Laser volumetric direct write optical lens additive manufacturing system and method

Abstract

The application discloses a kind of laser volume direct writing optical lens additive manufacturing system and method, first by single point printing experiment to photosensitive resin obtains the relationship between irradiation time and solidification shape and depth, and obtains solidification growth function model by fitting and correction;Second, the residence time required by design surface is calculated by linear convolution and nonlinear algorithm;Residence time is processed by two-dimensional Gaussian filtering again, finally the corresponding conversion between residence time and laser irradiation energy is realized by 3D printing equipment, and the additive manufacturing of precision optical parts is realized.The application combines growth function and 3D printing technology, and proposes a new laser direct writing volume forming 3D printing method with high customization.The forming speed, precision and optical performance of the optical lens printed by the application are far superior to the optical lenses processed by other additive manufacturing equipment of the same price, so that additive manufacturing has further breakthrough in the field of precision optical manufacturing.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing technology, and specifically to a laser volumetric direct-write optical lens additive manufacturing system and method. Background Technology

[0002] Additive manufacturing and 3D printing technologies are manufacturing processes that involve continuous layering from points to surfaces, and then from surfaces to solids. Combined with computer-aided design, complex computer models can be materialized. 3D printing technology can freely manipulate geometry. Compared with traditional manufacturing, 3D printing does not require customized molds or masks and has extremely high material utilization, thus bringing revolutionary changes at the level of customized structures. With the rapid development of various fields such as military defense, aerospace, and biomedical equipment, the requirements for the size and precision of customized microstructures are becoming increasingly stringent. The aforementioned characteristics of 3D printing can meet the requirements for the size and precision of customized parts, and it is gradually being applied more widely in these fields.

[0003] Fused Deposition Modeling (FDM) uses ABS and PLA as printing materials. A heating device melts the material, and nozzles spray and deposit it along a designated path to form the final model. Based on the G-code motion of the slicing file, the XYZ axes are controlled to create layers of the machined model cross-section, stacking them until the entire model is printed. In recent years, FDM printing technology has developed rapidly in China, thanks to its open-source software, allowing developers to modify it according to their needs. FDM printing technology offers high material utilization, low cost, and a wide variety of materials, but it also has drawbacks such as difficulty in printing complex models, lower printing accuracy, lower strength of the formed parts, and unsuitability for the production of large workpieces.

[0004] Selective laser sintering (SLS) uses solid powder as the printing material. A powder spreading device lays the solid powder evenly on a printing platform, and a high-energy-density laser selectively sintersulates the powder along a pre-defined path, causing the material to selectively melt and adhere to the solid. After printing one layer, the sintered solidified layer is moved downwards by Z-axis movement, and the solid powder material is re-laid on top of the previous layer. This process is repeated until the entire printing is complete. SLS has a wide range of printing materials, near 100% utilization, and is suitable for polymers and metal parts obtained by laser sintering metal powders. By controlling the process parameters of SLS, the microstructure of porous structures and scaffolds can be controlled.

[0005] Laminated object manufacturing (LOM) involves cutting a metal or plastic film of a certain thickness into slices of the 3D model's cross-sectional shape using a laser cutter. Hot melt adhesive is then applied to the film surface, and it's adhered to the previous layer. The process is repeated, cutting the film according to the shape of the next layer's slice, and then attaching the cut film to the previous layer using hot melt adhesive. This layer-by-layer cutting and bonding process continues until printing is complete. LOM technology requires no additional support structures, has a small number of cut pieces, minimal manufacturing deformation, and low cost. However, it results in poorer surface finish, more waste, fewer types of printing materials, and greater post-processing challenges.

[0006] Stereolithography Apparatus (SLA) is the earliest developed rapid prototyping technology. Hull et al. invented the first 3D printing device based on stereolithography in 1984. SLA is also one of the most researched, mature, and widely used rapid prototyping technologies today. SLA uses photosensitive resin as the printing material and utilizes its ultraviolet light curing reaction for processing. Through related technologies, the curing area of ​​the photosensitive resin is controlled to cure according to a specified shape, and layer-by-layer curing is performed by Z-axis movement until the printing is complete. In the past few years, stereolithography 3D printing has made great progress, offering high printing accuracy, high speed, low cost, and suitability for mass production. However, some problems still need to be solved, including limitations in printing materials, the need for support beams during printing, variations in ultraviolet light intensity, interference from the printing environment, and poor mixing and aging of the printing resin.

[0007] 3D printing has made significant progress, bringing about tremendous changes to the manufacturing and innovative design fields. Unlike traditional subtractive manufacturing technologies, additive manufacturing achieves greater economic efficiency and sustainability. However, traditional 3D printing methods still have some limitations when generating complex structures. Among them, two-photon polymerization 3D printers offer the highest manufacturing precision, but they are also extremely expensive, with prices reaching hundreds of thousands of dollars. While optical lenses manufactured using two-photon polymerization 3D printers can achieve dimensional accuracy at the sub-micron level of around 100nm, their surface roughness is limited to around 3nm, failing to reach sub-nanometer roughness. To date, no additive manufacturing method for optical lenses has emerged that can simultaneously achieve sub-micron level dimensional accuracy and sub-nanometer level surface roughness. Summary of the Invention

[0008] The purpose of this invention is to combine growth functions with 3D printing technology to propose a novel, highly customizable laser volumetric direct-write optical lens additive manufacturing system and method.

[0009] The technical solution adopted in this invention is: a laser volumetric direct-write optical lens additive manufacturing system, including a laser module, an XY two-axis motion platform, two stepper motors and a control system. The laser module, the XY two-axis motion platform and the two stepper motors are respectively connected to the digital signal output port of the control system.

[0010] Furthermore, it also includes a base, on which the laser module, the XY two-axis motion platform, and the two stepper motors are mounted.

[0011] Furthermore, the laser module is a 405nm laser module.

[0012] Furthermore, the control system is a PCIe multifunction data acquisition card.

[0013] The additive manufacturing method of the laser volumetric direct-write optical lens additive manufacturing system described above includes the following steps:

[0014] Step 1: Fitting the time-varying growth function model c(x, y, t): By controlling the system to output PWM signals with different duty cycles to the laser module, and by controlling the irradiation time and energy of the laser module, the marginal relationship between the curing depth, half-maximum width, and residence time of the photosensitive resin is obtained. After fitting and correcting the Gaussian function, the time-varying curing growth function model c(x, y, t) is obtained, where x and y are the coordinates of the XY axis motion platform, respectively, and t is the residence time.

[0015] Step 2: Calculate the linear residence time: Select the growth function c(x, y, t1) at a certain time t1 in the time-varying curing growth function model c(x, y, t), and calculate the linear residence time based on the given pre-design surface Z(x, y). The pre-design surface Z(x, y) is expressed by the convolution of the growth function and the residence time, as shown in the following formula:

[0016]

[0017] In the formula, the linear residence time t const The following is obtained using the nonnegativity least squares algorithm:

[0018] min ||c(x, y, t1)t const -Z(x, y)||

[0019] subject to t const >=0;

[0020] Step 3: Calculate the nonlinear residence time: Based on the obtained linear residence time t const The linear volume can be obtained using the following expression:

[0021] V desired (x, y) = t const (x,y)·∫∫c(u,v,t1)dudv

[0022] Then, based on the time-varying curing growth function model c(x, y, t), a time-varying curing volume model V(t) is established:

[0023]

[0024] Finally, the residence time obtained when the time-varying cured volume equals the linear cured volume is the nonlinear residence time t':

[0025] V(t')=V desired (x, y)

[0026] Step 4: Gaussian filtering: The calculated nonlinear residence time t' is smoothed using a two-dimensional Gaussian filter to obtain the final residence time t'. The expression for the two-dimensional Gaussian filter is as follows:

[0027]

[0028] t"(x,y)=∑(G(x,y)·t'(x,y));

[0029] In the formula, G(x,y) is a two-dimensional Gaussian kernel function, which is used to weight adjacent values. x0 and y0 are the coordinates of the center point of the printed model, and sigma is the standard deviation of the Gaussian filter.

[0030] Step 5: Convert the final dwell time t” into the duty cycle of the corresponding PWM signal, and transmit it to the laser module (1) through the TTL interface of the control system to realize the curing process of the resin.

[0031] Compared with existing technologies, the advantages of this invention are as follows: This invention, by combining computer-controlled fitting of the growth function and calculation of the residence time in the optical surface treatment process with laser volumetric direct-write curing additive manufacturing, opens up another solution for photopolymer additive manufacturing; the 3D printer has a simple structure, requiring only an XY-axis motion platform and a laser module; the processing cost is low, as the ultraviolet laser used in this invention is a traditional wire-cutting laser unit costing hundreds of yuan. As long as the corresponding growth function of the laser-cured resin can be fitted, no other requirements need to be placed on the laser, and additive manufacturing can be performed; a wide range of materials can be processed, as long as photopolymerizable resin materials can be processed using this method; the processing speed is relatively fast; processing a 4mm diameter optical lens only takes 366 seconds; the surface accuracy and surface roughness of the finished product have significant advantages compared to 3D printing equipment of the same price range.

[0032] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the figures. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of a laser volumetric direct-write 3D printer.

[0034] Figure 2 This is a schematic diagram of the control system of a 3D printer.

[0035] Figure 3 It is a schematic diagram of the processing procedure.

[0036] Figure 4 It is a graph of the curing growth model function obtained by measuring the rate of change of the resin curing height and half-peak width during laser unit irradiation experiments.

[0037] Figure 1 The components include: 1. Laser module, 2. XY two-axis motion platform and two stepper motors, and 3. Base. Detailed Implementation

[0038] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0039] The embodiments of the present invention are as follows Figure 1 and Figure 2 A laser-based direct-write volumetric additive manufacturing system for optical lenses includes a laser module 1, an XY-axis motion platform, two stepper motors 2, and a PCIe multifunction data acquisition card (control system). The laser module 1, the XY-axis motion platform, and the two stepper motors 2 are connected to the digital signal output ports of the PCIe multifunction data acquisition card. The computer outputs signals to the PCIe multifunction data acquisition card, transmitting the corresponding PWM output signals through the digital output ports of the data acquisition card for real-time control of the printing process. For a detailed explanation of the laser-based direct-write volumetric 3D printing principle, see [link to relevant documentation]. Figure 3 This invention is based on the idea of ​​growth function. By controlling the residence time of different residence points, the curing amount of different residence points is adjusted, and the final design surface is obtained through the cumulative molding of each curing point.

[0040] To obtain the final residence time, a growth function model must first be established, followed by a residence time solution model built using a combination of linear and nonlinear algorithms. During single-point curing experiments on photosensitive resin, the marginal relationship between the curing depth, half-maximum width at half-maximum (WHM), and residence time was determined by controlling the irradiation time and energy of the laser module. After fitting and correcting with a Gaussian-like function, the time-varying curing growth function model c(x, y, t) was obtained as follows: Figure 4 As shown. Select Figure 4In the time-varying curing growth function, the growth function c(x, y, t1) at a certain time t1 is given, and the pre-designed surface Z(x, y) is given.

[0041] The additive manufacturing method of the laser volumetric direct-writing optical lens additive manufacturing system includes the following steps:

[0042] Step 1: Fitting the time-varying growth function model c(x, y, t): By controlling the system to output PWM signals with different duty cycles to the laser module 1, and by controlling the irradiation time and energy of the laser module 1, the marginal relationship between the curing depth, half-maximum width, and residence time of the photosensitive resin is obtained. After fitting and correcting the Gaussian function, the time-varying curing growth function model c(x, y, t) is obtained, where x and y are the coordinates of the XY axis motion platform, respectively, and t is the residence time.

[0043] Step 2: Calculate the linear residence time: Select the growth function c(x, y, t1) at a certain time t1 in the time-varying curing growth function model c(x, y, t), and calculate the linear residence time based on the given pre-design surface Z(x, y). The pre-design surface Z(x, y) is expressed by the convolution of the growth function and the residence time, as shown in the following formula:

[0044]

[0045] In the formula, the linear residence time t const The following is obtained using the nonnegativity least squares algorithm:

[0046] min ||c(x, y, t1)t const -Z(x, ∑)||

[0047] subject to t const >=0;

[0048] Step 3: Calculate the nonlinear residence time: Based on the obtained linear residence time t const The linear volume can be obtained using the following expression:

[0049] V desired (x, y) = t const (x,y)·∫∫c(u,v,t1)dudv

[0050] Then, based on the time-varying curing growth function model c(x, y, t), a time-varying curing volume model V(t) is established:

[0051]

[0052] Finally, the residence time obtained when the time-varying cured volume equals the linear cured volume is the nonlinear residence time t':

[0053] V(t')=V desired (x,y)

[0054] Step 4: Gaussian filtering: The calculated nonlinear residence time t' is smoothed using a two-dimensional Gaussian filter to obtain the final residence time t'. The expression for the two-dimensional Gaussian filter is as follows:

[0055]

[0056] t"(x,y)=∑(G(x,y)·t'(x,y));

[0057] In the formula, G(x,y) is a two-dimensional Gaussian kernel function, which is used to weight adjacent values. x0 and y0 are the coordinates of the center point of the printed model, and sigma is the standard deviation of the Gaussian filter.

[0058] Step 5: Convert the final dwell time t” into the duty cycle of the corresponding PWM signal, and transmit it to the laser module 1 through the TTL interface via the control system to achieve the curing process of the resin.

[0059] Using the above method, a high-precision optical lens with a 4mm diameter and a surface error of sub-micron can be obtained within minutes using only a laser module 1, an XY-axis motion platform, and two stepper motors 2. This not only significantly reduces the manufacturing cost of additive manufacturing but also greatly increases the upper limit of additive manufacturing capabilities.

[0060] This invention adds a numerical calculation method to the traditional additive manufacturing process, thereby reducing equipment manufacturing costs and improving printing results, while simultaneously meeting submicron-level dimensional accuracy and subnanometer-level surface roughness requirements.

[0061] The above description is merely an advantageous embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A laser volumetric direct-write optical lens additive manufacturing system, characterized in that, It includes a laser module (1), an XY two-axis motion platform and two stepper motors (2) and a control system. The laser module (1), the XY two-axis motion platform and the two stepper motors (2) are respectively connected to the digital signal output port of the control system. The control system is used to perform the following operations: Step 1: Fitting the time-varying growth function model c(x,y,t): By controlling the system to output PWM signals with different duty cycles to the laser module (1), by controlling the irradiation time and energy of the laser module (1), the marginal relationship between the curing depth of the photosensitive resin and the half-peak width and residence time is obtained. After fitting and correcting the Gaussian function, the time-varying curing growth function model c(x,y,t) is obtained, where x and y are the coordinates of the XY axis motion platform, respectively, and t is the residence time. Step 2: Calculate the linear residence time: Select the growth function c(x,y,t1) at a certain time t1 in the time-varying curing growth function model c(x,y,t), and calculate the linear residence time based on the given pre-design surface Z(x,y). The pre-design surface Z(x,y) is expressed by the convolution of the growth function and the residence time, as shown in the following formula: In the formula, the linear residence time t const The following is obtained using the nonnegativity least squares algorithm: min||c(x,y,t1)t const -Z(x,y)|| subject to t const >=0; Step 3: Calculate the nonlinear residence time: Based on the obtained linear residence time t const The linear volume can be obtained using the following expression: V desired (x,y)=t const (x,y)·∫∫c(u,v,t1)dudv Then, based on the time-varying curing growth function model c(x,y,t), a time-varying curing volume model V(t) is established: Finally, the residence time obtained when the time-varying cured volume equals the linear cured volume is the nonlinear residence time t': V(t’)=V desired (x,y) Step 4: Gaussian filtering: The calculated nonlinear residence time t' is smoothed using a two-dimensional Gaussian filter to obtain the final residence time t'. The expression for the two-dimensional Gaussian filter is as follows: t"(x,y)=∑(G(x,y))·t'(x,y)); In the formula, G(x,y) is a two-dimensional Gaussian kernel function, which is used to weight adjacent values. x0 and y0 are the coordinates of the center point of the printed model, and sigma is the standard deviation of the Gaussian filter. Step 5: Convert the final dwell time t” into the duty cycle of the corresponding PWM signal, and transmit it to the laser module (1) through the TTL interface of the control system to realize the curing process of the resin.

2. The laser volumetric direct-write optical lens additive manufacturing system according to claim 1, characterized in that, It also includes a base (3), on which the laser module (1), the XY two-axis motion platform and the two stepper motors (2) are mounted.

3. The laser volumetric direct-write optical lens additive manufacturing system according to claim 1, characterized in that, The laser module (1) is a 405nm laser module.

4. The laser volumetric direct-write optical lens additive manufacturing system according to claim 1, characterized in that, The control system is a PCIe multifunction data acquisition card.

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