A nozzle pneumatic retraction system and method of operation

Abstract

The application discloses a nozzle pneumatic retraction system and a working method, and the system comprises a machine barrel and a suction mechanism. The machine barrel comprises a machine barrel body and a nozzle, the machine barrel body is internally provided with a cavity, the end of the cavity is provided with a discharge port, a melt channel and a suction channel that are in communication with each other are formed in the nozzle, the melt channel is connected with the discharge port, the suction channel and the melt channel are arranged at an acute angle, a gas-permeable net is arranged at the joint of the suction channel and the melt channel, and the gas-permeable net can only allow gas to pass through; the suction mechanism is connected with the suction channel through a pipeline. When retraction is performed, the suction mechanism generates negative pressure to retract the material, on the one hand, pneumatic adsorption has a faster response speed than screw reverse rotation, and the pressure of the negative pressure can be more accurately adjusted; on the other hand, the retraction load of the main extrusion motor is reduced, and material deterioration caused by reverse extrusion of the material is reduced.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing molten particle printing equipment technology, and in particular to a nozzle pneumatic retraction system and its working method. Background Technology

[0002] Fused particle manufacturing (FGF) is an additive manufacturing process that uses plastic granules as raw materials, relying on a screw extrusion mechanism to melt the material and build it up layer by layer. Compared with traditional FDM filament printing, FGF eliminates the filament extrusion and granulation process, resulting in lower raw material costs and higher molding efficiency. It is suitable for manufacturing large-sized parts such as aerospace components, automotive molds, and large architectural models, and its application scope continues to expand.

[0003] When the printing path switches to the non-printing idle stage, the combined effect of residual melt pressure and gravity inside the barrel makes the nozzle prone to leakage and stringing defects, severely reducing the surface quality and dimensional accuracy of the printed parts. Existing FGF equipment adopts the screw reversal retraction scheme, drawing on the FDM filament machine's retraction approach: after the CNC system recognizes the idle command, the main extrusion motor drives the screw to rotate in the opposite direction. The screw displacement drags the solid particles in the feeding section and the molten melt in the metering section upwards, temporarily creating a negative pressure at the nozzle to adsorb the melt and suppress leakage and stringing.

[0004] However, this single-screw mechanism will cause the following problems during retraction: (1) When the screw reverses, the solid particles and semi-molten material will be subjected to violent extrusion interference between the screw channel and the inner wall of the barrel. The reversal will generate huge reverse resistance, and the extrusion motor will be prone to frequent stalling; (2) Affected by the fluctuation of raw material viscosity, particle size distribution and extrusion density, the amount of retraction cannot be accurately quantified. Insufficient retraction will often result in stringing, or excessive retraction will cause the nozzle to suck in air bubbles; (3) When reversing and retracting, the molten material will be subjected to multiple high-intensity shear forces in the narrow flow channel. The long polymer chain will break, the rheological properties will change, and the material properties will deteriorate; (4) The screw itself has a large moment of inertia. There is a significant delay in the screw reversal start and stop, and it is impossible to achieve rapid action. Summary of the Invention

[0005] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. To this end, this application proposes a nozzle pneumatic retraction system that reduces the load on the main extrusion motor during no-load retraction, has a faster response speed, and provides precise and controllable retraction pressure, thereby reducing performance degradation caused by excessive material compression during retraction.

[0006] This application also proposes an additive manufacturing apparatus having the above-mentioned nozzle pneumatic retraction system, and a working method based on the above-mentioned nozzle pneumatic retraction system.

[0007] The nozzle pneumatic retraction system according to a first aspect embodiment of this application includes: The barrel includes a barrel body and a nozzle. The barrel body has an internal cavity, and a discharge port is provided at the end of the cavity. The nozzle has an interconnected melt channel and a suction channel. The melt channel is connected to the discharge port. The suction channel and the melt channel are arranged at an acute angle. A ventilated mesh is provided at the junction of the suction channel and the melt channel, and the ventilated mesh can only allow gas to pass through. An air intake mechanism, which is connected to the air intake channel via a pipe; The cavity of the barrel body is used to fill the material. The material can enter one end of the melt channel through the discharge port and be discharged from the other end of the melt channel. The gas in the melt channel can be drawn into the suction channel, thereby creating a negative pressure in the melt channel.

[0008] The nozzle pneumatic retraction system according to the embodiments of this application has at least the following beneficial effects: during no-load retraction, the negative pressure generated by the suction mechanism is used to retract the material. On the one hand, pneumatic adsorption has a faster response speed than screw reversal, and the pressure of the negative pressure can be adjusted more precisely. On the other hand, it reduces the retraction load on the main extrusion motor and reduces material deterioration caused by reverse extrusion of the material.

[0009] According to some embodiments of this application, there are at least two suction channels, and each suction channel is arranged in a circular array around the melt channel.

[0010] According to some embodiments of this application, the melt channel includes a variable diameter section and a constant diameter section. The two ends of the variable diameter section are a large diameter end with a larger inner diameter and a small diameter end with a smaller inner diameter, respectively. The inner diameter of the variable diameter section gradually decreases from the large diameter end to the small diameter end. The large diameter end is connected to the discharge port, and the small diameter end is connected to the constant diameter section.

[0011] According to some embodiments of this application, the air intake channel is connected to the junction of the variable diameter section and the constant diameter section.

[0012] According to some embodiments of this application, a pressure sensor is provided in the air intake channel.

[0013] According to some embodiments of this application, an air valve is further provided between the air intake mechanism and the air intake channel.

[0014] According to some embodiments of this application, the suction mechanism includes a cylinder, a piston, a suction motor, and a lead screw. The cylinder has a sliding cavity, one end of which is open and connected to the suction channel through a pipe. The piston moves within the sliding cavity, and the side of the piston is in contact with the inner wall of the sliding cavity. The lead screw is threadedly connected to the piston and connected to the rotating shaft of the suction motor.

[0015] An additive manufacturing apparatus according to a second aspect of this application includes an additive manufacturing apparatus body and the above-described nozzle pneumatic retraction system, wherein the nozzle pneumatic retraction system is connected to the additive manufacturing apparatus body.

[0016] The working method according to the third aspect of this application, which is based on the above-described nozzle pneumatic retraction system, includes the following steps: When empty runback is required, the material stops moving in the barrel body; The suction mechanism draws in air, creating a negative pressure within the suction channel; The gas in the melt channel enters the suction channel through the permeable mesh, while the material in the melt channel is blocked and retained in the melt channel by the permeable mesh. A negative pressure is generated in the melt channel, and the adsorption force counteracts part of the weight of the material, preventing the material from dripping out of the melt channel; After the empty run is completed, the suction mechanism exhausts the air, and the negative pressure in the suction channel and the melt channel is released, allowing the subsequent extrusion work to continue.

[0017] The working method according to the embodiments of this application has at least the following beneficial effects: by using the above-mentioned nozzle pneumatic retraction system, the negative pressure value during empty retraction can be precisely controlled, avoiding the problem of excessive negative pressure drawing in air bubbles or insufficient negative pressure failing to prevent material dripping, making empty retraction more controllable.

[0018] According to some embodiments of this application, a pressure sensor is provided in the air intake channel; before the empty-run retraction, a retraction threshold is set in the air intake channel; when the empty-run retraction occurs, the air intake mechanism draws air until the pressure sensor detects that the pressure in the current air intake channel reaches the retraction threshold.

[0019] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0020] The accompanying drawings are used to provide a further understanding of the technical solutions disclosed in this application and form part of the specification. They are used together with the embodiments disclosed in this application to explain the technical solutions of this application and do not constitute a limitation on the technical solutions disclosed in this application.

[0021] Figure 1 This is a schematic diagram of the structure of the barrel in the nozzle pneumatic retraction system according to the first aspect of this application; Figure 2 This is a schematic diagram of the nozzle structure in the nozzle pneumatic retraction system according to the first aspect of this application; Figure 3 This is a schematic diagram of the connection of the nozzle pneumatic retraction system according to the first aspect of this application.

[0022] Reference numerals: 100-Barrel, 110-Barrel body, 111-Cavity, 112-Feed inlet, 120-Nozzle, 121-Mel flow channel, 1211-Variable diameter section, 1212-Equal diameter section, 122-Suction channel, 123-Permeable mesh, 130-Extrusion motor, 140-Screw, 150-Heating device, 200-Suction mechanism, 210-Cylinder, 220-Piston, 230-Suction motor, 240-Lead screw, 300-Valve, 400-Controller. Detailed Implementation

[0023] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0024] In the description of this application, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0025] In the description of this application, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0026] In the description of this application, unless otherwise expressly defined, terms such as "setup," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this application in conjunction with the specific content of the technical solution.

[0027] In the description of this application, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0028] Fused particle manufacturing (FGF) is an additive manufacturing process that uses plastic granules as raw materials, relying on a screw extrusion mechanism to melt the material and build it up layer by layer. Compared with traditional FDM filament printing, FGF eliminates the filament extrusion and granulation process, resulting in lower raw material costs and higher molding efficiency. It is suitable for manufacturing large-sized parts such as aerospace components, automotive molds, and large architectural models, and its application scope continues to expand.

[0029] When the printing path switches to the non-printing idle stage, the combined effect of residual melt pressure and gravity inside the barrel makes the nozzle prone to leakage and stringing defects, severely reducing the surface quality and dimensional accuracy of the printed parts. Existing FGF equipment adopts the screw reversal retraction scheme, drawing on the FDM filament machine's retraction approach: after the CNC system recognizes the idle command, the main extrusion motor drives the screw to rotate in the opposite direction. The screw displacement drags the solid particles in the feeding section and the molten melt in the metering section upwards, temporarily creating a negative pressure at the nozzle to adsorb the melt and suppress leakage and stringing.

[0030] However, this single-screw mechanism will cause the following problems during retraction: (1) When the screw reverses, the solid particles and semi-molten material will be subjected to violent extrusion interference between the screw channel and the inner wall of the barrel. The reversal will generate huge reverse resistance, and the extrusion motor will be prone to frequent stalling; (2) Affected by the fluctuation of raw material viscosity, particle size distribution and extrusion density, the amount of retraction cannot be accurately quantified. Insufficient retraction will often result in stringing, or excessive retraction will cause the nozzle to suck in air bubbles; (3) When reversing and retracting, the molten material will be subjected to multiple high-intensity shear forces in the narrow flow channel. The long polymer chain will break, the rheological properties will change, and the material properties will deteriorate; (4) The screw itself has a large moment of inertia. There is a significant delay in the screw reversal start and stop, and it is impossible to achieve rapid action.

[0031] In response, this application proposes a nozzle pneumatic back-pull system. During no-load back-pull, the negative pressure generated by the suction mechanism is used to back-pull the material. On the one hand, pneumatic adsorption has a faster response speed than screw reversal and can also adjust the negative pressure more precisely. On the other hand, it reduces the back-pull load on the main extrusion motor and reduces material degradation caused by reverse extrusion.

[0032] In addition, this application also proposes an additive manufacturing equipment including the above-mentioned nozzle pneumatic retraction system, and a working method based on the above-mentioned nozzle pneumatic retraction system. By using the above-mentioned nozzle pneumatic retraction system, the negative pressure value during no-load retraction can be precisely controlled, avoiding the problem of excessive negative pressure causing air bubbles to be sucked in, or insufficient negative pressure causing material to drip, making no-load retraction more controllable.

[0033] Reference Figures 1 to 3 The nozzle pneumatic retraction system in the first aspect embodiment of this application includes a barrel 100 and a suction mechanism 200. The barrel 100 is used to squeeze the material and discharge the molten fluid material outward. The suction mechanism 200 is used to generate negative pressure in the barrel 100, so that when the nozzle is running idle, the suction force generated by the negative pressure counteracts the gravity of the material, preventing the material from dripping out of the barrel 100 and contaminating the workpiece below. This ensures the smoothness of the workpiece surface and reduces material waste.

[0034] Reference Figure 1 The barrel 100 includes a barrel body 110 and a nozzle 120. The barrel body 110 is the main structure of the barrel 100, and its interior is provided with a cavity 111 for filling material and accommodating the screw 140. A discharge port is provided at the end of the cavity 111. When the extrusion motor 130 starts and drives the screw 140 to rotate, the helical blades on the surface of the screw 140 will bring the material closer to the discharge port, thereby completing the discharge.

[0035] It is worth noting that, referring to Figure 2 The nozzle 120 has an interconnected melt channel 121 and a suction channel 122. The melt channel 121 is connected to the discharge port, allowing the material extruded from the discharge port to directly enter the melt channel 121 and eventually exit from the other end. The suction channel 122 is set at an acute angle to the melt channel 121, reducing the probability of material in the melt channel 121 entering the suction channel 122. A permeable mesh 123 is provided at the junction of the suction channel 122 and the melt channel 121, allowing only gas to pass through. Thus, gas in the material can be drawn into the suction channel 122, creating a negative pressure in the melt channel 121. The suction force of this negative pressure prevents material from dripping out.

[0036] The suction mechanism 200 is connected to the suction channel 122 through a pipe, and it can generate negative pressure, thereby causing the gas in the melt channel 121 to be drawn into the suction channel 122.

[0037] The working principle of this nozzle pneumatic retraction system is as follows: The cavity 111 of the barrel body 110 is filled with material. Under the combined action of the extrusion motor 130 and the screw 140, the material can move along the cavity 111 to the discharge port, and enter one end of the melt channel 121 through the discharge port, and finally be discharged from the other end of the melt channel 121. During the no-load retraction, the extrusion motor 130 stops, the suction mechanism 200 starts, and the gas in the melt channel 121 can be sucked into the suction channel 122, which creates a negative pressure in the melt channel 121. The suction force generated by the negative pressure can counteract the weight of the material, thereby reducing the probability of the material dripping out of the barrel 100.

[0038] Furthermore, a heating device 150 is installed on the outside of the barrel 100, which is used to apply heat to the barrel 100, thereby placing the material in the cavity 111 in a high temperature and high pressure environment, and thus causing the material to melt and transform into a fluid state.

[0039] Furthermore, there are at least two suction channels 122, and each suction channel 122 is arranged in a circular array around the melt channel 121. Thus, when the suction mechanism 200 is started, the gas in the melt channel 121 can be evenly sucked out by each suction channel 122, which can also improve the gas extraction efficiency and make the response faster during empty run retraction.

[0040] Furthermore, the melt channel 121 includes a variable diameter section 1211 and a constant diameter section 1212. The variable diameter section 1211 has a larger inner diameter end and a smaller inner diameter end, respectively. The inner diameter of the variable diameter section 1211 gradually decreases from the larger diameter end to the smaller diameter end. The larger diameter end connects to the discharge port, and the smaller diameter end connects to the constant diameter section 1212. Thus, after the material is discharged from the discharge port, it enters from the larger diameter end of the variable diameter section 1211. As the material moves along its path, the variable diameter section 1211 gradually narrows, further increasing the ambient pressure and promoting the melting of the material. Once the molten material enters the constant diameter section 1212, the constant inner diameter of the constant diameter section ensures that the pressure at the final discharge point tends to stabilize, which is beneficial for smooth discharge.

[0041] Furthermore, the suction channel 122 is connected to the junction of the variable diameter section 1211 and the constant diameter section 1212, which facilitates the intake of gas in the melt channel 121.

[0042] Furthermore, a pressure sensor is installed in the air intake channel 122, which can detect the negative pressure in the air intake channel 122, thereby enabling closed-loop control of the air intake mechanism 200. Specifically, the pressure sensor can be installed on the breathable mesh 123 for higher detection accuracy.

[0043] Furthermore, the breathable mesh 123 is made of stainless steel, which gives it sufficient structural strength so that it will not deform or break under high temperature and pressure conditions, thus preventing material from entering the air intake channel 122 due to structural damage.

[0044] Furthermore, referring to Figure 3 An air valve 300 is also provided between the air intake mechanism 200 and the air intake channel 122. The air valve 300 can control the opening degree, thereby controlling the opening and closing of the air intake mechanism 200 and the air intake channel 122. When there is no need to back-draw, the pipeline can be closed by the air valve 300, thereby reducing the chance of air leakage.

[0045] Furthermore, the suction mechanism 200 can employ suction devices such as vacuum pumps or negative pressure pumps that can directly generate negative pressure. In this embodiment, the suction mechanism 200 includes a cylinder 210, a piston 220, a suction motor 230, and a lead screw 240. The cylinder 210 has a sliding chamber, one end of which is open and connected to the suction channel 122 via a pipe. The piston 220 moves within the sliding chamber, with its side surface in contact with the inner wall of the chamber to ensure airtightness. The lead screw 240 is threadedly connected to the piston 220 and to the rotating shaft of the suction motor 230. Therefore, when the suction motor 230 drives the lead screw 240 to rotate, the piston 220 can move under the influence of the lead screw 240, thereby generating negative pressure within the cylinder 210.

[0046] Furthermore, the nozzle pneumatic retraction system also includes a controller 400, which is electrically connected to a pressure sensor, a pumping motor 230, and a valve 300, thereby enabling the monitoring and control of the no-load retraction process.

[0047] The additive manufacturing equipment in the second aspect of this application includes an additive manufacturing equipment body and the above-mentioned nozzle pneumatic retraction system, wherein the nozzle pneumatic retraction system is connected to the additive manufacturing equipment body.

[0048] The working method in the third aspect embodiment of this application, which is based on the above-described nozzle pneumatic retraction system, includes the following steps: S100. When empty running and retraction are required, the extrusion motor 130 stops rotating, the screw 140 stops rotating accordingly, and the material stops moving in the barrel body 110; S200. The suction mechanism 200 draws air, specifically by the suction motor 230 driving the piston 220 to move through the lead screw 240 to generate negative pressure. This negative pressure is transmitted to the suction channel 122 through the pipe, so that negative pressure is generated in the suction channel 122. S300. Under negative pressure attraction, the gas in the melt channel 121 enters the suction channel 122 through the breathable net 123, while the material in the melt channel 121 is blocked by the breathable net 123 and trapped in the melt channel 121. S400. As the gas in the melt channel 121 is drawn out, a negative pressure is generated in the melt channel 121. The adsorption force offsets part of the weight of the material, preventing the material from dripping out of the melt channel 121. S500. After the empty run is completed, the suction mechanism 200 exhausts the air, specifically by reversing the suction motor 230 so that the piston 220 moves to the initial position, and the negative pressure in the suction channel 122 and the melt channel 121 is released; the extrusion motor 130 continues to drive the screw 140 to rotate, and continues the subsequent extrusion work.

[0049] Furthermore, a pressure sensor is installed in the air intake channel 122. Before the empty run retraction is performed, the retraction threshold in the air intake channel 122 is set. When the empty run retraction is performed, the air intake mechanism 200 draws air until the pressure sensor detects that the pressure in the current air intake channel 122 has reached the retraction threshold. Then the air intake mechanism 200 is turned off to ensure that the predetermined pressure value can be reached each time air is drawn.

[0050] After the empty run retraction is completed, the vacuum motor 230 can restore the pressure in the melt channel 121 by reversing the phase synchronization; or, before the empty run retraction is performed, the pressure sensor is used to detect the current pressure value, and after the empty run retraction is completed, the vacuum motor 230 is reversed until the pressure sensor detects the previously detected pressure value. This makes the pressure recovery more accurate and avoids the negative pressure caused by the empty run retraction from affecting the subsequent extrusion.

[0051] The embodiments of this application have been described in detail above with reference to the accompanying drawings. However, this application is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of this application. Furthermore, unless otherwise specified, the embodiments and features described in the embodiments of this application can be combined with each other.

Claims

1. A nozzle pneumatic retraction system, characterized in that, include: The barrel includes a barrel body and a nozzle. The barrel body has an internal cavity, and a discharge port is provided at the end of the cavity. The nozzle has an interconnected melt channel and a suction channel. The melt channel is connected to the discharge port. The suction channel and the melt channel are arranged at an acute angle. A ventilated mesh is provided at the junction of the suction channel and the melt channel, and the ventilated mesh can only allow gas to pass through. An air intake mechanism, which is connected to the air intake channel via a pipe; The cavity of the barrel body is used to fill the material. The material can enter one end of the melt channel through the discharge port and be discharged from the other end of the melt channel. The gas in the melt channel can be drawn into the suction channel, thereby creating a negative pressure in the melt channel.

2. The nozzle pneumatic retraction system according to claim 1, characterized in that: The number of suction channels is at least two, and each suction channel is arranged in a circular array around the melt channel.

3. The nozzle pneumatic retraction system according to claim 1, characterized in that: The melt channel includes a variable diameter section and a constant diameter section. The two ends of the variable diameter section are a large diameter end with a larger inner diameter and a small diameter end with a smaller inner diameter, respectively. The inner diameter of the variable diameter section gradually decreases from the large diameter end to the small diameter end. The large diameter end is connected to the discharge port, and the small diameter end is connected to the constant diameter section.

4. The nozzle pneumatic retraction system according to claim 3, characterized in that: The air intake channel is connected to the junction of the variable diameter section and the constant diameter section.

5. The nozzle pneumatic retraction system according to claim 1, characterized in that: A pressure sensor is installed in the air intake channel.

6. The nozzle pneumatic retraction system according to claim 1, characterized in that: An air valve is also provided between the air intake mechanism and the air intake channel.

7. The nozzle pneumatic retraction system according to claim 1, characterized in that: The suction mechanism includes a cylinder, a piston, a suction motor, and a lead screw. The cylinder has a sliding chamber, one end of which is open and connected to the suction channel via a pipe. The piston moves within the sliding chamber, with its side surface in contact with the inner wall of the sliding chamber. The lead screw is threadedly connected to the piston and to the rotating shaft of the suction motor.

8. An additive manufacturing apparatus, characterized in that, It includes an additive manufacturing equipment body and a nozzle pneumatic retraction system as described in any one of claims 1 to 7, wherein the nozzle pneumatic retraction system is connected to the additive manufacturing equipment body.

9. A method of operation, which is based on the nozzle pneumatic retraction system according to any one of claims 1 to 7, characterized in that, include: When empty runback is required, the material stops moving in the barrel body; The suction mechanism draws in air, creating a negative pressure within the suction channel; The gas in the melt channel enters the suction channel through the permeable mesh, while the material in the melt channel is blocked and retained in the melt channel by the permeable mesh. A negative pressure is generated in the melt channel, and the adsorption force counteracts part of the weight of the material, preventing the material from dripping out of the melt channel; After the empty run is completed, the suction mechanism exhausts the air, and the negative pressure in the suction channel and the melt channel is released, allowing the subsequent extrusion work to continue.

10. The working method according to claim 9, characterized in that: A pressure sensor is installed in the air intake channel. Before the empty run retraction, a retraction threshold is set in the air intake channel. When the empty run retraction occurs, the air intake mechanism draws air until the pressure sensor detects that the pressure in the air intake channel has reached the retraction threshold.

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