CN114750382B - Injection molding pressure control system and control method - Google Patents

Abstract

The invention discloses an injection molding pressure control system and a control method, wherein the system comprises a mold pressure sensing module, a nozzle pressure sensing module, a comparison module, a driving control module, a speed measuring module, a PID control module and a main control module, wherein the mold pressure sensing module is connected with the main control module, the main control module is connected with the nozzle pressure sensing module, the nozzle pressure sensing module is connected with the PID control module, the driving control module is connected with the speed measuring module and the PID control module, the speed measuring module is connected with the comparison module, the comparison module is connected with the PID control module, and the main control module is connected with the PID control module. The invention also discloses a control method of the system. According to the invention, the PID control module is used for precisely controlling the pressure in the injection process and the pressure maintaining process, so that the quality of injection molded products is improved.

Description

Injection molding pressure control system and control method

Technical field

The invention relates to the technical field of injection molding machine control, and in particular to an injection molding pressure control system and a control method.

Background technique

At present, plastic products are widely used in modern society. From daily necessities to industrial accessories and medical equipment, plastic products are inseparable from everywhere. People's quality requirements for plastic products are also gradually increasing. However, traditional injection molding methods The plastic products produced may undergo some deformation due to the injection pressure during the injection molding process, or may shrink or warp due to insufficient holding pressure during the holding process. Therefore, how to effectively and accurately control the injection molding and forming processes? Pressure control has become an issue that must be considered in injection molding production.

The invention patent with patent number CN 103481479 B discloses a pressure control device for an injection molding machine. The patent is provided with a pressure maintaining part, a metering part and a preparatory injection part. The pressure maintaining part is based on the detection of the screw along the axis direction. The force detected by the force detection unit performs pressure control, and the preliminary injection unit performs pressure control based on the resin pressure detected by the resin pressure detection unit. It can more accurately detect the pressure in the injection molding machine and perform pressure control. However, this patent cannot accurately control the speed of pressure change and the pressure control lags behind. The control method has limitations.

Contents of the invention

In view of the above-mentioned injection pressure control lag and the inability to accurately control the pressure change rate, the present invention provides an injection molding pressure control system and a control method, which uses a PID control module to control the pressure change rate and injection pressure during injection molding to achieve In order to achieve the purpose of timely and precise control of injection molding pressure and pressure change rate.

The above technical problems of the present invention are mainly solved through the following technical solutions: an injection molding pressure control system of the present invention includes a mold pressure sensing module, a nozzle pressure sensing module, a comparison module, a drive control module, a speed measurement module, and a PID control module and the main control module, the mold pressure sensing module is connected to the main control module, the main control module is connected to the nozzle pressure sensing module, the nozzle pressure sensing module is connected to the PID control module, the drive control module is connected to the speed measurement module and The PID control module is connected, the speed measurement module is connected to the comparison module, the comparison module is connected to the PID control module, the mold pressure sensing module is connected to the PID control module, and the main control module is connected to the PID control module. Among them, the speed measurement module is used to obtain the rotation speed of the screw, and the comparison module is used to input the ideal pressure transformation curve during injection of the material to be injected.

Preferably, the mold pressure sensing module includes a mold cavity pressure sensor, and the mold cavity pressure sensor is connected to the main control module. The mold pressure sensing module also includes a warning module that issues an alarm when the pressure exceeds a pressure threshold required for material molding.

Preferably, the main control module includes a sampling module, a processing module and a parameter configuration module, the parameter configuration module is connected to the nozzle pressure sensing module, and the processing module is connected to the PID control module. The sampling module is used to obtain the pressure thresholds at each stage of injection molding of the material to be processed and the time thresholds at each stage of injection molding. The processing module is used to obtain pressure signals and transmit them to the PID control module. The nozzle pressure sensing module includes a high temperature melt pressure sensor.

Preferably, the drive control module includes a rotational speed signal shaping module, and the signal conversion module is connected to the PID control module. The signal conversion module converts the rotational speed signal into a control signal, and at the same time converts the feedback signal formed by the PID control module into a speed control signal.

An injection molding pressure control method includes the steps:

S1 sets the first pressure threshold, the second pressure threshold and the third pressure threshold to the nozzle pressure sensing module through the parameter configuration module;

S2 inputs the ideal pressure transformation curve during injection of the material to be injected into the comparison module;

S3 measures the speed of the screw through the speed measurement module and transmits it to the drive control module;

The drive control module in S4 converts the rotational speed signal into a control signal and transmits it to the PID control module;

S5 uses the mold pressure sensing module and the nozzle pressure sensing module to measure the pressure, and transmits the pressure signal to the PID control module;

The PID control module in S6 performs pressure control according to the ideal pressure transformation curve input by the comparison module.

The ideal pressure transformation curve during injection molding includes the pressure curve of the injection process, the pressure curve of the pressure holding process and the overall curve of the molding process. The parameter configuration module can also configure the time thresholds of each stage of the injection molding process.

Preferably, step S1 specifically includes:

S11 employees input the maximum injection pressure and holding pressure of the materials used for injection molding into the sampling module;

S12 sets 50% of the maximum injection pressure as the first pressure threshold, 90% as the second pressure threshold, and sets the holding pressure as the third pressure threshold.

According to needs, if the pressure holding process is divided into more stages, more pressure thresholds can be set according to each stage.

Preferably, step S6 specifically includes:

The PID control module in S61 generates the lower limit threshold K1 and the upper limit threshold K2 of the injection growth rate change rate based on the ideal pressure transformation curve;

S62 When the injection growth rate is outside the [K1, K2] interval, the PID control module generates a feedback signal to the drive control module to control the screw speed to increase/decrease until the injection growth rate change rate is within the [K1, K2] interval;

S63 When the pressure at the nozzle reaches the first pressure threshold, the processing module transmits a conversion reminder signal to the PID control module. The PID control module generates the injection rate change rate threshold K3 and controls the injection rate change rate transformation to [K2, K3 ];

S64 When the injection pressure reaches the second pressure threshold, the processing module determines whether to enter the pressure maintaining process. If so, the PID control module generates the injection drop rate change rate threshold K4, and controls the screw speed to control the injection drop rate change rate at [0.9 K4,1.1K4], until the pressure at the nozzle reaches the third pressure threshold.

If the pressure holding process is divided into multiple stages, the PID control module can also generate more injection drop rate changes in subsequent pressure holding stages.

Beneficial effects of the present invention:

1. The equipment parameters can be set according to the material to be injected, which improves the injection molding efficiency;

2. Improved the control accuracy and speed of injection molding pressure;

3. It can accurately control the growth rate of injection pressure during injection molding and the pressure conversion speed when converting to pressure holding process, making the products produced with higher quality.

Description of the drawings

Figure 1 is a schematic structural diagram of the present invention.

Figure 2 is a flow chart of a method of the present invention.

In the picture, 1. Mold cavity pressure sensor, 2. High temperature melt pressure sensor, 3. Mold, 4. Nozzle, 5. Drive motor.

Detailed ways

The specific embodiments described herein are merely illustrative of the spirit of the invention.

Embodiment: An injection molding pressure control system of this embodiment, as shown in Figure 1, includes a mold pressure sensing module. The mold pressure sensing module includes a mold cavity pressure sensor 1. The mold cavity pressure sensor 1 is located on In the mold 3, the mold pressure sensing module is connected to the main control module. The main control module includes a sampling module, a processing module and a parameter configuration module. The sampling module is used to obtain the pressure thresholds at each stage during injection molding of the material to be processed. And the time threshold of each stage of injection molding, the processing module is used to obtain the pressure signal, the processing module is connected to the PID control module, the processing module transmits the obtained pressure signal to the PID control module, and the parameter configuration module is used to Set the pressure threshold of the nozzle pressure sensing module. The nozzle pressure sensing module includes a high-temperature melt pressure sensor 2 . The high-temperature melt pressure sensor 2 is provided on the nozzle 4 .

The control system also includes a speed measurement module. The speed measurement module is connected to the drive motor 5. The speed measurement module is used to obtain the rotation speed of the screw. The speed measurement module transmits the rotation speed signal to the drive control module. The drive control module includes a signal. Conversion module, the signal conversion module is used to convert the rotation speed signal into a control signal, and at the same time convert the feedback signal formed by the PID control module into a speed control signal. The drive motor 5 is also connected to a comparison module, which is used to input the ideal pressure transformation curve during injection of the material to be injected. The PID control module is also connected to the drive control module for performing pressure control based on the ideal pressure transformation curve input by the comparison module.

An injection molding pressure control method in this embodiment, as shown in Figure 2, includes the steps:

S1 sets the first pressure threshold, the second pressure threshold and the third pressure threshold to the nozzle pressure sensing module through the parameter configuration module;

Specifically include:

S11 employees input the maximum injection pressure and holding pressure of the materials used for injection molding into the sampling module;

S12 sets 50% of the maximum injection pressure as the first pressure threshold, 90% as the second pressure threshold, and sets the holding pressure as the third pressure threshold.

According to needs, if the pressure holding process is divided into more stages, more pressure thresholds can be set according to each stage. The 50% and 90% can also be adjusted according to changes in the mold of the equipment and changes in injection molding materials.

S2 inputs the ideal pressure transformation curve during injection of the material to be injected into the comparison module;

S3 measures the speed of the screw through the speed measurement module and transmits it to the drive control module;

The drive control module in S4 converts the rotational speed signal into a control signal and transmits it to the PID control module;

S5 uses the mold pressure sensing module and the nozzle pressure sensing module to measure the pressure, and transmits the pressure signal to the PID control module;

The PID control module in S6 performs pressure control according to the ideal pressure transformation curve input by the comparison module.

Specifically include:

The PID control module in S61 generates the lower limit threshold K1 and the upper limit threshold K2 of the injection growth rate change rate based on the ideal pressure transformation curve;

S62 When the injection growth rate is outside the [K1, K2] interval, the PID control module generates a feedback signal to the drive control module to control the screw speed to increase/decrease until the injection growth rate change rate is within the [K1, K2] interval;

S63 When the pressure at the nozzle reaches the first pressure threshold, the processing module transmits a conversion reminder signal to the PID control module. The PID control module generates the injection rate change rate threshold K3 and controls the injection rate change rate transformation to [K2, K3 ];

S64 When the injection pressure reaches the second pressure threshold, the processing module determines whether to enter the pressure maintaining process. If so, the PID control module generates the injection drop rate change rate threshold K4, and controls the screw speed to control the injection drop rate change rate at [0.9 K4,1.1K4], until the pressure at the nozzle reaches the third pressure threshold. Among them, 0.9 and 1.1 can also be adaptively adjusted according to different pressure holding requirements.

If the pressure holding process is divided into multiple stages, the PID control module can also generate more injection drop rate changes in subsequent pressure holding stages.

Those skilled in the art to which the present invention belongs can make various modifications or additions to the described specific embodiments or substitute them in similar ways, but this will not deviate from the spirit of the present invention or exceed the definition of the appended claims. range.

Although this article uses terms such as main control module, processing module, mold pressure sensing module, and PID control module more often, it does not rule out the possibility of using other terms. These terms are used only to more conveniently describe and explain the essence of the present invention; interpreting them as any additional limitations is contrary to the spirit of the present invention.

Claims (7)

1. An injection molding pressure control system, characterized in that it includes a mold pressure sensing module, a nozzle pressure sensing module, a comparison module, a drive control module, a speed measurement module, a PID control module and a main control module. The mold pressure sensing module and the main control module The control module is connected, the main control module is connected to the nozzle pressure sensing module, the nozzle pressure sensing module is connected to the PID control module, the drive control module is connected to the speed measurement module and the PID control module, the speed measurement module is connected to the comparison module , the comparison module is connected to the PID control module, the main control module is connected to the PID control module, the main control module includes a sampling module, a processing module and a parameter configuration module, the comparison module is used to input the injection of the material to be injected When the ideal pressure transformation curve is obtained, the speed measurement module is used to obtain the rotation speed of the screw and transmit the rotation speed signal to the drive control module. 2. An injection molding pressure control system according to claim 1, characterized in that the mold pressure sensing module includes a mold cavity pressure sensor, and the mold cavity pressure sensor is connected to the main control module. 3. An injection molding pressure control system according to claim 1 or 2, characterized in that the main control module includes a sampling module, a processing module and a parameter configuration module, and the parameter configuration module is connected to the nozzle pressure sensing module, The processing module is connected to the PID control module. 4. An injection molding pressure control system according to claim 1, wherein the drive control module includes a signal conversion module, and the signal conversion module is connected to a PID control module. 5. A control method based on the injection molding pressure control system according to any one of claims 1 to 4, characterized in that it includes the steps: S1 sets the first pressure threshold, the second pressure threshold and the third pressure threshold to the nozzle pressure sensing module through the parameter configuration module; S2 inputs the ideal pressure transformation curve during injection of the material to be injected into the comparison module; S3 measures the speed of the screw through the speed measurement module and transmits it to the drive control module; The drive control module in S4 converts the rotational speed signal into a control signal and transmits it to the PID control module; S5 uses the mold pressure sensing module and the nozzle pressure sensing module to measure the pressure, and transmits the pressure signal to the PID control module; the PID control module in S6 performs pressure control based on the ideal pressure transformation curve input by the comparison module. 6. The control method according to claim 5, characterized in that step S1 specifically includes: S11 employees input the maximum injection pressure and holding pressure of the materials used for injection molding into the sampling module; S12 sets 50% of the maximum injection pressure as the first pressure threshold, 90% as the second pressure threshold, and sets the holding pressure as the third pressure threshold. 7. The control method according to claim 5, characterized in that step S6 specifically includes: The PID control module in S61 generates the lower limit threshold K1 and the upper limit threshold K2 of the injection growth rate change rate based on the ideal pressure transformation curve; S62 When the injection growth rate is outside the [K1, K2] interval, the PID control module generates a feedback signal to the drive control module to control the screw speed to increase/decrease until the injection growth rate change rate is within the [K1, K2] interval; S63 When the pressure at the nozzle reaches the first pressure threshold, the processing module transmits a conversion reminder signal to the PID control module. The PID control module generates the injection rate change rate threshold K3 and controls the injection rate change rate transformation to [K2, K3 ]; S64 When the injection pressure reaches the second pressure threshold, the processing module determines whether to enter the pressure maintaining process. If the PID control module generates the injection drop rate change rate threshold K4, and controls the screw speed to control the injection drop rate change rate at [0.9K4,1.1 K4] until the pressure at the nozzle reaches the third pressure threshold.