Fiber reinforced composite 3D printer and printing method

Abstract

The invention relates to the technical field of 3D printing, and discloses a fiber reinforced composite material 3D printer and a printing method, current deposition tows are heated / cooled under the action of a preset interlayer pressing force through an interlayer pressing device, interlayer fusion can be promoted, the interlayer bonding strength can be improved, the heat history in the wire cooling process can be eliminated, and the 3D printing quality of the fiber reinforced composite material is improved. The crystallization behavior, the grain size and the grain distribution of a polymer in a printing wire material are controlled, and the microscopic uniformity of a composite material printing product is improved. The side face and the upper surface of the current deposition tow are subjected to hot-pressing shaping through the inter-channel pressing device, meanwhile, secondary hot-pressing is conducted on the adjacent printing layer deposition tow, resin of the current deposition tow and resin of the adjacent printing layer deposition tow can be melted and flow, so that the inter-channel gap between the adjacent printing layers is filled, and the printing effect is improved. And the inter-track bonding strength is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of 3D printing, and discloses a fiber-reinforced composite material 3D printer and a printing method. BACKGROUND

[0002] The fiber composite material 3D printing technology is a process method for realizing the manufacturing of composite material parts by layer-by-layer accumulation of filaments composed of fibers and resins. Compared with traditional molding processes such as molding and pultrusion, the fiber composite material 3D printing technology has the advantages of strong designability, no mold dependency, and suitability for manufacturing complex structures. In particular, the fiber-reinforced thermoplastic composite material has the advantages of high heat resistance, good toughness, high bending strength, good interlayer shear performance, low water absorption, and reusability compared with traditional thermosetting materials. Therefore, it has important application value in advanced manufacturing fields such as aerospace, shipbuilding, and automobiles.

[0003] However, due to material properties, printing processes, and other reasons, the performance of the fiber-reinforced thermoplastic composite material prepared by printing is generally weak. Many researchers at home and abroad have made great efforts to improve the performance of 3D printed fiber composite materials. Most of them improve the fused deposition modeling 3D printing nozzle, but they do not comprehensively consider the multiple sources and multiple factors that affect the performance, and the strength of the printed parts has not been essentially improved. In particular, there are problems such as insufficient interlayer performance and poor interlayer bonding, which greatly limit its application and development in the field of 3D printing. SUMMARY

[0004] The purpose of the present application is to provide a fiber-reinforced composite material 3D printer and a printing method, which can improve the interlayer bonding strength and interlayer bonding strength of the printed product.

[0005] In order to achieve the above technical effects, the technical scheme adopted by the present application is as follows: A fiber-reinforced composite material 3D printer, comprising: A print head, the print head comprises a heat-insulating shell and a throat pipe, the throat pipe is arranged in the heat-insulating shell, the throat pipe is used for providing an extrusion channel for the printing filament, and a rotating member is arranged on the heat-insulating shell; An interlayer pressing and ironing device, the interlayer pressing and ironing device comprises a fixed seat, an interlayer pressing and ironing driving assembly, an interlayer pressing and ironing force sensor, and an interlayer pressing and ironing nozzle assembly; the fixed seat is installed in the heat-insulating shell; the interlayer pressing and ironing driving assembly is fixed with the fixed seat, and an actuator of the interlayer pressing and ironing driving assembly is connected with the interlayer pressing and ironing force sensor; the interlayer pressing and ironing force sensor is connected with the interlayer pressing and ironing nozzle assembly, the interlayer pressing and ironing nozzle assembly is used for heating and melting and cooling the current deposited filament and the adjacent printed layer deposited filament, and under the driving of the interlayer pressing and ironing driving assembly, the current deposited filament is hot-pressed and ironed with a preset interlayer pressing and ironing force; The inter-track hot pressing device comprises a connecting rod, a lateral pressing rod and an inter-track hot pressing part; one end of the connecting rod is fixed to the rotating part, and the other end is connected to the lateral pressing rod; the inter-track hot pressing part is installed on the lateral pressing rod; the end of the lateral pressing rod is used to travel with the print head during printing, and the lateral surface of the current deposited wire bundle is hot pressed and shaped at a first preset pressing temperature and a preset pressing distance; the inter-track hot pressing part is used to travel synchronously with the lateral pressing rod, and the upper surfaces of the current deposited wire bundle and the last deposited wire bundle are hot pressed at a second preset pressing temperature and a preset pressing height.

[0006] Further, the inter-layer pressing device further comprises an equalizing plate; the equalizing plate comprises an upper equalizing plate and a lower equalizing plate connected to the upper and lower ends of the inter-layer pressing force sensor respectively; the upper equalizing plate is connected to the actuator of the inter-layer pressing driving assembly; the lower equalizing plate is connected to the inter-layer pressing nozzle assembly; and a heat insulation plate is arranged between the lower equalizing plate and the inter-layer pressing nozzle assembly.

[0007] Further, the inter-layer pressing nozzle assembly comprises: a heating block connected to the lower equalizing plate and located at the outlet end of the throat pipe, used for heating the printing wire in the throat pipe; a concentric circular stepped temperature control module fixedly connected to the lower end of the heating block, and the throat pipe is located at the center of the concentric circular stepped temperature control module; the concentric circular stepped temperature control module is used to apply a preset inter-layer pressing force to the adjacent deposited wire bundle and the current deposited wire bundle, and simultaneously form a stepped temperature field to heat and cool the current deposited wire bundle and the adjacent deposited wire bundle.

[0008] Further, a heat insulation plate is arranged between the lower equalizing plate and the heating block.

[0009] Further, the concentric circular stepped temperature control module comprises: an ironing high-temperature metal ring surrounding the outside of the throat pipe with the axis of the throat pipe as the center; the ironing high-temperature metal ring is used to heat the current deposited wire bundle and the adjacent deposited wire bundle at a first preset temperature; a stepped temperature control metal ring comprising a plurality of concentric metal rings with different diameters; all the stepped temperature control metal rings are arranged outside the ironing high-temperature metal ring and are concentrically nested; the stepped temperature control metal ring is used to form a preset temperature field with the temperature decreasing step by step from the inside to the outside, to control the temperature of the current deposited wire bundle and the adjacent deposited wire bundle, and to hot press the current deposited wire bundle; cooling metal rings arranged outside the outermost stepped temperature control metal ring and arranged in concentric circles, and used for cooling the current deposition filament and the adjacent printing layer deposition filament at a second preset temperature; heat insulation rings arranged between the throat, the iron-type high-temperature metal ring, the stepped temperature control metal ring, the cooling metal ring, and arranged between two adjacent stepped temperature control metal rings.

[0010] Further, the concentric circular stepped temperature control module further comprises an additive spreading channel arranged between two adjacent heat insulation rings, and used for spreading additives to the current deposition filament during printing.

[0011] A fiber-reinforced composite material 3D printing method is realized by using the aforementioned fiber-reinforced composite material 3D printer, and comprises the following steps: determining the printing parameters of the interlayer pressing device and the inter-track pressing device, wherein the printing parameters comprise the optimal preset interlayer pressing force of the concentric circular stepped temperature control module, the temperatures of the iron-type high-temperature metal ring, the stepped temperature control metal ring and the cooling metal ring in the concentric circular stepped temperature control module, and the inter-track pressing temperature and pressing interval of the inter-track pressing device; based on the preset printing path and the preset layer thickness of the target printing part, the fiber-reinforced composite material 3D printer starts printing to obtain the target printing part.

[0012] Further, the optimal preset interlayer pressing force determination method of the concentric circular stepped temperature control module comprises: According to the material coefficient of the printing wire material, the interlayer shear strength of the product obtained by the printing wire material in the comparative forming process, the comparative forming process coefficient, and the preset printing line width, the contact length of the concentric circular stepped temperature control module along the radial direction with the printing wire material, the theoretical maximum preset interlayer pressing force of the concentric circular stepped temperature control module is calculated; In the range of zero to the theoretical maximum preset interlayer pressing force, a plurality of preset interlayer pressing force test values are selected according to the preset step length, and the fiber-reinforced composite material 3D printer is used to prepare an interlayer shear sample corresponding to each preset interlayer pressing force test value and test the interlayer shear strength, and the preset interlayer pressing force corresponding to the highest interlayer shear strength is selected as the optimal preset interlayer pressing force.

[0013] Further, the calculation formula of the theoretical maximum preset interlayer pressing force of the concentric circular stepped temperature control module is: ; wherein, is the theoretical maximum preset interlayer pressing force; is the material coefficient of the printing wire material; To print the interlayer shear strength of the product obtained in the contrast forming process; To contrast the coefficient of the forming process; To preset the printing line width; To the contact length of the concentric circular stepped temperature control module along the radial direction and the printing wire.

[0014] Compared with the prior art, the present application has the beneficial effects of: The present application can promote interlayer fusion and improve interlayer bonding strength by the interlayer pressing device under the action of the preset interlayer pressing force, can eliminate the thermal history in the cooling process of the wire material, control the crystallization behavior and grain size and distribution of the polymer in the printing wire material, and improve the micro-uniformity of the composite material printing product. The present application can make the resin of the current deposition wire and the adjacent printing layer deposition wire flow by hot pressing and shaping the side surface and the upper surface of the current deposition wire by the interlayer pressing device and the adjacent printing layer deposition wire by the interlayer pressing device, so as to fill the interlayer gap between the adjacent printing layers, and realize the improvement of the interlayer bonding strength. The present application can improve the interlayer bonding strength and the interlayer bonding strength of the printing product by the synergistic effect of the interlayer pressing device and the interlayer pressing device, and improve the comprehensive performance of the printing product. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 For the structure diagram of the fiber reinforced composite 3D printer in the embodiment; Figure 2 For the structure diagram of the interlayer pressing device of the printer in the embodiment; Figure 3 For the structure diagram of the concentric circular stepped temperature control module in the embodiment; Figure 4 For the structure diagram of the concentric circular stepped temperature control module in the embodiment; Figure 5 For the structure diagram of the concentric circular stepped temperature control module in the embodiment; Figure 6 For the structure diagram of the concentric circular stepped temperature control module in the embodiment; Figure 7 For the structure diagram of the concentric circular stepped temperature control module with additive scattering channel in the embodiment; Figure 8 For the structure diagram of the interlayer pressing device in the embodiment; Figure 9 For the structure diagram of the interlayer pressing device in the embodiment; Figure 10A flow chart of the fiber-reinforced composite 3D printing method with interlayer and inter-track pressing and ironing effect in the embodiment; Wherein, 11 is a heat insulation shell, 12 is a throat pipe, 21 is a fixed seat, 22 is an interlayer pressing and ironing driving assembly, 23 is an interlayer pressing and ironing force sensor, 241 is a heating block, 242 is a concentric circular step temperature control module, 243 is an iron type high temperature metal ring, 244 is a step temperature control metal ring, 245 is a cooling metal ring, 246 is a heat insulation ring, 247 is an additive scattering channel, 248 is a heating device, 249 is a temperature measuring device, 251 is an upper uniform pressure plate, 252 is a lower uniform pressure plate, 26 is a heat insulation plate, 31 is a connecting rod, 32 is a lateral pressing and ironing rod, 33 is an inter-track hot pressing and ironing part, 34 is a rotating part, 4 is a wire feeding mechanism, and 5 is a base plate. DETAILED DESCRIPTION

[0016] The application will be further described in conjunction with the embodiments and drawings. However, it should not be understood that the above-mentioned subject matter of the application is limited to the following embodiments. Any technology realized based on the content of the application belongs to the scope of the application.

[0017] Referring to Figures 1 to 9 The application provides a fiber-reinforced composite 3D printer, which comprises: A printing head, which comprises a heat insulation shell 11 and a throat pipe 12, the throat pipe 12 is arranged in the heat insulation shell 11, the throat pipe 12 is used to provide an extrusion channel for a printing wire material, and the heat insulation shell 11 is provided with a rotating part 34; An interlayer pressing and ironing device, which comprises a fixed seat 21, an interlayer pressing and ironing driving assembly 22, an interlayer pressing and ironing force sensor 23, and an interlayer pressing and ironing nozzle assembly; the fixed seat 21 is installed in the heat insulation shell 11; the interlayer pressing and ironing driving assembly 22 is fixed with the fixed seat 21, and an actuator of the interlayer pressing and ironing driving assembly 22 is connected with the interlayer pressing and ironing force sensor 23; the interlayer pressing and ironing force sensor 23 is connected with the interlayer pressing and ironing nozzle assembly, the interlayer pressing and ironing nozzle assembly is used to heat and melt and cool the current deposition tows and the adjacent printing layer deposition tows, and under the driving of the interlayer pressing and ironing driving assembly 22, the current deposition tows are hot pressed and ironed with a preset interlayer pressing and ironing force; The inter-track hot pressing device comprises a connecting rod 31, a lateral pressing rod 32 and an inter-track hot pressing part 33; one end of the connecting rod 31 is fixed with the rotating part 34, and the other end is connected with the lateral pressing rod 32; the inter-track hot pressing part 33 is installed on the lateral pressing rod 32; the end of the lateral pressing rod 32 is used for traveling with the print head in the printing process, and hot pressing and shaping the side surface of the current deposited wire bundle at a first preset pressing temperature and a preset pressing distance; the inter-track hot pressing part 33 is used for traveling synchronously with the lateral pressing rod 32, and hot pressing the upper surface of the current deposited wire bundle and the last deposited wire bundle at a second preset pressing temperature and a preset pressing height.

[0018] The inter-layer pressing device can heat / cool the current deposited wire bundle under the action of the preset inter-layer pressing force, promote inter-layer fusion and improve the inter-layer bonding strength, eliminate the thermal history in the cooling process of the wire material, control the crystallization behavior, grain size and distribution of the polymer in the printed wire material, and improve the micro-uniformity of the composite material printed product. The inter-track pressing device hot presses and shapes the side surface and the upper surface of the current deposited wire bundle, and simultaneously performs secondary hot pressing on the last deposited wire bundle, so as to promote the flow and fusion of the current deposited wire bundle and the last deposited wire bundle, fill the inter-track gap between the current deposited wire bundle and the last deposited wire bundle, and improve the inter-track bonding strength. The inter-layer pressing device and the inter-track pressing device can improve the inter-layer bonding strength and the inter-track bonding strength of the printed product, and improve the comprehensive performance of the printed product.

[0019] In some embodiments, referring to Figure 1 and Figure 2 , the print head further comprises a wire feeding mechanism 4 installed in the heat insulation shell 11. The wire feeding mechanism 4 can be composed of two wire feeding gears. The wire feeding mechanism 4 can realize wire feeding by rotating the wire feeding gears and driving the printing wire to move downward along the throat pipe 12. Moreover, the wire feeding mechanism 4 and its supporting motor and other components are away from the heating devices in the print head by a certain distance, and heat insulation protection is added as needed.

[0020] In some embodiments, referring to Figure 1 and Figure 2The interlayer pressing and ironing device driving assembly 22 of the interlayer pressing and ironing device can adopt a motor screw structure or a hydraulic cylinder driving structure capable of realizing linear reciprocating motion. One end of the interlayer pressing and ironing device driving assembly 22 is fixed on the fixed seat 21, the actuator of the interlayer pressing and ironing device driving assembly 22 is connected with the upper equalizing plate 251, the lower equalizing plate 252 is connected with the upper side of the interlayer pressing force sensor 23, the lower side of the interlayer pressing force sensor 23 is connected with the lower equalizing plate 252, and the lower equalizing plate 252 is connected with the interlayer pressing and ironing nozzle assembly through the heat insulation plate 26. In the printing process, the interlayer pressing and ironing nozzle assembly is used for heating the printing wire to be extruded in the throat pipe 12 and the current deposited wire bundle that has been extruded, and performing secondary heating on the surface of the uppermost adjacent printing layer deposited wire bundle at the outlet of the throat pipe 12, and heating and performing interlayer direction hot pressing on the printing wire that has been extruded, i.e., the current deposited wire bundle, to promote interlayer fusion and improve interlayer bonding strength.

[0021] It should be noted that, referring to Figure 1 and Figure 2 , the heat insulation plate 26 is made of a heat insulation material with certain rigidity and strength. In the printing process, if the actual preset interlayer pressing and ironing force of the current deposited wire bundle by the interlayer pressing and ironing device is less than a safety threshold, the heat insulation plate 26 remains stable and plays a role of heat insulation and force transmission. When the actual preset interlayer pressing and ironing force of the current deposited wire bundle by the interlayer pressing and ironing device exceeds the safety threshold, the heat insulation plate 26 is crushed and broken, unloading the preset interlayer pressing and ironing force, avoiding excessive pressing and ironing force generated in the abnormal state of the pressing and ironing force adjusting module from damaging other structures of the print head, and playing a role of a fuse. The safety threshold is set as a multiple of the preset interlayer pressing and ironing force, for example, the safety threshold is set as 1.2 times of the preset interlayer pressing and ironing force, and the multiple value can be set according to needs.

[0022] In some embodiments, referring to Figure 3 and Figure 4 , the interlayer pressing and ironing nozzle assembly includes a heating block 241 and a concentric circle type step temperature control module 242. The heating block 241 is fixedly connected with the heat insulation plate 26 and located at the outlet end of the throat pipe 12, and is used for heating the printing wire to be extruded in the throat pipe 12 to a molten state. The concentric circle type step temperature control module 242 is fixed at the lower end of the heating block 241, and the throat pipe 12 is located at the center of the concentric circle type step temperature control module 242.

[0023] In the printing process, the interlayer pressure ironing device of the present application applies a preset interlayer pressure ironing force to the current deposited filament and performs hot pressure ironing, and the reaction force of the preset interlayer pressure ironing force is transmitted to the interlayer pressure ironing force sensor 23 through the concentric circular stepped temperature control module 242, the heating block 241 and the heat insulation plate 26 in turn, and the real-time monitoring of the preset interlayer pressure ironing force is realized through the interlayer pressure ironing force sensor 23. In the printing process, the control device of the print head controls the interlayer pressure ironing drive assembly 22 to adjust the height of the interlayer pressure ironing nozzle assembly in real time according to the real-time change of the preset interlayer pressure ironing force measurement value. When the preset interlayer pressure ironing force detection value is greater than the set value, the interlayer pressure ironing drive assembly 22 drives the interlayer pressure ironing nozzle assembly to move slightly upward, so that the preset interlayer pressure ironing force is reduced to the set value. When the preset interlayer pressure ironing force detection value is less than the set value, the interlayer pressure ironing drive assembly 22 drives the interlayer pressure ironing nozzle assembly to move slightly downward, so that the preset interlayer pressure ironing force is increased to the set value. It should be noted that the throat pipe 12 is fixed in the print head, the outer wall of the throat pipe 12 is provided with a heat insulation layer, the part of the lower end of the throat pipe 12 corresponding to the heating block 241 is not provided with a heat insulation layer, and gaps are left between the upper and lower uniform pressure plates 251 and 252, the heat insulation plate 26, the heating block 241 and the concentric circular stepped temperature control module 242 and the throat pipe 12, and also between the heat insulation plate 26 and the heat insulation shell 11, so as to ensure that the upper and lower uniform pressure plates 251 and 252, the heat insulation plate 26, the heating block 241 and the concentric circular stepped temperature control module 242 can be lifted up and down under the drive of the interlayer pressure ironing drive assembly 22, thereby realizing the adjustment of the hot pressure ironing force applied to the current deposited filament and the preset interlayer pressure ironing force.

[0024] The concentric circular stepped temperature control module 242 includes multiple concentric circular rings, which are sequentially arranged from inside to outside around the axis of the throat pipe 12 and include a high-temperature metal ring 243, a stepped temperature control metal ring 244 and a cooling metal ring 245, and a heat insulation ring 246 is arranged between adjacent two metal rings to avoid mutual interference between different heating areas, and the width of each of the high-temperature metal ring 243, the stepped temperature control metal ring 244 and the cooling metal ring 245 can be set according to the material properties of the printing wire and experience, as shown in Figure 4

[0025] The high-temperature metal ring 243 surrounds the outside of the throat pipe 12 and has independent heating device 248 and temperature measuring device 249, and in the printing process, the first preset temperature of the high-temperature metal ring 243 is set as the melting point of the printing wire, which is used to heat the current deposited filament extruded by the throat pipe 12 to maintain its molten state, and to heat the adjacent deposited filament of the adjacent printing layer to the molten state. In the printing process, the high-temperature metal ring 243 applies a preset interlayer pressure ironing force to the current deposited filament to extrude downward, so as to promote the current deposited filament and the adjacent printing layer deposited filament in the molten state to begin to fuse.​

[0026] The stepped temperature control metal rings 244 are provided in several numbers, all of which are different in diameter and arranged in concentric nesting, all of which are arranged outside the ironing high-temperature metal ring 243, and each of which is provided with an independent heating device 248 and a temperature measuring device 249. The stepped temperature control metal ring 244 with the smallest diameter and adjacent to the ironing high-temperature metal ring 243 is the inner ring, and the stepped temperature control metal ring 244 with the largest diameter and adjacent to the cooling metal ring 245 is the outer ring, and the temperature of all the stepped temperature control metal rings 244 gradually decreases from inside to outside, forming a preset temperature field with a temperature gradient, ensuring that the current deposition wire bundle in a molten state and the adjacent adjacent printing layer deposition wire bundle can be gradually cooled according to the preset temperature field during printing, thereby regulating the grain size and uniformity of the crystalline resin inside the adjacent printing layer deposition wire bundle and the current deposition wire bundle, controlling the forming quality and internal stress distribution of the printing layer, and further fusing the current deposition wire bundle and the adjacent adjacent printing layer deposition wire bundle. The highest temperature of the preset temperature field is less than the melting point of the printing wire material, and the lowest temperature of the preset temperature field is greater than the glass transition temperature of the printing wire material, and the temperature difference between the two adjacent stepped temperature control metal rings 244 is set according to the material properties of the printing wire material.

[0027] The cooling metal ring 245 is arranged outside the outermost stepped temperature control metal ring 244 to cool the current deposition wire bundle and the adjacent printing layer deposition wire bundle in a stepped manner, and the cooling metal ring 245 is provided with a refrigeration device and a temperature measuring device 249, and the temperature of the cooling metal ring 245 is set to be 80℃ lower than the glass transition temperature of the printing wire material through the refrigeration device and the temperature measuring device 249, so that the fused current deposition wire bundle and adjacent printing layer deposition wire bundle can quickly pass through the glass transition temperature region during cooling, avoiding problems such as internal stress concentration, deformation or cracking of the printing layer wire bundle caused by improper cooling speed.

[0028] It should be noted that since the size of the concentric circular stepped temperature control module 242 is larger than the line width of the current deposition wire bundle, and only part of the concentric circular stepped temperature control module 242, i.e. the rear side of the concentric circular stepped temperature control module 242, acts on the current deposition wire bundle, the front side of the concentric circular stepped temperature control module 242 can preheat the upper surface of the adjacent printing layer deposition wire bundle of the wire bundle to be deposited during printing. As the print head advances, the current deposition wire bundle is deposited on the adjacent printing layer deposition wire bundle, and under the action of the hot pressing of the concentric circular stepped temperature control module 242, the current deposition wire bundle and the adjacent printing layer deposition wire bundle are fused, achieving the purpose of improving the interlayer bonding strength.

[0029] It should be noted that the heating device 248 can be a resistance heating device, induction heating device, etc.; the cooling device can be a water cooling device, radiant cooling device, etc. The temperature measuring device 249 can be a thermocouple or other non-contact temperature measuring device, such as infrared thermometry. Figure 3 In the structure shown, the heating device 248 uses resistance heating, and the temperature measuring device 249 uses a thermocouple.

[0030] It should be noted that the lower surface of the concentric step temperature control module 242 that contacts the current deposited filament bundle needs to be polished using a mirror polishing process, with a surface roughness not exceeding 0.2 μm, to reduce the friction between the current deposited filament bundle and the concentric step temperature control module 242.

[0031] In some embodiments, see Figure 7 The concentric circle stepped temperature control module 242 is also provided with an additive dispensing channel 247, see [link / reference]. Figure 6 The additive dispensing channel 247 can be made of heat-insulating material into a hollow dispensing ring. The upper end of the dispensing ring is connected to an external additive adding device through a pipe, and the lower end of the dispensing ring is an open end. Depending on the printing requirements, during the printing process, additives can be dispensed onto the surface of the current deposited filament and adjacent printed layer deposited filaments through the dispensing ring. The additives include functional powders, auxiliary slurries, etc. The additive dispensing channel 247 can be positioned at any location between the iron-type high-temperature metal ring 243, the stepped temperature-controlled metal ring 244, and the cooling metal ring 245, depending on the printing requirements. For example, the additive dispensing channel 247 can be positioned between the iron-type high-temperature metal ring 243 and the first stepped temperature-controlled metal ring 244. The number of additive dispensing channels 247 can also be set according to the printing requirements.

[0032] In some embodiments, see Figure 1 , Figure 8 and Figure 9 The rotating component 34 can be a rotating disk mounted on the heat insulation housing 11. Driven by a motor and gears, as the print head travels along a preset path, the rotating component 34 rotates around the axis of the print head, causing the lateral pressing rod 32 and the inter-pass hot pressing part to rotate circumferentially around the print head. This adjusts the distance between the axis of the lateral pressing rod 32 and the axis of the current deposited filament bundle, i.e., the pressing gap, ensuring that the pressing gap remains constant. (See [reference]). Figure 1 and Figure 8 The current deposition filament axis refers to the position where half the width of the current deposition filament is located.

[0033] In some embodiments, see Figure 1 , Figure 8 and Figure 9The inter-pass pressing device includes a connecting rod 31, a lateral pressing rod 32, and an inter-pass hot pressing unit 33. One end of the connecting rod 31 is fixed to the rotating component 34, and the other end is provided with a connecting cylinder. The lateral pressing rod 32 is inserted into the connecting cylinder, and the connecting cylinder is provided with an actuating wheel for driving the lateral pressing rod 32 to rise and fall, so that the lateral pressing rod 32 can move up and down as needed, avoiding interference between the lateral pressing rod 32 and the filaments deposited in adjacent printing layers when it rotates in a circle following the rotating component 34. Moreover, the connecting rod 31 is a telescopic rod, for example, an electric push rod is installed on the connecting rod 31. According to the follow-up needs of the hot pressing assembly, the connecting rod 31 can extend and retract radially along the rotating component 34, and drive the lateral pressing rod 32 to move synchronously, thereby adjusting the distance between the axis of the lateral pressing rod 32 and the axis of the print head.

[0034] In some embodiments, a high-temperature resistant ceramic heating rod and a temperature-sensing thermocouple are installed inside the lateral pressing rod 32 to achieve heating and temperature sensing and adjustment functions. The lateral pressing rod 32 is made of high thermal conductivity brass to ensure uniform heat transfer. The working section at the end of the lateral pressing rod 32 is polished to reduce the surface roughness to within Ra4, thereby reducing the friction between the lateral pressing rod 32 and the molten current deposited filament bundle. During the printing process, the working section at the end of the lateral pressing rod 32 contacts the side of the current deposited filament bundle, heating the side of the current deposited filament bundle at a first preset pressing temperature. Through a preset pressing interval, the working section at the end of the lateral pressing rod 32 applies lateral pressure to the side of the current deposited filament bundle, hot-pressing and shaping the side of the current deposited filament bundle, transforming the originally nearly elliptical side of the current deposited filament bundle into a nearly vertical plane, thereby increasing the contact area between the passes and improving the bonding strength between the passes. During printing, the preset pressing distance can be adjusted by rotating the rotating component 34, thereby adjusting the pressing force of the lateral pressing rod 32. Moreover, with the rotation of the rotating component 34 and the on-demand extension and retraction adjustment of the connecting rod 31, the lateral pressing rod 32 can always maintain lateral contact and compression with the currently deposited filament bundle at the preset pressing distance during the printing process, realizing accompanying hot pressing in various printing paths such as straight lines and corners.

[0035] In some embodiments, the inter-pass hot pressing ironing section 33 is a flat, circular plate-shaped structure. The diameter of the inter-pass hot pressing ironing section 33 is at least larger than the width of the currently deposited filament bundle. The inter-pass hot pressing ironing section 33 is made of high thermal conductivity brass to ensure uniform heat transfer. The lower surface of the inter-pass hot pressing ironing section 33 is polished to reduce the surface roughness to within Ra4, thereby reducing the friction between the inter-pass hot pressing ironing section 33 and the molten current deposited filament bundle. The inter-pass hot pressing ironing section 33 is equipped with a high-temperature resistant ceramic heating rod and a temperature-measuring thermocouple, which can heat the upper surfaces of the current deposited filament bundle and the previous deposited filament bundle at a second preset pressing temperature. The preset pressing height is set to the printing layer thickness, which is the distance between the lower surface of the inter-pass hot pressing ironing section 33 and the adjacent printed layer deposited filament bundle. When the lateral pressing rod 32 hot presses and shapes the side of the current deposited filament bundle, the lower surface of the inter-pass hot pressing part 33 constrains the flow direction of the current deposited filament bundle, causing the current deposited filament bundle to flow and merge with the next deposited filament bundle, while simultaneously achieving surface shaping.

[0036] Because the raw material filament for continuous fiber 3D printing has a circular cross-section, currently common continuous fiber 3D printing devices only use a printing nozzle to hot-press and shape the filament from its upper surface. This causes the circular cross-section continuous fiber filament to deform into a near-elliptical cross-section under the hot-pressing action on the upper surface and deposited on the forming platform. A large gap exists between two adjacent near-elliptical cross-section filaments, preventing them from fitting tightly together, resulting in a small contact area between the channels and ultimately low bonding strength. In this invention, the inter-channel hot-pressing iron 33 and the lateral pressing iron 32 work together to hot-press and shape the currently deposited filament bundle. The extrusion action causes the molten current deposited filament bundle to flow and fuse with the previous deposited filament bundle, filling the inter-channel gap between the current and previous deposited filament bundles, increasing the contact area between the printed channels, and enhancing the inter-channel bonding strength of continuous fiber 3D printing.

[0037] It should be noted that the inter-pass hot pressing ironing part 33 is mounted on the lateral pressing ironing rod 32. The inter-pass hot pressing ironing part 33 is provided with an actuating wheel that contacts the lateral pressing ironing rod 32, so as to drive the inter-pass hot pressing ironing part 33 to move up and down along the lateral pressing ironing rod 32, thereby realizing the adjustment of the preset pressing height of the inter-pass hot pressing ironing part 33. The preset pressing height refers to the distance between the lower surface of the inter-pass hot pressing ironing part 33 and the adjacent printed layer deposited filament bundle.

[0038] In some embodiments, the fiber-reinforced composite material 3D printer also includes a substrate 5 serving as a forming platform. The substrate 5 is supported by a base, and its normal direction is rigidly constrained. The number of bases is set as needed, and heaters can be installed on the bases to heat the substrate 5 to a suitable printing temperature during printing. During printing, molten printing filament is deposited on the substrate 5, and then printed layer by layer to finally obtain the target printed part. It should be noted that the substrate 5 is only rigidly (e.g., bolted) or flexibly (e.g., magnetically or vacuum-adhesive) fixed to the base in the central area. Other areas of the substrate 5 are only supported by the base, allowing the substrate 5 to expand and contract freely in the plane, avoiding unevenness of the substrate 5 due to heating or cooling.

[0039] This invention uses continuous carbon fiber reinforced polyaryletherketone (CF / PAEK) printing filament as an example to print target parts using a fiber-reinforced composite material 3D printer, to further illustrate the fiber-reinforced composite material 3D printing method of this invention, specifically including the following steps: Step 1: Determine the printing parameters of the interlayer ironing device and the inter-pass ironing device. These printing parameters include the optimal preset interlayer ironing force of the concentric circle stepped temperature control module 242, the temperatures of the iron-type high-temperature metal ring 243, the stepped temperature control metal ring 244, and the cooling metal ring 245 in the concentric circle stepped temperature control module 242, and the inter-pass ironing temperature and ironing spacing of the inter-pass ironing device. Specifically, this includes: Step 1.1: First, weigh an appropriate amount of CF / PAEK printing filament and place it in a crucible. Use a differential scanning calorimeter (DSC) to test the enthalpy change of the system during the heating and cooling process of the CF / PAEK printing filament. During the cooling process, select several temperature points at intervals near the temperature corresponding to the resin solidification peak to conduct isothermal crystallization tests. Obtain the relationship curve between the system enthalpy and time, i.e., the thermal analysis test curve, and record the time corresponding to the peak value.

[0040] Then, after cutting a certain length of CF / PAEK printing filament and heating it to its melting point, it was quickly placed under a polarizing microscope (POM) equipped with a hot stage to observe its isothermal crystallization process, and the crystallization time and grain size of the filament at the corresponding temperature were recorded simultaneously.

[0041] Finally, the optimal isothermal crystallization temperature and crystallization time of the CF / PAEK printing filament were determined using differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The optimal isothermal crystallization temperature of the CF / PAEK printing filament includes the glass transition temperature and melting point obtained from DSC testing.

[0042] Step 1.2: Based on the optimal isothermal crystallization temperature and crystallization time of the CF / PAEK printing filament, set the temperatures of the iron-type high-temperature metal ring 243, the stepped temperature-controlled metal ring 244, and the cooling metal ring 245. The first preset temperature of the iron-type high-temperature metal ring 243 is set to the melting point of the CF / PAEK printing filament. The preset temperature field of the stepped temperature-controlled metal ring 244 corresponds to the temperature range from the glass transition temperature to the melting point of the CF / PAEK printing filament. The number of stepped temperature-controlled metal rings 244 and the temperature difference between two adjacent stepped temperature-controlled metal rings 244 are set empirically. The second preset temperature of the cooling metal ring 245 is set to 80°C below the glass transition temperature of the CF / PAEK printing filament.

[0043] Step 1.3: Determine the printing speed of the iron-type high-temperature metal ring 243, the cooling metal ring 245, and each stepped temperature-controlled metal ring 244. The calculation formula is as follows: ; in: The printing speed of the iron-type high-temperature metal ring 243, the cooling metal ring 245, and the temperature-controlled metal ring 244 of each step; The widths of the iron-type high-temperature metal ring 243, the cooling metal ring 245, and each stepped temperature-controlled metal ring 244; The temperatures of the iron-type high-temperature metal ring 243, the cooling metal ring 245, and the temperature-controlled metal ring 244 at each step are specified. For printing filament at temperature The ratio of temperature to crystallization rate; given a type of printing filament material, observe the printing filament at a constant temperature using a polarizing microscope (POM). The crystallization behavior under the given conditions was analyzed to obtain the crystallization rate, and then the ratio was calculated. .

[0044] Finally, the minimum speed among the printing speeds of the iron-type high-temperature metal ring 243, the cooling metal ring 245, and each stepped temperature-controlled metal ring 244 is selected as the printing speed of the print head. This invention considers the size and temperature of each metal ring, as well as the ratio of temperature to crystallization rate of the printing filament at the corresponding temperature, when determining the printing speed of the print head. This ensures that the printing speed of the print head matches the residence time of each metal ring on the CF / PAEK filament during the printing process, avoiding printing defects caused by excessively fast or slow printing speeds, such as insufficient or excessive melting of the filament. This ensures that the printed continuous fiber-reinforced composite material has a uniform structure and excellent performance. Simultaneously, by selecting the minimum printing speed among the various metal rings as the printing speed of the print head, the stability and reliability of the printing process are ensured, improving print quality.

[0045] Step 1.4: Using traditional molding as a comparative molding process, and carbon fiber reinforced polyaryletherketone (CF / PAEK) filaments as raw materials, the interlaminar shear strength of the carbon fiber reinforced polyaryletherketone composite material prepared by traditional molding process is measured. The pressure is 50 MPa; compared with the molding process coefficient The value is 0.8; the material coefficient of the CF / PAEK printing filament. The value is 0.5; preset print line width. The value is 1mm; the radial contact length between the concentric circle stepped temperature control module 242 and the printing filament is 1mm. If the value is 8mm, then by formula... Calculate the theoretical maximum preset interlayer ironing force of the concentric circle stepped temperature control module 242 It is 160N. In the formula... middle, This is the material coefficient of the printing filament. The specific value is determined based on the material viscosity. For high melt viscosity materials such as PAEK (viscosity > 350 Pa·s), the value is more specific. The value ranges from 0.4 to 1, for low melt viscosity materials such as PLA (viscosity ≤ 350 Pa·s). The value range is 0.01 to 0.4; To determine the interlaminar shear strength of the printed filament under the comparative molding process, data was obtained through interlaminar shear strength testing. To compare the molding process coefficients, values ​​are determined based on experience. If the compared molding process is a standard compression molding process, then... The value range is 0.8~3; if the comparison molding process is a conventional winding process, then The value range is 0.3 to 1.2; Preset print line width; The contact length between the concentric circle stepped temperature control module 242 and the printing line along the radial direction is obtained by measurement.

[0046] Then, with a step size of 10N, within the range of 0~160N, 16 preset interlayer pressing force test values ​​were selected starting from 10N. Using the fiber-reinforced composite material 3D printer, interlayer shear samples corresponding to each preset interlayer pressing force test value were prepared, and the interlayer shear strength was tested. The preset interlayer pressing force corresponding to the highest interlayer shear strength was selected as the optimal preset interlayer pressing force. Statistical data showed that within the theoretical maximum preset interlayer pressing force range of 10N~160N, the interlayer shear strength exhibited a trend of first increasing and then decreasing. Furthermore, the sample with the highest interlayer shear strength was observed when the theoretical maximum preset interlayer pressing force was 120N; therefore, 120N was set as the optimal preset interlayer pressing force.

[0047] Step 1.5: Take 1.5 times the optimal preset interlayer pressing force as the safety threshold for activating the overload protection of the heat insulation plate 26, and calculate and select heat insulation material of appropriate strength to make the heat insulation plate 26 according to the safety threshold; and determine whether the additive dispensing channel 247 is open according to the requirements of the printing material system of the target printed part. If the additive dispensing channel 247 needs to be opened, the additive to be mixed in needs to be determined.

[0048] Step 1.6: Based on the resin matrix type of the CF / PAEK printing filament, select and set the heating temperatures of the lateral pressing rod 32 and the inter-pass hot pressing section 33. Specifically, to ensure that the resin of the printing filament is fully melted and to avoid thermal decomposition of the resin, the range of the first preset pressing temperature of the lateral pressing rod 32 and the second preset pressing temperature of the inter-pass hot pressing section 33 is set to the melting point of the printing filament ±30℃. Since the polyetheretherketone (PAEK) resin component of the carbon fiber reinforced polyaryletherketone (PAEK) filament has a melting point of 370℃ and a thermal decomposition temperature of 490℃, the first preset pressing temperature of the lateral pressing rod 32 and the second preset pressing temperature of the inter-pass hot pressing section 33 are set to 400℃.

[0049] Step 1.6: Conduct process experiments to determine the preset ironing spacing b. Specific steps include: (1) Calculate the ideal ironing spacing. The cross-section of the carbon fiber reinforced polyaryletherketone (PAEK) filament is a circle with a diameter of 0.5 mm. The preset printing layer thickness of the target printed part is 0.2 mm. The radius of the lateral ironing rod 32 is 1 mm. Therefore, the ideal ironing spacing = filament cross-sectional area ÷ preset printing layer thickness ÷ 2 + radius of lateral ironing rod 32 ≈ 1.5 mm.

[0050] (2) Determine the upper limit of the preset ironing spacing through process experiments. Print a 300mm long straight line using carbon fiber reinforced polyaryletherketone (PAEK) filament with a layer thickness of 0.2mm. After printing, set a measuring point every 10mm along the 300mm straight line, for a total of 30 measuring points. Use a vernier caliper to measure the width of the printed filament at each measuring point, i.e., the width of the printed layer. Then calculate the average value of the measured width of the printed layer at each measuring point, i.e., the line width, which is approximately 1.2mm. Then calculate the upper limit of the preset ironing spacing = line width ÷ 2 + radius of the lateral ironing rod 32 = 1.6mm.

[0051] (3) Determine the lower limit of the preset ironing distance through process experiments. Using the ideal ironing distance as the maximum value, a test gradient matrix of different ironing distances is generated by decreasing step by step with a fixed step size. Specifically, the ideal ironing distance is 1.5mm, and the step size is set to 0.05mm, so the test gradient matrix is ​​1.45mm, 1.4mm, 1.35mm, 1.3mm, 1.25mm, 1.2mm, 1.15mm, 1.1mm, 1.05mm, and 1.0mm. According to the above ironing distance matrix, start the 3D printing equipment to print samples. During the printing process, observe the accumulation of residual resin on the lateral ironing rod 32 and record the ironing distance when printing cannot be completed due to excessive resin extrusion at the beginning. When the ironing distance is 1.15mm, the resin accumulation on the outer contour of the sample occurs due to excessive residual resin on the lateral ironing rod 32, resulting in a large deviation between the sample size accuracy and the preset value. Therefore, the previous set of 1.2mm is taken as the lower limit of the preset ironing distance. Therefore, in this embodiment, the preset ironing distance can be selected from 1.2 to 1.6 mm, and is set to 1.4 mm. It should be noted that the preset ironing distance can be within the upper and lower limits of the ironing distance; the smaller the preset ironing distance, the stronger the ironing effect.

[0052] Step Two: Based on the preset printing path and preset layer thickness of the target printed part, input the above parameters and other relevant parameters into the 3D printer's control program, and after reading the given printing path code, perform continuous fiber 3D printing additive manufacturing of composite materials to obtain the target printed part. During the process of the print head moving along the preset path, the CF / PAEK filament first melts in the printing nozzle (temperature set to 400℃) and is deposited onto the printing platform. The deposited filament, i.e., the current deposited filament bundle, first passes through the high-temperature region (temperature set to 380℃) formed by the iron-shaped high-temperature metal ring 243 in the concentric stepped temperature control module 242. Figure 5 In region 1, downward pressure is applied to the current deposition filament via the concentric stepped temperature control module 242, ensuring good interlayer adhesion between the current deposition filament and the printing platform or the underlying deposition filament; simultaneously, as Figure 6 As shown, the previous deposited filament adjacent to the current deposited filament is also within the coverage area of ​​the high-temperature region, enabling secondary heating and melting of the adjacent deposited filament. This improves the interaction force between the previous and current deposited filaments, enhancing the inter-pass bonding strength of the printed product. Then, as the print head moves forward, the current deposited filament enters the second-step temperature segment formed by the stepped temperature control molding module, as shown... Figure 5In region 2, isothermal crystallization occurs under a preset temperature field. Under similar temperature and pressure, the PAEK resin grains grow at a similar rate, resulting in printed products with uniform grain size. Finally, the deposited filament bundle passes through a third-step temperature zone formed by the cooling metal ring 245, as shown... Figure 5 In region 3, the microstructure of the PAEK resin is rapidly cooled and fixed. At the same time, cooling under pressure can alleviate the degree of thermal deformation, thus preparing CF / PAEK composite material printed products.

[0053] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A fiber-reinforced composite material 3D printer, characterized in that, include: The print head includes a heat insulation shell (11) and a throat (12). The throat (12) is disposed inside the heat insulation shell (11) and is used to provide an extrusion channel for the printing filament. The heat insulation shell (11) is provided with a rotating part (34). An interlayer pressing device includes a fixed base (21), an interlayer pressing drive assembly (22), an interlayer pressing force sensor (23), and an interlayer pressing nozzle assembly. The fixed base (21) is installed inside a heat-insulating housing (11). The interlayer pressing drive assembly (22) is fixed to the fixed base (21), and the actuator of the interlayer pressing drive assembly (22) is connected to the interlayer pressing force sensor (23). The interlayer pressing force sensor (23) is connected to the interlayer pressing nozzle assembly. The interlayer pressing nozzle assembly is used to heat, melt, and cool the current deposited filament and the adjacent printed layer deposited filament, and under the drive of the interlayer pressing drive assembly (22), it performs hot pressing on the current deposited filament with a preset interlayer pressing force. An inter-pass pressing device includes a connecting rod (31), a lateral pressing rod (32), and an inter-pass hot pressing part (33). One end of the connecting rod (31) is fixed to the rotating part (34), and the other end is connected to the lateral pressing rod (32). The inter-pass hot pressing part (33) is installed on the lateral pressing rod (32). The end of the lateral pressing rod (32) is used to move with the print head during the printing process and to hot press and shape the side of the current deposited filament bundle with a first preset pressing temperature and a preset pressing interval. The inter-pass hot pressing part (33) is used to move synchronously with the lateral pressing rod (32) and to hot press and shape the upper surface of the current deposited filament bundle and the previous deposited filament bundle with a second preset pressing temperature and a preset pressing height.

2. The fiber-reinforced composite material 3D printer according to claim 1, characterized in that, The interlayer ironing device further includes a pressure equalizing plate; the pressure equalizing plate includes an upper pressure equalizing plate (251) and a lower pressure equalizing plate (252) connected to the upper and lower ends of the interlayer ironing force sensor (23), the upper pressure equalizing plate (251) is connected to the actuator of the interlayer ironing drive assembly (22), the lower pressure equalizing plate (252) is connected to the interlayer ironing nozzle assembly, and a heat insulation plate (26) is provided between the lower pressure equalizing plate (252) and the interlayer ironing nozzle assembly.

3. The fiber-reinforced composite material 3D printer according to claim 2, characterized in that, The interlayer pressing nozzle assembly includes: Heating block (241), which is connected to the lower equalizing plate (252) and located at the outlet end of the throat tube (12), is used to heat the printing filament in the throat tube (12); A concentric circle stepped temperature control module (242) is fixedly connected to the lower end of the heating block (241), and the throat tube (12) is located at the center of the concentric circle stepped temperature control module (242). The concentric circle stepped temperature control module (242) is used to apply a preset interlayer pressing force to the adjacent printing layer deposition filaments and the current deposition filaments, and at the same time form a stepped temperature field to heat and cool the current deposition filaments and the adjacent printing layer deposition filaments.

4. The fiber-reinforced composite material 3D printer according to claim 3, characterized in that, A heat insulation plate (26) is provided between the lower pressure equalizing plate (252) and the heating block (241).

5. The fiber-reinforced composite material 3D printer according to claim 4, characterized in that, The concentric circle stepped temperature control module (242) includes: An iron-type high-temperature metal ring (243) is used to heat the current deposition filament and the adjacent printing layer deposition filament at a first preset temperature. A stepped temperature-controlled metal ring (244) is provided, comprising several concentric metal rings with different diameters. All stepped temperature-controlled metal rings (244) are arranged concentrically outside the iron-type high-temperature metal ring (243). The stepped temperature-controlled metal ring (244) is used to form a preset temperature field with the temperature decreasing ring by ring from the inside to the outside, to control the temperature and cool the current deposition filament and the adjacent printing layer deposition filament, and to perform hot pressing on the current deposition filament. Cooling metal ring (245) is located outside the outermost stepped temperature-controlled metal ring (244) and is distributed in a concentric circle. The cooling metal ring (245) is used to cool the current deposition filament and the adjacent printed layer deposition filament at a second preset temperature. A heat insulation ring (246) is provided between the throat (12), the iron-type high-temperature metal ring (243), the stepped temperature-controlled metal ring (244), the cooling metal ring (245), and between two adjacent stepped temperature-controlled metal rings (244).

6. The fiber-reinforced composite material 3D printer according to claim 5, characterized in that, The concentric stepped temperature control module (242) also includes an additive dispensing channel (247), which is located between two adjacent heat insulation rings (246) and is used to dispense additives to the current deposited filament bundle during the printing process.

7. A method for 3D printing fiber-reinforced composite materials, implemented using the fiber-reinforced composite material 3D printer according to any one of claims 1-6, characterized in that, Includes the following steps: The printing parameters of the interlayer pressing device and the inter-pass pressing device are determined. The printing parameters include the optimal preset interlayer pressing force of the concentric circle stepped temperature control module (242), the temperature of the iron-type high temperature metal ring (243), the stepped temperature control metal ring (244), and the cooling metal ring (245) in the concentric circle stepped temperature control module (242), and the inter-pass pressing temperature and pressing distance of the inter-pass pressing device. Based on the preset printing path and preset layer thickness of the target printed part, the fiber-reinforced composite material 3D printer starts printing to obtain the target printed part.

8. The 3D printing method for fiber-reinforced composite materials according to claim 7, characterized in that, The optimal preset interlayer pressing force determination method of the concentric circle stepped temperature control module (242) includes: Based on the material coefficient of the printing filament, the interlayer shear strength of the finished product obtained by the printing filament under the comparative molding process, the comparative molding process coefficient, the preset printing line width, and the contact length of the concentric circle stepped temperature control module (242) with the printing filament in the radial direction, the theoretical maximum preset interlayer pressing force of the concentric circle stepped temperature control module (242) is calculated. Within the range of zero to the theoretical maximum preset interlayer pressing force, several preset interlayer pressing force test values ​​are selected according to preset step sizes. The interlayer shear sample corresponding to each preset interlayer pressing force test value is prepared using the fiber-reinforced composite material 3D printer, and the interlayer shear strength is tested. The preset interlayer pressing force corresponding to the highest interlayer shear strength is selected as the optimal preset interlayer pressing force.

9. The 3D printing method for fiber-reinforced composite materials according to claim 8, characterized in that, The theoretical maximum preset interlayer pressing force of the concentric circle stepped temperature control module (242) is calculated using the following formula: ； in, This is the theoretical maximum preset interlayer pressing force; The material coefficient of the printing filament; Interlaminar shear strength of the finished product obtained by printing filament under comparative molding process; To compare molding process coefficients; Preset print line width; The contact length between the concentric stepped temperature control module (242) and the printing wire in the radial direction is given.

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