts and the processing of infill parts. The requirements for printing are also different for the two types of processing areas. The processing of fine parts requires the use of small light spots to make the printing more accurate and ensure that the surface quality of the finished product is good. The processing of infill parts requires the use of large light spots to improve printing efficiency and complete the printing as quickly as possible.

[0003] In existing technologies, 3D printing devices typically use a fixed focal position when working normally. For example, when processing with a small spot, there is one fixed focal position, and when processing with a large spot, there is another fixed focal position. Therefore, 3D printing devices that use a fixed focal position cannot adaptively adjust the focal position according to the actual processing situation, resulting in low processing efficiency and processing accuracy.

[0004] Therefore, it is necessary to propose a variable focus 3D printing device and its working method to at least partially solve the problems existing in the prior art. Summary of the Invention

[0005] The summary section introduces a series of simplified concepts, which will be further explained in detail in the detailed description section. The summary section of this invention is not intended to limit the key features and essential technical features of the claimed technical solution, nor is it intended to determine the scope of protection of the claimed technical solution.

[0006] To at least partially solve the above problems, the present invention provides a variable focus 3D printing apparatus, comprising: a laser for generating laser light, a collimating lens and a galvanometer sequentially disposed in the light output path of the laser; and a focusing control system for adjusting the collimating lens according to the target spot size of the scanning area on the working plane, so that the actual spot size meets the target spot size.

[0007] Preferably, the focusing control system includes:

[0008] The autofocus module obtains the displacement control command of the collimating lens based on the size of the target spot in the area to be scanned on the working plane;

[0009] The prediction and compensation module is used to predict the amount of change in the spot size caused by temperature based on the working data that causes the change in spot size, and to obtain the compensation displacement command of the collimating lens.

[0010] The control module adjusts the collimating lens according to the displacement control command and compensation displacement command of the collimating lens so that the actual light spot size meets the target light spot size.

[0011] Preferably, the focusing control system further includes: multiple temperature sensors arranged in key locations for acquiring temperature data of the key locations; wherein, the key locations include multiple locations where the spot size changes due to thermal expansion.

[0012] Preferably, the working data includes: laser power, working time, ambient temperature, coolant temperature, and temperature data of key components.

[0013] Preferably, the prediction compensation module includes:

[0014] The first prediction unit predicts the change in spot size based on laser power, working time, ambient temperature and coolant temperature to obtain the initial predicted spot size.

[0015] The second prediction unit is used to predict the error of the initial predicted spot size based on the working data, and obtain the final predicted spot size.

[0016] The compensation unit obtains the compensation displacement command for the collimating lens based on the final predicted spot size and the target spot size.

[0017] Preferably, the first prediction unit uses a preset mathematical model to predict the change in spot size, the preset mathematical model including:

[0018] A thermal model is used to establish a mapping relationship between laser power, working time, coolant temperature, ambient temperature, and temperature distribution in key components. This model is used to predict the temperature data of key components and obtain their future temperature values.

[0019] A structural model is used to establish a mapping relationship between temperature changes and the displacement of the collimating mirror, which is used to predict the amount of collimating mirror displacement based on the future temperature value output by the thermal model.

[0020] An optical model is used to establish a mapping relationship between the displacement of the collimating lens and the change in the size of the light spot on the working plane. This model is used to predict the change in the size of the light spot based on the collimating lens displacement output by the structural and optical coupling model, thereby obtaining the initial predicted light spot size.

[0021] Preferably, the second prediction unit uses a trained machine learning model to predict the error of the initial predicted spot size;

[0022] The working data is used as the input to the machine learning model, and the error of the initial predicted spot size is used as the output to train the machine learning model and obtain a trained machine learning model. The error of the initial predicted spot size is the difference between the initial predicted spot size and its corresponding actual spot size.

[0023] Preferably, it also includes: a spot monitoring module, used to monitor the actual spot size of the current scanning area on the working plane in real time, obtain the displacement adjustment command of the collimating lens based on the real-time size deviation between the actual spot size and the target spot size, and adjust the collimating lens according to the displacement adjustment command of the collimating lens through the control module so that the actual spot size meets the target spot size.

[0024] Preferably, the focusing control system includes:

[0025] The autofocus module obtains the collimator displacement control command and the laser power control command based on the target spot size and the real-time acquired working distance, and using a preset mapping model; wherein, the preset mapping model is the correspondence between the target spot size, working distance, collimator displacement and laser power.

[0026] The prediction and compensation module is used to predict the amount of change in the spot size caused by temperature based on the working data that causes the change in spot size, and to obtain the compensation displacement command of the collimating lens.

[0027] The control module adjusts the collimating lens according to the displacement control command and compensation displacement command of the collimating lens so that the actual spot size meets the target spot size, and controls the laser according to the laser power control command.

[0028] The present invention also provides a method for operating a variable focus 3D printing apparatus, applicable to the variable focus 3D printing apparatus described herein, comprising:

[0029] Based on the size of the target spot in the area to be scanned on the working plane, the displacement control command of the collimating lens is obtained;

[0030] Based on the working data that causes changes in the spot size, the amount of change in spot size caused by temperature is predicted, and the compensation displacement command of the collimating lens is obtained.

[0031] Adjust the collimator according to the displacement control command and compensation displacement command of the collimator;

[0032] The actual spot size of the current scanning area on the working plane is monitored in real time. Based on the real-time size deviation between the actual spot size and the target spot size, the displacement adjustment command of the collimating lens is obtained. The collimating lens is adjusted according to the displacement adjustment command of the collimating lens so that the actual spot size meets the target spot size.

[0033] Compared with the prior art, the present invention has at least the following beneficial effects:

[0034] The variable focus 3D printing device and its working method described in this invention can adjust the position of the collimating lens according to the different scanning areas on the working plane through the focusing control system, thereby adjusting the focal length so that different scanning areas on the working plane are processed with different target spot sizes, improving processing accuracy and efficiency. In addition, when printing in the same scanning area, the actual spot size can also be adjusted in real time through the focusing control system to ensure the processing accuracy of fine processing of the scanning area and ensure the processing efficiency of filling the scanning area.

[0035] The variable focus 3D printing apparatus and its operating method described in this invention, along with other advantages, objectives, and features of the invention, will be partly apparent from the following description and partly understood by those skilled in the art through study and practice of the invention. Attached Figure Description

[0036] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0037] Figure 1 This is a schematic diagram of the variable focus 3D printing apparatus according to the present invention;

[0038] Figure 2 This is a block diagram of the focusing control system in the variable focus 3D printing device of the present invention.

[0039] Figure 3 This is a block diagram of the prediction compensation module in the variable focus 3D printing device of the present invention.

[0040] Figure 4 This is a block diagram of the focusing control system in the variable focus 3D printing device of the present invention, which includes a spot monitoring module.

[0041] Figure 5 This is a flowchart illustrating the operation method of the variable focus 3D printing apparatus described in this invention.

[0042] In the attached diagram, 1 is the laser, 2 is the collimating lens, 3 is the galvanometer, and 4 is the working plane. Detailed Implementation

[0043] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments, so that those skilled in the art can implement it based on the description.

[0044] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0045] like Figure 1 As shown, the present invention provides a variable focus 3D printing device, including: a laser 1 for generating laser light, a collimating lens 2 and a galvanometer 3 sequentially disposed on the light output path of the laser 1; and a focusing control system for adjusting the collimating lens 2 according to the target spot size of the scanning area on the working plane 4 so that the actual spot size meets the target spot size.

[0046] Specifically, the laser 1 is mounted on the base, and the upper limit of the base is provided with a lens barrel. The axis of the lens barrel is arranged coaxially with the optical axis of the laser 1. The collimating lens 2 is mounted inside the lens barrel. The lens barrel is connected to the adjustment component on the base. The focusing control system is used to control the adjustment component so that the lens barrel is driven to move axially through the adjustment component, thereby making the collimating lens 2 on the lens barrel move synchronously to achieve focusing and thus change the spot size of the scanning area.

[0047] Laser 1 is used to emit laser light, and collimating lens 2 is used to receive the beam from laser 1 and collimate it. The adjustment components are dynamically controlled according to the instructions of the focusing control system to adjust the focal length of the collimating lens, thereby changing the size of the light spot on the working plane 4.

[0048] In 3D printing, there are usually two scanning areas: one is the scanning area that needs fine processing, usually at the outline, and the other is the scanning area that needs filling, usually in the large filling area within the outline. The target spot size corresponding to the scanning area that needs fine processing is smaller, while the target spot size corresponding to the scanning area that needs filling is larger. Therefore, during printing, different target spot sizes need to be adapted according to different scanning areas. When switching between two different scanning areas, the position of the alignment mirror 2 needs to be adjusted according to the target spot size of the scanning area on the working plane 4 to change the spot size.

[0049] In addition, when 3D printing in the same scanning area, the actual spot size can be monitored in real time. Especially for scanning areas requiring fine processing, which require high printing accuracy, the actual spot size can be monitored in real time and the alignment mirror 2 can be adjusted in time to ensure that the actual spot size meets the target spot size, thereby improving processing accuracy. When printing scanning areas for filling processing, if the area to be filled is large, the position of the alignment mirror 2 can also be adjusted to adaptively increase the spot size, thereby improving processing efficiency.

[0050] Through the above design, the focusing control system can adjust the position of the collimating lens 2 according to the different scanning areas on the working plane 4, thereby adjusting the focal length so that different scanning areas on the working plane 4 can be processed with different target spot sizes, improving processing accuracy and efficiency. In addition, when printing in the same scanning area, the actual spot size can be adjusted in real time through the focusing control system to ensure the processing accuracy of fine processing scanning areas and the processing efficiency of filling processing scanning areas.

[0051] like Figure 2 As shown, in one embodiment, the focusing control system includes:

[0052] The autofocus module obtains the displacement control command of the collimating lens 2 based on the target spot size of the area to be scanned on the working plane 4.

[0053] The prediction and compensation module is used to predict the amount of change in the size of the light spot caused by temperature based on the working data that causes the change in the size of the light spot, and to obtain the compensation displacement command of the collimating mirror 2.

[0054] The control module adjusts the collimating lens 2 according to the displacement control command and compensation displacement command, so that the actual light spot size meets the target light spot size.

[0055] In this embodiment, the autofocus module is mainly used to control the displacement of the collimating lens 2 when switching between two different scanning areas. Specifically, the position of the collimating lens 2 has a one-to-one correspondence with the spot size. Therefore, the autofocus module can obtain the position of the collimating lens 2 corresponding to the target spot size of the area to be scanned on the working plane 4, thereby generating a displacement control command for the collimating lens 2.

[0056] Because laser 1 generates heat during operation, the temperature of components such as the base and lens barrel rises. This temperature increase easily leads to thermal expansion. Taking the lens barrel as an example, its axial dimensions change due to thermal expansion, causing a change in the axial position of the collimating lens 2 and affecting the beam size. Therefore, the prediction and compensation module can predict the beam size change based on current operating data, such as predicting the beam size change over a future period (i.e., a set time period), thereby generating a compensation displacement command for the collimating lens 2. The prediction and compensation module continuously predicts the beam size change over a future period to compensate for the displacement of the collimating lens 2 in real time.

[0057] The control module adjusts the position of the straight mirror 2 according to the displacement control command and the compensation displacement command. In the future, the control module will compensate for the displacement of the straight mirror 2 in real time according to the compensation displacement command to ensure the accuracy of the actual spot size on the working plane 4 and improve the processing accuracy.

[0058] In one embodiment, the focusing control system further includes: a plurality of temperature sensors arranged in key locations for acquiring temperature data of the key locations; wherein the key locations include a plurality of locations where the spot size changes due to thermal expansion.

[0059] Key components, such as the housing of laser 1, the barrel of collimating lens 2, the base, and the optical substrate.

[0060] In this embodiment, temperature sensors can be selectively arranged at key locations to acquire temperature data of the key locations in real time, so as to predict the amount of change in spot size caused by temperature.

[0061] In one embodiment, the operating data includes: laser power, operating time, ambient temperature, coolant temperature, and temperature data of key components.

[0062] Since the main heat source of the 3D printing device is the laser, the heat generated is usually directly related to the laser power and its working time. Ambient temperature affects heat dissipation. Cooling pipes are usually provided near the laser 1 and collimating lens 2. Therefore, it is also necessary to obtain the temperature of the coolant, which directly affects the temperature change of the lens barrel. The temperature data of key parts are the outer shell of the laser 1, the lens barrel or base of the collimating lens 2, the optical substrate, etc., among which the lens barrel is the most critical. With the above working data, the displacement change of the collimating lens 2 can be predicted by the prediction compensation module, thereby predicting the change in the spot size.

[0063] like Figure 3 As shown, in one embodiment, the prediction compensation module includes:

[0064] The first prediction unit predicts the change in spot size based on laser power, working time, ambient temperature and coolant temperature to obtain the initial predicted spot size.

[0065] The second prediction unit is used to predict the error of the initial predicted spot size based on the working data, and obtain the final predicted spot size.

[0066] The compensation unit obtains the compensation displacement command for the collimating mirror 2 based on the final predicted spot size and the target spot size.

[0067] The first prediction unit uses a physical model, while the second prediction unit uses a machine learning model. Both units use real-time collected working data to make predictions, thus building a prediction compensation module that can be continuously optimized.

[0068] In one embodiment, the first prediction unit uses a preset mathematical model to predict the change in spot size, the preset mathematical model including:

[0069] A thermal model is used to establish a mapping relationship between laser power, working time, coolant temperature, ambient temperature, and temperature distribution in key components. This model is used to predict the temperature data of key components and obtain their future temperature values.

[0070] Specifically, the thermal model is used to predict the temperature distribution of key components under heat inputs such as laser 1 heating and ambient temperature changes. The specific construction method is as follows: First, geometric modeling is performed by creating a 3D model of the optical system in finite element analysis software. This 3D model includes at least the outer shell and contact surfaces of laser 1, collimating lens 2 and its barrel, base, and optical substrate. Second, material properties are defined by assigning correct material properties to each component, such as thermal conductivity (representing the rate at which heat is transferred in a material), specific heat capacity (the material's ability to store heat), and density. Third, boundary conditions are applied. For heat sources, the operating power of laser 1 is converted into heat according to its efficiency coefficient and applied to the laser 1 mounting location; ambient temperature can also be used as a boundary condition. For heat dissipation, the heat dissipation methods of all surfaces are defined, such as convection (heat exchange with air, applying a convection coefficient), heat conduction (e.g., heat conduction between parts), and radiative heat transfer. Fourth, mesh generation and solution are performed, and simulation is conducted. After completion, the temperature value of the entire optical system at any time point and any location can be obtained.

[0071] A structural model is used to establish a mapping relationship between temperature changes and the displacement of collimating mirror 2, which is used to predict the displacement of collimating mirror 2 based on the future temperature value output by the thermal model.

[0072] Specifically, the structural model is used to calculate the thermal expansion or contraction caused by changes in the temperature field, which in turn leads to the displacement of the collimating lens 2. The specific construction method is as follows: First, based on the aforementioned thermal model analysis, a structural analysis is performed directly; second, new material properties are defined, such as the coefficient of thermal expansion, which defines how much the material's length will expand for every 1 degree Celsius increase in temperature; third, constraints are applied, fixing several points connecting the optical system to the external frame (such as screw holes), defining their degrees of freedom as zero; fourth, the temperature field obtained from the thermal model analysis is applied as a load to the structural model, and the stress and deformation generated under the combined action of thermal expansion and constraints are calculated using finite element analysis software; fifth, the displacement of the collimating lens 2 along the optical axis is output.

[0073] An optical model is used to establish a mapping relationship between the displacement of collimating lens 2 and the change in the size of the light spot on the working plane 4. This model is used to predict the change in the size of the light spot based on the displacement of collimating lens 2 output by the structural and optical coupling model, and to obtain the initial predicted light spot size.

[0074] Specifically, the optical model is used to establish the mathematical relationship between the displacement of collimating lens 2 and the size of the light spot on the working plane 4. It is mainly based on Gaussian optics theory. The displacement of collimating lens 2 changes the divergence angle of the beam, so there is a corresponding relationship between the displacement of collimating lens 2 and the light spot size. Its core formula can be: ,in, The size of the light spot on working plane 4. The beam quality factor is an inherent property of laser 1. The wavelength of the laser. The focal length of the field lens (in the optical path, the field lens is set after the galvanometer). Let be the diameter of the beam incident on the field mirror. It is the scanning angle (the angle between the optical axis and the scanning direction). The constant factor is used; when the collimating lens 2 moves, it changes the diameter of the beam incident on the field lens, thus affecting the spot size. In this embodiment, optical design software (such as Zemax or Code V) can be used to perform ray tracing, which can accurately establish the correspondence curve between the displacement of the collimating lens 2 and the spot size, or fit a formula about the two to use as an optical model for prediction.

[0075] After the above models are established, calibration and correction are required. The specific process is as follows: First, simulations of the above three models are performed to obtain the future temperature values ​​of key parts, the displacement of collimating lens 2, and the initial predicted spot size. Multidimensional experiments are conducted at different laser powers and at different times, and experimental data are collected. The experimental data includes the actual temperature values ​​of key parts, the actual displacement of collimating lens 2, and the actual spot size. Then, the future temperature values ​​of key parts, the displacement of collimating lens 2, and the initial predicted spot size are compared with the actual temperature values, the actual displacement of collimating lens 2, and the actual spot size, respectively. Based on the comparison results, the parameters of the thermal model (including thermal conductivity, convection coefficient, and heat source), the parameters of the structural model (including thermal expansion coefficient and constraint conditions), and the parameters of the optical model (including coefficients in the formula) are corrected respectively. The three models are updated and iterated until a high-precision calibrated preset mathematical model is obtained.

[0076] In one embodiment, the second prediction unit uses a trained machine learning model to predict the error of the initial predicted spot size;

[0077] The working data is used as the input to the machine learning model, and the error of the initial predicted spot size is used as the output to train the machine learning model and obtain a trained machine learning model. The error of the initial predicted spot size is the difference between the initial predicted spot size and its corresponding actual spot size.

[0078] Since the preset mathematical model is a physical model, its predictions may be biased, so a machine learning model is needed to correct them. In practical applications, real-time acquired working data is used to predict the initial predicted spot size through the preset mathematical model. The error of the initial predicted spot size is obtained through the prediction of the trained machine learning model. Then, the initial predicted spot size and its error are superimposed to obtain the final predicted spot size. The difference between the final predicted spot size and the target spot size can then be used to obtain the compensation displacement command of the collimating mirror 2 at a future moment. This avoids the spot size deviation during processing, which affects the processing accuracy of the fine processing scanning area, improves the processing quality, and enables the 3D printing device to print more delicate structures.

[0079] like Figure 4 As shown, in one embodiment, it further includes: a spot monitoring module, used to monitor the actual spot size of the current scanning area on the working plane 4 in real time, obtain the displacement adjustment command of the collimating lens 2 based on the real-time size deviation between the actual spot size and the target spot size, and adjust the collimating lens 2 according to the displacement adjustment command of the collimating lens 2 through the control module so that the actual spot size meets the target spot size.

[0080] In this embodiment, the actual spot size is monitored and adjusted in real time during the printing process for the same scanning area; especially in the fine processing scanning area, it is necessary to ensure the accuracy of the actual spot size and ensure processing precision.

[0081] In one embodiment, the system further includes a switching module, which is used to obtain the actual area of ​​the current scanning area on the working plane 4. If the actual area is greater than the set area, it indicates that the scanning time based on the current target spot size will be greater than the set time. Then, the switching module switches the current target spot size to the target spot size to be processed. The target spot size to be processed is greater than the current target spot size, and the scanning time using the target spot size to be processed is less than the set time.

[0082] In this embodiment, the focus is on the filling and scanning area. When processing a large filling and scanning area, the target spot size can be increased to improve processing efficiency and reduce processing time. Of course, when the target spot size is increased, the laser power also needs to be adjusted accordingly to meet processing requirements.

[0083] like Figure 2 As shown, in one embodiment, the focusing control system includes:

[0084] The autofocus module obtains the displacement control command and laser power control command of the collimating lens 2 based on the target spot size and the real-time acquired working distance, and using a preset mapping model; wherein, the preset mapping model is the correspondence between the target spot size, working distance, displacement of the collimating lens 2 and laser power.

[0085] The prediction and compensation module is used to predict the amount of change in the size of the light spot caused by temperature based on the working data that causes the change in the size of the light spot, and to obtain the compensation displacement command of the collimating mirror 2.

[0086] The control module adjusts the collimating lens 2 according to the displacement control command and compensation displacement command of the collimating lens 2 so that the actual spot size meets the target spot size, and controls the laser 1 according to the laser power control command.

[0087] The working distance is the distance from the working plane 4 to the reference plane of the galvanometer 3; if a field mirror is set after the galvanometer 3 in the optical path, the working distance is the distance from the working plane 4 to the reference plane of the field mirror; a height detection module can be set to detect the working distance in real time.

[0088] In this embodiment, another focusing control system is provided. Unlike the previous focusing control system, when adjusting the displacement of the straight lens 2, the laser power is controlled at the same time. This is because when the spot size changes, the laser energy density (the ratio of laser power to the target spot size) will change. Changes in energy density and working distance will affect the sintering or curing effect of the plastic material. Therefore, the energy density should be kept within the optimal setting range as much as possible.

[0089] Therefore, a preset mapping model needs to be established to reflect the correspondence between the target spot size, working distance, collimator 2 displacement, and laser power. The specific establishment process is as follows: at a fixed working distance, the collimator 2 is moved to the first position, and the spot size on the working plane 4 is measured at this time. At the fixed working distance and the current spot size, the curing or sintering effect under different laser powers is repeatedly tested. The effect can be observed under a microscope. The laser power corresponding to the optimal effect that can cure or sinter the current plastic material is found and taken as the optimal laser power. Then, this set of data is recorded. Through the above method, the working distance and the position of the collimator 2 can be changed to obtain multiple sets of data, thereby forming a database, which can be a table or a fitted formula, and thus used as a preset mapping model.

[0090] The above design allows for adjusting the laser power based on changes in the spot size, ensuring optimal laser power for scanning regardless of spot size variations during the scanning process, thus guaranteeing processing quality.

[0091] like Figure 5 As shown, the present invention also provides a method for operating a variable focus 3D printing apparatus, applicable to the variable focus 3D printing apparatus described in the present invention, comprising:

[0092] S1. Based on the target spot size of the area to be scanned on the working plane 4, obtain the displacement control command of the collimating lens 2;

[0093] S2. Based on the working data that causes the change in spot size, predict the amount of change in spot size caused by temperature, and obtain the compensation displacement command for collimating mirror 2.

[0094] S3. Adjust the collimating mirror 2 according to the displacement control command and compensation displacement command of the collimating mirror 2;

[0095] S4. Monitor the actual spot size of the current scanning area on the working plane 4 in real time. Based on the real-time size deviation between the actual spot size and the target spot size, obtain the displacement adjustment command of the collimating lens 2. Adjust the collimating lens 2 according to the displacement adjustment command of the collimating lens 2 so that the actual spot size meets the target spot size.

[0096] In this embodiment, step S1 is mainly for controlling the displacement of the collimating lens 2 when switching between two different scanning areas; specifically, the position of the collimating lens 2 has a one-to-one correspondence with the spot size, so the position of the collimating lens 2 corresponding to the target spot size of the area to be scanned on the working plane 4 is obtained, thereby generating the displacement control command of the collimating lens 2.

[0097] Because laser 1 generates heat during operation, the temperature of components such as the base and lens barrel rises. This temperature rise easily leads to thermal expansion. Taking the lens barrel as an example, its axial dimensions change due to thermal expansion, causing a change in the axial position of the collimating lens 2, which affects the beam size. Therefore, the prediction and compensation module can predict the beam size change based on current operating data, such as predicting the beam size change within a future period (i.e., a set time period), thereby generating a compensation displacement command for the collimating lens 2. Step S2 continuously predicts the beam size change within a future period to compensate for the displacement of the collimating lens 2 in real time.

[0098] Step S3 adjusts the position of the straight mirror 2 according to the displacement control command and the compensation displacement command. In the future, the displacement of the straight mirror 2 will be compensated in real time according to the compensation displacement command to ensure the accuracy of the actual spot size on the working plane 4 and improve the processing accuracy.

[0099] Step S4 mainly involves monitoring and adjusting the actual spot size in real time during the printing process for the same scanning area; especially in the fine processing scanning area, it is necessary to ensure the accuracy of the actual spot size and guarantee processing precision.

[0100] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the present invention, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A variable focus 3D printing device, characterized by, The application relates to a laser focusing control system. The laser focusing control system comprises: an automatic focusing module, which obtains a displacement control instruction of the collimating mirror (2) according to a target light spot size of a scanning area on a working plane (4); a prediction compensation module, which predicts a light spot size change amount caused by temperature according to working data causing the light spot size change, and obtains a compensation displacement instruction of the collimating mirror (2); a control module, which adjusts the collimating mirror (2) according to the displacement control instruction and the compensation displacement instruction of the collimating mirror (2), so that the actual light spot size meets the target light spot size. Alternatively, the laser focusing control system comprises: an automatic focusing module, which obtains a displacement control instruction of the collimating mirror (2) and a laser power control instruction according to the target light spot size and a real-time acquired working distance, and utilizes a preset mapping model; wherein the preset mapping model is a corresponding relationship among the target light spot size, the working distance, the displacement of the collimating mirror (2) and the laser power; a prediction compensation module, which predicts a light spot size change amount caused by temperature according to working data causing the light spot size change, and obtains a compensation displacement instruction of the collimating mirror (2); a control module, which adjusts the collimating mirror (2) according to the displacement control instruction and the compensation displacement instruction of the collimating mirror (2), so that the actual light spot size meets the target light spot size, and controls the laser (1) according to the laser power control instruction. The laser focusing control system further comprises: a plurality of temperature sensors arranged at key positions, which are used for acquiring temperature data of the key positions; wherein the key positions include a plurality of positions causing the light spot size change due to thermal expansion. The prediction compensation module comprises: a first prediction unit, which predicts the light spot size change amount according to the laser power, the working time, the environment temperature and the cooling liquid temperature, and obtains an initial prediction light spot size; a second prediction unit, which predicts an error of the initial prediction light spot size according to the working data, and obtains a final prediction light spot size; a compensation unit, which obtains the compensation displacement instruction of the collimating mirror (2) according to the final prediction light spot size and the target light spot size. The laser focusing control system further comprises: a light spot monitoring module, which is used for monitoring the actual light spot size of a current scanning area on the working plane (4) in real time, obtaining a displacement adjustment instruction of the collimating mirror (2) according to a real-time size deviation between the actual light spot size and the target light spot size, and adjusting the collimating mirror (2) according to the displacement adjustment instruction of the collimating mirror (2) through the control module, so that the actual light spot size meets the target light spot size. The working data comprises: the laser power, the working time, the environment temperature, the cooling liquid temperature and the temperature data of the key positions.

2. The variable focus 3D printing device of claim 1, wherein, The first prediction unit predicts the light spot size change amount by using a preset mathematical model, and the preset mathematical model comprises:

3. The variable focus 3D printing device of claim 2, wherein, ​ The thermal model establishes a mapping relationship between laser power, working time, coolant temperature, ambient temperature, and temperature distribution of the key position, and is used for predicting temperature data of the key position and obtaining future temperature values of the key position. The structure model establishes a mapping relationship between temperature change and displacement of the collimating mirror (2), and is used for predicting and obtaining the displacement amount of the collimating mirror (2) according to the future temperature values output by the thermal model. The optical model establishes a mapping relationship between the displacement of the collimating mirror (2) and the change of the spot size on the working plane (4), and is used for predicting the change amount of the spot size according to the displacement amount of the collimating mirror (2) output by the structure and optical coupling model, and obtaining the initial predicted spot size.

4. The variable focus 3D printing device of claim 2, wherein, The second prediction unit predicts the error of the initial predicted spot size by using the trained machine learning model. The working data is used as the input of the machine learning model, and the error of the initial predicted spot size is used as the output, and the machine learning model is trained to obtain the trained machine learning model. The error of the initial predicted spot size is the difference between the initial predicted spot size and the actual spot size corresponding thereto.

5. A method of operating a variable focus 3D printing device, suitable for use in a variable focus 3D printing device as claimed in any one of claims 1-4, characterized in that, The method comprises: obtaining the displacement control instruction of the collimating mirror (2) according to the target spot size of the to-be-scanned region on the working plane (4); predicting the change amount of the spot size caused by temperature according to the working data causing the change of the spot size, and obtaining the compensation displacement instruction of the collimating mirror (2); adjusting the collimating mirror (2) according to the displacement control instruction and the compensation displacement instruction of the collimating mirror (2); monitoring the actual spot size of the current scanning region on the working plane (4) in real time, obtaining the displacement adjustment instruction of the collimating mirror (2) according to the real-time size deviation between the actual spot size and the target spot size, and adjusting the collimating mirror (2) according to the displacement adjustment instruction of the collimating mirror (2) to make the actual spot size meet the target spot size.

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