A DLP printing method based on dual-initiator binder

Abstract

A DLP printing method based on a dual-initiator binder, specifically a DLP 3D printing method based on a light-heat-initiated polymer, is designed to solve the problems of incomplete curing of current DLP 3D printing, too long curing time caused by secondary curing, and difficulty in demolding during DLP printing. Make a photothermal dual-initiator printing polymer; a heating rod is installed in a rectangular shape on the bottom plate of the printing device; the printing device is installed on the DLP 3D printer, the printed part is installed between the bottom plate and the printing material tank, and the printer is positioned; a slice set of the printed model is obtained, the position of the printed pattern in each layer of the slice is read, and the corresponding heating rod number is recorded; the optimal constant temperature of each slice is determined; the photothermal dual-initiator printing polymer is poured into the printing material tank, and printed according to the printing pattern, heating rod number, and constant temperature of a certain layer, and the light curing setting time is waited to complete the single-layer printing; until all slices are printed.

Description

Technical Field

[0001] The present invention relates to a DLP 3D printing method, in particular to a DLP 3D printing method based on a light-heat initiated polymer, and belongs to the field of 3D printing.

[0002] Background Methods

[0003] Digital Light Procession (DLP) 3D printing technology is still the preferred method for printing high-surface quality polymer parts. The DLP forming method is based on low-viscosity liquid photopolymer resin, and the selective curing of the resin is achieved by controlling the light source to achieve layer-by-layer printing. DLP and Fused Deposition Modeling (FDM) printing methods have become the two most widely used 3D printing methods in daily life because of their relatively simple forming principles. Unlike DLP, FDM is based on a heating rod to heat the nozzle to a certain temperature (generally 200 degrees Celsius). Under the control of a computer, the heating nozzle moves in a plane according to the cross-sectional profile information of the product parts. The thermoplastic filament material is sent to the hot melt nozzle by the filament supply mechanism, heated and melted into a semi-liquid state in the nozzle, and then extruded out to selectively deposit the shape people need. Compared with FDM, DLP has higher molding accuracy and is not affected by the complexity of the printed structure, which can meet the geometric design requirements to the greatest extent.

[0004] Traditional photocurable resins are usually based on (meth)acrylates, and polymerization begins by generating free radicals through photosensitive photoinitiators. The mechanical properties of incompletely cured printed parts will change over time. Therefore, these printed parts need to be subjected to secondary curing treatment (secondary ultraviolet light irradiation of the printed parts) after printing to achieve their final mechanical properties. Secondary curing treatment can often only act on the surface area of ​​the printed parts. Therefore, researchers usually increase the curing time during the printing process to increase the curing degree inside the printed parts. This undoubtedly prolongs the DLP forming time. Moreover, for single-layer printing, the bonding force generated by the full curing of the near light source surface will be greater than the bonding force of the far light source surface (base plate), resulting in the occurrence of demolding. Although the curing degree of the printed parts can be effectively improved by adding thermal initiators, the overall curing of methacrylate is strongly affected by the curing temperature. A higher curing temperature will result in a higher conversion rate in the overall cured polymer. The curing degree of the printed parts can be effectively improved by post-heat curing, but this method inevitably prolongs the DLP forming cycle and cannot effectively solve the demolding phenomenon.

[0005] Compared with other 3D printing methods (such as SLS, SLM, FDM, etc.), DLP printing does not require much energy input (mainly heat), and there are relatively few studies on the effect of temperature on DLP forming. The main reason is that DLP printing usually has a small forming area, and the heating temperature field is usually difficult to control accurately, which will cause the resin outside the printing area to solidify under the influence of temperature and cause printing failure. Summary of the invention

[0006] In order to solve the problems of incomplete curing in current DLP 3D printing, long curing time caused by secondary curing, and difficulty in demolding during DLP printing, the present invention further proposes a DLP printing method based on a dual-initiator adhesive.

[0007] It includes the following steps:

[0008] S1, preparation of photothermal dual-initiation printing polymer;

[0009] S2. The printing device of the DLP 3D printer includes a DLP light source, an ultraviolet light, a DLP printing material tank, a bottom plate and a heating rod from bottom to top. The bottom plate is provided with a plurality of circular holes distributed in a rectangular shape, and a heating rod is installed in each circular hole.

[0010] Install the printing device on the DLP 3D printer, install the printed part between the base plate and the DLP printing material tank, and position the DLP 3D printer;

[0011] Slice the printed model to obtain a slice set, read the position of the printed pattern in each slice, and record the heating rod number corresponding to each printed pattern;

[0012] S3, heating the heating rod corresponding to each slice printing pattern to a different constant temperature T. When each constant temperature T is stable, a thermal imager is used to record the temperature distribution of all heating rods and each slice at different heating temperatures to obtain the optimal constant temperature T of each slice;

[0013] S4, pour the photothermal dual-initiation printing polymer in S1 into the DLP printing material tank, heat the heating rod to the corresponding constant temperature T according to the printing pattern of the mth layer and the corresponding heating rod number, move the DLP base plate to the printing position, wait for the light curing set time, complete the single-layer printing, and preheat the heating rod within the range of the next layer of printing pattern during the printing process; until the printing of all slices is completed.

[0014] Furthermore, the photothermal dual-initiation printing polymer is prepared in S1, and the specific process is as follows:

[0015] S11, take ng of methacrylate, add thermal initiator, photoinitiator and light absorber thereto, and stir magnetically at 60°C for 2 hours;

[0016] S12. Perform a routine test on the viscosity of the polymer, and adjust the viscosity of the polymer by adding a high-viscosity or low-viscosity methacrylate monomer of the same type according to the viscosity test result, so that the viscosity of the polymer meets the DLP printing viscosity.

[0017] Furthermore, the value of n in S11 is [50-500 g]; the contents of the thermal initiator and the photoinitiator are both 1-1000 ppm.

[0018] Furthermore, in S11, the thermal initiator is tert-butyl benzoyl peroxide, the photoinitiator is photoinitiator phenylenediphosphine oxide, and the light absorber is 2-hydroxy-4-n-octyloxybenzophenone.

[0019] Furthermore, the viscosity of the polymer in S13 is in the range of 50-500 mPa.s.

[0020] Furthermore, the thickness of the slice in S2 is 30-200 microns.

[0021] Furthermore, the heating rods in S2 are numbered (u, v), where u is the heating rod in the uth column and v is the heating rod in the vth row.

[0022] Furthermore, the constant temperature T in S3 ranges from 25°C to 200°C.

[0023] Furthermore, the light curing time in S4 is set to 5-60s.

[0024] Furthermore, S4 also includes that, each time a slice layer is added, the constant temperature T of the previous slice layer is lower than the constant temperature T of the current slice layer.

[0025] Beneficial effects:

[0026] The present invention uses (meth)acrylate, thermal initiator, photoinitiator and light absorber to prepare photothermal dual-initiation printing polymer. A heating rod is installed on the printing device of the DLP 3D printer, and the heating rod is installed on the bottom plate in a rectangular array. The position of the printed pattern in each layer of slices is identified according to the slice information, and the heating rod number corresponding to each printed slice (pattern) is recorded. The optimal constant temperature T of each slice is selected, and the photothermal dual-initiation printing polymer is poured into the DLP printing material tank. According to the printing pattern of the mth layer and the corresponding heating rod number, the heating rod is heated to the corresponding constant temperature T, the DLP bottom plate moves to the printing position, waits for the light curing setting time, completes the single-layer printing, and preheats the heating rod within the range of the next layer of printing pattern during the printing process; until the printing of all slices is completed. With each additional layer of slices, the constant temperature T of the previous layer of slices is lower than the constant temperature T of the current layer of slices.

[0027] The present invention is based on photothermal dual-initiation printing of polymers, and utilizes a controlled heating matrix to achieve full curing during the DLP printing process, thereby improving the degree of curing of the polymer in the printed pattern area (especially the degree of curing in the distant light source area), reducing the curing time, and solving the problem of demolding of the printed part during the printing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a flow chart of the present invention;

[0029] Figure 2 It is a schematic diagram of the structure of a DLP 3D printer printing device;

[0030] Figure 3 It is a schematic diagram of the structure of the base plate and the heating rod;

[0031] Figure 4 is a schematic diagram of the structure of the DLP 3D printer printing device after the print part is added;

[0032] Figure 5 is a schematic diagram of the printing model structure in Example 1;

[0033] Figure 6 This is a schematic diagram of the 5th layer printing slice structure, and the corresponding heating rods are numbered (2, 2) and (4, 4); DETAILED DESCRIPTION

[0034] Specific implementation method 1: Combination Figure 1-Figure 4 The present embodiment is described. The present embodiment describes a DLP printing method based on a dual-initiator binder, which comprises the following steps:

[0035] S1. Preparation of photothermal dual-initiation printing polymer. The specific process is as follows:

[0036] Take ng of (meth)acrylate, add thermal initiator, photoinitiator and light absorber, and carry out magnetic stirring at 60°C for 2 hours. Perform routine test on the viscosity of the polymer, and adjust the viscosity of the polymer by adding high-viscosity or low-viscosity (meth)acrylate monomer of the same type according to the viscosity test results to meet the DLP printing viscosity requirements.

[0037] The general value of n is [50-500g], which is selected according to the size of the printed part; the thermal initiator is tert-butyl benzoyl peroxide; the photoinitiator is photoinitiator 2,4,6-trimethylbenzoyl)phosphine oxide; the light absorber is UV-531 (2-hydroxy-4-n-octyloxybenzophenone), UV-1995, etc.; the content of thermal initiator and photoinitiator are both 1-1000ppm; the viscosity range of the polymer is 50-500mPa.s.

[0038] S2. The printing device of the DLP 3D printer includes a DLP light source, ultraviolet light, a DLP printing material tank, a base plate and a heating rod from bottom to top. There are multiple circular holes distributed in a rectangular shape on the base plate, and a heating rod is installed in each circular hole. The printing device is installed on the DLP 3D printer, and the printed part is installed between the base plate and the DLP printing material tank. The DLP 3D printer is positioned, and the printed model is sliced ​​to obtain a slice set. The position of the printed pattern in each layer of the slice is read, and the heating rod number corresponding to each printed pattern is recorded.

[0039] The thickness of the slice is 30-200 microns; the heating rods are numbered (u, v), u is the heating rod in the uth column, and v is the heating rod in the vth row. The bottom plate and the heating rods can be regarded as a heating matrix.

[0040] S3. Heat the heating rod corresponding to each slice printing pattern to a different constant temperature T. When each constant temperature T is stable, use a thermal imager to record the temperature distribution of all heating rods and each slice at different heating temperatures to obtain the optimal constant temperature T for each slice.

[0041] The range of the constant temperature T is 25°C-200°C. This step belongs to the preparation stage. It is necessary to change the size of T (for example, select T at intervals of 10, 20, and 30 degrees Celsius) to determine the temperature field distribution under different temperatures T, reduce the impact of heating on the non-printing area, and determine the optimal constant temperature T for each slice, laying the foundation for the selection of T of the heating rod in S4 and 5.

[0042] S4, pour the photothermal dual-initiation printing polymer in S1 into the DLP printing material tank, heat the heating rod to the corresponding constant temperature T according to the printing pattern of the mth layer and the corresponding heating rod number, move the DLP base plate to the printing position, wait for the light curing set time, complete the single-layer printing, and preheat the heating rod within the range of the next layer of printing pattern during the printing process.

[0043] The value of m is 1, 2, 3...k, where k is the total number of slices; the light curing setting time is about 5-60s;

[0044] S5. As the number of printed layers increases, in order to ensure the heat-induced curing effect of the new printed layer, the set temperature of the heating rod is gradually increased, and S3-S4 are repeated to complete the printing of the entire print.

[0045] Because as the number of printing layers increases, the heating rod is farther and farther away from the printing area of ​​the bottom layer, such as Figure 4 ,In order to ensure the curing effect of the printing layer, the set temperature of the ,heating rod is gradually increased as the number of printing layers increases, but the final ,temperature is mainly determined based on the distribution of the temperature field in S3.

[0046] Example

[0047] like Figures 1 to 6 As shown, 100g of (meth)acrylate is taken, 10mg of tert-butyl benzoyl peroxide, 600mg of ethoxylated (2) bisphenol a-dimethacrylate (SR348L) and 27mg of UV-1995 are added thereto, and the printed polymer is magnetically stirred at 60°C for 2 hours. The viscosity of the polymer is tested and the viscosity is measured to be 300mPa.s, which meets the viscosity requirement of DLP printing. The DLP 3D printer is positioned, the printed model is sliced, and slices with a layer thickness of 50 microns are obtained. The position of the printed pattern in each layer is read, and the number of the heating rod within the printed pattern range is recorded. The heating rods in the local heating matrix are heated to a constant temperature of 60 degrees Celsius. When the temperature stabilizes, the distribution of the heating temperature field of different heating rods and different heating temperatures is recorded using a thermal imager. Pour the polymer configured in S1 into the DLP printing tank, read the print pattern of the first layer and the number of the heating rod in S2, heat the corresponding numbered heating rod to 60 degrees Celsius, move the DLP base plate to the printing position, wait for the light curing setting time of 15 seconds, complete the single-layer printing, and preheat the heating rod within the range of the next layer of print pattern during the printing process. As the number of printing layers increases, gradually increase the set temperature of the heating matrix heating rod to 100 degrees Celsius, and repeat S3-S4 to complete the printing of the entire print.

Claims

1. A DLP printing method based on a dual-initiator binder, characterized in that: It includes the following steps: S1, preparation of photothermal dual-initiation printing polymer; S2. The printing device of the DLP 3D printer includes a DLP light source, an ultraviolet light, a DLP printing material tank, a bottom plate and a heating rod from bottom to top. The bottom plate is provided with a plurality of circular holes distributed in a rectangular shape, and a heating rod is installed in each circular hole. Install the printing device on the DLP 3D printer, install the printed part between the base plate and the DLP printing material tank, and position the DLP 3D printer; Slice the printed model to obtain a slice set, read the position of the printed pattern in each slice, and record the heating rod number corresponding to each printed pattern; S3, heating the heating rod corresponding to each slice printing pattern to a different constant temperature T. When each constant temperature T is stable, a thermal imager is used to record the temperature distribution of all heating rods and each slice at different heating temperatures to obtain the optimal constant temperature T of each slice; S4, pouring the photothermal dual-initiation printing polymer in S1 into the DLP printing material tank, heating the heating rod to the corresponding constant temperature T according to the printing pattern of the mth layer and the corresponding heating rod number, moving the DLP base plate to the printing position, waiting for the light curing setting time, completing the single-layer printing, and preheating the heating rod within the range of the next layer of printing pattern during the printing process; until the printing of all slices is completed; In S1, the photothermal dual-initiation printing polymer is prepared, and the specific process is as follows: S11, take ng of methacrylate, add thermal initiator, photoinitiator and light absorber thereto, and stir magnetically at 60°C for 2 hours; S12, performing a conventional test on the viscosity of the polymer, and adjusting the viscosity of the polymer by adding a high-viscosity or low-viscosity methacrylate monomer of the same type according to the viscosity test result, so that the viscosity of the polymer meets the DLP printing viscosity; The value of n in S11 is [50-500 g]; the contents of the thermal initiator and the photoinitiator are both 1-1000 ppm; In S11, the thermal initiator is tert-butyl benzoyl peroxide, the photoinitiator is photoinitiator phenyl diphosphine oxide, and the light absorber is 2-hydroxy-4-n-octyloxybenzophenone; The viscosity of the polymer in S13 ranges from 50 to 500 mPa.s; The thickness of the sections in S2 was 30–200 μm; The heating rods in S2 are numbered (u, v), where u is the heating rod in the uth column and v is the heating rod in the vth row; The constant temperature T in S3 ranges from 25°C to 200°C; The light curing setting time in S4 is 5-60s; S4 also includes that, each time a slice layer is added, the constant temperature T of the previous slice layer is lower than the constant temperature T of the current slice layer.

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