JPH11207791A - Controller for injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively prevent the occurrence of a warp by sufficiently reducing a stress retained at a molding. SOLUTION: The controller for an injection molding machine comprises a screw 12 telescopically movably arranged in a heating cylinder 11, a driving means for filling a resin in a cavity space by forwarding the screw 12, a completely filling position detecting means for detecting a screw position for completely filling the resin in the space, and a screw stopping means for temporarily stopping the screw 12 when the screw position is detected. In this case, since the screw 12 is temporarily stopped at this position, a more than necessary force is not applied to the resin in the space, and a resin pressure can be lowered. Accordingly, the stress is not retained at the molded product, and occurrence of a warp can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Conventionally, in an injection molding machine, a resin heated and melted in a heating cylinder is filled in a cavity space of a mold apparatus, and solidified in the cavity space. The apparatus can be opened to obtain a molded product. By the way, when molding molded products such as uneven thickness products with locally different thickness, long products with large longitudinal dimension, and thin products with small thickness, molding is performed by resin pressure when filling the cavity space with resin. Stress remains on the product,
Warpage may occur.

Therefore, in the injection step or the pressure holding step,
By temporarily stopping the screw, the resin pressure is reduced, the stress remaining on the molded product is reduced, and warpage is prevented from occurring.

[0004]

However, in the control device of the conventional injection molding machine, it is necessary to stop the screw while checking the movement of the screw.
Injection speed, filling / holding pressure switching position, first-stage holding pressure, first-stage holding time, second-stage holding pressure, second-stage holding time, third-stage holding pressure, third-stage holding time Molding conditions consisting of a large number of parameters must be set up. Therefore, an unskilled person cannot easily assemble the molding conditions, so that the stress remaining on the molded product cannot be sufficiently reduced, and warpage cannot be reliably prevented.

The present invention solves the problems of the conventional control device of an injection molding machine, and makes it possible to sufficiently reduce the stress remaining in a molded product and to reliably prevent warpage from occurring. The purpose of the present invention is to provide a machine control device.

[0006]

For this purpose, in the control device of the injection molding machine according to the present invention, a screw arranged to be able to move forward and backward in the heating cylinder, and the screw is advanced to fill the cavity space with the resin. Driving means, a complete filling position detecting means for detecting a screw position at which the resin is completely filled in the cavity space, and a screw stopping means for temporarily stopping the screw when the screw position is detected. Have.

[0007]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 2 is a schematic diagram of an injection molding machine according to the embodiment of the present invention. In the figure, reference numeral 11 denotes a heating cylinder.
An injection nozzle 18 is provided at the front end (left end in the figure) of the nozzle. A screw 12 is rotatably and reciprocally disposed within the heating cylinder 11. The screw 12 is connected at a rear end (right end in the drawing) to an injection cylinder 13 as a driving means and a hydraulic motor 14. Is done.

In a state immediately before the start of the weighing process, the screw 12 is placed at the forward limit position as shown in the figure. Then, when the measuring step is started, the hydraulic motor 14 is driven, and the screw 12 is moved backward (moved rightward in the figure) while being rotated. At this time, the resin in the hopper 15
1, is heated and melted in the heating cylinder 11 while moving forward (to the left in the drawing) along the groove 17 with the rotation of the screw 12, and is stored in front of the screw 12. In addition, with the melting of the resin, the pressure of the resin in the heating cylinder 11 is increased by the screw 1
It becomes a reaction force against 2. Then, when the screw 12 reaches the predetermined position, the measuring step is completed.

Subsequently, an injection step is started, and by driving the injection cylinder 13, the screw 1
2 is moved forward (moved to the left in the figure) without rotating. At this time, the resin stored in front of the screw 12 is injected from the injection nozzle 18 and the mold device 19
Is filled in the cavity space 21. In this way,
When the injection step is completed, the resin in the cavity space 21 is cooled and solidified, but contracts with the solidification. Then, the pressure holding step is started, and the pressure of the resin in the cavity space 21 is held to compensate for the shrinkage of the resin, and the pressure holding is started. When the pressure holding step is completed, the measuring step is started again.

In the injection cylinder 13, a piston 23 is provided in the cylinder body 22 so as to be able to advance and retreat, and an oil chamber 24 is formed behind the piston 23 (to the right in the drawing). When the oil chamber 24 is connected to the injection servo valve 25, and the oil pressure is supplied to the oil chamber 24 via the injection servo valve 25, the piston 23 is advanced, and the screw 12 Can also be advanced.

At this time, the position of the screw 12 is controlled by a position sensor (not shown) which operates in accordance with the movement of the screw 12.
, That is, the screw position is detected, and the pressure in the oil chamber 24, that is, the resin pressure in the cavity space 21 is detected by the pressure sensor 32 disposed facing the oil chamber 24. Next, a control device of the injection molding machine having the above configuration will be described.

FIG. 1 is a block diagram of a control device of an injection molding machine according to an embodiment of the present invention. In the figure, 11
Is a heating cylinder, 12 is a screw, 13 is an injection cylinder, 25 is an injection servo valve, 32 is a pressure sensor, 33 is a position sensor, and 35 is a sensor output reading device that reads each sensor output of the pressure sensor 32 and the position sensor 33. , 3
6 is a control device.

In the injection molding machine having the above structure, the pressure sensor 32 detects the resin pressure in the cavity 21 (FIG. 2), and the position sensor 33 detects the screw position. When the screw 12 is advanced in the injection step, speed control is performed, and the injection speed is changed in multiple stages corresponding to a plurality of screw positions.

That is, when the screw position detected by the position sensor 33 is input to the control device 36 via the sensor output reading device 35, the screw position is differentiated by the control device 36, and the differential value is obtained as the injection speed v. Is calculated. Next, in the control device 36, the differential value is subtracted from the speed setting signal during the injection process to obtain a deviation signal. The deviation signal is subjected to compensation calculation in a compensator (not shown) in the control device 36 to become a command signal. The command signal is output to the injection servo valve 25, and the injection cylinder 13 is driven.

The resin pressure detected by the pressure sensor 32 is supplied to a control device 36 via a sensor output reading device 35.
Is input to the controller 36, a complete filling position detecting means (not shown) in the control device 36 compares the switching pressure setting signal with the resin pressure, and when the resin is completely filled in the cavity space 21, the switching pressure setting signal When the resin pressure becomes higher,
Switching between filling and holding pressure, and switching from speed control to pressure control.

Then, the pressure-holding step is started, and the resin pressure is subtracted (feedback) from the pressure-holding setting signal in the pressure-holding step, to obtain a pressure deviation signal. The pressure deviation signal is subjected to compensation calculation in another compensator (not shown) in the control device 36 to become an operation signal. At this time, the operation signal is used instead of the speed setting signal, and the control device 3
At 6, the differential value is subtracted from the operation signal to obtain a deviation signal. The deviation signal is subjected to compensation calculation in the compensator to become a command signal. The command signal is output to the injection servo valve 25, and the injection cylinder 13 is driven. Thus, the pressure holding step is completed.

Incidentally, when molding a molded product such as an uneven thickness product having a locally different thickness, a long product having a large longitudinal dimension, or a thin product having a small thickness, the cavity space 21 is required.
In some cases, stress remains in the molded product due to the resin pressure when the resin is filled into the resin, and warpage may occur. Therefore, in the injection step, the control device 36 fills the cavity space 21 with the resin little by little by using the short shot method,
The resin is completely filled in the cavity space 21.
The position where the holding pressure switching is performed, that is, the complete filling position is detected by the complete filling position detecting means. Then, when the screw filling means (not shown) of the control device 36 detects the full filling position, the screw 12 stops the screw 12 for the stop time set at the full filling position. At this time, the control device 36 detects the resin pressure in the cavity space 21 by the pressure sensor 32 and holds the resin pressure so that the screw 12 does not retreat.

As described above, since the screw 12 is temporarily stopped at the complete filling position, unnecessary force is not applied to the resin in the cavity 21 and the resin pressure can be reduced. it can. Therefore, no stress remains in the molded product, and occurrence of warpage can be prevented. In addition, molding conditions consisting of only two parameters, the complete filling position and the stop time, may be set up. Therefore, even an unskilled person can easily assemble the molding conditions, so that the stress remaining on the molded product can be sufficiently reduced, and the occurrence of warpage can be reliably prevented.

The present invention is not limited to the above embodiment, but can be variously modified based on the gist of the present invention, and they are not excluded from the scope of the present invention.

[0020]

As described above in detail, according to the present invention, in a control device for an injection molding machine, a screw disposed in a heating cylinder so as to be able to move forward and backward, and the screw is advanced to form a cavity space. A driving means for filling the resin into the resin, a complete filling position detecting means for detecting a screw position at which the resin is completely filled in the cavity space, and a screw for temporarily stopping the screw when the screw position is detected. Stopping means.

In this case, since the screw is temporarily stopped at the above position, unnecessary force is not applied to the resin in the cavity space, and the resin pressure can be reduced. Therefore, no stress remains in the molded product, and occurrence of warpage can be prevented. In addition, since molding conditions consisting of only two parameters, the position and the stop time for stopping the screw, need only be set up, even an unskilled person can easily set up the molding conditions. Further, the stress remaining in the molded product can be sufficiently reduced, and the occurrence of warpage can be reliably prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram of a control device of an injection molding machine according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of an injection molding machine according to an embodiment of the present invention.

[Description of Signs] 11 Heating cylinder 12 Screw 13 Injection cylinder 21 Cavity space 36 Control device

Claims (1)

[Claims] (A) a screw disposed so as to be able to advance and retreat in a heating cylinder; (b) driving means for moving the screw forward to fill the cavity space with a resin;
(C) complete filling position detecting means for detecting a screw position at which the resin is completely filled in the cavity space;
And (d) a screw stopping means for temporarily stopping the screw when the screw position is detected.