Internal stereoscopic light projection curing molding 3D printing device and molding method thereof

Abstract

An internal stereoscopic light projection curing molding 3D printing device mainly includes a laser projection module, an optical reference plane module, an optical reference plane module lifting system, a resin tank, a molding platform, a molding platform lifting system, a control system, a power supply system and a main frame, and adopts curing molding inside the liquid resin. Use multiple beams of light of specific wavelengths to irradiate the photosensitive resin, and the unit light intensity of each beam of light is lower than the unit light intensity of light required for curing the photosensitive resin, but the unit light intensity after the overlap of several beams of light is higher than the unit light intensity required for curing this photosensitive resin. When the light intensity reaches the light intensity required for the curing reaction of the photosensitive resin used, this part of the liquid photosensitive resin will undergo a polymerization reaction and solidify into a solid. The liquid resin is continuously cured from bottom to top according to the cross-section of the desired molded object to obtain the actual object of this model.

Description

Technical Field

[0001] The present invention relates to the technical field of 3D printing, and in particular to an internal stereoscopic light projection solidification molding 3D printing device and a molding method thereof. Background Art

[0002] In recent years, the research and application of 3D printer technology has been increasingly valued by academia and the business community. It is known as one of the important signs of the third industrial revolution. Traditional 3D printing technology is now roughly divided into the following categories according to the different materials and molding methods: fused deposition molding (FDM) of plastics, laser sintering or bonding molding of metal powder and plastic powder, and photocuring molding of photosensitive resins. The cost of fused deposition technology is low, but the speed is very slow and the precision is not high; the laser sintering or bonding of powders is high in precision but the speed is very slow and the cost is high; the photocuring of resins is high in precision and the speed is between the first two. On the other hand, although 3D printing technology can form high-precision objects, the molding speed is much lower than that of traditional manufacturing production molding technology, which limits the large-scale promotion and use of 3D printing technology.

[0003] The forming principle of traditional resin photocuring 3D printing technology is basically the same. It can be mainly divided into laser scanning SLA, digital light projection DLP, and liquid crystal imaging LCD according to the light source; it can be divided into bottom forming and top forming according to the forming position. Taking the bottom forming SLA technology as an example, the working process of the equipment is as follows: after printing, the forming platform descends from the top to a position very close to the bottom of the resin tank. This distance is equal to the thickness of the first layer of the model. The bottom of the resin tank is a transparent material. At this time, the laser scans the cross-sectional pattern of the first layer on the bottom to complete the curing of the first layer. After curing, the solid resin will stick to the bottom of the forming platform and the resin tank. The bottom material of the resin tank is made of a special release film and can be easily detached. At this time, the forming platform and the cured model move upward for a certain distance, so that the bottom of the model is separated from the release film on the bottom of the resin tank, and then the forming platform and the model descend again to a certain position from the bottom of the resin tank, and the laser continues to scan and form the next surface. In this way, the actual 3D object model is finally formed.

[0004] Currently, all light-curing 3D printing devices on the market perform layered molding on the upper or lower surface of the resin tank. During the printing process, the model needs to move continuously with the molding platform. This step will waste a lot of time and increase the instability of printing.

[0005] It can be seen that the slow molding speed is the biggest factor hindering its development at this stage. The speed of existing light-curing 3D printing technology is limited by the mechanical equipment itself, which cannot give full play to the maximum performance of photosensitive resin and makes the equipment molding speed very low, which cannot meet the actual production and manufacturing needs. For example, because the traditional SLA and DLP (LCD) molding technology is formed on the bottom or surface, due to the limitation of this structure, the molding platform and the molding object need to continuously move up and down, so the molding speed is greatly reduced, generally not more than 50mm / h at the fastest, and because the molding object is in continuous motion, the molding process is not stable and the molded object is easy to fall off. In addition, the existence of the layered concept also makes the precision and surface smoothness of the molded object insufficient. In terms of molding speed, the fastest molding technology in this field is the CLIP (Continuous Variable Liquid Surface Forming) technology of 3D Carbon Company in the United States, with a molding rate of about 8.3 mm Z-axis height per minute (500mm / h). However, CLIP technology, which has great advantages over traditional technologies, has improved the disadvantage of requiring reciprocating motion for surface molding and eliminated the concept of layers, making the surface of the molded object very smooth. However, the liquid resin on the molding surface needs to be continuously replenished and the fluidity of the liquid resin is poor, so it cannot quickly mold large-area solid objects. Although the speed is greatly improved compared to traditional molding technology, reaching the fastest Z-axis molding height of 500mm / h, it is still far from meeting the large-scale high-speed manufacturing requirements required in actual industrial production. Summary of the invention

[0006] In view of the deficiencies of the prior art, the present invention provides an internal stereoscopic light projection solidification molding 3D printing device and a molding method thereof. Different from the molding method of curing from the upper surface or lower surface of the liquid resin by the existing light-curing 3D printing technology, the curing molding is performed inside the liquid resin. Multiple beams of light of a specific wavelength are used to irradiate the photosensitive resin. The unit light intensity of each beam of light is lower than the unit light intensity of the light required for curing the photosensitive resin, but the unit light intensity after the overlap of several beams of light is higher than the unit light intensity required for curing the photosensitive resin. When the light intensity reaches the light intensity required for the curing reaction of the photosensitive resin used, the liquid photosensitive resin in the intersecting part will undergo a polymerization reaction and solidify into a solid. The liquid resin is continuously cured from bottom to top according to the cross-section of the desired molded object to obtain the actual object of this model.

[0007] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: an internal stereoscopic light projection curing molding 3D printing device, mainly comprising a laser projection module, an optical reference plane module, an optical reference plane module lifting system, a resin tank, a molding platform, a molding platform lifting system, a control system, a power supply system and a main frame, wherein the main frame is the base of the entire device, and other components are installed on the main frame; the laser projection module is fixed on the top of the main frame, provides a molding projection beam for the entire device, and projects the beam into the resin tank; the optical reference plane module lifting system is installed inside the main frame, and an optical reference plane module mounting plate is provided in the middle, the optical reference plane module is installed thereon, a square through hole is opened in the middle of the optical reference plane module mounting plate, and the resin tank is installed on the bottom plate of the main frame through the hole; the molding platform lifting system is installed on the upper and lower end surfaces of the main frame, and the molding platform is suspended in the resin tank by a support rod; the power supply system is a power supply with sufficient power to provide accurate voltage output for all modules; the control system is connected to each module to control each module to operate in coordination.

[0008] Furthermore, the laser projection module mainly uses a light-emitting semiconductor that can emit laser of a specific wavelength as a light source. The light is refracted by the front-stage lens and then irradiated onto the DMD chip. The refracted light is processed by the DMD chip and then irradiated onto the rear-stage refractive lens. The rear-stage lens has an automatic focus system that can focus the image in real time according to the operation of the machine. The refracted light is the formed projection light beam, which is reflected by a reflector and vertically enters the resin tank. The DMD chip is part of the DLP technology of Texas Instruments in the United States.

[0009] Furthermore, the optical reference plane module includes a laser light source, a laser refractive lens group, a laser filter plate and a mounting plate. The laser light source is four light-emitting semiconductor lasers that can emit light of a specific wavelength. The lasers are placed opposite each other in pairs, with the lasers between the two groups forming a 90-degree angle, and the four lasers are in the same plane and fixed on the mounting plate. The laser refractive lens group is installed on the front side of the laser light source and the rear side of the laser filter plate. A laser filter is provided on the laser filter plate. After the laser light source emits light, it is first refracted by the laser refractive lens group and then irradiated onto a serrated refractive lens, refracting the incident light into a straight line of light and irradiating it. The excess light is filtered by the laser filter and blocked, eventually forming a straight line of thin laser with a width of 0.5 to 0.1 mm. The four laser beams completely overlap on the same plane to form a laser irradiated plane, which is the optical reference plane.

[0010] Furthermore, the optical reference surface module lifting system includes an optical axis guide, a linear bearing, a ball screw, a ball bearing, a stepper motor, a synchronous belt, a synchronous wheel and an optical reference surface module mounting plate. The linear bearing and the ball bearing are respectively fixed on the four sides of the optical reference surface module mounting plate through mounting seats. The optical axis guide passes through the linear bearing and is fixed on the upper and lower end surfaces of the main frame. The ball screw passes through the ball bearing, and the lower end is connected to the stepper motor through a synchronous belt and a synchronous wheel. The optical reference surface module is installed as a whole on the optical reference surface module lifting system, and the entire module is driven by the ball screw to move up and down through the rotation of the stepper motor.

[0011] Furthermore, the resin tank is made of highly transparent material and is a rectangular structure with an open top. The bottom of the resin tank is a square. The size of the resin tank is determined by the actual molding size of the equipment. The resin tank is a movable part and can be removed from the bottom plate of the main frame for cleaning or replacement.

[0012] Furthermore, the molding platform is a resin curing molding platform, a flat plate structure made of metal aluminum with a thickness of 3 mm, and circular holes with a diameter of 4.5 mm are evenly distributed on it. The upper surface of the platform is completely flat, and the edges of the holes on the lower surface and the edges of the platform are rounded to prevent the generation of bubbles during the lifting of the platform.

[0013] Furthermore, the molding platform lifting system includes an upper structure, an optical axis, a linear bearing I, a screw, a screw nut, a support rod, a stepper motor, a synchronous belt and a synchronous wheel. The molding platform is connected to the upper structure by four support rods of equal length. The upper structure is a square ring structure, and the size of the middle square is slightly larger than the size of the bottom surface of the resin tank; the linear bearing I and the screw nut are symmetrically installed at the four corners of the upper structure, and the optical axis passes through the linear bearing I and is fixed on the upper and lower end surfaces of the main frame. The screw passes through the screw nut, and the lower end is connected to the stepper motor through a synchronous belt and a synchronous wheel. The entire lifting system is driven by the screw to move up and down through the rotation of the stepper motor.

[0014] Furthermore, the control system includes a main control board, a stepper motor controller and various sensors. The main control board is a hardware platform composed of a single-chip computer system with a high-performance microprocessor, which can simultaneously process and output control parameters and the working conditions of various components, and the main control board has a port for outputting high-resolution image signals for the signal output of the laser projection module, and at the same time performs real-time control of the automatic focusing device of the rear lens group of the laser projection module; the stepper motor controller controls the stepper motors of each part through the signal of the main control board, so that the entire device can operate in coordination; various sensors are installed in each module, detect each module, and transmit signals to the main control board.

[0015] A molding method for an internal stereoscopic light projection curing molding 3D printing device comprises the following steps:

[0016] (1) Model cross-cutting: The model to be printed is cross-cut on the computer using dedicated software, and the generated print file is then input into the device control system. The total number of cross-cut layers is the same as the total number of frames of the animation projected by the molding projection;

[0017] (2) Forming an optical reference plane: Turn on the laser light source of the optical reference plane module, and form four straight laser beams of a specific wavelength, which are shot into the liquid resin from the four vertical faces of the square transparent resin tank parallel to the bottom of the resin tank. At the same time, the four straight laser beams completely overlap on one surface, thus forming a plane of light irradiated by the laser beam of the specific wavelength inside the liquid resin, which is called the optical reference plane;

[0018] (3) forming a molding projection: a laser projection module emits light of the same wavelength as the four laser beams in step 2) to irradiate the cross-cutting pattern obtained in step 1) perpendicularly to the light reference plane from top to bottom into the light-curing resin in the resin tank, which is called molding projection;

[0019] (4) forming a curing zone: the two light sources work simultaneously, and the projection beam formed in step 2) intersects with the light reference plane in step 1). The intersecting area is called the curing zone. The cross section of this area is a cross section of the figure projected by the projection beam, and the height is the height of the light reference plane. The photosensitive resin in the curing zone undergoes a curing reaction and solidifies into a solid because the unit light intensity reaches the unit light intensity required for curing the photosensitive resin.

[0020] (5) Printing: When the laser light source of the laser projection module continuously projects a dynamically changing graphic consisting of the bottom-up cross-sections of the desired molded object, and the light reference plane moves from bottom to top at the same rate, the curing zone will gradually move from bottom to top inside the liquid photosensitive resin, thereby curing the photosensitive resin and ultimately forming the actual object to be obtained.

[0021] Furthermore, suppose the unit light intensity of a specific wavelength of light required for curing a photosensitive resin is: L,

[0022] Assume that the unit light intensity of a single beam of the four laser beams on this optical reference plane is Lp, then Lp must be lower than 1 / 4L, that is, the unit light intensity at each point on the optical reference plane is lower than L, and Lp is as close to 1 / 4L as possible under the premise that no curing reaction will occur at any point within the range of the optical reference plane, so at this time, no photosensitive resin will undergo curing reaction on the optical reference plane;

[0023] Assuming that the unit light intensity of the molding projection beam is Lt, then Lt needs to be lower than L, that is, only under the irradiation of the molding projection beam, no curing reaction will occur at any point in the liquid photosensitive resin, and Lt should be as close to L as possible under the premise that no curing reaction will occur at any point within the irradiation range of the molding projection beam;

[0024] When the formed projection beam intersects the light reference plane, the unit light intensity Lt and 4*Lp of the two light sources are lower than L but very close to L, so the unit light intensity of the overlapping curing area will be higher than L, that is: Lt+4*Lp>L.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1) Compared with the traditional photosensitive resin molding technology, the inherent way of surface molding is changed, so that the model is molded inside the photosensitive resin. In the molding process, the molding model and the molding platform do not need to do any activities and remain completely still. At the same time, there is no concept of layers. Therefore, the speed, stability, precision and surface smoothness of the molded object are greatly improved compared with traditional technologies.

[0027] 2) It breaks the bottleneck of existing 3D printing additive manufacturing technology, improves the molding rate of 3D printing technology to a higher level, and at the same time minimizes the variable factors during molding, breaking through the limits of what 3D printing equipment can achieve. The theoretical molding rate is 100 to 150 mm Z-axis height per minute (ie: 6000mm-9000mm / h), which is more than ten times the molding speed of CLIP technology.

[0028] 3) Due to the fast molding speed and the fact that the molded object is immersed in liquid photosensitive resin, the supporting part of the model itself can be minimized or even eliminated during the molding process due to buoyancy, so as to maximize the utilization rate of photosensitive resin consumables. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without independent creative work.

[0030] Figure 1 A schematic diagram of forming an optical reference plane for the present invention;

[0031] Figure 2 A schematic diagram of a projection forming process for the present invention;

[0032] Figure 3 A schematic diagram of forming a solidification zone according to the present invention;

[0033] Figure 4 Print model path diagram for this work

[0034] Figure 5 It is a schematic diagram of the structure of the laser projection module of the present invention;

[0035] Figure 6 It is a schematic diagram of the structure of the optical reference plane module of the present invention;

[0036] Figure 7 It is a structural schematic diagram of the optical reference surface module lifting system of the present invention;

[0037] Figure 8 It is a schematic diagram of the resin tank structure of the present invention;

[0038] Fig. 9 It is a schematic diagram of the structure of the molding platform of the present invention;

[0039] Fig.10 It is a structural schematic diagram of the molding platform lifting system of the present invention;

[0040] Fig.11 It is a structural schematic diagram of the molding platform of the present invention installed on the molding platform lifting system;

[0041] Fig.12 It is a structural schematic diagram of the optical reference plane module of the present invention installed on the optical reference plane module lifting system;

[0042] Fig.13 It is a brief structural schematic diagram of the present invention;

[0043] Among them, laser projection module 1, optical reference surface module 2, optical reference surface module lifting system 3, resin tank 4, molding platform 5, molding platform lifting system 6, main frame 7, optical reference surface 8, molding projection 9, curing area 10, reflector 11, laser light source 21, laser filter plate 23, mounting plate 24, laser filter 231, optical reference surface module mounting plate 31, optical axis guide rail 32, linear bearing 33, ball screw 34, ball bearing 35, upper structure 61, optical axis 62, linear bearing I 63, screw 64, screw nut 65, support rod 66, base plate 71, model 0. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] Embodiment 1:

[0046] like Figures 5 to 13 As shown: an internal stereoscopic light projection curing molding 3D printing device, mainly comprising a laser projection module 1, an optical reference surface module 2, an optical reference surface module lifting system 3, a resin tank 4, a molding platform 5, a molding platform lifting system 6, a control system, a power supply system and a main frame 7, wherein the main frame 7 is the base of the entire device, and other components are installed on the main frame 7; the laser projection module 1 is fixed on the top of the main frame 7, provides a molding projection beam for the entire device, and projects the beam into the resin tank 4; the optical reference surface module lifting system 3 is installed inside the main frame 7, and an optical reference surface module mounting plate 31 is provided in the middle, on which the optical reference surface module 2 is installed, and a square through hole is opened in the middle of the optical reference surface module mounting plate 31, and the resin tank 4 is installed on the bottom plate 71 of the main frame 7 through the hole; the molding platform lifting system 6 is installed on the upper and lower end surfaces of the main frame 7, and the molding platform 5 is suspended in the resin tank 4 by a support rod 66; the power supply system is a power supply with sufficient power, which provides accurate voltage output for all modules; the control system is connected to each module to control the coordinated operation of each module.

[0047] The laser projection module 1 mainly uses a light-emitting semiconductor that can emit laser light of a specific wavelength as a light source. The light is refracted by a front-stage lens and then irradiated onto a DMD chip. The refracted light processed by the DMD chip is then irradiated onto a rear-stage refracting lens. The rear-stage lens has an automatic focus system that can focus the image in real time according to the operation of the device. The refracted light is a formed projection beam, which is reflected by a reflector 11 and vertically enters a resin tank 4. The DMD chip is a part of the DLP technology of Texas Instruments of the United States.

[0048] The optical reference plane module 2 includes a laser light source 21, a laser refractive lens group, a laser filter plate 23 and a mounting plate 24. The laser light source 21 is four light-emitting semiconductor lasers that can emit light of a specific wavelength. The lasers in the two groups are placed opposite to each other, and the lasers in the two groups are 90 degrees. The four lasers are in the same plane and fixed on the mounting plate 24. The laser refractive lens group is installed on the front side of the laser light source 21 and the rear side of the laser filter plate 23. A laser filter slit 231 is provided on the laser filter plate 23. After the laser light source 21 emits light, it is first refracted by the laser refractive lens group and then irradiated onto the serrated refractive lens, refracting the incident light into a straight line of light and irradiating it. The excess light is blocked by the filtering of the laser filter slit 231, and finally a straight line of thin laser with a width of 0.5 to 0.1 mm is formed. The four laser beams completely overlap on the same plane to form a laser irradiated plane, which is the optical reference plane 8.

[0049] The optical reference surface module lifting system 3 includes an optical axis guide rail 32, a linear bearing 33, a ball screw 34, a ball bearing 35, a stepping motor, a synchronous belt, a synchronous wheel and an optical reference surface module mounting plate 31. The linear bearing 33 and the ball bearing 35 are respectively fixed on the four sides of the optical reference surface module mounting plate 31 through mounting seats. The optical axis guide rail 32 passes through the linear bearing 33 and is fixed on the upper and lower end surfaces of the main frame 7. The ball screw 34 passes through the ball bearing 35, and the lower end is connected to the stepping motor through the synchronous belt and the synchronous wheel. The optical reference surface module 2 is installed as a whole on the optical reference surface module lifting system 3, and the entire module is driven by the ball screw 34 to move in the up and down directions through the rotation of the stepping motor.

[0050] The resin tank 4 is made of highly transparent material and is a rectangular structure with an open top. The bottom surface of the resin tank 4 is a square. The size of the resin tank is determined by the actual molding size of the equipment. The resin tank is a movable part and can be removed from the bottom plate 71 of the main frame 7 for cleaning or replacement.

[0051] The molding platform 5 is a resin curing molding platform, which is a flat plate structure made of metal aluminum with a thickness of 3 mm. Circular holes with a diameter of 4.5 mm are evenly distributed on it. The upper surface of the platform is completely flat, and the edges of the holes and the edges of the platform on the lower surface are rounded to prevent the generation of bubbles during the lifting and lowering of the platform.

[0052] The molding platform lifting system 6 includes an upper structure 61, an optical axis 62, a linear bearing I63, a screw 64, a screw nut 65, a support rod 66, a stepping motor, a synchronous belt and a synchronous wheel. The molding platform 5 is connected to the upper structure 61 by four equal-length support rods 66. The upper structure 61 is a square ring structure, and the size of the middle square is slightly larger than the bottom size of the resin tank 4; the linear bearing I63 and the screw nut 65 are symmetrically installed at the four corners of the upper structure 61, and the optical axis 62 passes through the linear bearing I63 and is fixed on the upper and lower end surfaces of the main frame 7. The screw 64 passes through the screw nut 65, and the lower end is connected to the stepping motor through a synchronous belt and a synchronous wheel. The entire lifting system is driven by the screw 64 to move in the up and down directions through the rotation of the stepping motor.

[0053] The control system includes a main control board, a stepper motor controller and various sensors. The main control board is a hardware platform composed of a single-chip microcomputer system with a high-performance microprocessor, which can simultaneously process and output control parameters and the working conditions of various components. The main control board has a port for outputting high-resolution image signals for the signal output of the laser projection module, and at the same time performs real-time control of the automatic focusing device of the rear lens group of the laser projection module; the stepper motor controller controls the stepper motors of each part through the signal of the main control board, so that the entire device can operate in coordination; various sensors are installed in each module, detect each module, and transmit signals to the main control board.

[0054] Four laser beams of a specific wavelength are injected into the liquid resin from the four vertical faces of the square transparent resin tank 4 parallel to the bottom of the resin tank 4, and the four laser beams completely overlap on one surface, so that a plane of light irradiated by the laser beam of a specific wavelength is formed inside the liquid resin (such as Figure 1 As shown), it is called the light reference plane 8. At the same time, assuming that the unit light intensity of a single beam of the four laser beams on this light reference plane is Lp, then Lp must be lower than 1 / 4L, that is, the unit light intensity of each point on the light reference plane 8 is lower than L (Lp is as close to 1 / 4L as possible on the premise that no curing reaction will occur at any point within the range of the light reference plane 8), so at this time, no photosensitive resin will undergo a curing reaction only on the light reference plane 8. In addition, above the photosensitive resin, there is a laser light source 21 with the same wavelength as the four laser beams, and a pattern of light of this wavelength is irradiated from top to bottom through the laser projection module 1 perpendicular to the horizontal light reference plane 8 into the interior of the photocurable resin in the resin tank 4 (as shown in FIG. 1 ). Figure 2 As shown), it is called molding projection 9. Assuming the unit light intensity of the molding projection 9 light beam is Lt, Lt needs to be lower than L, that is, only under the irradiation of the molding projection 9 light beam, no curing reaction will occur at any point in the liquid photosensitive resin (Lt is as close to L as possible under the premise that no curing reaction will occur at any point within the irradiation range of the molding projection light beam).

[0055] When two laser light sources work simultaneously, the beam of the formed projection 9 will intersect with the light reference plane 8. The intersecting area is called the curing area 10 (such as Figure 3 As shown, the cross section of this area is a cross section of the figure projected by the molding projection 9 light beam, and the height is the height of the light reference plane 8. At this time, because the unit light intensity Lt and 4*Lp of the two groups of light sources are lower than L but very close to L, the unit light intensity of the curing area 10 in the overlapping part will be higher than L (i.e.: Lt+4*Lp>L). Because the unit light intensity of the photosensitive resin in this part reaches the unit light intensity required for the curing of the photosensitive resin, a curing reaction will occur and the photosensitive resin will be cured into a solid. When the molding projection laser light source continues to project a dynamically changing figure composed of the bottom-up cross sections of the desired molding object, and the light reference plane moves from bottom to top at the same rate, the curing area 10 will gradually move from bottom to top inside the liquid photosensitive resin to cure the photosensitive resin, and finally form the actual object to be obtained.

[0056] The working principle of the present invention is:

[0057] A light reference plane 8 of a specific wavelength is formed inside the photosensitive resin by laser irradiation. The unit light intensity of this light reference plane 8 is lower than the unit light intensity required for curing the photosensitive resin, and the unit light intensity of the shaping projection 9 light beam irradiated by the laser projection module 1 is also lower than the unit light intensity required for curing the photosensitive resin. However, when the shaping projection 9 light beam intersects with the light reference plane 8, the unit light intensity of the curing area 10 of the intersecting part is higher than the unit light intensity required for curing the photosensitive resin. At this time, the photosensitive resin in this part will undergo a polymerization reaction and thus be cured.

[0058] A molding method for an internal stereoscopic light projection curing molding 3D printing device comprises the following steps:

[0059] The model 0 to be printed is cross-cut from bottom to top (the total number of cross-cut layers is the same as the total number of frames of the animation projected by the molding projection), so that the light reference plane 8 moves at a constant speed from the bottom to the top from the bottom of the photosensitive resin tank. At the same time, the molding projection 9 light beam projects the animation generated by the screenshot after the cross-section of the model 0 into the photosensitive resin, and the laser projection module 1 will adjust the focus of the molding projection 9 light beam on the light reference plane in real time. At this time, the part where the molding projection 9 light beam intersects with the light reference plane 8 is the curing area 10, which is a cross section of the model 0 to be formed. The unit light intensity of this curing area is higher than the minimum unit light intensity required for the curing of the photosensitive resin, and the photosensitive resin in the curing area 10 is cured, thereby forming a cross section of the molded model 0. By making the light reference plane and the laser projection module work simultaneously, the required printed model 0 can be continuously generated from bottom to top (such as Figure 4 shown).

[0060] The operation process of the device of the present invention is as follows: before the device starts working, the position of each module (such as Fig.13 As shown), the model 0 to be printed is sliced ​​on the computer side using special software, and then the generated print file is input into the device control system. Then, under the control of the control system, the molding platform 5 descends to the bottom of the resin tank 4, and then the laser light source 21 of the optical reference surface module 2 is turned on to form an optical reference surface 8 on the molding platform 5. Then, the laser projection module 1 projects the molding projection 9 light beam onto the optical reference surface 8 to form a curing area 10. The molding work begins, and the optical reference surface module 2 rises upward. At the same time, the laser projection module 1 continuously irradiates the molding projection 9 light beam generated by the animation in the print file. After the molding work is completed, the laser light source 21 of the optical reference surface module is turned off, and the optical reference surface module 2 descends back to the initial position. At the same time, the laser projection module 1 is turned off, and then the molding platform 5 rises to take out the molded model 0.

[0061] The present invention brings the performance of existing 3D printing equipment to its limit. The molding speed will not be limited by the equipment, but will depend entirely on the performance of the photosensitive resin consumables. The curing reaction speed of the current photosensitive resin can reach within 0.6 seconds, that is, the potential of the photosensitive resin photocuring molding technology is very large. The present invention can make the molding speed completely depend on the performance of the photosensitive resin. If the molding speed of the photosensitive resin in the curing zone reaches the fastest molding speed that the photosensitive resin can reach, then the entire molding time will be greatly shortened, and the Z-axis molding speed will be able to exceed 6000mm / h.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An internal stereoscopic light projection curing 3D printing device, characterized in that: It mainly includes a laser projection module, an optical reference surface module, an optical reference surface module lifting system, a resin tank, a molding platform, a molding platform lifting system, a control system, a power supply system and a main frame. The main frame is the base of the entire device, and other components are installed on the main frame; The laser projection module is fixed on the top of the main frame, provides a shaped projection beam for the entire device, and projects the beam into the resin tank; The optical reference plane module lifting system is installed inside the main frame, with an optical reference plane module mounting plate in the middle, on which the optical reference plane module is mounted, a square through hole is opened in the middle of the optical reference plane module mounting plate, and the resin tank is installed on the bottom plate of the main frame through the hole; The molding platform lifting system is installed on the upper and lower end surfaces of the main frame, and the molding platform is suspended in the resin tank through the support rods; The power supply system is a power supply with sufficient power to provide accurate voltage output for all modules; The control system is connected with each module to control the coordinated operation of each module; The laser projection module mainly uses a light-emitting semiconductor that can emit lasers of a specific wavelength as a light source. After being refracted by the front-stage lens, the light is irradiated onto the DMD chip. After being processed by the DMD chip, the refracted light is irradiated onto the rear-stage refracting lens. The rear-stage lens has an automatic focusing system that can focus the image in real time according to the operation of the machine. The refracted light is the formed projection beam, which is reflected by the reflector and vertically enters the resin tank. The DMD chip is part of the DLP technology of Texas Instruments in the United States. The optical reference plane module includes a laser light source, a laser refractive lens group, a laser filter plate and a mounting plate. The laser light source is four light-emitting semiconductor lasers that can emit light of a specific wavelength, which are placed opposite to each other in pairs, with the lasers between the two groups at 90 degrees, and the four lasers are in the same plane and fixed on the mounting plate; The laser refractive lens group is installed at the front side of the laser light source and at the rear side of the laser filter plate; a laser filter plate is provided with a laser filter. After the laser light source emits light, it is refracted by the laser refractive lens group and then irradiated onto the sawtooth-shaped refractive lens, refracting the incident light into a straight line of light and irradiating it. The excess light is filtered by the laser filter and blocked, and finally a straight line of thin laser with a width of 0.5 to 0.1 mm is formed. The four laser beams completely overlap on the same plane, forming a laser irradiated plane, which is the light reference plane. The optical reference surface module lifting system includes an optical axis guide rail, a linear bearing, a ball screw, a ball bearing, a stepper motor, a synchronous belt, a synchronous wheel and an optical reference surface module mounting plate. The linear bearing and the ball bearing are respectively fixed on the four sides of the optical reference surface module mounting plate through mounting seats. The optical axis guide rail passes through the linear bearing and is fixed on the upper and lower end surfaces of the main frame. The ball screw passes through the ball bearing, and the lower end is connected to the stepper motor through the synchronous belt and the synchronous wheel. The optical reference surface module is installed on the optical reference surface module lifting system as a whole, and the entire module is driven by the ball screw to move in the up and down directions through the rotation of the stepper motor; The molding platform is a resin curing molding platform, which is a flat plate structure made of metal aluminum with a thickness of 3 mm, and circular holes with a diameter of 4.5 mm are evenly distributed on it. The upper surface of the platform is completely flat, and the edges of the holes and the edges of the platform on the lower surface are rounded to prevent the generation of bubbles during the lifting and lowering of the platform; The molding platform lifting system includes an upper structure, an optical axis, a linear bearing I, a lead screw, a lead screw nut, a support rod, a stepping motor, a synchronous belt and a synchronous wheel. The molding platform is connected to the upper structure by four support rods of equal length. The upper structure is a square ring structure, and the size of the middle square is slightly larger than the size of the bottom surface of the resin tank. The linear bearing I and the lead screw nut are symmetrically installed at the four corners of the upper structure. The optical axis passes through the linear bearing I and is fixed on the upper and lower end surfaces of the main frame. The lead screw passes through the lead screw nut, and the lower end is connected to the stepper motor through a synchronous belt and a synchronous wheel. The entire lifting system is driven by the lead screw to move up and down through the rotation of the stepper motor.

2. The internal stereoscopic light projection curing 3D printing device according to claim 1, characterized in that: The resin tank is made of highly transparent material and is a rectangular structure with an open top. The bottom of the resin tank is a square. The size of the resin tank is determined by the actual molding size of the equipment. The resin tank is a movable part and can be removed from the bottom plate of the main frame for cleaning or replacement.

3. The internal stereoscopic light projection curing 3D printing device according to claim 1, characterized in that: The control system includes a main control board, a stepper motor controller and various sensors. The main control board is a hardware platform composed of a single-chip microcomputer system with a high-performance microprocessor, which can simultaneously process and output various control parameters and the working conditions of various components. The main control board has a port for outputting high-resolution image signals for the signal output of the laser projection module, and at the same time, it performs real-time control on the automatic focusing device of the rear lens group of the laser projection module. The stepper motor controller controls the stepper motors of each part through the signal of the main control board, so that the whole device can operate in coordination; Various sensors are installed in each module to detect each module and transmit signals to the main control board.

4. A molding method for an internal stereoscopic light projection curing molding 3D printing device, characterized in that: The following steps are involved: (1) Model cross-cutting: The model to be printed is cross-cut on the computer using dedicated software, and the generated print file is then input into the device control system. The total number of cross-cut layers is the same as the total number of frames of the animation projected by the molding projection; (2) Forming an optical reference plane: Turn on the laser light source of the optical reference plane module, and form four straight laser beams of a specific wavelength, which are shot into the liquid resin from the four vertical faces of the square transparent resin tank parallel to the bottom of the resin tank. At the same time, the four straight laser beams completely overlap on one surface, thus forming a plane of light irradiated by the laser beam of the specific wavelength inside the liquid resin, which is called the optical reference plane; (3) forming a molding projection: a laser projection module emits light of the same wavelength as the four laser beams in step 2) to irradiate the cross-cutting pattern obtained in step 1) perpendicularly to the light reference plane from top to bottom into the light-curing resin in the resin tank, which is called molding projection; (4) forming a curing zone: the two light sources work simultaneously, and the projection beam formed in step 2) intersects with the light reference plane in step 1). The intersecting area is called the curing zone. The cross section of this area is a cross section of the figure projected by the projection beam, and the height is the height of the light reference plane. The photosensitive resin in the curing zone undergoes a curing reaction and solidifies into a solid because the unit light intensity reaches the unit light intensity required for curing the photosensitive resin. (5) Printing: When the laser light source of the laser projection module continuously projects a dynamically changing graphic consisting of the bottom-up cross-sections of the desired molded object, and the light reference plane moves from bottom to top at the same rate, the curing zone will gradually move from bottom to top inside the liquid photosensitive resin, thereby curing the photosensitive resin and ultimately forming the actual object to be obtained.

5. A molding method for internal stereoscopic light projection curing molding 3D printing equipment according to claim 4, characterized in that: Suppose the unit light intensity of a light of a specific wavelength required for curing a photosensitive resin is L, and the unit light intensity of a single beam of the four laser beams on the light reference plane is Lp, then Lp must be lower than 1 / 4L, that is, the unit light intensity at each point on the light reference plane is lower than L, and Lp is as close to 1 / 4L as possible on the premise that no curing reaction will occur at any point within the light reference plane, so at this time, no photosensitive resin will undergo curing reaction on the light reference plane; Assuming that the unit light intensity of the molding projection beam is Lt, then Lt needs to be lower than L, that is, only under the irradiation of the molding projection beam, no curing reaction will occur at any point in the liquid photosensitive resin, and Lt should be as close to L as possible under the premise that no curing reaction will occur at any point within the irradiation range of the molding projection beam; When the formed projection beam intersects the light reference plane, the unit light intensity Lt and 4*Lp of the two light sources are lower than L but very close to L, so the unit light intensity of the overlapping curing area will be higher than L, that is: Lt+4*Lp>L.

Images