JPH04272818A - Injection process control method and its device - Google Patents

Abstract

PURPOSE:To control the pressure of molten resin flowing into a cavity constant by controlling the injection speed in the whole or a part of the injection and filling process of molten resin into the cavity. CONSTITUTION:A control circuit consisting of a pressure sensor 34 installed on a nozzle 20 at the end of a heating cylinder and converting the pressure of molten resin 14 flowing in the nozzle 20 and outputting the same, a flow rate control valve 30 for controlling the hydraulic force fed into an oil chamber 26 to control the injection speed and a controller for comparing the value of electrical quantity input from the pressure sensor 34 without the set value and regulating the value of electrical quantity corresponding to the deviation and outputting the same to the flow rate control valve is provided in an injection molding machine.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for controlling the injection process of an injection molding machine.

0002

2. Description of the Related Art In the injection process of conventional injection molding operations, the injection speed is relatively high when injecting and filling a cavity with molten resin. This is to shorten the molding cycle time and to reduce temperature changes in the molten resin.

0003

[Problem to be Solved by the Invention] However, in the conventional injection process as described above, the higher the injection speed is, the more the resin pressure within the cavity becomes significantly uneven, resulting in residual stress in the molded product. This may cause deformation such as bending or warping, or lack of strength. Since high injection pressure is required to increase the injection speed, excessive energy is required. Furthermore, if the injection pressure is increased, the mold clamping force must also be increased, which requires a large mold clamping device. Furthermore, in the case of lamination molding in which a skin material is inserted into a cavity and molded, the skin material is damaged by the flow and pressure of the molten resin. The present invention aims to solve such problems.

0004

[Means for Solving the Problems] The present invention solves the above problems by providing means for controlling the pressure of molten resin flowing into the cavity at a constant level. In other words, the method for controlling the injection process of an injection molding machine according to the present invention is to control the pressure of the molten resin injected from the nozzle of the injection molding machine in all or part of the process of injecting and filling the cavity of a clamped mold with molten resin. Alternatively, the injection speed is controlled in order to keep the pressure of molten resin flowing into the cavity from the gate of the mold constant. Further, the injection process control device for an injection molding machine according to the present invention includes: a pressure detection device that converts molten resin pressure into an electrical quantity value and outputs it; an injection speed adjustment device for controlling the injection speed of the molten resin; a controller that compares the electric quantity value obtained from the pressure detection device with a set value and outputs an operation command signal corresponding to the deviation to the injection speed adjustment device;
The controller monitors whether the molten resin pressure is at the set value and outputs the operation command signal to correct the injection speed in accordance with the amount of deviation when it deviates from the set value. It is composed of Further, the injection speed adjusting device includes a hydraulic injection drive device that can drive the injection plunger, and a flow control valve that can adjust the amount of oil supplied to the oil chamber of the injection drive device. The pressure detection device can also be a pressure sensor that detects the oil pressure supplied to the oil chamber of the injection drive device.

[0005] By using the injection process control method according to the present invention, it becomes possible to perform injection molding at a relatively low constant pressure, thereby correcting nonuniform resin pressure within the cavity. Further, in bonding molding, the inserted skin material will not be damaged.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of an injection molding machine controlled by the injection process control method according to the present invention. A gate 16 is provided on one side of the mold 10 as a flow path for injecting the molten resin 14 into the cavity 12 of the mold 10 that has been clamped. It is possible to connect the mold 10 and the heating cylinder 18 by bringing the end of the gate 16 into close contact with the nozzle 20 provided at the tip of the heating cylinder 18. The gate 16 and the nozzle 20 serve as a flow path through which the molten resin 14 stored in the heating cylinder 18 is injected into the cavity 12. Heating tube 18
Inside is an injection plunger 2 for extruding the molten resin 14.
2 is inserted so that it can be moved back and forth. Injection plunger 22 is connected to piston 24 . The piston 24 fitted into the cylinder 25 defines an oil chamber 26 for moving the piston 24 by hydraulic pressure. The cylinder 25 and the piston 24 constitute an injection drive device 28. In the oil chamber 26,
A hydraulic circuit 31 for supplying oil from the hydraulic source 29 is connected, and the hydraulic circuit 31 is provided with a flow control valve 30 for controlling the amount of oil supplied to the oil chamber 26 . The injection drive device 28 and the flow rate control valve 30 constitute an injection speed adjustment device. The flow control valve 30 is controlled by an electrical signal from a controller 32 connected thereto. Controller 3
2 includes a pressure sensor 34 (
A signal from a pressure detection device) is input. Pressure sensor 3
4 detects the resin pressure flowing through the nozzle 20, converts it into an electrical quantity, and outputs it to the controller 32.

Next, the injection process will be explained. Oil chamber 2
6 to move the piston 24 forward (move toward the mold 10). As the piston 24 moves, the injection plunger 22 connected to the piston 24 also moves forward, so that the molten resin 1 stored at the tip of the heating cylinder 18
4 is pushed by the injection plunger 22 and is injected and filled into the cavity 12 through the nozzle 20 and the gate 16. At this time, the pressure sensor 34 detects the resin pressure passing through the nozzle 20, converts it into an electrical quantity value, and outputs it to the controller 32. The optimum resin pressure is set in advance in the controller 32, and the input electric quantity value is compared with the set value.
The quantity of electricity corresponding to the deviation is adjusted and output to the flow rate control valve 30. The flow rate control valve 30 controls the amount of oil supplied to the oil chamber 26 according to the input amount of electricity.
6 and adjusts the moving speed of the piston 24. By doing so, the molten resin 14 is injected and filled into the cavity 12 with a relatively low constant resin pressure.

[0008] In this example, the resin pressure was kept constant throughout the entire process of injection and filling.
For example, in the first half of the injection process, the injection speed is relatively high,
It is also possible to perform the above-described control only in the latter half of the injection process.

Another embodiment is shown in FIGS. 2 and 3. These are modifications of the pressure detection device of the injection molding machine shown in FIG. The embodiment shown in FIG.
The pressure of the molten resin flowing into the molten resin is detected and controlled to be constant. In the embodiment shown in FIG. 3, a pressure sensor 34 is attached to the oil chamber 26 of the injection drive device 28 to detect the oil pressure in the oil chamber 26 and control the injection speed of the molten resin 14 to a constant value. It is something to do.

0010

[Effects of the Invention] As explained above, according to the present invention, since the injection pressure does not rise above a certain pressure, the uneven resin pressure within the cavity is corrected, and a high-quality molded product without distortion is produced. can get. Since large molded products can be obtained with small mold clamping force, equipment costs are low. It becomes possible to perform lamination by inserting cloth or vinyl sheets. Since there is no need to unnecessarily increase the injection speed or injection pressure, energy savings can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing the configuration of another embodiment of the present invention.

FIG. 3 is a diagram showing the configuration of another embodiment of the present invention.

[Explanation of symbols]

10 Mold 12 Cavity 14 Molten resin 16 Gate 18 Heating cylinder 20 Nozzle 22 Injection plunger 24 Piston 26 Oil chamber 28 Injection drive device (injection speed adjustment device) 30 Flow rate control valve (injection speed adjustment device) 32 Control device 34 Pressure sensor ( pressure detection device)

Claims (3)

[Claims] Claim 1: In all or part of the process of injecting and filling the cavity (12) of the clamped mold (10) with the molten resin (14), the nozzle (20) of the injection molding machine
The pressure of the molten resin injected from the gate (10) of the mold (10)
16) An injection process control method for an injection molding machine, comprising controlling the injection speed in order to keep the pressure of the molten resin flowing from the cavity (12) constant. 2. A pressure detection device (34) that converts the molten resin pressure into an electrical quantity value and outputs it, and an injection speed adjustment device (28 and 3) that controls the injection speed of the molten resin (14).
0), a controller (32) that compares the electric quantity value obtained from the pressure detection device (34) with a set value and outputs an operation command signal corresponding to the deviation to the injection speed adjustment device (30).
), and the controller (32) monitors whether the molten resin pressure is at the set value or not, and if it deviates from the set value, the controller (32) performs the above operation so as to correct the injection speed in accordance with the amount of deviation. An injection process control device for an injection molding machine, characterized in that it is configured to output a command signal. 3. The injection speed adjustment device adjusts the amount of oil supplied to a hydraulic injection drive device (28) capable of driving the injection plunger (22) and an oil chamber (26) of the injection drive device (28). The pressure detection device is a pressure sensor (34) that detects the oil pressure supplied to the oil chamber (26) of the injection drive device (28). An injection process control device for an injection molding machine according to claim 2.