Ribbon melt channel piston controlled melt pressure screw 3d printing extrusion device

Abstract

This utility model relates to a screw 3D printing extrusion device that controls melt pressure using a branch melt channel piston. The melt pressure is controlled by the volume change of the branch melt channel piston, thereby achieving retraction, transitional extrusion, and continuous precise extrusion in the screw 3D printing extrusion device. It includes a main melt channel and branch melt channels, with a piston device installed within each branch melt channel. The main melt channel is connected to the branch melt channel on the left, and the screw extrusion device is installed on the right. A nozzle is installed below the branch melt channel, and an external piston drive device is installed above it. A piston control system controls the rotation of a piston drive motor, thereby driving the piston to reciprocate within the branch melt channel. The beneficial effects of this utility model are: by adjusting the piston speed and stroke, melt pressure fluctuations are reduced, completely solving the problems of non-retraction and precise controllable extrusion in screw extrusion 3D printing systems, thus improving the printing quality of screw extrusion 3D printing systems.

Description

Technical Field

[0001] This invention relates to the field of 3D printing technology, and in particular to the precise and controllable extrusion of a screw 3D printing extrusion device by changing the volume of the melt channel and adjusting the melt pressure in real time through a branch melt channel piston device. Background Technology

[0002] In recent years, with the rapid development of 3D printing technology, screw extrusion 3D printing systems, which use plastic granules as printing materials, offer advantages such as lower printing costs, faster printing speeds, and a wider range of printable materials. However, when printing models with complex contours using screw extrusion 3D printing systems, extrusion needs to be paused (pulled back). Although the screw stops rotating at this time, residual melt pressure is formed due to the combined effects of accumulated pressure in the barrel, the viscoelasticity of the melt, and flow resistance. Under the action of this residual melt pressure, the melt in the melt channel is pushed out of the nozzle, leading to stringing, ultimately reducing the printing accuracy of the part, causing material waste, and increasing post-processing work.

[0003] Currently, the mainstream solution for achieving the retraction function in screw extrusion 3D printing systems is through screw reversal. However, this method not only has a short retraction distance and long response time, but also causes significant fluctuations in the melt pressure within the heated hopper. Other researchers have proposed using a motor-driven needle valve to block the melt channel entering the nozzle, thus achieving the retraction function. However, this solution extrudes excess material from the nozzle, resulting in significant waste (assuming a part has hundreds to thousands of layers, with five retractions per layer, and each retraction wastes 0.3g of material, printing 1000 layers would waste 1500g of material on retraction alone; in the case of printing hollow parts, the wasted material would exceed the required material for the part itself). It also increases printing time (assuming each retraction takes 3 seconds, with 5 retractions per layer, printing 1000 layers would require 15000 seconds of retraction time). The latest technology proposes using valve locking and negative air pressure to achieve retraction. This method uses a solenoid valve to regulate high-pressure gas, which drives a push rod to prevent the molten material from entering the nozzle's melt channel through a plug on the push rod. Negative pressure forces the molten material upwards within the nozzle, preventing dripping. However, this approach uses air as a medium to indirectly act on the melt, resulting in a slow retraction response. It cannot retract high-viscosity materials, and high-pressure air bubbles can form under negative pressure, entering the melt. When melt containing these high-pressure air bubbles is extruded from the nozzle, it not only causes the extruded filament to break but also damages the already printed part, leading to printing failure. Furthermore, this method neglects the transitional extrusion state after retraction. After retraction, the melt pressure decreases, and when printing the next continuous path, the melt pressure needs to smoothly return to the pre-retraction range. Currently, the mainstream solution for addressing this transitional extrusion state is to gradually increase the melt pressure by slowly rotating the screw forward. However, this method has a long response time, large overshoot, high inertia, and low control precision.

[0004] Furthermore, screw-type 3D printing extrusion devices require stable, precise, and controllable filament extrusion when printing continuous paths. However, due to factors such as melt compression and springback effects, screw conveying characteristics, material viscosity variations, back pressure influence, and screw dimensions and structure, the relationship between screw speed and extrusion volume is non-linear. Current similar solutions monitor melt pressure in real time using melt pressure and temperature sensors and feed this feedback to the control system to adjust the screw motor speed, bringing the melt pressure closer to stability and achieving stable and precise extrusion. However, this method suffers from drawbacks such as slow response leading to dynamic control lag; large system inertia causing overshoot or oscillation; poor control precision; and limitations under complex operating conditions (high-speed printing mode and frequent retraction, etc.), making it difficult to maintain precise extrusion. Utility Model Content

[0005] The purpose of this invention is to propose a screw extrusion 3D printing system that uses a branch melt channel piston auxiliary device to achieve stable, precise and controllable extrusion, so as to completely solve the problem that screw extrusion 3D printing systems cannot perform continuous extrusion, transition extrusion and retraction with precision and control.

[0006] To achieve the above objectives, this utility model provides the following technical solution:

[0007] A screw 3D printing extrusion device with a branch-channel melt flow piston controlling melt pressure, including a screw extrusion device, and further including:

[0008] Main melting channel, the right side of which is connected to the screw extrusion device;

[0009] The main melt channel is connected to the branch melt channel on the left. The branch melt channel is composed of an upper branch melt channel and a lower branch melt channel. The cross-sectional area of ​​the upper branch melt channel is larger than that of the lower branch melt channel. The main melt channel is connected to the upper branch melt channel and the lower branch melt channel on the left.

[0010] A heating assembly that heats the main melt channel and branch melt channels to ensure the fluidity of the melt;

[0011] The nozzle is connected to the lower end of the lower section of the branch melt channel;

[0012] A piston is connected to the upper section of the branch channel and is used to pump and pressurize the melt in the branch channel.

[0013] A piston drive device is connected to the piston and is used to control the piston to make linear reciprocating motion in the upper section of the branch channel.

[0014] Furthermore, the screw extrusion device includes a screw drive motor mounted on the frame, the lower end of the screw drive motor being connected to the screw via a coupling, and a barrel fixed on the frame, with the screw inserted downward into the barrel, and the lower end of the barrel being connected to the main melting channel.

[0015] Furthermore, the main melt channel is composed of a horizontal melt channel portion and a vertical melt channel portion. The left end of the horizontal melt channel portion is connected to the branch melt channel, and the vertical melt channel portion is connected to the screw extrusion device.

[0016] Furthermore, the piston is composed of an aluminum rod and a piston sleeve fitted onto the aluminum rod.

[0017] Furthermore, the piston is composed of an aluminum rod and a piston sleeve fitted onto the aluminum rod;

[0018] The piston drive device includes,

[0019] Piston-driven motor;

[0020] A drive wheel, which is mounted on the drive shaft of a piston-driven motor;

[0021] A driven wheel, wherein an aluminum rod is held between the driven wheel and the driving wheel.

[0022] Furthermore, the driven wheel is rotatably connected to a swing arm, which is hinged to the frame above the driven wheel. The swing arm is vertically connected to a bolt below the driven wheel, with the bolt end threaded onto the frame after passing through the swing arm. A spring is fitted on the bolt between the bolt head and the swing arm. Tightening the bolt can adjust the clamping force of the driven wheel and the driving wheel on the aluminum rod by adjusting the spring force.

[0023] Furthermore, it also includes a steel pipe connected to the upper section of the branch melting channel, wherein the aluminum rod is placed inside the steel pipe and can reciprocate inside the steel pipe.

[0024] Furthermore, a pressure sensor and / or temperature sensor are installed near the nozzle in the branch melting channel.

[0025] Furthermore, the aluminum rod and the piston sleeve are detachably connected.

[0026] A screw 3D printing extrusion device and method for controlling melt pressure with a branch melt channel piston, wherein during the printing process of a 3D printer using a screw extrusion system, the melt fills the main melt channel and the branch melt channel at the bottom of the piston;

[0027] When the screw extrusion 3D printer finishes printing the current continuous path, the screw extrusion device stops. At this time, the piston control system captures the signal that the screw drive motor has stopped rotating, and controls the piston drive device to drive the piston to move upward to increase the volume of the melt channel, reduce the pressure of the residual melt, and thus achieve retraction.

[0028] After the retraction is complete, when further extrusion is needed, the piston device needs to perform a transition extrusion first. When the screw extruder continues to work, the piston control system captures the signal that the screw drive motor of the screw extruder has started to rotate, and controls the piston drive device to drive the piston downward to bring the residual melt pressure back to the range before the retraction.

[0029] After the transition extrusion is completed, the stable extrusion stage, which prints a continuous path, begins. Due to factors such as melt compression and springback effects, screw conveying characteristics, material viscosity variations, back pressure, and screw dimensions, the relationship between screw speed and extrusion rate is non-linear. At this point, data from melt pressure and temperature sensors are collected to adjust the piston stroke, enabling fine-tuning of the melt pressure and ultimately achieving continuous and precise extrusion.

[0030] The beneficial effects of this utility model are as follows:

[0031] 1. By using a branch-type melt channel piston to change the melt channel volume and thus control the melt pressure, the problem of unstable, precise, and controllable extrusion in screw extrusion 3D printing systems is completely solved. It not only has a fast response but also allows for precise control of the retraction stroke, effectively preventing excess material from being extruded and causing stringing under the residual melt pressure when extrusion is paused in the screw extrusion 3D printing system, thereby improving the quality and precision of 3D printing.

[0032] 2. By directly contacting the melt with the piston, the volume of the branch melt channel is directly changed during retraction, without the need for a medium. Complex air pressure devices are unnecessary; only materials with good high-temperature resistance, wear resistance, and sealing properties are required to manufacture the piston sleeve. For high-viscosity melts, high-precision pressure control can be directly applied to the melt to achieve retraction.

[0033] 3. During the transition extrusion after the retraction action, when the residual melt pressure returns to the range before retraction, this invention uses melt pressure and temperature sensors to monitor and control the piston stroke in real time, enabling fine-tuning of melt pressure and viscosity to ultimately complete the transition extrusion. This method features fast response speed (millisecond-level adjustment, suitable for high-speed 3D printing), low inertia, low screw load, precise melt pressure control, and high system durability, making it suitable for high-volume, high-speed printing scenarios.

[0034] 4. During continuous extrusion, the screw speed and extrusion volume have a non-linear relationship. This invention uses melt pressure and temperature sensors to monitor these parameters and fine-tunes the piston stroke through a piston control system to reduce melt pressure fluctuations and achieve continuous and precise extrusion. This system features faster response, higher precision, and better flow stability, making it particularly suitable for high-precision, high-speed extrusion scenarios. Attached Figure Description

[0035] To more clearly illustrate the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of the structure of this utility model;

[0037] Figure 2 This is a utility model Figure 1 A schematic diagram of the external piston drive device in the structure shown;

[0038] Figure 3 This is a utility model Figure 1A schematic diagram of the screw extrusion device in the structure shown;

[0039] Figure 4 This is a utility model Figure 1 A schematic diagram showing the connection between the branch melt channel and the main melt channel in the structure shown.

[0040] Figure 5 This is a block diagram of the piston control system of this utility model;

[0041] Figure 6 This is a diagram showing the slot connection structure between the aluminum rod and the piston sleeve of this utility model;

[0042] Figure 7 This is a schematic diagram of the cooling channel in the aluminum rod of this utility model.

[0043] Explanation of reference numerals in the attached drawings: 1. Screw drive motor; 2. Coupling; 3. Screw; 4. Hopper; 5. Barrel; 6. Heating assembly; 7. Main melting channel; 8. Branch melting channel; 801. Upper branch melting channel; 802. Lower branch melting channel; 9. Nozzle; 10. Melt pressure and temperature sensor; 11. Piston sleeve; 12. Piston drive device; 13. Bolt; 14. Spring; 15. Steel pipe; 16. Frame; 17. Piston drive motor shaft; 18. Piston drive motor; 19. Drive wheel; 20. Aluminum rod; 21. Swing arm; 22. Driven wheel; 23. Screw extrusion device; 24. Slot; 25. Annular boss; 26. Inner hole; 27. Cooling channel. Specific Implementation

[0044] The following will refer to the appendix in the embodiments of this utility model. Figure 1-5 The technical solutions in the embodiments of this utility model are clearly and completely described herein. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0045] The piston control system captures the signal emitted when the screw drive motor 1 stops rotating, and controls the external piston drive device 12 to drive the piston to reciprocate within the branch melt channel 8. During the 3D printing process, the piston directly contacts the melt (the melt fills the branch melt channel below the piston), eliminating the need for medium transmission delay. During retraction, the volume of the branch melt channel 8 increases, reducing the internal residual melt pressure. Simultaneously, the external air pressure further reduces the residual melt pressure. The melt pressure and temperature data collected by the external melt pressure and temperature sensors 10 control the rotation angle or speed of the piston drive motor 18. Through precise control of the piston's movement rate and stroke, the problems of inaccurate and uncontrollable extrusion and retraction in screw extrusion 3D printing systems are completely solved. A specific implementation example is provided below.

[0046] A 3D printing screw extrusion system that uses a branch melt channel piston to control melt pressure to achieve precise and controllable operation includes a main melt channel 7 and a branch melt channel 8. The branch melt channel 8 is equipped with a piston device. The left side of the main melt channel is connected to the branch melt channel, and the right side is equipped with a screw extrusion device 23.

[0047] The screw extrusion device 23 includes a screw drive motor 1, which is mounted on a frame. A coupling 2 is mounted below the screw drive motor 1, and the coupling 2 is connected to a screw 3. The screw 3 is inserted into a barrel 5. A hopper 4 is mounted above the barrel 5, and a main melt channel 7 is located below it. The main melt channel 7 is connected to a branch melt channel 8 on its left side and to the barrel 5 on its right side. A heating assembly 6 is provided outside the main melt channel 7 to heat the main melt channel 7 and the branch melt channel 8, ensuring the fluidity of the melt. As one embodiment of the main melt channel, the main melt channel 7 consists of a horizontal melt channel portion and a vertical melt channel portion. The left end of the horizontal melt channel portion is connected to the branch melt channel 8, and the vertical melt channel portion is connected to the screw extrusion device. In this embodiment, the screw 3 extends downward into the vertical portion of the main melt channel.

[0048] The branch molten channel 8 is divided into upper and lower sections. The diameter of the upper section of the branch molten channel 8 is larger than that of the lower section. The main molten channel 7 connects the upper branch molten channel 801 and the lower branch molten channel 802. As an example, the left side of the upper branch molten channel 801 and the left side of the lower branch molten channel 802 are vertically aligned in the same plane. The right side of the upper branch molten channel extends beyond the right side of the lower branch molten channel, causing the upper branch molten channel to penetrate more into the main molten channel than the lower branch molten channel. The vertical axes of the centers of the upper branch molten channel 801 and the lower branch molten channel 802 are parallel to each other. Figure 1As shown. The lower section of the branch melt channel 802 is fixed to the nozzle 9 via a threaded connection (the nozzle is directly fixed to the lower end of the branch melt channel 8, which is preferably a vertical channel. The structure of the branch melt channel, which is larger at the top and smaller at the bottom, not only makes it easier for the melt to fill the upper section of the branch melt channel, but also makes it easier to retract the melt through the larger piston cavity in the upper section during piston retraction). The upper section of the branch melt channel 801 is connected to an external piston drive device 12. The upper section of the branch melt channel is equipped with a piston, which includes an aluminum rod 20 and a piston sleeve 11. The end of the aluminum rod that fixes the piston sleeve has a slot 24, which allows the piston sleeve to be directly fixed to the aluminum rod through the slot 24, making it easy to disassemble and replace the piston sleeve. The slot 24 has a trapezoidal cross-section, with the upper bottom of the slot close to the central axis of the aluminum rod and the lower bottom close to the outer surface of the aluminum rod. The piston sleeve 11 has an annular boss 25 on its back and an inner hole 26 on its back. The inner hole 26 is a blind hole, and the annular boss 25 is located in the blind hole. The bottom edge of the aluminum rod 20 is chamfered to allow the bottom of the aluminum rod to pass smoothly through the annular boss 25, the shape of which matches the shape of the slot 24. The annular boss 25 is made of an elastic material, such as elastic rubber. During piston sleeve installation, the aluminum rod is inserted into the blind hole, and the trapezoidal slot provides guidance for the annular boss of the piston sleeve, facilitating its quick and accurate insertion. Simultaneously, this structure allows the slot to effectively limit the axial and radial displacement of the piston sleeve along the aluminum rod during operation, ensuring the stability of the connection. The aluminum rod 20 can conduct the temperature of the piston sleeve to the outside and achieve free cooling or forced convection cooling by a fan. Regarding the piston structure, a piston body can also be used directly, with internal threads on the back of the piston body and external threads on the aluminum rod. In use, the aluminum rod is threadedly connected to the back of the piston body to form the piston. A sealed sliding connection is formed between the piston and the branch molten channel 8. In another embodiment of the piston, an electric linear telescopic rod or linear hydraulic cylinder is directly connected to the piston to drive the linear reciprocating motion of the piston.

[0049] An external piston drive device 12 is fixed on the frame and includes a piston drive motor 18. A drive wheel 19 is mounted on the shaft 17 of the piston drive motor. The right side of the drive wheel 19 is engaged with a driven wheel 22. The driven wheel 22 is rotatably connected to the swing arm 21 and clamps the aluminum rod 20 under the action of spring tension.

[0050] In this embodiment, a piston sleeve made of polytetrafluoroethylene (PTFE) is used and fitted onto the aluminum rod 20. The piston sleeve needs to reciprocate under high temperature and high pressure for a long time, resulting in rapid wear. To extend the service life of the piston sleeve, a cooling channel 27 is provided inside the aluminum rod 20. This channel is formed by a longitudinal channel running through the axis and a transverse channel with an opening in the middle of the side of the aluminum rod, which are connected in a cross shape. After the heat from the piston sleeve is transferred to the aluminum rod, the channel opening is connected to the outside air. Hot air rises and cold air replenishes, forming convection. The air flows in the channel and carries away the heat, thereby reducing the temperature of the piston sleeve and extending its service life.

[0051] In this embodiment, the piston sleeve 11 can also be filled with modified PTFE (such as glass fiber, graphite or carbon fiber filled PTFE) to enhance the wear resistance and deformation resistance of the piston sleeve. The optimal initial fit clearance is designed according to the thermal expansion coefficient of the aluminum rod and the piston sleeve to solve the problem of tight connection and sealing between the aluminum rod 20 and the piston sleeve 11. And through thermal cycling test, stability at different temperatures is ensured.

[0052] In this embodiment, the external piston drive device 12 further includes a spring 14, which is pressed by a bolt 13. One end of the bolt 13 is threaded to the frame 16. The tension of the spring 14 presses the swing arm 21, so that the driving force of the driving wheel 19 and the driven wheel 22 on the aluminum rod is maintained by the tension of the spring. The swing arm 21 is located above the driven wheel and is hinged to the frame. The bolt 13 is vertically movably connected to the swing arm located below the driven wheel. The structure of this vertical sliding connection can be: a long groove is opened on the swing arm, and the bolt is movably fitted in the long groove, so that the swing arm can swing along its hinge end. A steel pipe 15 is provided at the connection between the external piston drive device 12 and the branch melting channel 8. One end of the steel pipe 15 is fixed to the frame 16 by a threaded connection, and the other end is fixed to the inner side of the upper section of the branch melting channel 8 by a threaded connection, so that the aluminum rod 20 reciprocates in the steel pipe 15.

[0053] The process of using a branch melt channel piston auxiliary device to achieve precise and controllable extrusion in a screw 3D printing extrusion device includes the following steps:

[0054] Retraction: After the screw extrusion 3D printing system completes the printing of the current continuous path, the screw drive motor 1 stops rotating. At this time, the piston control system captures the signal from the main control system that causes the screw drive motor 1 to stop rotating, and controls the rotation of the piston drive motor 18 based on the captured signal to drive the piston to move upward, thereby realizing the retraction action. During retraction, the piston moves upward, and the volume of the branch melt channel 8 increases. According to Boyle's law, the residual pressure of the internal melt decreases at this time. Since the nozzle 9 outlet diameter is very small, the melt needs to overcome a lot of resistance when it is extruded from the nozzle 9. In addition, under the action of the external air pressure on the melt near the nozzle outlet, the residual melt pressure will decrease sharply, and the excess melt will not flow out of the nozzle, thus realizing the retraction of the residual melt. At the same time, based on the melt pressure and temperature data measured by the melt pressure and temperature sensor 10, and on the basis of a large number of experiments, a data-driven and machine learning-based intelligent piston control system is developed to control the speed and angle of the piston drive motor, thereby achieving precise control of the piston retraction rate and distance, and thus realizing precise and controllable retraction.

[0055] Transitional extrusion: After the retraction action is completed, when further extrusion is needed, the screw drive motor 1 will continue to rotate. At this time, the piston control system captures the signal from the main control system to start the screw drive motor 1 rotating, and controls the piston drive motor 18 to rotate based on the captured signal, thereby driving the piston to move downward. At the same time, based on the melt pressure and temperature data measured by the melt pressure and temperature sensor 10, the intelligent piston control system developed on the basis of data-driven and machine learning controls the rate and distance at which the piston drive motor 18 drives the piston to move downward, so that the residual melt is restored to the state before retraction, and finally the melt pressure is restored and exceeds the resistance of the nozzle 9 outlet, completing the transitional extrusion, and simultaneously proceeding to the next continuous path printing.

[0056] Continuous Precision Extrusion: After the piston completes the transition extrusion, a stable extrusion stage for continuous printing is required. Due to the influence of factors such as melt compression and springback effects, screw conveying characteristics, material viscosity changes, back pressure, and screw size and structure, the screw speed and extrusion volume have a non-linear relationship. Therefore, during continuous extrusion, the piston speed and stroke need to be adjusted based on the data collected by the melt pressure and temperature sensors 10 to achieve fine-tuning of the melt pressure, reduce melt pressure fluctuations, and thus achieve continuous precision extrusion.

[0057] This invention directly controls the piston stroke to increase or decrease the melt channel volume, thereby regulating the melt pressure within the channel. There is no media transmission delay, enabling rapid retraction, transitional extrusion, and continuous precise extrusion of the melt pressure. Furthermore, this invention has a simple and easy-to-implement structure, requiring only a piston sleeve made of materials with good sealing, wear resistance, and high-temperature resistance. It allows for direct, high-precision pressure control of high-viscosity melt materials.

[0058] By using a piston device to adjust the melt channel volume and thus precisely control the melt pressure, the screw extrusion 3D printing system achieves retraction, transition extrusion, and continuous precision extrusion. This solution improves printing accuracy: reduces pressure fluctuations, makes the extrusion flow more stable, and improves print quality; optimizes retraction effect: reduces stringing and improves detail rendering; improves print consistency: reduces flow errors, improves surface smoothness and overall precision; supports high-speed printing: the piston device can effectively control melt pressure changes during high-speed printing, improving print quality; and improves adaptability to complex materials: for materials with high viscosity or complex rheological properties, piston control ensures stable and precise extrusion. In summary, the piston device effectively overcomes the problems of slow response, large melt pressure fluctuations, and uneven extrusion flow in traditional screw 3D printing extrusion devices.

[0059] Finally, it should be noted that the above are only some embodiments of this utility model. Any scheme that uses a series of devices to change the volume of the melt channel to adjust the melt pressure and achieve retraction, transition extrusion and continuous precision extrusion; any scheme that slightly modifies the structure and features of this utility model (for example, adding a piston to assist retraction in multi-screw mixed extrusion, co-extrusion and hopper feeding extrusion); and any scheme that uses changes in the volume of the melt channel to adjust the melt pressure at the die orifice of a single or multi-screw plastic extruder to achieve high-precision 3D printing filament production should also be included within the scope of this utility model.

Claims

1. A screw 3D printing extrusion device with branch-channel melt channel piston controlling melt pressure, comprising a screw extrusion device, characterized in that, It also includes, Main melting channel, the right side of which is connected to the screw extrusion device; The main melt channel is connected to the branch melt channel on the left. The branch melt channel is composed of an upper branch melt channel and a lower branch melt channel. The cross-sectional area of ​​the upper branch melt channel is much larger than that of the lower branch melt channel. The main melt channel is connected to the upper branch melt channel and the lower branch melt channel on the left. A heating assembly that heats the main melting channel, branch melting channels, and the barrel to ensure the fluidity of the melt; The nozzle is connected to the lower end of the lower section of the branch melt channel; A piston is connected to the upper section of the branch channel and is used to pump and pressurize the melt in the branch channel. A piston drive device is connected to the piston and used to control the piston to make linear reciprocating motion in the upper melt channel of the branch line; the screw extrusion device includes a screw drive motor, which is mounted on the frame and the lower end of the screw drive motor is connected to the screw through a coupling; it also includes a material cylinder fixed on the frame, the screw is inserted downward into the material cylinder, and the lower end of the material cylinder is connected to the main melt channel; The main melt channel consists of a horizontal melt channel section and a vertical melt channel section. The left end of the horizontal melt channel section is connected to the branch melt channel, and the vertical melt channel section is connected to the screw extrusion device.

2. The side-arm crucible-piston controlled melt pressure screw 3D printing extrusion apparatus of claim 1, wherein, The piston consists of an aluminum rod and a piston sleeve fitted onto the aluminum rod.

3. The branch-channel-piston-controlled-melt-pressure screw 3D printing extrusion apparatus of claim 1, wherein, The piston consists of an aluminum rod and a piston sleeve fitted onto the aluminum rod; The piston drive device includes: Piston-driven motor; A drive wheel, which is mounted on the drive shaft of a piston-driven motor; A driven wheel, wherein an aluminum rod is held between the driven wheel and the driving wheel.

4. The branch-channel-piston-controlled-melt-pressure screw 3D printing extrusion apparatus of claim 3, wherein, The driven wheel is rotatably connected to a swing arm. The swing arm is hinged to the frame above the driven wheel. A bolt is vertically connected to the swing arm below the driven wheel. The end of the bolt passes through the swing arm and is threaded to the frame. A spring is fitted on the bolt between the bolt head and the swing arm. Tightening the bolt can adjust the clamping force of the driven wheel and the driving wheel on the aluminum rod by the elastic force of the spring.

5. The branch-channel-piston-controlled-melt-pressure screw 3D printing extrusion apparatus of claim 3, wherein, It also includes a steel pipe connected to the upper section of the branch melting channel, wherein the aluminum rod is placed inside the steel pipe and can reciprocate inside the steel pipe.

6. The side-arm crucible-piston controlled melt pressure screw 3D printing extrusion apparatus of claim 1, wherein, The branch melt channel is equipped with melt pressure and temperature sensors near the nozzle.

7. The branch-channel-piston-controlled-melt-pressure screw 3D printing extrusion apparatus of claim 2, wherein, The aluminum rod and the piston sleeve are detachably connected.

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