CN-121989430-A - Double-layer gas-assisted extrusion control method and system for multi-cavity pipe with radial blade pressure regulator

CN121989430ACN 121989430 ACN121989430 ACN 121989430ACN-121989430-A

Abstract

The invention discloses a double-layer gas-assisted extrusion control method and a double-layer gas-assisted extrusion control system for a multi-cavity pipe with a radial blade pressure regulator, and relates to the technical field of high polymer material precision machining. The core of the regulating loop is an integrated double-channel radial blade pressure regulating assembly, a first regulating channel and a second regulating channel which are physically isolated are integrated in the regulating loop, and a variable throttling annular gap surrounded by a plurality of radial swing blades is arranged in the channels and is independently driven by a double-shaft servo driving unit. The invention realizes the thermal decoupling of the precise pressure regulating mechanism and the high-temperature die through an external independent design, solves the problems of thermal expansion blocking and leakage of the traditional device, simultaneously realizes the real-time response to the melt pressure fluctuation by utilizing the variable flow resistance characteristic of the bionic blade, ensures the independent stable control of the inner air cushion layer and the outer air cushion layer of the multi-cavity pipe, and can obviously improve the molding quality of products.

Inventors

JIANG SHIYU
RONG HAO
LIU HESHENG
YU ZHONG
HUANG YIBIN
WANG SONGTAO

Assignees

江西水利电力大学

Dates

Publication Date: 20260508
Application Date: 20260119

Claims (10)

1. A multi-cavity pipe double-layer gas-assisted extrusion control system with radial blade pressure regulators is characterized by comprising a control system, wherein the control system comprises a screw extruder and a multi-cavity gas-assisted extrusion die device which are sequentially arranged along the flow direction of materials, the control system further comprises a gas regulating and monitoring circuit which is independently arranged outside the multi-cavity gas-assisted extrusion die device, the circuit comprises an integrated dual-channel radial blade pressure regulating component and is arranged at the downstream of a high-pressure gas source, a first regulating channel and a second regulating channel which are physically isolated are integrated in a shell of the integrated dual-channel radial blade pressure regulating component and are respectively used for regulating the flow of auxiliary gas of an inner layer and an outer layer, the first regulating channel and the second regulating channel are internally connected with a variable throttling annular gap and a double-shaft servo driving unit which are respectively surrounded by a plurality of radial swinging blades, the variable throttling annular gap, the double-shaft servo driving unit and the double-shaft servo driving unit are respectively driven by the two groups of radial swinging blades to deflect, a pressure stabilizing and monitoring integrated module is arranged between the pressure regulating component and the die device, the pressure stabilizing and the integrated module is used for buffering the gas, and the integrated pressure is respectively detecting the pressure of the inner layer P g_in and the outer layer P5326, the pressure sensor, the pressure controller, the pressure regulator and the pressure sensor are respectively connected with the melt control system.
2. The multi-cavity pipe double-layer gas-assisted extrusion control system with the radial blade pressure regulator according to claim 1, wherein the integrated double-channel radial blade pressure regulating assembly comprises a device shell and a central regulating hub, two groups of radial swing blades are arranged in layers along the axial direction, an overlapped sealing area is arranged between adjacent blades, and the effective flow area of the variable throttling annular gap is continuously changed by synchronous swing around the central regulating hub.
3. The double-cavity pipe double-layer gas-assisted extrusion control system with the radial blade pressure regulator according to claim 1, wherein a first pressure stabilizing cavity and a second pressure stabilizing cavity which are not communicated with each other are arranged inside the double-channel pressure stabilizing and monitoring integrated module and are respectively connected in an inner-layer gas circuit and an outer-layer gas circuit in series, and a probe of the pressure sensor directly stretches into the first pressure stabilizing cavity or the second pressure stabilizing cavity.
4. The dual-cavity tube gas-assist extrusion control system with radial vane pressure regulator of claim 1, wherein independent inner-layer gas-assist passages and outer-layer gas-assist passages are arranged in the multi-cavity gas-assist extrusion die device, the inner-layer gas-assist passages extend to the tail end of the core rod through the split support, and the outer-layer gas-assist passages are communicated with an outer gas-assist cylinder at the tail end of the die.
5. The dual-cavity tubing dual-layer gas-assisted extrusion control system with radial vane pressure regulator according to claim 1, wherein a nonlinear compensation module is configured in the controller, and the nonlinear compensation module stores a mapping relation table of vane swing angle and flow area and is used for converting a pressure control signal into an angle instruction of a servo motor.
6. A method of controlling a dual lumen tubing gas assisted extrusion control system having radial vane pressure regulators according to any of claims 1-5, comprising the steps of: S1, synchronously acquiring data, namely acquiring melt pressure P m at a machine head in real time through a melt pressure sensor in the extrusion process, and simultaneously acquiring inner-layer air pressure P g_in and outer-layer air pressure P g_out in real time through a dual-channel pressure stabilizing and monitoring integrated module; S2, based on melt pressure P m acquired in real time, the double-loop independent discrimination controller is combined with preset inner layer target pressure difference P in and outer layer target pressure difference P out to respectively calculate first pressure deviation E in of an inner layer air path and second pressure deviation E out of an outer layer air path; S3, respectively generating blade angle adjusting instructions for a first adjusting channel and a second adjusting channel by a dynamic strategy generating controller according to the first pressure deviation E in and the second pressure deviation E out ; S4, the radial blade dynamic compensation controller sends the blade angle adjusting instruction to the servo driving unit, and drives the corresponding radial swing blades to deflect so as to change the area of the variable throttling annular gap until the inner layer air pressure P g_in and the outer layer air pressure P g_out respectively reach preset dynamic balance conditions with the melt pressure P m ; s5, after the two paths of gas subjected to pressure stabilizing forming and adjusting are buffered and eliminated by the double-channel pressure stabilizing and monitoring integrated module, the two paths of gas are respectively injected into an inner layer gas-assisted runner and an outer layer gas-assisted runner of the multi-cavity gas-assisted extrusion die device.
7. The method of claim 6, wherein in step S3, a feed-forward and feedback combined control strategy is adopted, and when the change rate of the melt pressure P m is monitored to exceed a threshold value, the estimated blade angle correction is directly superimposed before the feedback adjustment is effective.
8. The method of claim 6, further comprising the step of initializing and pre-pressurizing the system by driving the radial swing blades to a preset opening degree before the extrusion is started, pre-filling the air pressure in the pressure stabilizing cavity to a starting threshold value by using a high-pressure air source, and then returning the blades to a standby small opening degree.
9. The control method of the multi-cavity pipe double-layer gas-assisted extrusion control system with the radial blade pressure regulator according to claim 6, wherein the dynamic balance condition is that the inner layer gas pressure meets the following conditions And the outer air pressure is satisfied Where P is the target pressure differential, To allow for errors.
10. The method of claim 6, further comprising the step of providing an anomaly protection for the dual-lumen tubing dual-layer gas-assist extrusion control system, wherein when a sudden drop in melt pressure P m is detected and the pressure deviation continues to exceed a safety threshold, a burst of tubing is determined, and the closing of the radial blade pressure regulating assembly is immediately commanded.

Description

Double-layer gas-assisted extrusion control method and system for multi-cavity pipe with radial blade pressure regulator Technical Field The invention relates to the technical field of high polymer material processing and precise extrusion, in particular to an air inlet pressure regulating device for air-assisted extrusion, foaming extrusion and pipe molding, and an intelligent air pressure control system and method based on melt pressure feedback. Background In the field of polymer material processing, plastic extrusion molding is a core process for producing products such as pipes, profiles and the like. In order to solve the problems of die swell, surface shark skin disease, long cooling time of thick-wall products and the like in the traditional extrusion, the Gas-assisted extrusion Gas-Assisted Extrusion technology is developed. According to the technology, a micron-sized high-pressure air cushion layer is injected between the polymer melt and the wall surface of the die or the inside of the melt, so that the friction resistance is obviously reduced by utilizing the lubrication action of air, and the extrusion efficiency and the product surface quality are improved. For high precision gas-assisted extrusion, the core challenge is to maintain a dynamic balance of gas pressure P g and melt pressure P m. However, in actual production, melt pressure P m at the head tends to exhibit nonlinear high-frequency fluctuations, affected by the periodic rotation of the extruder screw, fluctuations in raw material viscosity, and temperature variations. The prior art generally employs mechanical pressure reducing valves, manual needle valves, or the integration of damper adjustment devices directly inside the mold to control the gas pressure. However, these conventional approaches suffer from the following significant drawbacks: 1. The prior art often tries to directly design a gas regulating valve core or a damping slide block in an extrusion die or a machine head body so as to pursue the compactness of the structure. However, the working temperature of the extrusion die is typically up to 180-250 ℃. Under this high temperature environment, precise metal regulating components such as valve pins, sliders can undergo non-negligible thermal expansion, resulting in micron-sized changes in the mating gap. The device is easy to cause the blocking of moving parts, can also cause gas sealing failure, causes serious drift of control precision along with temperature change, and is difficult to realize stable operation for a long period. 2. The response is lagged, the high-frequency fluctuation of the melt cannot be followed, the traditional needle valve or screw rod type regulating mechanism is mostly based on the aperture throttling principle, the flow characteristic is linear or quasi-linear, the mechanical stroke is long, and the action inertia is large. When a severe fluctuation in the melt pressure P m occurs in the millisecond range, the conventional apparatus cannot accomplish a wide range of switching of the flow resistance in a very short time. The result is that when the melt pressure is instantaneously raised, the air pressure is not built up, the air cushion layer is compressed and even disappears, and when the melt pressure is instantaneously lowered, the air pressure is not released, so that the wall surface of the pipe is blown or the airway is collapsed, and the yield is seriously affected. 3. The 'variable damping' characteristic is lacking, and the adjusting range is limited. The existing device is difficult to realize large-scale nonlinear adjustment of the fluid resistance coefficient by changing the attack angle of the turbulence element like an airplane wing deflector or a bionic bird wing. When facing the process switching of different viscosity materials or different specification moulds, the traditional valve is often limited in adjusting range and poor in universality, and once blockage or failure occurs, the whole high-temperature mould is often required to be disassembled for maintenance, so that the maintenance cost is extremely high. 4. The double-layer gas assist lacks independent decoupling control, and in the production of multi-cavity pipes, an inner layer gas cushion is used for supporting a cavity, an outer layer gas cushion is used for lubricating a wall surface, and the optimal pressure and flow required by the inner layer gas cushion and the outer layer gas cushion are often different. In the prior art, single air source split flow or simple parallel pipelines are mostly adopted, and an independent closed-loop adjusting mechanism is lacked. This results in the pressure of the outer layer being disturbed when the pressure of the inner layer is regulated, and it is difficult to establish a stable air cushion at the same time between the inner layer and the outer layer, and the phenomenon of "inner layer collapse" or "outer layer blow-through" is very easy to occur. Disclosure of Invention