Mirror image additive manufacturing system and geometric error prediction and compensation method in manufacturing process of mirror image additive manufacturing system

Abstract

The invention discloses a mirror image additive manufacturing system and a geometric error prediction and compensation method in the manufacturing process of the mirror image additive manufacturing system, the system comprises a printing planning module, an additive manufacturing module and a control module which are connected with one another, and the printing planning module generates a printing tail end motion path and technological parameters of next-step manufacturing; during manufacturing, a sensor in the additive manufacturing module performs multi-sensor fusion, senses manufacturing physical information in a multi-mode manner and sends the information to the control module; and the control module performs manufacturing contour precision regulation and control based on a geometric error prediction and compensation method, generates an update path and process parameter information and sends the information to the printing planning module to form a manufacturing cycle. Materials are laid in a mirror symmetry mode, the left printing head and the right printing head support each other, tool-free manufacturing is achieved, and manufacturing flexibility and process applicability are improved.

Description

Technical Field

[0001] The present invention relates to a technology in the field of material processing, specifically a mirror additive manufacturing system and a method for predicting and compensating geometric errors in the manufacturing process thereof. Background Art

[0002] Thermoplastics are easy to melt and can be efficiently solidified into the desired shape without high energy input and complex equipment design, which makes the printing technology of carbon fiber reinforced thermoplastic composites (CFRTP) both economical and energy-saving, and widely used in the field of material processing. Existing printing technology relies on rigid tools as the support of molded parts. The design and production of such tools are costly and time-consuming, and the bulky tools are not easy to carry and cannot be used in some special scenarios, further increasing the technical threshold and cost investment. Summary of the invention

[0003] In view of the above-mentioned deficiencies in the prior art, the present invention proposes a mirror-image additive manufacturing system and a method for predicting and compensating geometric errors in the manufacturing process thereof. By laying materials in a mirror-image symmetrical manner and allowing the left and right print heads to support each other, tool-free manufacturing is achieved, thereby improving manufacturing flexibility and process applicability.

[0004] The present invention is achieved through the following technical solutions:

[0005] The present invention relates to a mirror additive manufacturing system, comprising: a printing planning module, an additive manufacturing module and a control module connected to each other, wherein: the printing planning module generates a printing end motion path and process parameters for the next step of manufacturing; during manufacturing, the sensors in the additive manufacturing module perform multi-sensor fusion and multi-modal perception of manufacturing physical information, and send it to the control module; the control module performs manufacturing contour accuracy control based on a geometric error prediction and compensation method, generates an updated path and process parameter information and sends it to the printing planning module, forming a manufacturing cycle.

[0006] The printing planning module includes: a process parameter generation submodule, a printing terminal functional mechanism control submodule, a printing terminal motion mechanism control submodule and a printing path generation submodule, wherein: the process parameter generation submodule generates target values ​​of process parameters such as printing terminal motion speed, temperature, pressure, etc. in the manufacturing process according to model characteristics, printing requirements, and printing path, and sends them to the control module; the printing terminal functional mechanism control submodule processes the control instructions and updates the heater output power in real time; the printing terminal motion mechanism control submodule processes the control instructions and updates the printing terminal motion mechanism path in real time; the printing path generation submodule determines the reference surface for three-dimensional model printing according to model characteristics and printing requirements and generates a neutral surface, and then uses the generated neutral surface printing path as the basis, performs mirror offset and filtering processing in a loop, and generates a three-dimensional model printing path.

[0007] The neutral plane is determined by, in the imported three-dimensional model, based on the printing direction, determining the three-dimensional model printing reference boundary surface, converting the printing reference boundary surface solid model into a triangular mesh surface model, extracting the triangular mesh information of the printing reference boundary surface, and then generating a neutral plane equidistant from the two printing reference boundary surfaces according to the mesh node number, node coordinates, mesh unit number and mesh unit normal vector.

[0008] The neutral plane printing path is generated based on the generated neutral plane triangular mesh unit information, and the neutral plane printing path is generated by the intersection method of equidistant plane and neutral plane. Given the printing reference axis, printing angle, and printing width, the equidistant plane is generated based on the above parameters and the intersection points of the equidistant plane and each triangular mesh unit of the neutral plane are calculated. The intersection points are sorted and the path is smoothed to generate the path on the neutral plane.

[0009] The mirror offset is to perform mirror equidistant offset on the path point on the neutral plane along the normal positive direction and the normal negative direction of the triangular unit where the path point is located according to the preset layer thickness.

[0010] The filtering process determines the relative position between the generated mirror printing path points and the printing reference plane, filters the generated mirror printing path, removes the path points outside the two printing reference boundary surfaces, and only retains the path points inside the two printing reference boundary surfaces.

[0011] The described cycle is performed, the mirror offset distance is gradually increased according to the layer thickness, and new mirror printing paths are generated and filtered, until all the generated mirror printing paths are located outside the two printing reference boundary surfaces, at which time all the generated mirror printing paths can accurately cover the three-dimensional model.

[0012] The additive manufacturing module includes: a first manufacturing subunit and a second manufacturing subunit that are symmetrically arranged and have the same structure. The manufacturing subunit includes: a main plate, a pressure sensing unit, a shearing unit, a re-feeding unit, a tension unit, a heat source unit, a pressure roller rotation unit, a connecting piece and a printing end motion mechanism.

[0013] The heat source unit includes: a heater and an infrared thermal imager. The heater heats the material, and the infrared thermal imager takes real-time photos of the printing area to obtain the temperature field data of the material, wherein: the infrared thermal imager obtains the real material temperature in real time during the printing process, and sends the real material temperature to the control module in real time. The heater is fixed on the main board, and the infrared thermal imager is fixed on the main board through the support plate.

[0014] The connecting piece is fixed on the main body plate and connected to the end of the multi-axis motion mechanism, that is, the printing end motion mechanism.

[0015] The pressure sensing unit includes: a pressure sensor, a pressure roller, a supporting device, an insulating asbestos board and a first cylinder, wherein: the pressure sensor obtains the actual material pressure in real time during the printing process, and sends the actual material pressure to the control module in real time; the central axis of the pressure roller is parallel to the front-to-back direction, the pressure roller, the supporting device, the insulating asbestos board, the pressure sensor, and the first cylinder are connected in sequence from left to right, the first cylinder is fixed on the main plate and pushes the pressure roller to the left, and cooperates with the pressure roller on the opposite side to squeeze and generate compaction pressure; the insulating asbestos board can isolate the heat on the pressure roller to avoid damaging the pressure sensor.

[0016] The shearing unit comprises: a third cylinder and a blade. The third cylinder drives the blade to shear the material. The third cylinder is fixed on the main plate.

[0017] The re-feeding unit comprises: a driving wheel, a driven wheel, a first motor and a second cylinder. The driving wheel and the driven wheel are arranged vertically and parallel to the left and right directions. The first motor drives the driving wheel to rotate, and the second cylinder presses the driven wheel onto the driving wheel. The first motor and the second cylinder are fixed on the main body plate. Before the material is installed and printing starts, the second cylinder is not started, and the driving wheel and the driven wheel are separated. When printing starts, the material is installed in the channel and passes between the driving wheel and the driven wheel. The second cylinder is started, and the driven wheel presses the material onto the driving wheel to achieve material compression. The first motor drives the driving wheel, which rotates during printing, driving the driven wheel to extrude the material together.

[0018] The tension unit includes: a material roll, a brake and a tension sensor. The material roll is wound around the material. During the printing process, the material roll is forced to rotate under the drive of the re-feeding unit to realize the feeding of the material. The brake provides torque for the material roll to maintain a stable tension force for the wire feeding to prevent unstable feeding of the material caused by the high-speed rotation of the material roll, or even falling off. The tension sensor obtains the material tension data in real time. The material roll, the brake and the tension sensor are all fixed on the main plate.

[0019] The pressure roller rotation unit also includes: a second motor, a supporting device, a synchronous belt, a motor synchronous wheel, and a pressure roller synchronous wheel. The second motor is fixed to the main plate through the supporting device, the motor synchronous wheel is installed on the shaft of the second motor, and the pressure roller synchronous wheel is installed on the shaft of the pressure roller. The synchronous belt transmits the rotation of the second motor to the pressure roller through belt transmission, so that the pressure roller can rotate actively.

[0020] The present invention relates to a method for predicting and compensating geometric errors in a manufacturing process based on the above system. By analyzing the force on the printed material part in the manufacturing process of the mirror additive manufacturing system and calculating the bending moment M, the curvature change ΔK and length change Δl of the uncooled deformable micro-element segment in the printed material part after the force is calculated according to the bending moment formula and the stretching formula in material mechanics, and then the central angle change corresponding to the uncooled deformable micro-element segment in the printed material part after the force is obtained. Finally, the infinitesimal segment is integrated to obtain the length change ΔL and the center angle change ΔΦ of the entire material relative to the design contour after manufacturing. Then, by adjusting the tension T on the material, the length change ΔL and the center angle change ΔΦ of the material after manufacturing are reduced.

[0021] The printed material portion includes: a cooled non-deformable segment with a length of l and an uncooled deformable micro-element segment with a length of dl, wherein the cooled non-deformable segment can be restored to its original curvature after the bending moment M is removed due to only elastic deformation, and the uncooled deformable micro-element segment undergoes plastic deformation and maintains the curvature K' and length change Δl when the bending moment M is applied after cooling.

[0022] The bending moment is generated by the force at the pressure rollers at the left and right printing ends of the mirror additive manufacturing system, including: the friction between the material and the pressure roller, the tension of the material itself, the centripetal force when the left and right printing ends perform curved motion, etc.

[0023] The bending moment formula is Where K is the curvature, M is the bending moment, E is the elastic modulus of the material, and I is the moment of inertia of the cross section.

[0024] The stretching formula is Where T is the tension on the material, dl is the initial length of the uncooled deformable microelement, E is the elastic modulus, and A is the cross-sectional area of ​​the material.

[0025] The central angle, i.e. the central angle of the arc corresponding to the curved segment material, can be obtained by It is concluded that is the central angle, K is the curvature of the material, and dl is the length of the material.

[0026] The length change ΔL is Where: T is the tension on the material, L is the set length of the material after manufacturing, that is, the length of the material after manufacturing without any error, E is the elastic modulus, and A is the cross-sectional area of ​​the material.

[0027] The central angle change ΔΦ is Where: L is the set length of the material after manufacturing, that is, the length of the material after manufacturing without any error, E is the elastic modulus, I is the moment of inertia of the section, T is the tension on the material, and K is the curvature.

[0028] The tension T of the adjusted material is: It can be found from the above formula that E, I, and A are related to the material properties, and L and K are related to the set values ​​of the material profile before manufacturing, and none of them can be adjusted by the mirror image additive manufacturing system. T not only has a great influence on the size of ΔL and ΔΦ, but can also be adjusted by the mirror image additive manufacturing system, so the purpose of reducing the length change ΔL and the central angle change ΔΦ of the material after manufacturing can be achieved by reducing the value of T.

[0029] The expression formula of the length change ΔL and the center angle change ΔΦ is obtained by the following derivation process:

[0030] a) Calculate the length change of the uncooled deformable micro-element in the printed material after the force is applied according to the tensile formula in material mechanics

[0031] b) Taking the material fixed point as the reference point, calculate the bending moment generated by the force T at the printing end rollers of the left and right parts of the mirrored additive manufacturing system

[0032] c) Calculate the curvature change of the uncooled deformable micro-element in the printed material after being stressed according to the bending moment formula in material mechanics

[0033] d) By Calculate the change in the central angle of the uncooled deformable micro-element in the printed material after being stressed Since Δl is too small compared to dl (the ratio is less than 0.001), Δl can be ignored, and we can get

[0034] e) The length change Δl and the central angle change of the microelement segment Integrate to obtain the length change of the entire section of material relative to the designed contour after manufacturing is completed Central angle change

[0035] The adjustment of the tension T of the material is achieved by actively rotating the pressure roller, which specifically includes:

[0036] When the pressure roller is not actively rotating, due to the influence of friction, the length of the material printed from the pressure roller and the length of the movement path of the multi-axis motion mechanism do not match, causing the printed material part to be stretched straight between the fixed point and the pressure roller. As the multi-axis motion mechanism moves, the stretched material will gradually pull the new printed material from the pressure roller, causing relative sliding between the material and the pressure roller, introducing additional sliding friction.

[0037] When the pressure roller rotates actively, rolling friction is introduced between the pressure roller and the material, so that the length of the material printed from the pressure roller matches the length of the movement path of the multi-axis motion mechanism, avoiding additional tension and additional sliding friction.

[0038] The force at the end roller of the left and right parts of the mirrored additive manufacturing system is split, where T = 2(F1+f2-f1), where F1 is the tension of the material itself, f2 is the additional sliding friction introduced when the material is stretched, and f1 is the rolling friction introduced when the roller rotates actively. It can be found that T decreases after the roller rotates actively, thereby achieving the purpose of reducing the length change ΔL and the center angle change ΔΦ of the material after manufacturing. Technical Effects

[0039] The present invention analyzes the force of the printed material part during the manufacturing process, and obtains the relationship between the length change and the center angle change of the whole section of material relative to the design contour after the manufacturing is completed and the various parameters of the printing process. The geometric error compensation method realizes precision control by actively rotating the pressure roller. The present invention clarifies the influencing factors and generation mechanism of the precision error in the mirror additive manufacturing process, and proposes a precision error compensation method that can be applied to a wider range of manufacturing requirements, thereby ensuring the accuracy and consistency of the mirror additive process products. Compared with the dependence on molds in the existing printing technology, the present invention avoids the problem that different components require different molds, can quickly adapt to the diverse component shapes, and also saves the time and material costs required for mold manufacturing, improves the flexibility of production, and thus significantly improves production efficiency. By proposing a method for predicting geometric errors in the manufacturing process, it intuitively represents the influence of various relevant parameters in the manufacturing process on the length change and center angle change of the whole section of material relative to the design contour after the manufacturing is completed, and it is convenient to select key parameters for adjustment to achieve the purpose of reducing the length change and center angle change. By proposing a mirror additive manufacturing system, hardware support and control modules are provided for the precision control of mirror additive manufacturing, which facilitates the realization of a complete mirror additive manufacturing process and can be applied to the precision control of a wider range of manufacturing requirements. By proposing a geometric error compensation method in the manufacturing process, the precision control problem of the mirror additive manufacturing system in the manufacturing process is effectively solved, providing a precision control solution for similar structure manufacturing systems that is suitable for higher curvature manufacturing requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Schematic diagram of the system of the present invention.

[0041] Figure 2 It is a rear structural schematic diagram of the first manufacturing subunit of the additive manufacturing module of the mirror image additive manufacturing system of the present invention.

[0042] Figure 3 It is a front view structural schematic diagram of the first manufacturing subunit of the additive manufacturing module of the mirror image additive manufacturing system of the present invention.

[0043] Figure 4 Flowchart for material installation.

[0044] Figure 5 This is a diagram of the geometric error theoretical prediction model of the present invention.

[0045] Figure 6 Comparison of theoretical and experimental curves of layer number-angle error between experimental group 1 and control group 1.

[0046] Figure 7 Comparison of theoretical and experimental curves of layer number-angle error between experimental group 2 and control group 2.

[0047] Figure 8 Comparison of theoretical and experimental curves of layer number-angle error between experimental group 3 and control group 3.

[0048] Fig. 9 Comparison of material profile curves after printing between experimental group 1 and control group 1.

[0049] Fig.10 Comparison of material profile curves after printing between experimental group 2 and control group 2.

[0050] Fig.11 Comparison of material contour curves after printing between experimental group 3 and control group 3.

[0051] Fig.12 It is a schematic diagram of temperature stabilization control and pressure stabilization control in the control module of the mirror image additive manufacturing system of the present invention.

[0052] Fig.13 A schematic diagram of a print path generation process of the print planning module of the present invention.

[0053] Fig.14 The following is a flow chart of an embodiment.

[0054] Among them, 1 is a pressure sensor, 2 is a first cylinder, 3 is a connecting piece, 4 is a material roll, 5 is a support plate, 6 is a heater, 7 is an infrared thermal imager, 8 is a third cylinder, 9 is a pressure roller, 10 is a driving wheel, 11 is a second cylinder, 12 is a driven wheel, 13 is a first motor, 14 is a blade, 15 is a brake, 16 is a heat-insulating asbestos board, 17 is a main body plate, 18 is a second motor, 19 is a motor synchronous wheel, 20 is a pressure roller synchronous wheel, 21 is a tension sensor, 22 is a material, and 23 is a bracket (fixed point). DETAILED DESCRIPTION

[0055] like Fig.14 As shown, the manufacturing method described is based on the mirror additive manufacturing system of this embodiment, and the printing end motion path and process parameters for the next manufacturing step are generated through the printing planning module; the sensor in the additive manufacturing module multi-sensor fusion and multi-modal perception manufacturing physical information are sent to the control module; the control module performs manufacturing contour accuracy control based on the geometric error prediction and compensation method, generates an updated path and process parameter information and sends it to the printing planning module, forming a manufacturing cycle.

[0056] like Figure 1 , Figure 2 , Figure 3 As shown, the additive manufacturing module includes: a symmetrical first manufacturing subunit and a second manufacturing subunit, and the second manufacturing subunit includes: a main plate 17, a pressure sensing unit, a shearing unit, a re-feeding unit, a tension unit, a heat source unit, a pressure roller rotation unit, a connecting part 3 and a printing end motion mechanism.

[0057] like Figure 1 , Figure 3 As shown, the pressure sensing unit includes: a pressure sensor 1, a pressure roller 9, a supporting device, an insulating asbestos board 16 and a first cylinder 2; the central axis of the pressure roller 9 is parallel to the front-to-back direction, the pressure roller 9, the supporting device, the insulating asbestos board 16, the pressure sensor 1, and the first cylinder 2 are connected in sequence from left to right, and the first cylinder 2 is fixed on the main plate 17 and pushes the pressure roller 9 to the left.

[0058] The shearing unit comprises: a third cylinder 8 and a blade 14 . The third cylinder 8 drives the blade 14 to shear the material 22 . The third cylinder 8 is fixed on the main plate 17 .

[0059] like Figure 2 and Figure 3 As shown, the re-delivery unit includes: a driving wheel 10, a driven wheel 12, a first motor 13 and a second cylinder 11. The driving wheel 10 and the driven wheel 12 are arranged vertically and parallel to the left and right directions. The first motor 13 drives the driving wheel 10 to rotate, and the second cylinder 11 presses the driven wheel 12 onto the driving wheel 10. The first motor 13 and the second cylinder 11 are fixed on the main plate 17.

[0060] The tension unit includes: a material roll 4, a brake 15 and a tension sensor 21. The material roll 4 is wound with material 22. The brake 15 provides torque for the material roll 4 to maintain a stable tensioning force for wire feeding. The tension sensor 21 obtains material tension data in real time. The material roll 4, the brake 15 and the tension sensor 21 are all fixed on the main plate 17.

[0061] The heat source unit includes: a heater 6, an infrared thermal imager 7 and a support plate 5; the heater 6 heats the material 22; the infrared thermal imager 7 photographs the printing area in real time to obtain temperature field data of the material 22; the heater 6 is fixed on the main plate 17, and the infrared thermal imager 7 is fixed on the main plate 17 through the support plate 5.

[0062] The pressure roller rotation unit includes: a second motor 18, a support device, a synchronous belt, a motor synchronous wheel 19, and a pressure roller synchronous wheel 20. The second motor 18 is fixed to the main plate 17 through the support device, the motor synchronous wheel 19 is installed on the shaft of the second motor 18, and the pressure roller synchronous wheel 20 is installed on the shaft of the pressure roller 9. The synchronous belt transmits the rotation of the second motor 18 to the pressure roller 9 through belt transmission, so that the pressure roller 9 can rotate actively.

[0063] The connecting member 3 is fixed on the main body plate 17 and connected to the end of the multi-axis motion mechanism, that is, the printing end motion mechanism.

[0064] like Fig.12 As shown, the infrared thermal imager 7 also obtains the real material temperature in real time during the printing process, and sends the real material temperature to the control module in real time.

[0065] like Fig.12 As shown, the pressure sensor 1 obtains the actual material pressure in real time during the printing process, and sends the actual material pressure to the control module in real time.

[0066] The control module includes: a temperature stabilization control module, a pressure stabilization control module and a control instruction generation subsystem, wherein: the control instruction generation subsystem generates a control instruction according to the modification value of the heater output power and the modification value of the print end motion mechanism path, and then sends it to the print end functional mechanism control subsystem and the print end motion mechanism control subsystem; the temperature stabilization control module calculates the temperature difference in real time, calculates the modification value of the heater output power in real time according to the temperature difference, and sends the modification value of the heater power output to the control instruction generation subsystem in real time; the pressure stabilization control module calculates the pressure difference in real time, calculates the modification value of the print end motion mechanism path in real time according to the pressure difference, and sends the modification value of the print end motion mechanism path to the control instruction generation subsystem in real time.

[0067] The temperature stabilization control module calculates the temperature difference in real time, specifically: temperature difference = actual material temperature - target material temperature difference, heater output power modification value = Kp * ×T+Ki * ×∑T+Kd * ×ΔT, where: T is the temperature difference at the current moment of the current printing process, ∑T is the sum of all temperature differences from the current printing process up to the current moment, ΔT = the temperature difference at the current moment of the current printing process - the temperature difference at the previous moment of the current printing process; Kp * 、Ki * , Kd * The controller parameter combination that meets the requirements is found by simulating in a virtual environment and continuously iteratively optimizing using a reinforcement learning model.

[0068] The pressure stabilization control module calculates the pressure difference in real time, specifically: pressure difference = actual material pressure - target material pressure difference; modification value of the printing end motion mechanism path = Kp′×F+Ki′×∑F+Kd′×ΔF, wherein: F is the pressure difference at the current moment of the current printing process, ∑F is the sum of all pressure differences from the current printing process to the current moment, ΔF = the pressure difference at the current moment of the current printing process - the pressure difference at the previous moment of the current printing process; Kp′, Ki′, and Kd′ are controller parameter combinations that meet the requirements and are found by simulation in a virtual environment and continuous iterative optimization using a reinforcement learning model.

[0069] The printing planning module includes: a process parameter generation submodule, a printing terminal functional mechanism control submodule, a printing terminal motion mechanism control submodule and a printing path generation submodule.

[0070] The process parameter generation submodule generates the target values ​​of process parameters such as the movement speed, temperature, and pressure of the printing end during the manufacturing process according to the model characteristics, printing requirements, and printing path, and sends them to the control module.

[0071] After the printing terminal functional mechanism control submodule processes the control instruction, it updates the heater output power in real time.

[0072] After the printing end motion mechanism control submodule processes the control instruction, it updates the printing end motion mechanism path in real time.

[0073] like Fig.13 As shown, the printing path generation submodule of the printing planning module determines the reference surface for printing the three-dimensional model based on the model features and printing requirements, and then generates the neutral surface of the three-dimensional model, and then generates the neutral surface printing path and based on this, generates the mirror printing path through a loop by mirror offset and performs filtering processing, and finally ends the loop after all the printing paths are filtered to generate the final three-dimensional model printing path.

[0074] For the mirror additive manufacturing system, the present invention also proposes a method for predicting and compensating geometric errors during the manufacturing process, such as Figure 5 As shown, the geometric error prediction method is to analyze the force on the printed material part in the manufacturing process of the mirror additive manufacturing system and calculate the bending moment M, and then calculate the curvature change ΔK and length change Δl of the uncooled deformable micro-element segment in the printed material part after the force is applied according to the bending moment formula and the stretching formula in material mechanics, and then obtain the central angle change corresponding to the uncooled deformable micro-element segment in the printed material part after the force is applied Finally, the infinitesimal segment is integrated to obtain the length change ΔL and the center angle change ΔΦ of the entire material relative to the designed contour after manufacturing.

[0075] Taking the printing process of three times as an example, that is, the number of printed layers is six, the steps of printing using the system of the present invention are described:

[0076] 1) Material installation: Figure 4 As shown, after the material is wound on the material roll, the material passes between the driving wheel and the driven wheel, passes through the blade to the pressure roller, and the material is fixed on the bracket 23, which is a vertical frame or a truss fixed on the ground. After that, the connecting piece is connected to the end of the printing end motion mechanism. When the material passes between the driven wheel and the driving wheel, the second cylinder is started to press the material between the driven wheel and the driving wheel. When the material reaches the pressure roller, the first cylinder is started to push out the pressure rollers on both sides and cooperate with the pressure rollers on the opposite side to squeeze the material.

[0077] 2) The first printing includes:

[0078] 2.1 The printing end motion mechanism starts to move along the printing path. At the same time, the heater is started to heat the material. The infrared thermal imager starts to capture the temperature field data of the printing area in real time and monitors the material temperature. The pressure sensor obtains the material pressure in real time. The first motor drives the active wheel and the driven wheel to rotate to drive the material forward. The second motor drives the pressure roller to rotate through the belt drive to drive the material away from the pressure roller to avoid the material being tightened, effectively reducing the tension of the material at the pressure rollers at the printing ends of the left and right parts of the mirror additive manufacturing system, so as to achieve the purpose of reducing the length change and the central angle change of the material after the manufacturing is completed, and achieve the effect of precision control in the manufacturing process; in this process, the temperature stabilization control module and the pressure stabilization control module respectively calculate the modified value of the heater output power and the modified value of the printing end motion mechanism path according to the real-time data, and send them to the corresponding control subsystem (i.e., the printing end functional mechanism control subsystem or the printing end motion mechanism control subsystem) through the control instruction generation subsystem, and adjust the heating power and printing path in real time to ensure that the material temperature and pressure remain within the target range.

[0079] 2.2 When the laying is about to be completed, start the third cylinder to drive the blade to shear the material and cut off the excess part. After shearing, the third cylinder is reset.

[0080] 2.3 Continue laying the reserved material from the blade to the pressure roller until the first laying is completed.

[0081] 3) The second printing includes:

[0082] 3.1 The printing end motion mechanism moves to the initial position.

[0083] 3.2 Same as the first printing, the motion mechanism at the end of the printing starts to move along the printing path, and the pressure roller is driven to rotate by the second motor. When the laying is about to be completed, the third cylinder is started to drive the blade to shear the material and cut off the excess part. After shearing, the third cylinder is reset.

[0084] 3.3 Continue laying the reserved material from the blade to the pressure roller until the second laying is completed.

[0085] 4) The third printing includes:

[0086] 4.1 The printing end motion mechanism moves to the initial position.

[0087] 4.2 Same as the first printing, the motion mechanism at the end of the printing starts to move along the printing path, and the pressure roller is driven to rotate by the second motor. When the laying is about to be completed, the third cylinder is started to drive the blade to shear the material and cut off the excess part. After shearing, the third cylinder is reset.

[0088] 4.3 Continue laying the reserved material from the blade to the pressure roller until the third laying is completed, turn off the heater, the first motor, the second motor, the infrared thermal imager, the first cylinder, the second cylinder, and disconnect the connector from the end of the printing end motion mechanism.

[0089] After specific experiments, the printing path is set to a straight line segment of 100mm vertically downward, so that the multi-axis motion mechanism can complete the posture adjustment, followed by an arc segment with a central angle of the set value. The starting and end points of the arc segment are located on the same vertical line and the vertical distance is 400mm. Finally, a straight line segment of 100mm vertically downward is set to complete the posture adjustment of the multi-axis motion mechanism.

[0090] Experimental group 1: using the mirror additive manufacturing system of the present invention, setting the material contour central angle to 50°, the initial speed of the printing end motion mechanism to 10 mm / s, the material pressure to 30 N, and printing 1 time, 2 times, and 3 times (2 layers, 4 layers, and 6 layers) respectively; Control group 1: basically the same as experimental group 1, the only difference is that there is no pressure roller rotating unit in the mirror additive manufacturing system.

[0091] Experimental Group 2: Using the mirror-image additive manufacturing system of the present invention, the material contour central angle was set to 50°, the initial speed of the printing end motion mechanism was 20 mm / s, the material pressure was 10 N, and printing was performed 1 time, 2 times, and 3 times (2 layers, 4 layers, and 6 layers) respectively; Control Group 2: Basically the same as Experimental Group 2, the only difference is that there is no pressure roller rotation unit in the mirror-image additive manufacturing system.

[0092] Experimental Group 3: Using the mirror-image additive manufacturing system of the present invention, the material contour central angle was set to 50°, the initial speed of the printing end motion mechanism was 20 mm / s, the material pressure was 30 N, and printing was performed 1 time, 2 times, and 3 times (2 layers, 4 layers, and 6 layers) respectively; Control Group 3: Basically the same as Experimental Group 3, the only difference is that there is no pressure roller rotation unit in the mirror-image additive manufacturing system.

[0093] The comparison of layer number-angle error curves between experimental group 1 and control group 1, experimental group 2 and control group 2, and experimental group 3 and control group 3 during printing is shown in Figure 2. Figure 6 , Figure 7 and Figure 8 As shown, the Figure 6 to Figure 8 It can be seen that the theoretically calculated change in the center angle is close to the experimentally obtained change in the center angle. Since the theoretically calculated and experimentally obtained length changes are too small compared to the length of the material after manufacturing, the experimentally obtained length change is difficult to measure. It can be considered that at the length scale of the material after manufacturing, the theoretically calculated length change is close to the experimentally obtained length change. From the above analysis, it can be considered that the above-mentioned geometric error prediction method is more accurate; the comparison of the material contour curves after printing between experimental group 1 and control group 1, experimental group 2 and control group 2, and experimental group 3 and control group 3 are shown below. Fig. 9 , Fig.10 and Fig.11 As shown, from Figure 6 to Figure 11 It can be seen that compared with control groups 1 to 3, experimental groups 1 to 3 can reduce the changes in the central angle and length so that the contour of the material after manufacturing is more consistent with the design contour. It can be considered that the above-mentioned geometric error compensation method has a compensation effect.

[0094] The above-mentioned specific implementation can be partially adjusted in different ways by those skilled in the art without departing from the principle and purpose of the present invention. The protection scope of the present invention shall be based on the claims and shall not be limited by the above-mentioned specific implementation. Each implementation scheme within its scope shall be subject to the constraints of the present invention.

Claims

1. A mirror additive manufacturing system, characterized in that: include: A printing planning module, an additive manufacturing module and a control module are interconnected, wherein: the printing planning module generates a printing end motion path and process parameters for the next step of manufacturing; During manufacturing, the sensors in the additive manufacturing module use multi-sensor fusion and multi-modal perception to perceive the manufacturing physical information and send it to the control module; the control module controls the manufacturing contour accuracy based on the geometric error prediction and compensation method, generates an updated path and process parameter information and sends it to the printing planning module, forming a manufacturing cycle.

2. The mirror-image additive manufacturing system according to claim 1, characterized in that: The printing planning module includes: a process parameter generation submodule, a printing terminal functional mechanism control submodule, a printing terminal motion mechanism control submodule and a printing path generation submodule, wherein: the process parameter generation submodule generates target values ​​of process parameters such as printing terminal motion speed, temperature, pressure, etc. in the manufacturing process according to model characteristics, printing requirements, and printing path, and sends them to the control module; the printing terminal functional mechanism control submodule processes the control instructions and updates the heater output power in real time; the printing terminal motion mechanism control submodule processes the control instructions and updates the printing terminal motion mechanism path in real time; the printing path generation submodule determines the reference surface for three-dimensional model printing according to model characteristics and printing requirements and generates a neutral surface, and then uses the generated neutral surface printing path as the basis, performs mirror offset and filtering processing in a loop, and generates a three-dimensional model printing path.

3. The mirror-image additive manufacturing system according to claim 2, characterized in that: The neutral surface is obtained by determining the three-dimensional model printing reference boundary surface based on the printing direction in the imported three-dimensional model, converting the printing reference boundary surface solid model into a triangular mesh surface model, extracting the triangular mesh information of the printing reference boundary surface, and generating a neutral surface equidistant from the two printing reference boundary surfaces according to the mesh node number, node coordinates, mesh unit number and mesh unit normal vector; The neutral plane printing path is generated based on the generated neutral plane triangular mesh unit information, using the equidistant plane and neutral plane intersection method to generate the neutral plane printing path, given the printing reference axis, printing angle, and printing width, based on the above parameters, generating the equidistant plane and calculating the intersection of the equidistant plane and each triangular mesh unit of the neutral plane, sorting the intersection points and performing path smoothing to generate the path on the neutral plane; The mirror offset is to perform mirror equidistant offset on the path point on the neutral plane along the normal positive direction and the normal negative direction of the triangular unit where the path point is located according to the preset layer thickness; The filtering process determines the relative position between the generated mirror printing path points and the printing reference plane, filters the generated mirror printing path, removes the path points outside the two printing reference boundary surfaces, and only retains the path points inside the two printing reference boundary surfaces; The described cycle is performed, the mirror offset distance is gradually increased according to the layer thickness, and new mirror printing paths are generated and filtered, until all the generated mirror printing paths are located outside the two printing reference boundary surfaces, at which time all the generated mirror printing paths can accurately cover the three-dimensional model.

4. The mirror-image additive manufacturing system according to claim 1, characterized in that: The additive manufacturing module comprises: a first manufacturing subunit and a second manufacturing subunit which are symmetrically arranged and have the same structure, and the manufacturing subunit comprises: a main plate, a pressure sensing unit, a shearing unit, a re-feeding unit, a tension unit, a heat source unit, a pressure roller rotating unit, a connecting piece and a printing end motion mechanism; The heat source unit includes: a heater and an infrared thermal imager, the heater heats the material, and the infrared thermal imager takes real-time photos of the printing area to obtain the temperature field data of the material, wherein: the infrared thermal imager obtains the real material temperature in real time during the printing process, and sends the real material temperature to the control module in real time, the heater is fixed on the main board, and the infrared thermal imager is fixed on the main board through the support plate; The connecting piece is fixed on the main plate and connected to the end of the multi-axis motion mechanism, that is, the printing end motion mechanism; The pressure sensing unit comprises: a pressure sensor, a pressure roller, a supporting device, an insulating asbestos board and a first cylinder, wherein: the pressure sensor obtains the real material pressure in real time during the printing process, and sends the real material pressure to the control module in real time; the central axis of the pressure roller is parallel to the front-back direction, the pressure roller, the supporting device, the insulating asbestos board, the pressure sensor, and the first cylinder are connected in sequence from left to right, the first cylinder is fixed on the main plate and pushes the pressure roller to the left, and cooperates with the pressure roller on the opposite side to squeeze and generate compaction pressure; the insulating asbestos board can isolate the heat on the pressure roller to avoid damaging the pressure sensor; The shearing unit comprises: a third cylinder and a blade, the third cylinder drives the blade to shear the material, and the third cylinder is fixed on the main plate; The re-feeding unit comprises: a driving wheel, a driven wheel, a first motor and a second cylinder. The driving wheel and the driven wheel are arranged vertically and parallel to the left and right directions. The first motor drives the driving wheel to rotate, and the second cylinder presses the driven wheel onto the driving wheel. The first motor and the second cylinder are fixed on the main body plate. Before the material is installed and printing starts, the second cylinder is not started, and the driving wheel and the driven wheel are separated. When printing starts, the material is installed in the channel and passes between the driving wheel and the driven wheel. The second cylinder is started, and the driven wheel presses the material onto the driving wheel to achieve material compression. The first motor drives the driving wheel to rotate during printing, driving the driven wheel to extrude the material together. The tension unit includes: a material roll, a brake and a tension sensor. The material roll is wound around the material. During the printing process, the material roll is forced to rotate under the drive of the re-feeding unit to realize the feeding of the material. The brake provides torque for the material roll to maintain a stable tension force for the wire feeding to prevent the material from being unstablely fed or even falling off due to the high-speed rotation of the material roll. The tension sensor obtains material tension data in real time. The material roll, the brake and the tension sensor are all fixed on the main plate. The pressure roller rotation unit also includes: a second motor, a supporting device, a synchronous belt, a motor synchronous wheel, and a pressure roller synchronous wheel. The second motor is fixed to the main plate through the supporting device, the motor synchronous wheel is installed on the shaft of the second motor, and the pressure roller synchronous wheel is installed on the shaft of the pressure roller. The synchronous belt transmits the rotation of the second motor to the pressure roller through belt transmission, so that the pressure roller can rotate actively.

5. The mirror-image additive manufacturing system according to claim 1, characterized in that: The control module includes: a temperature stabilization control module, a pressure stabilization control module and a control instruction generation subsystem, wherein: the control instruction generation subsystem generates a control instruction according to the modification value of the heater output power and the modification value of the print end motion mechanism path, and then sends it to the print end functional mechanism control subsystem and the print end motion mechanism control subsystem; the temperature stabilization control module calculates the temperature difference in real time, calculates the modification value of the heater output power in real time according to the temperature difference, and sends the modification value of the heater power output to the control instruction generation subsystem in real time; the pressure stabilization control module calculates the pressure difference in real time, calculates the modification value of the print end motion mechanism path in real time according to the pressure difference, and sends the modification value of the print end motion mechanism path to the control instruction generation subsystem in real time.

6. The mirror-image additive manufacturing system according to claim 5, characterized in that: The temperature stabilization control module calculates the temperature difference in real time, specifically: temperature difference = actual material temperature - target material temperature difference, heater output power modification value = Kp * ×T+Ki * ×∑T+Kd * ×ΔT, where: T is the temperature difference at the current moment of the current printing process, ∑T is the sum of all temperature differences from the current printing process up to the current moment, ΔF = the temperature difference at the current moment of the current printing process - the temperature difference at the previous moment of the current printing process; Kp * 、Ki * , Kd * It is through simulation in a virtual environment and continuous iterative optimization using a reinforcement learning model to find a controller parameter combination that meets the requirements; The pressure stabilization control module calculates the pressure difference in real time, specifically: pressure difference = actual material pressure - target material pressure difference; modification value of the printing end motion mechanism path = Kp′×F+Ki′×ΣF+Kd′×ΔF, wherein: F is the pressure difference at the current moment of the current printing process, ∑F is the sum of all pressure differences from the current printing process to the current moment, ΔF = the pressure difference at the current moment of the current printing process - the pressure difference at the previous moment of the current printing process; Kp′, Ki′, and Kd′ are controller parameter combinations that meet the requirements and are found by simulation in a virtual environment and continuous iterative optimization using a reinforcement learning model.

7. A method for predicting and compensating geometric errors in a manufacturing process based on the system described in any one of claims 1 to 6, characterized in that: By analyzing the stress of the printed material part in the manufacturing process of the mirror additive manufacturing system and calculating the bending moment M, the curvature change ΔK and length change Δl of the uncooled deformable micro-element segment in the printed material part after stress are calculated according to the bending moment formula and tensile formula in material mechanics, and then the central angle change of the uncooled deformable micro-element segment in the printed material part after stress is obtained. Finally, the infinitesimal segment is integrated to obtain the length change ΔL and the center angle change ΔΦ of the entire material relative to the design contour after manufacturing. Then, by adjusting the tension T on the material, the length change ΔL and the center angle change ΔΦ of the material after manufacturing are reduced.

8. The geometric error prediction and compensation method according to claim 7, characterized in that: The printed material portion comprises: a cooled non-deformable segment with a length of l and an uncooled deformable micro-element segment with a length of dl, wherein the cooled non-deformable segment recovers to its original curvature due to only elastic deformation after the bending moment M is removed, and the uncooled deformable micro-element segment undergoes plastic deformation, and after cooling, maintains the curvature K' and length change Δl when the bending moment M is applied.

9. The geometric error prediction and compensation method according to claim 7, characterized in that: The adjustment of the tension T of the material is achieved by actively rotating the pressure roller, which specifically includes: When the pressure roller does not rotate actively, due to the influence of friction, the length of the material printed from the pressure roller does not match the length of the movement distance of the multi-axis motion mechanism, causing the printed material to be stretched between the fixed point and the pressure roller. As the multi-axis motion mechanism moves, the stretched material will gradually pull the new printed material from the pressure roller, causing relative sliding between the material and the pressure roller, introducing additional sliding friction; When the pressure roller rotates actively, rolling friction is introduced between the pressure roller and the material, so that the length of the material printed from the pressure roller matches the length of the moving distance of the multi-axis motion mechanism, avoiding additional tension and additional sliding friction; The force at the pressure roller at the printing end of the left and right parts of the mirrored additive manufacturing system is decomposed, where T=2(f1+f2-f1), where F1 is the tension of the material itself, f2 is the additional sliding friction introduced when the material is stretched straight, and f1 is the rolling friction introduced when the pressure roller actively rotates. It is found that T decreases after the pressure roller actively rotates, thereby achieving the purpose of reducing the length change ΔL and the central angle change ΔΦ of the material after manufacturing is completed.

10. The geometric error prediction and compensation method according to claim 7, characterized in that: The expression formula of the length change ΔL and the center angle change ΔΦ is obtained by the following derivation process: a) Calculate the length change of the uncooled deformable micro-element in the printed material after the force is applied according to the tensile formula in material mechanics b) Taking the material fixed point as the reference point, calculate the bending moment generated by the force T at the printing end rollers of the left and right parts of the mirrored additive manufacturing system c) Calculate the curvature change of the uncooled deformable micro-element in the printed material after being stressed according to the bending moment formula in material mechanics d) By Calculate the change in the central angle of the uncooled deformable micro-element in the printed material after being stressed Since Δl is too small compared to dl (the ratio is less than 0.001), ignoring Δl, we can get e) The length change Δl and the central angle change of the microelement segment Integrate to obtain the length change of the entire section of material relative to the designed contour after manufacturing is completed Central angle change

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