Extrusion and projection composite 3D printing method and device

Abstract

The application discloses a kind of extrusion and projection composite 3D printing method and device.The application is first segmented to composite printing model, obtains photocuring model and extrusion model;Then, according to photocuring model and extrusion model, 3D printing path is planned, and 3D printing planning path is obtained;Finally, according to 3D printing planning path, photocuring printing and extrusion printing are alternately carried out until printing is completed, and extrusion and projection composite printing piece is obtained.The application can be printed by the printing mode of the combination of extrusion and photocuring, integrate the advantages of extrusion printing forming speed, printing method is more, material range is wide and the advantages of photocuring printing high resolution, large area rapid forming, so as to conveniently print multiple material complex structure.

Description

Technical Field

[0001] The present invention relates to a 3D printing method and device in the field of additive manufacturing technology, and specifically relates to a 3D printing method and device that combines extrusion and projection. Background Art

[0002] Additive manufacturing (AM), also known as 3D printing, is the process of building 3D objects by adding material layer by layer to form the desired 2D shape. Unlike traditional manufacturing processes such as milling and forming, AM offers flexibility and can build complex objects directly from digital models.

[0003] Common 3D printing technologies include fused deposition modeling (FDM), aerosol jet printing (AJP), direct ink writing (DIW), laminated object manufacturing (LOM), and digital light processing-based stereolithography (DLP).

[0004] In extrusion-based 3D printing, material is extruded directly from a nozzle using methods such as pneumatic extrusion or screw extrusion, depositing the resulting model. Extrusion printing is primarily used to construct macrostructures at the millimeter and micron scale. It offers advantages such as fast build speed, multiple printing methods, and a wide range of materials, allowing structures to be constructed anywhere in space.

[0005] DLP stereolithography 3D printing technology is based on a photocuring reaction. Photosensitive materials composed of monomers, low-molecular-weight compounds, or polymers undergo a cross-linking reaction and solidify when exposed to ultraviolet light. Through the selective exposure of layers of patterns, a 3D solid model can be constructed from two-dimensional flat patterns. DLP stereolithography offers higher resolution, enabling the construction of fine structures at the microscale and the adjustment of mechanical properties by designing patterns, grayscale intensity, and exposure time. It also enables rapid prototyping over large areas.

[0006] However, traditional 3D printing based on a single process has many limitations. Due to different mechanisms of action, each printing technology has its own limitations in the range of usable materials, precision, efficiency, etc. It is often difficult to overcome these limitations by improving hardware performance, printing parameters, materials, etc. without changing the printing method. Summary of the Invention

[0007] To address the problems and needs of the background art, the present invention provides a 3D printing method and apparatus that combines extrusion and projection. The present invention combines two different extrusion processes with a DLP light-curing process, wherein the DLP light-curing light-curing material constitutes the external structure, and the extruded material constitutes the internal structure. The two printing structures alternate in an orderly manner in the vertical direction, thereby printing a model with a complex internal structure. The present invention combines different printing processes, thereby combining various materials with different mechanical, chemical, or electrical properties, ultimately combining the advantages of each material.

[0008] In order to achieve the above object, the technical solution of the present invention is as follows:

[0009] 1. A 3D printing method combining extrusion and projection

[0010] Step 1: Segment the composite printed model to obtain a photocurable model and an extrusion model;

[0011] Step 2: Plan the 3D printing path based on the photocuring model and the extrusion model to obtain the 3D printing planning path;

[0012] Step 3: Alternately perform photocuring printing and extrusion printing according to the 3D printing planning path until printing is completed to obtain an extrusion and projection composite print.

[0013] The step 1 is specifically as follows:

[0014] The composite printing model includes at least one extruded filament segment, and each extruded filament segment is divided into a plane with a vertically symmetrical structure, which is marked as its central cross-section. If the two ends of an extruded filament segment are located on the same horizontal plane, the horizontal plane where the central cross-section of the extruded filament segment is located is used as a dividing plane, and the photocured area of ​​the extruded filament segment in the composite printing model is divided into upper and lower parts using this dividing plane.

[0015] If the two ends of an extruded filament segment are not located on the same horizontal plane and there is no overlapping area in the vertical projection of the extruded filament segment, the central cross-section of the extruded filament segment and the vertical projection plane together form a dividing plane to divide the light-cured area of ​​the extruded filament segment in the composite print model into upper and lower parts;

[0016] If there is an overlapping area in the vertical projection of an extruded filament segment and the corresponding parts of the overlapping area are arranged in a stacked manner, for the composite printing model in the non-overlapping area, the central cross-section of the extruded filament segment in the non-overlapping area and the vertical projection surface together form a dividing surface; for the composite printing model in the overlapping area, the central cross-section of the topmost extruded filament segment in the overlapping area and the vertical projection surface together form a dividing surface, thereby dividing the light-cured area of ​​the extruded filament segment in the composite printing model into upper and lower parts.

[0017] In step 3, the control direction of the light-curing printing is the vertical direction, and the control surface of the extrusion printing is the horizontal surface. The light-curing printing and the extrusion printing are controlled independently.

[0018] The extrusion printing includes one of direct ink writing extrusion printing (DIW), fused deposition modeling (FDM), and coaxial extrusion printing (Coaxial Extrusion).

[0019] 2. A 3D printing device combining extrusion and projection

[0020] A model segmentation unit is used to segment the composite printed model to obtain a light-cured model and an extruded model;

[0021] A 3D printing path planning unit is used to plan a 3D printing path based on the photocuring model and the extrusion model to obtain a 3D printing planning path;

[0022] The printing control unit is used to control the 3D composite printer according to the 3D printing planning path until an extruded and projected composite print is obtained.

[0023] The 3D composite printer includes an XY plane drive component, a Z-axis linear motion module, a printing platform, an ultraviolet light source, an extrusion needle print head and a light-curing pre-crosslinking tank; the printing platform is installed in the Z-axis linear motion module, the Z-axis linear motion module controls the printing platform to move up and down along the Z axis, and the ultraviolet light source is fixedly installed in the Z-axis linear motion module on the printing platform; the light-curing pre-crosslinking tank is placed below the printing platform; the XY plane drive component is installed on the side of the printing platform, the extrusion needle print head is installed in the XY plane drive component, and the XY plane drive component controls the extrusion needle print head to move on the XY plane.

[0024] The XY plane drive assembly includes a connected X-axis linear motion module, a Y-axis linear motion module and an auxiliary screw guide rail. The X-axis linear motion module and the auxiliary screw guide rail are arranged in parallel and at intervals. The two ends of the Y-axis linear motion module are respectively connected to the X-axis linear motion module and the auxiliary screw guide rail. The extruder needle print head is fixedly installed in the Y-axis linear motion module.

[0025] A photoelectric limiter is also installed in the Z-axis linear motion module.

[0026] Corresponding limit switches are installed in the X-axis linear motion module and the Y-axis linear motion module.

[0027] The beneficial effects of the present invention are:

[0028] The present invention combines DLP light-curing printing technology with different extrusion processes to achieve a unique extrusion / projection composite 3D printing process, which allows them to combine their respective advantages to rapidly manufacture complex structures with adjustable mechanical properties, from micron to meter level, cross-scale, multi-material, and high resolution; or it can efficiently achieve mixed printing of multiple biomaterials to form complex functional three-dimensional tissues, including tissues containing nutrient channels. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic structural diagram of the 3D composite printer of the present invention;

[0030] Figure 2 Schematic diagram of the process of alternating light-curing printing and extrusion printing in the present invention;

[0031] Figure 3 Schematic diagram of the printing model containing the two-dimensional extrusion part and its pre-segmentation processing in the present invention;

[0032] Figure 4 Schematic diagram of a printed model containing three-dimensional non-overlapping extrusion parts and its pre-segmentation processing in the present invention;

[0033] Figure 5 Schematic diagram of the printing model containing the three-dimensional overlapping extrusion part and its pre-segmentation processing in the present invention;

[0034] Figure 6 Flow chart of the method of the present invention.

[0035] Serial numbers in the figure: 1. Z-axis linear motion module; 2. Printing platform; 3. X-axis linear motion module; 4. UV light source; 5. Auxiliary screw guide; 6. Y-axis linear motion module; 7. Connecting plate; 8. Extrusion needle print head; 9. Light-curing pre-cross-linking tank. DETAILED DESCRIPTION

[0036] In order to make the purposes and advantages of the technology and equipment mentioned in the present invention clearer, the technology and equipment of the present invention are further described below in conjunction with embodiments and drawings.

[0037] Example 1

[0038] The present invention proposes a 3D printing method combining extrusion and projection, such as Figure 6 As shown, the method includes the following steps:

[0039] Step 1: Segment the composite printed model to obtain a photocurable model and an extrusion model;

[0040] Step 1 is as follows:

[0041] The composite printing model contains at least one extruded filament segment. Each extruded filament segment is divided into a plane with a vertically symmetrical structure and its central cross section is recorded. If the two ends of an extruded filament segment are located on the same horizontal plane, that is, the extruded filament segment is a two-dimensional filament, the horizontal plane where the central cross section of the extruded filament segment is located is used as the dividing plane, and the photocuring area of ​​the extruded filament segment in the composite printing model is divided into upper and lower parts by using the dividing plane. Figure 3 As shown in (a), each extruded filament segment is located on its own single XY two-dimensional plane. Due to the characteristic of stereolithography printing starting from the bottom layer, and in order to assist in positioning the falling filament, when the stereolithography printing reaches the layer covered by the filament, it will continue to print to the layer height of the filament centerline, that is, print a groove with a cross-section of the lower semicircle. Therefore, when the entire model containing only two-dimensional filaments is divided into the stereolithography part and the extruded part, it is performed based on the XY plane where the centerline of each extruded filament segment is located, as shown in the figure. Figure 3 As shown in (b).

[0042] If the two ends of an extruded filament segment are not located on the same horizontal plane (i.e., the extruded filament segment is a three-dimensional filament) and there is no overlapping area in the vertical projection of the extruded filament segment, the central cross-section of the extruded filament segment and the vertical projection plane together form a dividing plane to divide the light-cured area of ​​the extruded filament segment in the composite print model into upper and lower parts, such as Figure 4 (a) and Figure 4 as shown in (b);

[0043] If the two ends of an extruded filament segment are not located on the same horizontal plane (i.e., the extruded filament segment is a three-dimensional filament), and there is an overlapping area in the vertical projection of the extruded filament segment, and the corresponding parts of the overlapping area are stacked (i.e., there is no gap between the adjacent upper and lower layers), for the composite printing model in the non-overlapping area, the central cross-section of the extruded filament segment in the non-overlapping area and the vertical projection surface together form a dividing surface. For the composite printing model in the overlapping area, the central cross-section of the topmost extruded filament segment in the overlapping area and the vertical projection surface together form a dividing surface, thereby dividing the light-cured area of ​​the extruded filament segment in the composite printing model into upper and lower parts, as shown in FIG. Figure 5 (a) and Figure 5As shown in (b). For the case where there is an overlapping area in the projection of the Z-axis of the extrusion model, the present invention is only applicable to the case where there is no gap between the two adjacent upper and lower extrusion parts. This is due to the following three reasons: first, the extruded filaments are extruded from top to bottom to the specified position; second, the extruded filaments are tough and soft in physical properties, and after extrusion, they need to be positioned and supported by the grooves formed by the photocuring below; third, if the ultraviolet light projected by the upper projection light source is blocked by the extruded filaments, it will have a certain impact on the photocuring effect of the material below. After meeting the above conditions, when a printable model with overlapping three-dimensional extrusion parts is divided into two printed parts, the overall principle is similar to the division of a model containing only two-dimensional filaments, but an additional principle needs to be met during the division, that is, the two parts of the photocuring model adjacent to the filament segment are divided in the XY plane where the center line of the filament segment with the highest height can be seen in the top view of this filament segment is located.

[0044] Step 2: Plan the 3D printing path based on the photocuring model and the extrusion model to obtain the 3D printing planning path; that is, process the model into two-dimensional slices for photocuring and G code for controlling the XYZ three-axis motor.

[0045] Step 3: Alternate between photocuring and extrusion printing according to the planned 3D printing path until printing is complete, resulting in a composite extrusion and projection print. The photocuring material generally forms the exterior structure of the print, while the extrusion material generally forms the interior structure. Therefore, the present invention can achieve high-precision structures with complex internal structures, and these structures can be rapidly formed.

[0046] In step 3, the control direction of the light-curing printing is the vertical direction, and the control surface of the extrusion printing is the horizontal surface. The light-curing printing and the extrusion printing are controlled independently.

[0047] The present invention also proposes a 3D printing device combining extrusion and projection, comprising:

[0048] A model segmentation unit is used to segment the composite printed model to obtain a light-cured model and an extruded model;

[0049] A 3D printing path planning unit is used to plan a 3D printing path based on the photocuring model and the extrusion model to obtain a 3D printing planning path;

[0050] The printing control unit is used to control the 3D composite printer according to the 3D printing planning path until an extruded and projected composite print is obtained.

[0051] like Figure 1As shown, the 3D hybrid printer includes an XY plane drive assembly, a Z-axis linear motion module 1, a printing platform 2, a UV light source 4, an extruder print head 8, and a photocuring pre-crosslinking tank 9. The printing platform 2 is mounted within the Z-axis linear motion module 1 to ensure high precision on each XY plane. The Z-axis linear motion module 1 controls the vertical movement of the printing platform 2 along the Z axis. The UV light source 4 is fixedly mounted within the Z-axis linear motion module 1 on the printing platform 2 at a fixed height. The UV light source 4 emits light parallel to the Z axis, meaning that the photocuring printing method is top-down projection. The photocuring pre-crosslinking tank 9 is positioned below the printing platform 2. The XY plane drive assembly is mounted to the side of the printing platform 2. The extruder print head 8 is mounted within the XY plane drive assembly via a connecting plate 7. The XY plane drive assembly controls the movement of the extruder print head 8 along the XY plane, resulting in a printing mode in which the printing platform remains stationary while the print head moves along the XY plane. Since the Z-axis linear motion module 1 allows the printing platform 2 to move in the opposite direction relative to the needle on the Z axis, it can achieve the effect of positive Z-axis motion with the needle, thereby achieving the printing requirements of different heights of the extruded filament on the Z axis. In this embodiment, the XY plane is the horizontal plane and the Z axis is the vertical direction.

[0052] The XY plane drive assembly includes a connected X-axis linear motion module 3, a Y-axis linear motion module 6, and an auxiliary screw guide 5. The X-axis linear motion module 3 and the auxiliary screw guide 5 are arranged on both sides of the Z-axis linear motion module 1. The X-axis linear motion module 3 and the auxiliary screw guide 5 are arranged parallel and spaced apart. The ends of the Y-axis linear motion module 6 are respectively connected to the X-axis linear motion module 3 and the auxiliary screw guide 5. The extruder print head 8 is fixedly mounted in the Y-axis linear motion module 6 via a connecting plate 7. In this embodiment, the Z-axis linear motion module 1, the X-axis linear motion module 3, and the Y-axis linear motion module 6 are all modules composed of a stepper motor, a P-grade ball screw, a slider, and a guide rod mounting seat.

[0053] A photoelectric limiter is also installed in the Z-axis linear motion module 1 to limit the minimum position and serve as the home point, preventing the slider from exceeding the travel range and damaging the ball screw. Soft limiters are used below the Z-axis to limit the maximum position and prevent the print platform from moving downward beyond the trough forming range, squeezing the trough and damaging the lead screw.

[0054] Limit switches are installed in both the X-axis linear motion module 3 and the Y-axis linear motion module 6 to prevent them from colliding with the light-curing equipment. During installation, it is important to ensure that the X-axis linear motion module 3 and the Y-axis linear motion module 6 do not collide with the light machine from above or the light-curing tank and other external frames from below, while also minimizing the time it takes for the print platform to rise to the extrusion position each time.

[0055] The most important issue in achieving a hybrid 3D printing process is the interaction logic between photocuring and coaxial extrusion printing, as well as the corresponding printing timing. The basic logic is to use photocuring as the main body. According to the normal photocuring process, the platform is lowered to the height of the next curing layer below the surface of the prepolymer solution and cured. Then, the platform is lowered one layer at a time and the image of that layer is projected one by one. When the layer containing the coaxial extrusion part is reached, the platform is moved to a height above the liquid surface suitable for coaxial extrusion and the coaxial filament is extruded at the specified position. After extrusion is completed, the remaining part is cured by photocuring, and this process is repeated multiple times until the printing is complete.

[0056] However, due to differences in materials and processes, the layer thickness of photocuring printing is too different from the diameter of the filament printed by coaxial extrusion. Generally speaking, the diameter of the coaxial extrusion filament is several times the thickness of the photocuring layer. Therefore, in composite 3D printing, continuous multi-layer photocuring is required to match the diameter of the coaxial filament.

[0057] The following are the detailed steps:

[0058] 1) The extrusion printing module selects the fused deposition printing module, that is, the FDM print head and the connecting plate with the corresponding mounting holes are installed on the Y-axis linear motion module 6, and a stepper motor is installed for remote feeding.

[0059] 2) Lower the printing platform 2 to the focal length of the optical machine, that is, the curing plane, solidify a center cross, raise it to a position close to the nozzle of the print head, manually adjust the extrusion position so that the nozzle is aligned with the center of the cross, and use this coordinate to set the platform range in the slicing software to calibrate the center position to ensure that the extrusion center and the optical circularization center are in the same position.

[0060] 3) Create a digital model of the entire printed model, including the photocuring part and the extrusion part, and segment the model. The obtained data is linked to the control program on the computer.

[0061] 4) Add the UV photosensitive resin to be cured into the light-curing pre-crosslinking tank 9 until it reaches a predetermined liquid level, load the PCL filament into the FDM extrusion head, and preheat the FDM extrusion head.

[0062] 5) If Figure 2 As shown in (a), according to the printing model and printing plan, the computer controls the printing platform 2 to descend to a certain distance below the liquid surface in the Z-axis direction, and then lifts it upward to a height of one printing thickness below the liquid surface. Then the computer controls the ultraviolet light source 4 to project a predetermined slice shape on the liquid surface for curing.

[0063] 6) If Figure 2As shown in (b), after the photocuring of the previous layer is completed, the computer controls the printing plane 2 to continue to move down a printing thickness, and the liquid UV resin to be cured will slowly cover the printing plane 2. Then the computer controls the ultraviolet light source 4 to project a predetermined slice shape on the liquid surface for curing. After curing, this layer forms a whole with the previously cured layer.

[0064] 7) If Figure 2 As shown in (c), the light-curing printing is continued according to the established printing plan until the layer containing the extruded printing part is printed.

[0065] 8) If Figure 2 As shown in (d), when printing to the layer containing the extrusion printing part, the computer controls the printing platform 2 to move upward out of the liquid surface to a height suitable for FDM extrusion, and then the computer controls the X-axis linear motion module 3 and the Y-axis linear motion module 6 to move according to the predetermined printing plan of the part to be extruded, and at the same time drives the stepper motor for remote feeding, so that the FDM extrusion head 7 installed on the Y-axis linear motion module 6 extrude a predetermined pattern on the printing plane.

[0066] 9) If Figure 2 As shown in (e), after the extrusion of the previous layer is completed, the computer controls the X-axis linear motion module 3 and the Y-axis linear motion module 6 to return the FDM print head 8 to a safe berth, and then controls the printing platform 2 to descend below the liquid surface, so that the light-curing printing work plane of the next layer is located below the page at a height of one printing thickness from the liquid surface.

[0067] 10) If Figure 2 As shown in (f), repeat steps 6) to 9) until the entire object is printed.

[0068] In this embodiment, the printing of more complex functional structures can be achieved through the composite of multiple materials, such as 4D smart material printing, flexible electronic printing, etc.

[0069] Example 2

[0070] The present invention proposes a 3D printing method combining extrusion and projection, such as Figure 6 As shown, the method includes the following steps:

[0071] Step 1: Segment the composite printed model to obtain a photocurable model and an extrusion model;

[0072] Step 1 is as follows:

[0073] The composite printing model contains at least one extruded filament segment. Each extruded filament segment is divided into a plane with a vertically symmetrical structure and its central cross section is recorded. If the two ends of an extruded filament segment are located on the same horizontal plane, that is, the extruded filament segment is a two-dimensional filament, the horizontal plane where the central cross section of the extruded filament segment is located is used as the dividing plane, and the photocuring area of ​​the extruded filament segment in the composite printing model is divided into upper and lower parts by using the dividing plane. Figure 3 As shown in (a), each extruded filament segment is located on its own single XY two-dimensional plane. Due to the characteristic of stereolithography printing starting from the bottom layer, and in order to assist in positioning the falling filament, when the stereolithography printing reaches the layer covered by the filament, it will continue to print to the layer height of the filament centerline, that is, print a groove with a cross-section of the lower semicircle. Therefore, when the entire model containing only two-dimensional filaments is divided into the stereolithography part and the extruded part, it is performed based on the XY plane where the centerline of each extruded filament segment is located, as shown in the figure. Figure 3 As shown in (b).

[0074] If the two ends of an extruded filament segment are not located on the same horizontal plane (i.e., the extruded filament segment is a three-dimensional filament) and there is no overlapping area in the vertical projection of the extruded filament segment, the central cross-section of the extruded filament segment and the vertical projection plane together form a dividing plane to divide the light-cured area of ​​the extruded filament segment in the composite print model into upper and lower parts, such as Figure 4 (a) and Figure 4 as shown in (b);

[0075] If the two ends of an extruded filament segment are not located on the same horizontal plane (i.e., the extruded filament segment is a three-dimensional filament), and there is an overlapping area in the vertical projection of the extruded filament segment, and the corresponding parts of the overlapping area are stacked (i.e., there is no gap between the adjacent upper and lower layers), for the composite printing model in the non-overlapping area, the central cross-section of the extruded filament segment in the non-overlapping area and the vertical projection surface together form a dividing surface. For the composite printing model in the overlapping area, the central cross-section of the topmost extruded filament segment in the overlapping area and the vertical projection surface together form a dividing surface, thereby dividing the light-cured area of ​​the extruded filament segment in the composite printing model into upper and lower parts, as shown in FIG. Figure 5 (a) and Figure 5As shown in (b). For the case where there is an overlapping area in the projection of the Z-axis of the extrusion model, the present invention is only applicable to the case where there is no gap between the two adjacent upper and lower extrusion parts. This is due to the following three reasons: first, the extruded filaments are extruded from top to bottom to the specified position; second, the extruded filaments are tough and soft in physical properties, and after extrusion, they need to be positioned and supported by the grooves formed by the photocuring below; third, if the ultraviolet light projected by the upper projection light source is blocked by the extruded filaments, it will have a certain impact on the photocuring effect of the material below. After meeting the above conditions, when a printable model with overlapping three-dimensional extrusion parts is divided into two printed parts, the overall principle is similar to the division of a model containing only two-dimensional filaments, but an additional principle needs to be met during the division, that is, the two parts of the photocuring model adjacent to the filament segment are divided in the XY plane where the center line of the filament segment with the highest height can be seen in the top view of this filament segment is located.

[0076] Step 2: Plan the 3D printing path based on the photocuring model and the extrusion model to obtain the 3D printing planning path; that is, process the model into two-dimensional slices for photocuring and G code for controlling the XYZ three-axis motor.

[0077] Step 3: Alternate between photocuring and extrusion printing according to the planned 3D printing path until printing is complete, resulting in a composite extrusion and projection print. The photocuring material generally forms the exterior structure of the print, while the extrusion material generally forms the interior structure. Therefore, the present invention can achieve high-precision structures with complex internal structures, and these structures can be rapidly formed.

[0078] In step 3, the control direction of the light-curing printing is the vertical direction, and the control surface of the extrusion printing is the horizontal surface. The light-curing printing and the extrusion printing are controlled independently.

[0079] The present invention also proposes a 3D printing device combining extrusion and projection, comprising:

[0080] A model segmentation unit is used to segment the composite printed model to obtain a light-cured model and an extruded model;

[0081] A 3D printing path planning unit is used to plan a 3D printing path based on the photocuring model and the extrusion model to obtain a 3D printing planning path;

[0082] The printing control unit is used to control the 3D composite printer according to the 3D printing planning path until an extruded and projected composite print is obtained.

[0083] like Figure 1As shown, the 3D hybrid printer includes an XY plane drive assembly, a Z-axis linear motion module 1, a printing platform 2, a UV light source 4, an extruder print head 8, and a photocuring pre-crosslinking tank 9. The printing platform 2 is mounted within the Z-axis linear motion module 1 to ensure high precision on each XY plane. The Z-axis linear motion module 1 controls the vertical movement of the printing platform 2 along the Z axis. The UV light source 4 is fixedly mounted within the Z-axis linear motion module 1 on the printing platform 2 at a fixed height. The UV light source 4 emits light parallel to the Z axis, meaning that the photocuring printing method is top-down projection. The photocuring pre-crosslinking tank 9 is positioned below the printing platform 2. The XY plane drive assembly is mounted to the side of the printing platform 2. The extruder print head 8 is mounted within the XY plane drive assembly via a connecting plate 7. The XY plane drive assembly controls the movement of the extruder print head 8 along the XY plane, resulting in a printing mode in which the printing platform remains stationary while the print head moves along the XY plane. Since the Z-axis linear motion module 1 allows the printing platform 2 to move in the opposite direction relative to the needle on the Z axis, it can achieve the effect of positive Z-axis motion with the needle, thereby achieving the printing requirements of different heights of the extruded filament on the Z axis. In this embodiment, the XY plane is the horizontal plane and the Z axis is the vertical direction.

[0084] The XY plane drive assembly includes a connected X-axis linear motion module 3, a Y-axis linear motion module 6, and an auxiliary screw guide 5. The X-axis linear motion module 3 and the auxiliary screw guide 5 are arranged on both sides of the Z-axis linear motion module 1. The X-axis linear motion module 3 and the auxiliary screw guide 5 are arranged parallel and spaced apart. The ends of the Y-axis linear motion module 6 are respectively connected to the X-axis linear motion module 3 and the auxiliary screw guide 5. The extruder print head 8 is fixedly mounted in the Y-axis linear motion module 6 via a connecting plate 7. In this embodiment, the Z-axis linear motion module 1, the X-axis linear motion module 3, and the Y-axis linear motion module 6 are all modules composed of a stepper motor, a P-grade ball screw, a slider, and a guide rod mounting seat.

[0085] A photoelectric limiter is also installed in the Z-axis linear motion module 1 to limit the minimum position and serve as the home point, preventing the slider from exceeding the travel range and damaging the ball screw. Soft limiters are used below the Z-axis to limit the maximum position and prevent the print platform from moving downward beyond the trough forming range, squeezing the trough and damaging the lead screw.

[0086] Limit switches are installed in both the X-axis linear motion module 3 and the Y-axis linear motion module 6 to prevent them from colliding with the light-curing equipment. During installation, it is important to ensure that the X-axis linear motion module 3 and the Y-axis linear motion module 6 do not collide with the light machine from above or the light-curing tank and other external frames from below, while also minimizing the time it takes for the print platform to rise to the extrusion position each time.

[0087] The most important issue in achieving a hybrid 3D printing process is the interaction logic between photocuring and coaxial extrusion printing, as well as the corresponding printing timing. The basic logic is to use photocuring as the main body. According to the normal photocuring process, the platform is lowered to the height of the next curing layer below the surface of the prepolymer solution and cured. Then, the platform is lowered one layer at a time and the image of that layer is projected one by one. When the layer containing the coaxial extrusion part is reached, the platform is moved to a height above the liquid surface suitable for coaxial extrusion and the coaxial filament is extruded at the specified position. After extrusion is completed, the remaining part is cured by photocuring, and this process is repeated multiple times until the printing is complete.

[0088] However, due to differences in materials and processes, the layer thickness of photocuring printing is too different from the diameter of the filament printed by coaxial extrusion. Generally speaking, the diameter of the coaxial extrusion filament is several times the thickness of the photocuring layer. Therefore, in composite 3D printing, continuous multi-layer photocuring is required to match the diameter of the coaxial filament.

[0089] The following are the detailed steps:

[0090] 1) Extrusion printing module: A coaxial extrusion printing module is selected, that is, a coaxial extrusion printing head 8 and a connecting plate 7 with corresponding mounting holes are installed on the Y-axis linear motion module 6, and two-channel syringe pumps are used to control the two cross-linking solutions of the inner and outer needles respectively.

[0091] 2) Lower the printing platform 2 to the focal length of the optical machine, that is, the curing plane, solidify a center cross, and raise it to a position close to the needle 8. Manually adjust the extrusion position so that the needle is aligned with the center of the cross. Use this coordinate to set the platform range in the slicing software to calibrate the center position to ensure that the extrusion center and the optical circularization center are in the same position.

[0092] 3) Create a digital model of the entire printed model, including the photocuring part and the extrusion part, and segment the model. The obtained data is linked to the control program on the computer.

[0093] 4) Add the PEGDA solution to be cured into the light-curing pre-crosslinking tank 9 until the predetermined liquid level is reached, prepare a calcium chloride solution of a certain concentration as the solution to be crosslinked for injection into the inner needle of the coaxial extrusion head 8, and prepare a sodium alginate solution of a certain concentration as the solution to be crosslinked for injection into the outer needle of the coaxial extrusion head 8.

[0094] 5) If Figure 2 As shown in (a), according to the printing model and printing plan, the computer controls the printing platform 2 to descend to a certain distance below the liquid surface in the Z-axis direction, and then lifts it upward to a height of one printing thickness below the liquid surface. Then the computer controls the ultraviolet light source 4 to project a predetermined slice shape on the liquid surface for curing.

[0095] 6) If Figure 2 As shown in (b), after the photocuring of the previous layer is completed, the computer controls the printing plane 2 to continue to move down a printing thickness, and the PEGDA solution to be cured will slowly cover the printing plane 2. Then the computer controls the ultraviolet light source 4 to project a predetermined slice shape on the liquid surface for curing. After curing, this layer forms a whole with the previously cured layer.

[0096] 7) If Figure 2 As shown in (c), the light-curing printing is continued according to the established printing plan until the layer containing the extruded printing part is printed.

[0097] 8) If Figure 2 As shown in (d), when printing to the layer containing the extruded print part, the computer controls the printing platform 2 to move upward out of the liquid surface to a height suitable for coaxial extrusion, sets the flow rate of the two cross-linking solutions of the inner and outer needles on the injection pump respectively, and starts the injection. Then the computer controls the X-axis linear motion module 3 and the Y-axis linear motion module 6 to move according to the predetermined printing plan of the part to be extruded, so that the coaxial extrusion head 8 installed on the Y-axis linear motion module 6 extrude a predetermined pattern on the printing plane. After the extrusion of this layer is completed, the injection pump is controlled to stop working.

[0098] 9) If Figure 2 As shown in (e), after the extrusion of the previous layer is completed, the computer controls the X-axis linear motion module 3 and the Y-axis linear motion module 6 to return the coaxial extrusion needle 8 to a safe berth, and then controls the printing platform 2 to descend below the liquid surface, so that the light-curing printing work plane of the next layer is located below the page at a height of one printing thickness from the liquid surface.

[0099] 10) If Figure 2 As shown in (f), repeat steps 6) to 9) until the entire object is printed.

[0100] In this embodiment, the printing of an in vitro tissue model containing nutrient channels with a specific complex structure is achieved.

[0101] The present invention combines DLP light-curing printing technology with multiple extrusion processes to achieve a unique extrusion / projection composite 3D printing process. By combining the respective advantages of projection and extrusion printing processes, it can achieve the rapid manufacturing of complex structures with adjustable mechanical properties, from micron to meter level, cross-scale, multi-material, and high resolution; or it can efficiently realize the mixed printing of multiple biomaterials to form complex functional three-dimensional tissues including tissues containing nutrient channels.

[0102] Finally, it should be noted that the above embodiments and explanations are intended only to illustrate the technical solutions of the present invention and are not intended to limit the present invention. It should be understood by those skilled in the art that modifications or equivalent substitutions to the technical solutions of the present invention may be made without departing from the spirit and scope of the technical solutions disclosed herein, and all such modifications or equivalent substitutions shall be encompassed within the scope of protection of the claims of the present invention.

Claims

1. A 3D printing method combining extrusion and projection, characterized in that: The following steps are involved: Step 1: Segment the composite printed model to obtain a photocurable model and an extrusion model; The step 1 is specifically as follows: The composite printing model includes at least one extruded filament segment, and each extruded filament segment is divided into a plane with a vertically symmetrical structure, which is marked as its central cross-section. If the two ends of an extruded filament segment are located on the same horizontal plane, the horizontal plane where the central cross-section of the extruded filament segment is located is used as a dividing plane, and the photocured area of ​​the extruded filament segment in the composite printing model is divided into upper and lower parts using this dividing plane. If the two ends of an extruded filament segment are not located on the same horizontal plane and there is no overlapping area in the vertical projection of the extruded filament segment, the central cross-section of the extruded filament segment and the vertical projection plane together form a dividing plane to divide the light-cured area of ​​the extruded filament segment in the composite print model into upper and lower parts; If there is an overlapping area in the vertical projection of an extruded filament segment and the corresponding parts of the overlapping area are arranged in a stacked manner, for the composite printing model in the non-overlapping area, the central cross-section of the extruded filament segment in the non-overlapping area and the vertical projection plane together form a dividing plane. For the composite printing model in the overlapping area, the central cross-section of the topmost extruded filament segment in the overlapping area and the vertical projection plane together form a dividing plane, thereby dividing the light-cured area of ​​the extruded filament segment in the composite printing model into upper and lower parts; Step 2: Plan the 3D printing path based on the photocuring model and the extrusion model to obtain the 3D printing planning path; Step 3: Alternately perform photocuring printing and extrusion printing according to the 3D printing planning path until printing is completed to obtain an extrusion and projection composite print.

2. The 3D printing method of extrusion and projection composite according to claim 1, characterized in that: In step 3, the control direction of the light-curing printing is the vertical direction, and the control surface of the extrusion printing is the horizontal surface. The light-curing printing and the extrusion printing are controlled independently.

3. The 3D printing method of extrusion and projection composite according to claim 1, characterized in that: The extrusion printing includes one of ink direct writing extrusion printing, fused deposition extrusion printing, and coaxial extrusion printing.

4. A 3D printing device combining extrusion and projection for implementing the method of claim 1, characterized in that: include: A model segmentation unit is used to segment the composite printed model to obtain a light-cured model and an extruded model; A 3D printing path planning unit is used to plan a 3D printing path based on the photocuring model and the extrusion model to obtain a 3D printing planning path; The printing control unit is used to control the 3D composite printer according to the 3D printing planning path until an extruded and projected composite print is obtained.

5. The extrusion and projection composite 3D printing device according to claim 4, characterized in that: The 3D composite printer comprises an XY plane drive component, a Z-axis linear motion module (1), a printing platform (2), an ultraviolet light source (4), an extrusion needle print head (8) and a light-curing pre-crosslinking pool (9); the printing platform (2) is installed in the Z-axis linear motion module (1), the Z-axis linear motion module (1) controls the printing platform (2) to move up and down along the Z axis, and the ultraviolet light source (4) is fixedly installed in the Z-axis linear motion module (1) on the printing platform (2); The photocuring pre-crosslinking tank (9) is placed below the printing platform (2); an XY plane drive assembly is installed on the side of the printing platform (2), an extrusion needle print head (8) is installed in the XY plane drive assembly, and the XY plane drive assembly controls the extrusion needle print head (8) to move on the XY plane.

6. The extrusion and projection composite 3D printing device according to claim 5, characterized in that: The XY plane drive assembly comprises an X-axis linear motion module (3), a Y-axis linear motion module (6) and an auxiliary lead screw guide rail (5) connected to each other, the X-axis linear motion module (3) and the auxiliary lead screw guide rail (5) being arranged in parallel and spaced apart, the two ends of the Y-axis linear motion module (6) being respectively connected to the X-axis linear motion module (3) and the auxiliary lead screw guide rail (5), and the extruder needle print head (8) being fixedly mounted in the Y-axis linear motion module (6).

7. The extrusion and projection composite 3D printing device according to claim 5, characterized in that: A photoelectric limiter is also installed in the Z-axis linear motion module (1).

8. The extrusion and projection composite 3D printing device according to claim 6, characterized in that: Corresponding limit switches are installed in the X-axis linear motion module (3) and the Y-axis linear motion module (6).

Images