Extrusion and projection composite 3D printing method and device

Abstract

The invention discloses an extrusion and projection composite 3D printing method and device. The method comprises the following steps: firstly, segmenting a composite printing model to obtain a photocuring model and an extrusion model; then, a 3D printing path is planned according to the photocuring model and the extrusion model, and a 3D printing planned path is obtained; and finally, light curing printing and extrusion printing are alternately carried out according to the 3D printing planning path until printing is completed, and an extrusion and projection composite printing piece is obtained. According to the invention, the advantages of high extrusion printing forming speed, multiple printing methods and wide material range as well as the advantages of high resolution and large-area rapid forming of photocuring printing can be integrated in a printing mode of compounding extrusion and photocuring, so that a multi-material complex structure can be conveniently printed.

Description

Technical Field

[0001] The present invention belongs to the technical field of additive manufacturing and relates to a 3D printing method and device, and in particular to an extrusion and projection composite 3D printing method and device. 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. Additive manufacturing is flexible and can build complex objects directly from digital models, unlike traditional manufacturing processes such as milling and molding.

[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 (DLP).

[0004] In the extrusion-based 3D printing method, the material can be extruded directly from the nozzle by air pressure extrusion or screw extrusion and deposited as a model. The extrusion printing process is mostly used to construct millimeter and micron-scale macro structures. It has the advantages of fast molding speed, multiple printing methods, and a wide range of materials. Structures can be constructed at any position in space.

[0005] The basis of DLP photocuring 3D printing technology is photocuring reaction. Photosensitive materials composed of monomers, small molecular weight compounds or polymers will undergo cross-linking reaction and solidify when exposed to ultraviolet light. Through selective exposure of layers of patterns, a three-dimensional solid model can be superimposed from a two-dimensional plane pattern. DLP photocuring printing technology has higher resolution and can construct fine structures and adjust the mechanical properties of the structure on a microscopic scale by designing patterns, grayscale intensity and exposure time, and can project large areas for rapid prototyping.

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

[0007] In order to solve the problems and needs in the background technology, the present invention provides a 3D printing method and device that combines extrusion and projection. The present invention combines two different extrusion processes with DLP light-curing processes, wherein the light-curing material of DLP light-curing constitutes the external structure, and the extruded material constitutes the internal structure. The two printing structures are alternated in an orderly manner in the vertical direction, thereby printing out 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, and finally 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 photocuring model and an extrusion model;

[0011] Step 2: Plan the 3D printing path according to 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 the 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 wire segment, and each extruded wire segment is divided into a plane with a vertically symmetrical structure, and the plane is recorded as its central cross section. If two ends of an extruded wire segment are located on the same horizontal plane, the horizontal plane where the central cross section of the extruded wire segment is located is the dividing plane, and the light-cured area at the extruded wire segment in the composite printing model is divided into upper and lower parts by using the dividing plane;

[0015] If the two ends of an extruded filament segment are not located in the same horizontal plane and there is no overlapping area in the projection of the extruded filament segment in the vertical direction, 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 at the extruded filament segment in the composite printing model up and down;

[0016] If there is an overlapping area in the projection of an extruded wire segment in the vertical direction 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 wire segment in the non-overlapping area and the vertical projection surface together form a dividing surface, and for the composite printing model in the overlapping area, the central cross-section of the topmost extruded wire segment in the overlapping area and the vertical projection surface together form a dividing surface, thereby dividing the light-cured area at the extruded wire segment in the composite printing model into upper and lower parts.

[0017] In step 3, the control direction of the photocuring printing is the vertical direction, the control surface of the extrusion printing is the horizontal surface, and the photocuring 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, used for segmenting the composite printing model to obtain a light-curing model and an extrusion model;

[0021] A 3D printing path planning unit is used to plan a 3D printing path according to a photocuring model and an 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 comprises an XY plane driving 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 pool; 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 pool is placed below the printing platform; an XY plane driving component is installed on the side of the printing platform, an extrusion needle print head is installed in the XY plane driving component, and the XY plane driving 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 lead screw guide rail. The X-axis linear motion module and the auxiliary lead 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 lead 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 quickly manufacture complex structures with adjustable mechanical properties, from microns to meters, across scales, multiple materials, 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 It is a schematic diagram of the structure of the 3D composite printer of the present invention;

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

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

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

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

[0034] Figure 6 The figure is a 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 lead screw guide; 6. Y-axis linear motion module; 7. Connecting plate; 8. Extrusion needle print head; 9. Photocuring pre-cross-linking tank. DETAILED DESCRIPTION

[0036] In order to make the purposes, advantages, etc. 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 comprises the following steps:

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

[0040] Step 1 is as follows:

[0041] The composite printing model contains at least one extruded wire segment. Each extruded wire segment is divided into a plane with a vertically symmetrical structure and recorded as its central cross section. If the two ends of an extruded wire segment are located on the same horizontal plane, that is, the extruded wire segment is a two-dimensional filament, the horizontal plane where the central cross section of the extruded wire segment is located is the dividing plane, and the light-cured area at the extruded wire segment in the composite printing model is divided up and down 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 filaments, when the stereolithography printing reaches the layer covered by the filaments, 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 FIG. 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 at the extruded filament segment in the composite printing model up and down, such as Figure 4 (a) and Figure 4 as shown in (b);

[0043] If there is an extruded filament whose two ends are not located in the same horizontal plane (i.e., the extruded filament is a three-dimensional filament), there is an overlapping area in the vertical projection of the extruded filament, and the corresponding parts of the overlapping area are arranged in layers (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 in the non-overlapping area and the vertical projection surface together form a dividing surface, and for the composite printing model in the overlapping area, the central cross-section of the topmost extruded filament in the overlapping area and the vertical projection surface together form a dividing surface, thereby dividing the light-cured area at the extruded filament segment in the composite printing model into upper and lower parts, such as Figure 5 (a) and Figure 5As shown in (b). For the case where there is an overlapping area in the Z-axis projection of the extruded model, the present invention is only applicable to the case where there is no gap between the adjacent upper and lower extruded 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 physical properties of the extruded filaments are tough and soft, 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 extruded 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 photocured 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 codes for controlling the XYZ three-axis motor.

[0045] 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. Among them, the photocuring material generally constitutes the external structure of the print, and the extrusion material generally constitutes the internal structure of the print, so the present invention can realize a high-precision structure with a complex internal structure, and the structure can be quickly formed.

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

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

[0048] A model segmentation unit, used for segmenting the composite printing model to obtain a light-curing model and an extrusion model;

[0049] A 3D printing path planning unit is used to plan a 3D printing path according to a photocuring model and an 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 composite printer includes 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 to ensure that it has a high precision on each printed XY plane. 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, and the height of the ultraviolet light source 4 is fixed. The emission direction of the ultraviolet light source 4 is set parallel to the Z axis, that is, the projection mode of the light curing printing is a top-down projection mode; the light curing pre-crosslinking pool 9 is placed below the printing platform 2; the XY plane drive component is installed on the side of the printing platform 2, and the extrusion needle print head 8 is installed in the XY plane drive component through the connecting plate 7, and the XY plane drive component controls the extrusion needle print head 8 to move on the XY plane, that is, the printing mode is adopted in which the printing platform is stationary on the XY plane and the needle moves on 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 motion with the needle on the Z-axis, and can realize the printing requirements of the extruded filaments at different heights on the Z-axis. In this embodiment, the XY plane is a horizontal plane and the Z-axis is a vertical direction.

[0052] The XY plane drive assembly includes 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, and the X-axis linear motion module 3 and the auxiliary lead screw guide rail 5 are arranged on both sides of the Z-axis linear motion module 1. The X-axis linear motion module 3 and the auxiliary lead screw guide rail 5 are arranged in parallel and at intervals, and the two ends of the Y-axis linear motion module 6 are 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 is fixedly installed in the Y-axis linear motion module 6 through 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-level 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 zero return point to prevent the slider from exceeding the stroke and damaging the ball screw. A soft limiter is used below the Z-axis to limit the maximum position to prevent the printing platform from exceeding the forming range of the material slot downward, squeezing the material slot and damaging the lead screw.

[0054] Corresponding limit switches are installed in the X-axis linear motion module 3 and the Y-axis linear motion module 6 to prevent the modules from hitting the light-curing equipment. During the actual installation, it is necessary to consider that the X-axis linear motion module 3 and the Y-axis linear motion module 6 do not hit the light machine on the top and the light-curing material tank and other outer shell frames when moving, and at the same time save the time of each printing platform rising to the extrusion position.

[0055] The most important thing to realize the composite 3D printing process is the interactive logic of the two parts of photocuring printing and coaxial extrusion printing and the corresponding printing timing. The basic logic is to use photocuring printing as the main body, and according to the normal process of photocuring, move the platform down to the height of the next curing layer under the surface of the prepolymer solution and cure it. Then, move down a single layer thickness each time and project the image of the layer one by one until the layer containing the coaxial extrusion part, move the platform to a height above the liquid surface suitable for coaxial extrusion and extrude the coaxial filament at the specified position. After the extrusion is completed, continue to photocuring the remaining part, repeat multiple times until the printing is completed.

[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 specific steps are described in detail below:

[0058] 1) The extrusion printing module selects a fused deposition printing module, that is, an FDM print head and a connecting plate with 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) Establish a digital model of the entire printed model, including the photocuring part and the extrusion part, and segment the model, and associate the obtained data with the control program on the computer.

[0061] 4) Add the UV photosensitive resin to be cured into the photocuring pre-crosslinking tank 9 until the predetermined liquid level is reached, 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 the 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 a printing thickness below the liquid surface. Then the computer controls the ultraviolet light source 4 to project a predetermined slice shape onto 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 photocuring 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 the 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) As Figure 2 As shown in (f), steps 6) to 9) are repeated 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 comprises the following steps:

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

[0072] Step 1 is as follows:

[0073] The composite printing model contains at least one extruded wire segment. Each extruded wire segment is divided into a plane with a vertically symmetrical structure and recorded as its central cross section. If the two ends of an extruded wire segment are located on the same horizontal plane, that is, the extruded wire segment is a two-dimensional filament, the horizontal plane where the central cross section of the extruded wire segment is located is the dividing plane, and the light-cured area at the extruded wire segment in the composite printing model is divided up and down 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 filaments, when the stereolithography printing reaches the layer covered by the filaments, 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 FIG. 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 at the extruded filament segment in the composite printing model up and down, such as Figure 4 (a) and Figure 4 as shown in (b);

[0075] If there is an extruded filament whose two ends are not located in the same horizontal plane (i.e., the extruded filament is a three-dimensional filament), there is an overlapping area in the vertical projection of the extruded filament, and the corresponding parts of the overlapping area are arranged in layers (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 in the non-overlapping area and the vertical projection surface together form a dividing surface, and for the composite printing model in the overlapping area, the central cross-section of the topmost extruded filament in the overlapping area and the vertical projection surface together form a dividing surface, thereby dividing the light-cured area at the extruded filament segment in the composite printing model into upper and lower parts, such as Figure 5 (a) and Figure 5As shown in (b). For the case where there is an overlapping area in the Z-axis projection of the extruded model, the present invention is only applicable to the case where there is no gap between the adjacent upper and lower extruded 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 physical properties of the extruded filaments are tough and soft, 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 extruded 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 photocured 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 codes for controlling the XYZ three-axis motor.

[0077] 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. Among them, the photocuring material generally constitutes the external structure of the print, and the extrusion material generally constitutes the internal structure of the print, so the present invention can realize a high-precision structure with a complex internal structure, and the structure can be quickly formed.

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

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

[0080] A model segmentation unit, used for segmenting the composite printing model to obtain a light-curing model and an extrusion model;

[0081] A 3D printing path planning unit is used to plan a 3D printing path according to a photocuring model and an 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 composite printer includes 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 to ensure that it has a high precision on each printed XY plane. 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, and the height of the ultraviolet light source 4 is fixed. The emission direction of the ultraviolet light source 4 is set parallel to the Z axis, that is, the projection mode of the light curing printing is a top-down projection mode; the light curing pre-crosslinking pool 9 is placed below the printing platform 2; the XY plane drive component is installed on the side of the printing platform 2, and the extrusion needle print head 8 is installed in the XY plane drive component through the connecting plate 7, and the XY plane drive component controls the extrusion needle print head 8 to move on the XY plane, that is, the printing mode is adopted in which the printing platform is stationary on the XY plane and the needle moves on 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 motion with the needle on the Z-axis, and can realize the printing requirements of the extruded filaments at different heights on the Z-axis. In this embodiment, the XY plane is a horizontal plane and the Z-axis is a vertical direction.

[0084] The XY plane drive assembly includes 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, and the X-axis linear motion module 3 and the auxiliary lead screw guide rail 5 are arranged on both sides of the Z-axis linear motion module 1. The X-axis linear motion module 3 and the auxiliary lead screw guide rail 5 are arranged in parallel and at intervals, and the two ends of the Y-axis linear motion module 6 are 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 is fixedly installed in the Y-axis linear motion module 6 through 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-level 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 zero return point to prevent the slider from exceeding the stroke and damaging the ball screw. A soft limiter is used below the Z-axis to limit the maximum position to prevent the printing platform from exceeding the forming range of the material slot downward, squeezing the material slot and damaging the lead screw.

[0086] Corresponding limit switches are installed in the X-axis linear motion module 3 and the Y-axis linear motion module 6 to prevent the modules from hitting the light-curing equipment. During the actual installation, it is necessary to consider that the X-axis linear motion module 3 and the Y-axis linear motion module 6 do not hit the light machine on the top and the light-curing material tank and other outer shell frames when moving, and at the same time save the time of each printing platform rising to the extrusion position.

[0087] The most important thing to realize the composite 3D printing process is the interactive logic of the two parts of photocuring printing and coaxial extrusion printing and the corresponding printing timing. The basic logic is to use photocuring printing as the main body, and according to the normal process of photocuring, move the platform down to the height of the next curing layer under the surface of the prepolymer solution and cure it. Then, move down a single layer thickness each time and project the image of the layer one by one until the layer containing the coaxial extrusion part, move the platform to a height above the liquid surface suitable for coaxial extrusion and extrude the coaxial filament at the specified position. After the extrusion is completed, continue to photocuring the remaining part, repeat multiple times until the printing is completed.

[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 specific steps are described in detail below:

[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 injection 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) Establish a digital model of the entire printed model, including the photocuring part and the extrusion part, and segment the model, and associate the obtained data with the control program on the computer.

[0093] 4) Add the PEGDA solution to be cured into the photocuring pre-crosslinking pool 9 until the predetermined liquid level is reached, prepare a calcium chloride solution of a certain concentration as the solution to be crosslinked to be injected 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 to be injected 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 the 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 a printing thickness below the liquid surface. Then the computer controls the ultraviolet light source 4 to project a predetermined slice shape onto 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 photocuring 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 extrusion printing 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 rates of the two cross-linking solutions of the inner and outer needles on the injection pump respectively, and starts the injection, 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, so that the coaxial extrusion head 8 installed on the Y-axis linear motion module 6 extrude a predetermined pattern on the printing plane, and controls the injection pump to stop working after the extrusion of this layer is completed.

[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 the 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) As Figure 2 As shown in (f), steps 6) to 9) are repeated until the entire object is printed.

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

[0101] The present invention combines DLP light-curing printing technology with a variety of extrusion processes to achieve a unique extrusion / projection composite 3D printing process. By combining the respective advantages of the projection and extrusion printing processes, it can achieve rapid manufacturing of complex structures with adjustable mechanical properties, from microns to meters, cross-scale, multi-materials, 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.

[0102] Finally, it should be noted that the above embodiments and explanations are only used to illustrate the technical solution of the present invention rather than to limit it. Those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope disclosed in the technical solution of the present invention, which should be included in 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 photocuring model and an extrusion model; Step 2: Plan the 3D printing path according to 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 the printing is completed to obtain an extrusion and projection composite print.

2. The method of 3D printing of extrusion and projection composite according to claim 1, characterized in that: The step 1 is specifically as follows: The composite printing model includes at least one extruded wire segment, and each extruded wire segment is divided into a plane with a vertically symmetrical structure, and the plane is recorded as its central cross section. If two ends of an extruded wire segment are located on the same horizontal plane, the horizontal plane where the central cross section of the extruded wire segment is located is the dividing plane, and the light-cured area at the extruded wire segment in the composite printing model is divided into upper and lower parts by using the dividing plane; If the two ends of an extruded filament segment are not located in the same horizontal plane and there is no overlapping area in the projection of the extruded filament segment in the vertical direction, 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 at the extruded filament segment in the composite printing model up and down; If there is an overlapping area in the projection of an extruded wire segment in the vertical direction 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 wire segment in the non-overlapping area and the vertical projection surface together form a dividing surface, and for the composite printing model in the overlapping area, the central cross-section of the topmost extruded wire segment in the overlapping area and the vertical projection surface together form a dividing surface, thereby dividing the light-cured area at the extruded wire segment in the composite printing model into upper and lower parts.

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

4. The method of 3D printing 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.

5. A 3D printing device combining extrusion and projection, characterized in that: include: A model segmentation unit, used for segmenting the composite printing model to obtain a light-curing model and an extrusion model; A 3D printing path planning unit is used to plan a 3D printing path according to a photocuring model and an 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.

6. The extrusion and projection composite 3D printing device according to claim 5, 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 pool (9) is placed below the printing platform (2); an XY plane driving component is installed on the side of the printing platform (2), an extrusion needle printing head (8) is installed in the XY plane driving component, and the XY plane driving component controls the extrusion needle printing head (8) to move on the XY plane.

7. The extrusion and projection composite 3D printing device according to claim 6, 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) which are connected to each other; the X-axis linear motion module (3) and the auxiliary lead screw guide rail (5) are arranged in parallel and at intervals; two ends of the Y-axis linear motion module (6) are respectively connected to the X-axis linear motion module (3) and the auxiliary lead screw guide rail (5); and an extruder pin print head (8) is fixedly installed in the Y-axis linear motion module (6).

8. The extrusion and projection composite 3D printing device according to claim 6, characterized in that: A photoelectric limiter is also installed in the Z-axis linear motion module (1).

9. 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).

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