Slide positioning control system under high pressure injection process of composite material press

Abstract

The application discloses a slider positioning control system under a high-pressure injection process of a composite material press, and belongs to the technical field of process control of a composite material hydraulic press, which comprises a four-corner leveling control system, the four-corner leveling control system comprises a general control motion controller, a leveling cylinder bidirectional pressure sensor, a displacement sensor, a high-frequency response flow control servo valve for controlling bidirectional motion of the leveling cylinder, the displacement sensor is used for detecting the position of the slider, the displacement sensor and a PLC realize data interaction, an electro-hydraulic servo control card is used for closed-loop control of the pressure of a main cylinder of the press, an input interface of the electro-hydraulic servo control card is connected with a PLC analog quantity module, an output interface of the electro-hydraulic servo control card is connected with a press main servo motor driver, and position loop control is developed on the basis of pressure loop control, a servo drive pump set is used for providing a power source for the press, the servo drive pump set provides hydraulic oil with stable flow and stepless adjustment, and is used for driving the down pressure and return action of the slider of the press.

Description

Technical Field

[0001] This invention belongs to the field of process control technology for composite material hydraulic presses, and in particular relates to a slider positioning control system for high-pressure injection process of composite material presses. Technical Background

[0002] With the continuous development of lightweighting in industries such as automobiles, high-speed rail, subways, and agricultural machinery, carbon fiber molding is one of the main methods, and RTM (Resin Transfer Molding) technology is gradually emerging. The general process flow is as follows:

[0003] Fiber preform placed in mold cavity → Press slide unlocked → Rapid descent → Slow descent → Contact leveling cylinder for synchronous descent → Mold closing and pressurization to zero tonnage → Main cylinder tonnage reduced to micro-mold opening tonnage → Four corners leveled and micro-mold opening → Vacuuming → Injection gun head opened for glue injection → Secondary slow pressurization → Multi-stage pressure holding and curing → Pressure release and demolding → Slow slide return → Rapid return → Deceleration return → Slide safety locking → Remove part;

[0004] In the aforementioned micro-mold opening process, the slider needs to remain parallel and stop precisely at the preset position; otherwise, it will affect the thickness of the part and seriously affect the pass rate.

[0005] In the injection process of the injection machine, as the injection time increases, the pressure inside the mold cavity gradually increases, which will generate a gradually increasing reaction force on the slider. At this time, the upper cavity of the main cylinder must simultaneously apply a matching pressure, i.e., clamping force, to prevent the slider position from becoming unstable and to ensure the accuracy of the part. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a slider positioning control system for high-pressure injection molding of composite materials. During the micro-mold opening stage, the advantages of the four-corner leveling controller—fast response, high precision, and built-in closed-loop positioning control function—are utilized to synchronously drive four leveling cylinders to eject the slider and achieve the specified position. During the injection stage, the pressure closed-loop control function of the electro-hydraulic servo control card is utilized, and a position closed-loop function is developed based on this to achieve precise slider positioning during this stage.

[0007] A slider positioning control system based on high-pressure injection molding process of composite material press, comprising:

[0008] (1) A four-corner leveling control system for precise micro-mold opening, including:

[0009] 1) The master motion controller D includes four axis modules: D1, D2, D3, and D4;

[0010] 2) Leveling cylinder bidirectional pressure sensor A and displacement sensor B;

[0011] 3) High-frequency response flow control servo valve C for controlling the bidirectional movement of the leveling cylinder;

[0012] 4) An accumulator E that provides stable hydraulic power to the four-corner leveling system and a switching valve F that controls its opening and closing;

[0013] The aforementioned bidirectional pressure sensor A, displacement sensor B, and high-frequency response flow control servo valve C of the leveling cylinder are connected to the I / O terminals of the master motion controller D via data lines.

[0014] (2) A displacement sensor for detecting the position of the slider communicates with the press PLC via Ethernet;

[0015] (3) An electro-hydraulic servo control card for closed-loop control of the main cylinder pressure of the press, with the input interface connected to the PLC analog module and the output interface connected to the main servo motor driver of the press, and a position loop control developed on the basis of pressure loop control.

[0016] The servo-driven pump set, which provides power to the press, can provide hydraulic oil with stable flow and stepless adjustment, used to drive the press slide for downward pressurization and return motion.

[0017] The advantages and positive effects of this invention are:

[0018] By adopting the above-mentioned technical solutions, this invention enables the slider to maintain precise positioning and a constant position even when subjected to multiple and real-time changing external forces during the micro-mold opening and high-pressure injection processes. It includes: a four-corner leveling control system for precise micro-mold opening; a high-precision displacement sensor for real-time monitoring of the slider position; an electro-hydraulic servo control card for closed-loop control of the press master cylinder pressure; a PLC and its corresponding modules for controlling the overall operation of the press; and a servo-driven pump system for providing power to the press.

[0019] This invention makes full use of the existing hydraulic and electrical control systems, without the need for additional hardware. Once the existing hardware configuration and software are integrated, it can be molded in one step without repeated testing. Through software development, the control accuracy during micro-mold opening and high-pressure injection processes can reach ±0.01mm. Attached image description:

[0020] Figure 1 This is a schematic diagram of the four-corner leveling control system for micro-mold making according to the present invention;

[0021] Figure 2 This is the wiring diagram of the pressure ring of the electro-hydraulic servo control card in this invention;

[0022] Figure 3 This is the wiring diagram of the position ring based on the pressure ring invention in this invention. Detailed Implementation

[0023] To further understand the content, features, and effects of this invention, the following embodiments are provided, and detailed descriptions are given below in conjunction with the accompanying drawings:

[0024] A slider positioning control system based on high-pressure injection molding process of composite material press, comprising:

[0025] (1) A four-corner leveling control system for precise micro-mold opening, the four-corner leveling control system includes: a master motion controller D, a bidirectional pressure sensor A and a displacement sensor B for the leveling cylinder, and a high-frequency response flow control servo valve C for controlling the bidirectional movement of the leveling cylinder; wherein: the bidirectional pressure sensor A, the displacement sensor B, and the high-frequency response flow control servo valve C are connected to the I / O terminals of the master motion controller D via data lines;

[0026] (2) A displacement sensor for detecting the position of the slider communicates with the press PLC via Ethernet.

[0027] (3) An electro-hydraulic servo control card for closed-loop control of the main cylinder pressure of the press, with the input interface connected to the PLC analog module and the output interface connected to the main servo motor driver of the press, and a position loop control developed on the basis of pressure loop control.

[0028] Please see Figure 1 A is a bidirectional pressure sensor for the leveling cylinder; B is a displacement sensor; C is a high-frequency response flow control servo valve that controls the bidirectional movement of the leveling cylinder; D is a master motion controller, which includes modules D1, D2, D3, and D4; and E is an accumulator that provides stable hydraulic power to the four-corner leveling system, along with a switching valve F.

[0029] The working principle of this invention is as follows:

[0030] 1. Micro-mold opening stage:

[0031] S1, such as Figure 1 The diagram shows the components of the four-corner position synchronous closed-loop control system used in this invention. When the slider is first pressed down to zero tonnage (usually based on the mold sealing ring being fully compacted and the mold closed), the mold closing positions of the slider and the leveling cylinder are simultaneously acquired. Based on the preset micro-mold opening gap height in the human-machine interface, the target positions of the leveling cylinder and the slider can be calculated. For example, if the mold closing positions of the slider and the leveling cylinder are 0.05mm and 0.02mm respectively, and the preset micro-mold opening gap is 1mm, then the target position of the slider is 0.05 + 1 = 1.05mm.

[0032] S2. After step 1 above, the main cylinder tonnage is reduced to the micro-mold opening tonnage (generally 5% of the press's full tonnage and not exceeding the maximum leveling tonnage). At this time, the instantaneous position of the slider after the pressure drop is collected again. For example, if it changes from 0.05mm before the pressure drop to 0.07mm after the pressure drop, the slider only needs to be raised by 1.05-0.07=0.98mm to reach the target position. Therefore, the target position of the leveling cylinder is the position when the mold is closed plus the height that the slider needs to be raised, i.e., 0.02+0.98=2mm.

[0033] S3. After determining the target position of the leveling cylinder according to the above 2, the four leveling cylinders are synchronously driven and the slider is lifted to open the mold by using the closed-loop control positioning function of the four corner leveling position. When the leveling cylinder reaches the target position, the slider position also reaches the required process parameter position, and then the next process action is entered.

[0034] 2. High-pressure injection stage

[0035] S1, Electro-hydraulic servo pressure closed-loop control card and its principle

[0036] like Figure 2 The diagram shows a closed-loop control card widely used in electro-hydraulic servo presses and its connection with a PLC. This card is used to precisely control the press's main cylinder pressure, with a control accuracy of ±0.1 MPa.

[0037] The QV1 analog output channel is 0-10V, corresponding to a pressure adjustment range of 0-27.5MPa, and can be connected to the AI1 pressure setpoint channel on the board.

[0038] The QV2 analog output channel is 0-10V, corresponding to the maximum motor speed set in the driver, and is connected to the AI0 flow rate input channel of the board.

[0039] The 4-20mA circuit signal of the master cylinder pressure sensor is connected in series with a 250-ohm resistor, which generates a 1-5V voltage signal across the resistor, corresponding to a pressure range of 0-40MPa, and is connected to the AI3 pressure feedback channel of the control card.

[0040] The control card output channel AO0 is connected to the servo driver, with a signal range of 0-5V, and is used to adjust the servo speed.

[0041] The control card has a built-in pressure closed-loop control algorithm. For example, if 10MPa is set, the motor runs at the set speed during the slider pressurization process. When the pressure approaches 10MPa, the motor speed gradually decreases. When the actual pressure reaches 10MPa, the speed is 0. When the pressure decreases, that is, the feedback value is less than the target value, the speed output will be triggered again until the target value is reached. Therefore, the so-called pressure closed loop is actually the process of comparing and outputting signals from various channels. AI1 is the target pressure, AI3 is the actual pressure, AI0 is the maximum speed output, and AO1 is the real-time output.

[0042] S2, Position closed loop invented based on pressure closed loop

[0043] like Figure 3 The diagram shown is a wiring diagram for a position loop based on a pressure loop invention. It is largely similar to a pressure closed loop, but the difference lies in the fact that the AI3 feedback input channel of the control card originates from the analog output channel of the PLC. The feedback here is actually the position of the slider. Since the slider displacement gauge is already connected to the PLC bus and full-stroke position control is not required, the real-time slider position within the required range is converted via the analog output channel and connected to the control card's feedback channel. For example, the slider position within the range of -0.75 to 2mm (this range completely covers the gap range required for the micro-mold process) is converted into a 0-10V electrical signal and sent to the control card as a feedback value. During high-pressure injection, when the injection force gradually increases until it exceeds the slider's own weight and the reserve pressure provided by the micro-mold tonnage, the slider will inevitably be pushed upwards, meaning the slider position increases. Since the slider position has already been converted into an electrical signal and sent to the control card for feedback, the program calculates the increase in slider position and converts it into a decrease in the feedback value. At this time, the control card triggers a signal output to the servo driver, driving the servo pump group to provide pressure to the main cylinder until the slider position is pressurized to the target position value, forming a closed-loop control.

[0044] The embodiments of the present invention have been described in detail above, but the content described is only a preferred embodiment of the present invention and should not be considered as limiting the scope of the present invention. All equivalent changes and improvements made in accordance with the scope of the present invention should still fall within the patent coverage of the present invention.

Claims

1. A slider positioning control system for high-pressure injection molding of composite materials, characterized in that, include: A four-corner leveling control system for precise micro-mold opening includes a central motion controller. The I / O terminals of the central motion controller are respectively connected to a bidirectional pressure sensor of the leveling cylinder, a displacement sensor, and a high-frequency response flow control servo valve that controls the bidirectional movement of the leveling cylinder. The central motion controller includes four axis modules. An accumulator that provides stable hydraulic power to the four-corner leveling control system and a switching valve that controls its opening and closing; A displacement sensor is used to detect the position of the slider, and the displacement sensor interacts with the PLC via Ethernet; An electro-hydraulic servo control card for closed-loop control of the main cylinder pressure of a press is provided. The input interface of the electro-hydraulic servo control card is connected to a PLC analog module, and the output interface of the electro-hydraulic servo control card is connected to the main servo motor driver of the press. A position closed-loop control is developed based on the pressure closed-loop control. A servo-driven pump unit is used to provide a power source for the press. The servo-driven pump unit provides hydraulic oil with a stable flow rate and stepless adjustment, which is used to drive the downward pressurization and return motion of the press slide. During the high-pressure injection stage, the following process is performed: S11, Electro-hydraulic servo pressure closed-loop control card is in operation; The closed-loop control card is connected to the PLC for precise control of the press main cylinder's pressurization pressure, with a control accuracy range of ±0.1MPa. Specifically: the QV1 analog output channel is 0-10V, corresponding to a pressure adjustment range of 0-27.5MPa, and is connected to the AI1 pressure setpoint channel on the board; the QV2 analog output channel is 0-10V, corresponding to a range from 0 to the maximum motor speed set within the driver, and is connected to the AI0 flow setpoint channel on the board; the 4-20mA circuit signal of the main cylinder pressure sensor is connected in series with a 250-ohm resistor, forming a 1-5V voltage signal across the resistor, corresponding to a pressure range of 0-40MPa, and is connected to the AI3 pressure feedback channel on the control card; the control card's output channel AO0 is connected to the servo driver, with a signal range of 0-5V, used to adjust the servo speed; the control card has a built-in pressure closed-loop control algorithm. During the slider pressurization process, the motor runs at the set speed. The so-called pressure closed loop is actually the process of comparing and outputting signals from each channel, i.e., AI1 is the target pressure, AI3 is the actual pressure, AI0 is the maximum speed output, and AO0 is the real-time output; S22, Position closed loop based on pressure closed loop; The AI3 feedback input channel of the control card comes from the analog output channel of the PLC. This feedback is the position of the slider. The slider displacement gauge is connected to the PLC bus. The real-time position of the slider within the required range is converted by the analog output channel and then connected to the control card feedback channel. During high-pressure injection, when the injection force gradually increases until it exceeds the self-weight of the slider and the reserve pressure brought by the micro-mold opening tonnage, the slider will have an upward reverse push tendency, that is, the slider position increases. Since the slider position has been converted into an electrical signal and sent to the control card for feedback, the program calculates the increase in slider position and converts it into a decrease in feedback value. At this time, the control card triggers a signal output to the servo driver, which drives the servo drive pump group to provide pressure to the main cylinder until the slider position is pressurized to the target position value, forming a closed-loop control.

2. The slider positioning control system under high-pressure injection process of composite material press according to claim 1, characterized in that, During the micro-mold opening stage, the following processes are performed: S1. When the slider is pressed down to zero tonnage for the first time, the mold closing position of the slider and the leveling cylinder is collected at the same time. Then, based on the micro mold opening gap height preset by the human-machine interface, the target position of the leveling cylinder and the slider is calculated. S2. When the tonnage of the main cylinder drops to the micro-mold opening tonnage, collect the instantaneous position after the pressure drop of the slider to determine the target position of the leveling cylinder. S3. Utilizing the closed-loop control positioning function of the four corner leveling positions, the four leveling cylinders are driven synchronously to lift the slider and micro-open the mold. When the leveling cylinder reaches the target position, the slider position also reaches the required process parameter position, and then the next process action is entered.

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