Thermosetting composite material 3D printing head with high frequency compaction function and pressure control method

Abstract

A thermosetting composite material 3D printing head with high-frequency compaction function and pressure control method, comprising a whole mounting frame, a rotating module is connected to the top of the whole mounting frame, and an adjustable nozzle and a compaction mechanism are installed on the whole mounting frame; the fiber tows wound on the feeding mechanism are driven by the driving force provided by the heavy feeding roller to enter the adjustable nozzle, the inside of the adjustable nozzle is provided with a heating device, the fiber tows are extruded from the adjustable nozzle after being heated to a set temperature, and are compacted and shaped by the high-frequency linear reciprocating motion of the compaction mechanism before cooling; the compaction mechanism is connected with a follow-up ultraviolet light source for irradiating the fiber tows for pre-curing, and the compaction mechanism is connected with a peripheral control system; by means of the coupling relationship between the compaction frequency and the motion speed, the continuous and smooth shaping of the wire material is realized, at the same time, the ventilation cooling auxiliary shaping and the follow-up ultraviolet light source irradiation pre-curing are realized, and the 3D printing manufacturing of the fiber-reinforced thermosetting composite material component with high interlayer performance is realized.

Description

Technical Field

[0001] This invention relates to the field of thermosetting composite material 3D printing technology, specifically to a thermosetting composite material 3D printing head with high-frequency compaction function and a pressure control method. Background Technology

[0002] Currently, the mainstream technology for 3D printing fiber-reinforced thermosetting composites involves heating the filament in the 3D print head to above the viscosity fluidization temperature of the thermosetting resin prepolymer and below the critical temperature at which the high-temperature curing agent begins to initiate the thermosetting reaction. This causes the material to melt and pass through the print head. Once the filament is extruded and adheres to the printing platform, it is immediately ventilated and cooled, then solidified and shaped on the printing platform, and pre-cured under the assistance of ultraviolet light. In this process, after the molten filament is extruded, it relies solely on its own gravity and adhesive force to bond with the shaped filament before pre-curing. This results in low bonding strength between the filaments, high interlayer porosity, and poor interlayer shear strength in the final molded component. Furthermore, the filament extrusion direction in the nozzle is at a 90° angle to the printing surface, causing continuous friction between the filament and the nozzle, leading to wear of the continuous fibers in the filament and severely affecting the molding quality and performance of the final component.

[0003] Chinese patent (application number: 202110288334.3, entitled "A Deformable Hot Press 3D Printing Device") uses a pressure roller to apply pressure to the filament for compaction and shaping. The pressure roller is connected by a bearing and rolls with the filament. However, in the 3D printing process of carbon fiber reinforced thermosetting composite materials, the molten material will continuously stick to the bearing. After pre-curing, the bearing will fail, and the rolling friction will become sliding friction, which will cause greater wear on the fiber bundle and affect the performance of the component. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the present invention aims to provide a thermosetting composite material 3D printing head and pressure control method with high-frequency compaction function. By using a high-frequency linear reciprocating compaction mechanism to compact the printed filament, and by leveraging the coupling relationship between compaction frequency and movement speed, the filament can be continuously flattened and shaped. At the same time, ventilation and cooling assist in shaping and follow-up ultraviolet light source irradiation pre-curing, thereby realizing the 3D printing manufacturing of fiber-reinforced thermosetting composite material components with high interlayer performance.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A thermosetting composite material 3D printing head with high-frequency compaction function is used for 3D printing of fiber-reinforced thermosetting composite materials. It includes an integral mounting frame 6, a rotating module 5 connected to the top of the integral mounting frame 6, and an adjustable nozzle 2 and a compaction mechanism 4 mounted on the integral mounting frame 6. The fiber bundle 9 wound on the feeding mechanism 1 is driven by the heavy-duty roller 3 to enter the adjustable nozzle 2. The adjustable nozzle 2 is equipped with a heating device. After the fiber bundle 9 is heated to the set temperature, it is extruded from the adjustable nozzle 2. Before cooling, it is compacted and shaped by the high-frequency linear reciprocating motion of the compaction mechanism 4. The follow-up ultraviolet light source 8 connected to the compaction mechanism 4 irradiates the fiber bundle 9 for pre-curing, completing the printing action. The compaction mechanism 4 is connected to the peripheral control system 7.

[0007] The fiber-reinforced thermosetting composite material is composed of a reinforcing material and a matrix material; the reinforcing material is a fibrous solid, which is one of carbon fiber, glass fiber, or nylon; the matrix material is a thermosetting resin, which is phenolic resin or epoxy resin.

[0008] The adjustable nozzle 2 includes a high-temperature printing nozzle 202, which is installed at the bottom of the molten pool 201. The high-temperature printing nozzle 202 and the internal cavity of the molten pool 201 are connected. A heating rod 204 is embedded in the side wall of the molten pool 201. The molten pool 201 is connected to the arc-shaped groove on the overall mounting frame 6 by an adjustable positioning screw 203. The molten pool 201 can rotate the filament exit point of the high-temperature printing nozzle 202 through the arc-shaped groove. The rotation angle includes a range of 45°-80°.

[0009] The arc-shaped groove is centered on the filament exit point of the high-temperature printing nozzle 202.

[0010] The compaction mechanism 4 includes a high-frequency linear reciprocating motion element 401. A ring pressure sensor 404 is connected between the lower moving part and the top fixed part of the high-frequency linear reciprocating motion element 401. A pressure shoe base 403 is installed at the bottom of the lower moving part of the high-frequency linear reciprocating motion element 401. A flexible pressure shoe 402 is covered and installed on the pressure shoe base 403. The pressure shoe base 403 is connected to a ball slider 405. The ball slider 405 is installed on a ball slide rail 406. The ball slide rail 406 is connected to the overall mounting frame 6. The ring pressure sensor 404, the high-frequency linear reciprocating motion element 401, and the peripheral control system 7 are connected to form a pressure control system.

[0011] The high-frequency linear reciprocating motion element 401 is an electrical component with a frequency of at least 10Hz, including an electromagnetic push rod, an electric push rod, or a servo electric cylinder; the high-frequency linear reciprocating motion element 401 has an adjustable linear reciprocating motion frequency, adjustable stroke, and adjustable thrust.

[0012] The flexible pressure shoe 402 is made of a flexible material, including polymer materials or rubber; the bottom surface of the flexible pressure shoe 402 is a rectangular plane or a wavy curved surface, and the width is at least twice the diameter of a single fiber bundle 9; the flexible pressure shoe 402 is a cold pressure shoe with an internal channel-type hollow structure, and an air inlet and an air outlet are provided on the surface. The air inlet and the air outlet are respectively connected to the cold air pipe 407, which is mounted on the overall mounting frame 6; the initial height of the flexible pressure shoe 402 is higher than that of the high-temperature printing nozzle 202.

[0013] The reciprocating motion frequency f of the high-frequency linear reciprocating motion element 401, the effective shaping length l of the flexible pressure shoe 402, and the printing speed v satisfy the following relationship: That is, the effective shaping length of the flexible pressure shoe 402 is greater than the length of the fiber bundle 9 delivered by the adjustable nozzle 2 within the time consumed by the compaction mechanism 4 in one reciprocating motion, so as to ensure the 100% compaction rate of the fiber bundle 9; the effective shaping length l is the length of the rectangular bottom surface of the flexible pressure shoe 402.

[0014] The rotating module 5 is a programmable drive element, including a servo motor or a steering gear; the axis of the rotating module 5 is perpendicular to the horizontal plane and passes through the filament exit point of the high-temperature printing nozzle 202.

[0015] The pressure control method for a thermosetting composite material 3D printing head with high-frequency compaction function includes the following steps:

[0016] Step 1: Run the high-frequency linear reciprocating motion element 401 in the suspended state of the compaction mechanism 4, and record the average value of the peak force measured by the annular pressure sensor 404 as F0.

[0017] Step two: Adjust the height of the compaction mechanism 4 so that it contacts the printing base plate. The average value of the peak force measured by the annular pressure sensor 404 at this time is F. k ;

[0018] Step 3: The actual output pressure F' is received and calculated through the external control system 7. n ,F' n =F0-F k ;

[0019] Step four: Utilizing the relationship between pressure and current under constant voltage of the high-frequency linear reciprocating motion element 401, repeat steps one through three to calibrate the actual output pressure F' under different currents. n The curve of change;

[0020] Step 5, the peripheral control system 7 uses the calibrated actual output pressure F' n The pressure control is achieved by adjusting the current according to the set pressure using a changing curve.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1) The present invention uses a compaction mechanism 4 to compact the filament material, and a flexible pressure shoe 402 is a cold pressure shoe. The resin is shaped by the coupling effect of pressure and cooling, and is assisted by ultraviolet light irradiation for pre-curing. This solves the problem of poor interlayer density of fibers caused by pressureless cooling and shaping in the existing mainstream fiber-reinforced thermosetting composite material 3D printing technology. It has the advantages of low porosity and good interlayer strength of the prepared components.

[0023] 2) The present invention adopts a high-frequency linear reciprocating motion element 401 as the driving element of the compaction mechanism 4. During the shaping process, the flexible pressure shoe 402 has a short contact time with the fiber bundle 9 and less friction occurs, which solves the problem of easy bearing failure in the pressure roller shaping method. It has the advantages of high reliability, good compaction effect and less fiber damage.

[0024] 3) The compaction mechanism 4 of this invention adopts closed-loop feedback control to output compaction force, which has good control effect and high consistency of compaction effect, and is beneficial to improving the comprehensive performance of the component.

[0025] 4) The adjustable nozzle 2 of this invention has an adjustable filament feeding angle, which can be adjusted according to the actual situation. This solves the problem of mutual wear between the vertically fed filament bundle and the nozzle, and has the advantages of less fiber damage and strong spatial adaptability. Attached Figure Description

[0026] Figure 1 This is a three-dimensional schematic diagram of an embodiment of the present invention.

[0027] Figure 2 This is a three-dimensional schematic diagram of the adjustable nozzle in the embodiment.

[0028] Figure 3 This is a diagonal sectional view of the adjustable nozzle in the embodiment.

[0029] Figure 4 This is a three-dimensional schematic diagram of the compaction mechanism in the embodiment.

[0030] Figure 5 This is a schematic diagram of the electromagnetic actuator in an embodiment.

[0031] Figure 6 This is a schematic diagram of the flexible pressure shoe in the embodiment; wherein (a) is a flexible pressure shoe with a rectangular plane as the bottom surface; (b) is a flexible pressure shoe with a wavy curved bottom surface; (c) is a top view of the flexible pressure shoe with a rectangular plane; and (d) is an interface view of the flexible pressure shoe with a rectangular plane.

[0032] Figure 7 This is a schematic diagram illustrating the auxiliary shaping principle of the embodiment. Detailed Implementation

[0033] The present invention will now be described in detail with reference to the embodiments and accompanying drawings.

[0034] like Figure 1 As shown, a thermosetting composite material 3D printing head with high-frequency compaction function is used for 3D printing of fiber-reinforced thermosetting composite materials. It includes a feeding mechanism 1, an adjustable nozzle 2, a feed roller 3, a compaction mechanism 4, a rotating module 5, an overall mounting frame 6, a peripheral control system 7, a follow-up ultraviolet light source 8, and fiber bundles 9. The rotating module 5 is connected to the top of the overall mounting frame 6, and the adjustable nozzle 2 and the compaction mechanism 4 are mounted on the overall mounting frame 6. The fiber bundles 9, wound on the feeding mechanism 1, are driven by the feed roller 3 to enter the adjustable nozzle 2. The adjustable nozzle 2 has a heating device inside. After the fiber bundles 9 are heated to a set temperature, they are extruded from the adjustable nozzle 2. Before cooling, they are compacted and shaped by the high-frequency linear reciprocating motion of the compaction mechanism 4. The follow-up ultraviolet light source 8 connected to the compaction mechanism 4 irradiates the fiber bundles 9 for pre-curing, completing the printing action. The compaction mechanism 4 and the peripheral control system 7 are connected.

[0035] The fiber-reinforced thermosetting composite material is composed of a reinforcing material and a matrix material; the reinforcing material is a fibrous solid, namely carbon fiber; the matrix material is a thermosetting resin, namely epoxy resin.

[0036] The feeding mechanism 1 includes a feeding drive element and a material cylinder. The material cylinder is a hollow cylindrical structure, and fiber bundles 9 are evenly wound on its surface. The feeding drive element is a magnetic powder brake or a motor.

[0037] like Figure 2 , Figure 3 As shown, the adjustable nozzle 2 includes a molten pool 201, a high-temperature printing nozzle 202, two adjustable positioning screws 203, and a heating rod 204. The high-temperature printing nozzle 202 is installed at the bottom of the molten pool 201, and the high-temperature printing nozzle 202 and the internal cavity of the molten pool 201 are connected. The heating rod 204 is embedded in the side wall of the molten pool 201. The heating rod 204 is the heat source of the adjustable nozzle 2 and heats the fiber bundle 9. The molten pool 201 is connected to the arc-shaped groove on the overall mounting frame 6 through the adjustable positioning screws 203. The arc-shaped groove allows the filament exit point of the high-temperature printing nozzle 202 to rotate, with the rotation angle ranging from 45° to 80°. The arc-shaped groove is centered on the filament exit point of the high-temperature printing nozzle 202.

[0038] The heavy-duty conveying roller 3 includes a driving roller and a driven roller. The driving roller is driven by a motor, the surface of the roller is made of flexible material, and there are no gaps between the rollers.

[0039] like Figure 4As shown, the compaction mechanism 4 includes a high-frequency linear reciprocating motion element 401, a flexible pressure shoe 402, a pressure shoe base 403, an annular pressure sensor 404, a ball bearing slider 405, a ball bearing slide rail 406, and a cooling pipe 407. An annular pressure sensor 404 is connected between the lower moving part and the top fixed part of the high-frequency linear reciprocating motion element 401. The pressure shoe base 403 is installed at the bottom of the lower moving part of the high-frequency linear reciprocating motion element 401, and the flexible pressure shoe 402 is mounted on the pressure shoe base 403. The pressure shoe base 403 is connected to the ball bearing slider 405, which is mounted on the ball bearing slide rail 406, which is connected to the overall mounting frame 6. The annular pressure sensor 404, the high-frequency linear reciprocating motion element 401, and the peripheral control system 7 are connected to form a pressure control system.

[0040] The high-frequency linear reciprocating motion element 401 is an electromagnetic push rod, with adjustable reciprocating motion frequency, adjustable stroke, and adjustable thrust. Theoretically, the highest reciprocating motion frequency can reach 120Hz. Figure 5 As shown, the electromagnetic push rod includes a moving iron core 401A, a stationary iron core 401B, a compression spring 401C, a frame 401D, and a stroke adjustment washer 401E. The stationary iron core 401B is a hollow cylinder and is installed inside the frame 401D. The moving iron core 401A passes through the frame 401D and the stationary iron core 401B. The lower end of the moving iron core 401A is connected to the pressure shoe base 403. The moving iron core 401A can make linear reciprocating motion inside the stationary iron core 401B. The compression spring 401C is installed between the moving iron core 401A and the frame 401D. The stroke adjustment washer 401E is installed below the frame 401D.

[0041] The stationary iron core 401B consists of a heating coil and a fixed iron core. When the heating coil is energized with current to generate a magnetic field, a magnetic force is generated between the moving iron core 401A and the fixed iron core, which quickly pushes the moving iron core 401A out, causing the flexible pressure shoe 402 to act on the fiber bundle 9. When the current disappears, the magnetic force disappears, and the moving iron core 401A returns to its initial position under the action of the compression spring 401C, causing the flexible pressure shoe 402 to return to its initial position, completing one reciprocating motion.

[0042] Several stroke adjustment washers 401E can be installed. Their function is to adjust the reciprocating stroke of the moving iron core 401A, ensuring that the bottom surface of the flexible pressure shoe 402 reaches the same height each time it is pressed down, and that this height is lower than the highest position of the fiber bundle 9, so as to ensure the compaction effect.

[0043] like Figure 6As shown, the flexible pressure shoe 402 is made of polyurethane polymer material. The bottom surface is a rectangular plane or a wavy curved surface with a width of 7mm and a length of 6mm. The rectangular plane can ensure the flatness of the printed part surface, while the wavy curved surface can effectively improve the interlayer density of the printed part, thereby improving the overall mechanical properties of the printed part. The initial installation height is slightly higher than the high-temperature printing nozzle 202. It adopts an internal channel-type hollow structure 402A, with an air inlet 402B and an air outlet 402C on the surface. The air inlet 402B and the air outlet 402C are respectively connected to the cooling pipes 407. There are two cooling pipes 407, which are flexible pipes. The cooling pipes 407 are installed on the overall mounting frame 6. Cooling air is passed through to cool the flexible pressure shoe 402. The purpose is to solidify the resin through the coupling effect of pressure and cooling.

[0044] like Figure 7 As shown, the linear reciprocating motion frequency f of the compaction mechanism 4, the effective shaping length l of the flexible pressure shoe 402, and the printing speed v satisfy the following relationship: That is, the effective shaping length of the flexible pressure shoe 402 is greater than the length of the fiber bundle 9 delivered by the adjustable nozzle 2 within the time consumed by the compaction mechanism 4 in one reciprocating motion, so as to ensure the 100% compaction rate of the fiber bundle 9; the effective shaping length l is the length of the rectangular bottom surface of the flexible pressure shoe 402.

[0045] The rotating module 5 is a servo motor; the servo motor 5 is installed on the top of the overall mounting frame 6, and its rotation axis is perpendicular to the horizontal plane and passes through the filament exit point of the high-temperature printing nozzle 202.

[0046] The following parameters in the static iron core 401B are fixed values: the pitch of the heating coil, the number of coil turns, the coil diameter, and the material properties. Therefore, in this embodiment, the pressure feedback regulation is achieved by controlling the current. The relationship between pressure F and current I is: F = μ·I, where μ is the mathematical calculation result of other fixed parameters. It can be seen that the pressure of the compaction mechanism 4 is linearly related to the current passing through the heating coil in the static iron core 401B.

[0047] The follow-up ultraviolet light source 8 is a square ultraviolet light source, which is installed at the lower end of the compaction mechanism 4 and irradiates downwards, always maintaining the irradiation state to pre-cur the fiber bundle 9.

[0048] The pressure control method for a thermosetting composite material 3D printing head with high-frequency compaction function includes the following steps:

[0049] Step 1: Run the high-frequency linear reciprocating motion element 401 in the suspended state of the compaction mechanism 4, and record the average value of the peak force measured by the annular pressure sensor 404 as F0.

[0050] Step two: Adjust the height of the compaction mechanism 4 so that it contacts the printing base plate. The average value of the peak force measured by the annular pressure sensor 404 at this time is F. k ;

[0051] Step 3: The actual output pressure F' is received and calculated through the external control system 7. n ,F' n =F0-F k ;

[0052] Step four: Utilizing the relationship between pressure and current under constant voltage of the high-frequency linear reciprocating motion element 401, repeat steps one through three to calibrate the actual output pressure F' under different currents. n The curve of change;

[0053] Step 5, the peripheral control system 7 uses the calibrated actual output pressure F' n The pressure control is achieved by adjusting the current according to the set pressure using a changing curve.

[0054] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Those skilled in the art can make many other forms under the guidance of the embodiments without departing from the spirit and scope of the claims, and all such forms are within the protection scope of the present invention.

Claims

1. A thermoset composite 3D printing head with high frequency compaction function for fiber-reinforced thermoset composite 3D printing, comprising an integral mounting frame (6), characterized in that: The top of the overall mounting frame (6) is connected to a rotating module (5). The overall mounting frame (6) is equipped with an adjustable nozzle (2) and a compaction mechanism (4). The fiber bundle (9) wound on the feeding mechanism (1) is driven by the heavy-duty roller (3) to enter the adjustable nozzle (2). The adjustable nozzle (2) is equipped with a heating device. After the fiber bundle (9) is heated to the set temperature, it is extruded from the adjustable nozzle (2). Before cooling, it is compacted and shaped by the high-frequency linear reciprocating motion of the compaction mechanism (4). The follow-up ultraviolet light source (8) connected to the compaction mechanism (4) irradiates the fiber bundle (9) for pre-curing, thus completing the printing action. The compaction mechanism (4) is connected to the peripheral control system (7). The compaction mechanism (4) includes a high-frequency linear reciprocating motion element (401), a ring pressure sensor (404) is connected between the lower moving part and the top fixed part of the high-frequency linear reciprocating motion element (401), a pressure shoe base (403) is installed at the bottom of the lower moving part of the high-frequency linear reciprocating motion element (401), and a flexible pressure shoe (402) is covered and installed on the pressure shoe base (403); the pressure shoe base (403) is connected to the ball slider (405), the ball slider (405) is installed on the ball slide rail (406), and the ball slide rail (406) is connected to the overall mounting frame (6); the ring pressure sensor (404), the high-frequency linear reciprocating motion element (401) and the peripheral control system (7) are connected to form a pressure control system; The flexible pressure shoe (402) is made of a flexible material, including polymer materials or rubber; the bottom surface of the flexible pressure shoe (402) is a rectangular plane or a wavy curved surface, and the width is at least twice the diameter of a single fiber bundle (9); the flexible pressure shoe (402) is a cold pressure shoe with a channel-type hollow structure inside, and an air inlet and an air outlet are provided on the surface. The air inlet and the air outlet are respectively connected to the cold air pipe (407), and the cold air pipe (407) is installed on the overall mounting frame (6); the initial height of the flexible pressure shoe (402) is higher than that of the high-temperature printing nozzle (202). The reciprocating frequency of the high-frequency linear reciprocating motion element (401) f Effective shaping length of flexible pressure shoe (402) l The printing speed v satisfies the following relationship: That is, the effective shaping length of the flexible pressure shoe (402) is greater than the length of the fiber bundle (9) delivered by the adjustable nozzle (2) within the time consumed by the compaction mechanism (4) in one reciprocating motion, ensuring a 100% compaction rate of the fiber bundle (9); effective shaping length l The length of the rectangular bottom surface of the flexible pressure shoe (402) is given.

2. The 3D printing head according to claim 1, characterized in that: The fiber-reinforced thermosetting composite material is composed of a reinforcing material and a matrix material; the reinforcing material is a fibrous solid, which is one of carbon fiber, glass fiber, or nylon; the matrix material is a thermosetting resin, which is phenolic resin or epoxy resin.

3. The 3D printing head according to claim 1, characterized in that: The adjustable nozzle (2) includes a high-temperature printing nozzle (202), which is installed at the bottom of the molten pool (201). The high-temperature printing nozzle (202) and the internal cavity of the molten pool (201) are connected. A heating rod (204) is embedded in the side wall of the molten pool (201). The molten pool (201) is connected to the arc groove on the overall mounting frame (6) by an adjustable positioning screw (203). The molten pool (201) can rotate the filament exit point of the high-temperature printing nozzle (202) through the arc groove. The rotation angle includes a range of 45°-80°.

4. The 3D printing head according to claim 3, characterized in that: The arc-shaped groove is centered on the filament exit point of the high-temperature printing nozzle (202).

5. The 3D printing head according to claim 1, characterized in that: The high-frequency linear reciprocating motion element (401) is an electrical element with a frequency of at least 10Hz, including an electromagnetic push rod, an electric push rod, or a servo electric cylinder; the high-frequency linear reciprocating motion element (401) has an adjustable linear reciprocating motion frequency, adjustable stroke, and adjustable thrust.

6. The 3D printing head according to claim 3, characterized in that: The rotating module (5) is a programmable drive element, including a servo motor or a servo motor; the axis of the rotating module (5) is perpendicular to the horizontal plane and passes through the filament exit point of the high-temperature printing nozzle (202).

7. The pressure control method for the 3D printing head according to any one of claims 1-6, characterized in that, Includes the following steps: Step 1: Run the high-frequency linear reciprocating motion element (401) while the compaction mechanism (4) is suspended, and record the average value of the peak force measured by the annular pressure sensor (404). ; Step 2: Adjust the height of the compaction mechanism (4) so ​​that it contacts the printing base plate. The average value of the peak force measured by the annular pressure sensor (404) at this time is... ; Step 3: Receive and calculate the actual output pressure through the external control system (7). , ; Step four: Utilizing the relationship between pressure and current under constant voltage of the high-frequency linear reciprocating motion element (401), repeat steps one through three to calibrate the actual output pressure under different currents. The curve of change; Step 5, the peripheral control system (7) uses the calibrated actual output pressure The pressure control is achieved by adjusting the current according to the set pressure using a changing curve.

Images