JPH0857920A - Method for controlling drive of injection screw in injection molding machine - Google Patents

Abstract

PURPOSE: To provide a method for controlling drive of an injection screw in an excellent injection molding machine capable of preventing certainly resin from leaking by a method wherein the pressure of stayed injection molten material is always continuously reduced, the resin can be certainly prevented from leaking, and even if the process deviates from an ordinary molding cycle, or injection standby time becomes longer than that in ordinary time, those conditions can be easily coped with. CONSTITUTION: An injection screw in an injection molding machine is controlled as follows; a specific amount of injection molten material 4 is fed to an injection nozzle part 3 at the tip of an injection cylinder 1 by making the injection screw 2 pivot; and until the injection screw 2 is moved to the tip side of the injection cylinder 1 to be injected thereafter, the injection screw 2 is continuously retreated gradually at a specific speed without pivoting behind an opposite side to the tip side of the injection cylinder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive control method for an injection screw in an injection molding machine.

[0002]

2. Description of the Related Art For example, a resin injection molding machine has the following structure.

An injection screw is movably provided in the injection cylinder, and a resin material is put in the injection cylinder.
When the injection screw is rotated, the resin material is heated by the heater and sent forward along the injection screw, and a predetermined amount of molten resin retracts the injection screw and stays at the injection nozzle section at the tip of the injection cylinder.

In this state, the injection screw is moved to the front end side so that the molten resin is pushed out from the nozzle portion and injected into the mold.

In addition, in order to improve the molding efficiency, the molten resin is injected into the mold, cooled by holding pressure, the mold is opened, the molded product is discharged, and the mold is clamped again. Is controlled so that a predetermined amount of molten resin is retained at the injection nozzle portion (lightweight standby) in preparation for the next molding shot.

On the other hand, this non-retained resin has a risk of resin leaking from the injection hole of the nozzle portion (backflow phenomenon) due to back pressure for generation of gas and measurement, and the resin pressure is reduced in order to prevent this. The injection screw is retracted for the purpose.

Driving this injection screw backward is called screw suck back, and this conventional suck back is constant after injection is completed or after a predetermined amount of molten resin is retained in the injection nozzle section (after measurement is completed). The amount (up to a constant retracted position) is simply retracting the injection screw.

[0008]

That is, since the conventional suck back is simply moved backward by a predetermined amount at a constant timing, it is stopped during the entire molding cycle. The injected molten material cannot always be in a reduced pressure state.

Therefore, during the cooling process, the mold opening process, and the mold clamping process, the retained resin cannot always be depressurized to reliably prevent resin leakage, and when the molding cycle changes due to other factors, the depressurization is performed accordingly. You can't deal with it so that the condition is maintained.

According to the present invention, it is possible to continuously reduce the pressure of the stationary injection molten material to prevent the resin from leaking without fail, and even if the injection standby time becomes longer than the normal time even if the normal molding cycle is deviated, the resin can be easily removed. Correspondingly, it is an object of the present invention to provide a drive control method for an injection screw in an excellent injection molding machine, which can maintain a reduced pressure state and reliably prevent resin leakage.

[0011]

The gist of the present invention will be described with reference to the accompanying drawings.

An injection screw 2 is movably provided in the injection cylinder 1, and the injection screw 2 is rotated so that the injection cylinder 1 is attached to an injection nozzle portion 3 at the tip of the injection cylinder 1.
Of the injection screw in the injection molding machine for injecting the injection molten material 4 into the die 5 by injecting the injection molten material 4 into the die 5 by making the injection screw 2 move to the tip end side of the injection cylinder 1 and hold it. In the drive control method, the injection screw 2 is rotated to feed a predetermined amount of the injection molten material 4 to the injection nozzle portion 3 at the tip of the injection cylinder 1 and to hold it there. Then, the injection screw 2 is moved to the tip side of the injection cylinder 1. In the injection molding machine, the injection screw 2 is controlled so that the injection screw 2 continues to move backward continuously at a predetermined speed without rotating backward to the side opposite to the tip end side of the injection cylinder 1. The present invention relates to a drive control method for an injection screw.

[0013]

[Function] The injection cylinder 2 is rotated by rotating the injection screw 2.
After a predetermined amount of the injection molten material 4 is fed into the injection nozzle portion 3 at the tip and stopped, the injection screw 2 is attached to the injection cylinder 1.
Injection screw 2 until injection is made to move to the tip side
Is continuously moved backward at a predetermined speed without rotating rearward on the side opposite to the tip side of the injection cylinder 1.

Therefore, the retained molten injection material 4 is always decompressed, and even if gas or the like is generated, the decompressed state is maintained and the resin leakage is always reliably prevented.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The drawings show an example of a preferred embodiment of the present invention, in which an injection molten material 4 (a molten resin in a resin molding machine) is used.
In an injection molding machine that injects and injects into the mold 5 from the injection nozzle part 3, after rotating the injection screw 2 and sending a predetermined amount of the injection molten material 4 to the injection nozzle part 3 at the tip of the injection cylinder 1 and stopping it , Until the injection screw 2 is ejected to the tip side of the injection cylinder 1, the injection screw 2 is slowly and gradually rotated at a predetermined constant speed and continuously without being rotated backward from the tip side of the injection cylinder 1. The movement is controlled by the backward movement control device 6 so as to continue the backward movement.

The speed at which the injection screw 2 is continuously moved backward is set according to various conditions such as the type of the injection molten material 4.

When a change occurs in the normal molding cycle and the injection material 4 is made to stand by longer than the normal time, the backward movement control device 6 is provided so that the injection screw 2 can be further retracted accordingly. Adjustable and configurable.

Further, when the injection molten material 4 is injectable and movable, the injection screw 2 is controlled to move backward, so that the injection stroke of the injection screw 2 becomes longer, so that the injection movable speed, injection pressure, and holding pressure of the injection screw 2 are controlled accordingly. The injection drive control of 1 becomes easy, and there is an advantage that the injection control can be performed with high accuracy.

[0019]

Since the present invention is configured as described above, the injected molten material is always depressurized during the cooling process, the mold opening process, and the mold clamping process, and even if the pressure rises due to the gas, the back pressure for metering is increased. Also, the continuous increase in depressurizing action is an excellent method for controlling the drive of the injection screw in the injection molding machine, which can surely prevent the leakage phenomenon from the injection hole of the nozzle portion.

Further, when a change occurs in the normal molding cycle and the injection molten material is made to stand by longer than the normal time, the injection screw can be easily further retracted in response to this.

Further, when the injection molten material is injected and moved, the injection screw is continuously controlled to move backward, so that the injection stroke of the injection screw becomes long. For example, the injection screw driven by the long stroke is moved at the maximum speed to inject the injection molten material. The injection drive control such as the injection movable speed of the injection screw, the injection pressure, and the pressure holding control can be facilitated, and the injection control can be performed with high accuracy.

[Brief description of drawings]

FIG. 1 is a schematic configuration explanatory diagram of the present embodiment.

[Explanation of symbols]

 1 injection cylinder 2 injection screw 3 injection nozzle part 4 injection melt 5 mold

Claims (1)

[Claims] 1. An injection screw is movably provided in an injection cylinder, and the injection screw is rotated to feed an injection molten material in the injection cylinder to an injection nozzle portion at the tip of the injection cylinder to stop the injection screw. In a drive control method of an injection screw in an injection molding machine in which the injection molten material is injected and injected into a mold by being moved to the tip side, the injection screw is rotated to the injection nozzle portion of the injection cylinder tip. After feeding and stopping a predetermined amount of injection melt, until the injection screw is moved to the injection cylinder tip side, the injection screw gradually rotates backward at the prescribed speed opposite to the injection cylinder tip side. The injection molding machine is characterized in that it is controlled so as to continuously move backward without moving. Drive screw drive control method.