JPS63182126A - Control method of molding of injection molding machine - Google Patents

Abstract

PURPOSE:To facilitate control by keeping a quality of a molded product constant, by a method wherein a temperature is controlled by changing frictional heat of molten resin circulating through a nozzle by performing variation control of an opening area of the nozzle according to a change of a mold temperature. CONSTITUTION:A mold 5 is provided with a mold temperature detecting instrument 15. A detected temperature T is sent to a comparator 17 of a controller 16 and compared with a reference temperature T0 set up by a reference mold temperature setting instrument 18. The deviation value epsilon of the temperatures T, T0 is sent to a correction arithmetic unit 19 and a correction value is operated by the same along with a correction coefficient k set up at a correction coefficient setting instrument 20 and a preset opening Vs of a nozzle valve opening setting instrument 21. The correction value is sent to a control instrument 22, a control electric current is sent to a proportional solenoid 14, an opening of a nozzle valve 11 is changed. When the detected temperature T is lower than the reference temperature T0, a control electric current reducing the opening is sent to the proportional solenoid 14, the opening of the nozzle valve 11 is reduced, frictional heat of molten resin becomes high and a temperature of the molten resin becomes high. In the case where the detected temperature is higher than the reference temperature, the opening of the nozzle valve 11 is made large and the frictional heat is made low.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a molding control method for an injection molding machine that fills a molten resin into a cavity of a mold for molding.

(Prior art) As shown in Japanese Patent Publication No. 57-59060, there is an injection molding machine in which a rotatably driven screw is reciprocated by an injection cylinder and molten resin is injected from a nozzle to fill a mold cavity. or known.

In such injection molding machines, it is known that precise and accurate control of mold temperature, resin temperature, resin pressure, etc. is essential for precision and stable molding of molded products.

For example, if the mold temperature or resin temperature decreases, the temperature of the molten resin filled in the mold cavity also decreases, and the specific volume of the resin decreases. When injection molding is used, the molded product becomes larger than normal.

Therefore, a molding control method is known in which the correlation between mold temperature or resin temperature and resin pressure is determined in advance, and the mold temperature or resin temperature during actual injection molding is detected to control the resin pressure. For example, the holding pressure is reduced in order to reduce the resin pressure by an amount commensurate with the reduction in mold temperature or resin temperature.

[The problem that the invention attempts to solve]

Such molding control method is very troublesome and requires precision If
Since f is also poor, it is difficult to say that it is an optimal molding control method. In particular, changing the resin pressure is undesirable because it may change the internal stress distribution within the mold, resulting in defects in the molded product.

In addition, if the mold temperature or resin temperature fluctuates, is it possible to correct the temperature? For example, is it possible to compensate for the mold temperature fluctuation with the resin temperature? It is actually impossible to control molding in this way because it is quite slow.

In addition, stable molding can be achieved by accurately controlling the mold temperature and resin temperature so that they do not fluctuate, but since the mold temperature fluctuates depending on the outside temperature, it is necessary to accurately control this. The room temperature in the factory where the injection molding machine is installed must be controlled to a constant level, which increases costs significantly.

Accordingly, one object of the present invention is to provide a molding control method for an injection molding machine that can accurately control the mold temperature to a set temperature, and that is simple and inexpensive.

(Means and actions for solving the problem) By controlling the opening area of the nozzle to increase or decrease depending on changes in the mold temperature, the frictional heat of the molten resin flowing through the nozzle is changed and the temperature is controlled. By keeping the temperature constant, the mold temperature can be controlled to a constant temperature with high accuracy, and the control is easy, there is no change in the internal stress of the mold, and the cost can be reduced.

〔Example〕

As shown in FIG. 1, a screw 2 is slidably and rotatably inserted into a cylindrical housing l to melt the resin in a hopper 3 and fill it into a cavity 6 of a mold 5 through a nozzle 4. In addition, the screw 2 is connected to a piston rod 8 of an injection cylinder 7, and a drive shaft 10 rotated by a hydraulic motor 9 is spline-fitted to the piston rod 8.

The nozzle 4 is provided with a wenzhou control mechanism 1 such as a nozzle valve 11 for controlling its opening area, and the nozzle valve 11 is connected to a nozzle valve drive mechanism such as a proportional solenoid 14 via a lever 12 and a rod 13. By controlling the current supplied to the proportional solenoid 14, the opening degree of the nozzle valve 11 can be changed, thereby controlling the opening area of the nozzle 4.

The mold 5 is provided with a mold temperature detector 15, and this detected temperature T is sent to a comparator 17 of a controller 16, and is set as a reference temperature T by a reference mold temperature setter 18. The deviation value e is sent to the correction calculator 19, and a correction value is calculated based on the correction coefficient k set in the correction coefficient setting device 20 and the set opening Vs of the nozzle valve opening setting device 21, and the correction value is The value is sent to the controller 22 and a control current is sent to the proportional solenoid 14 to change the opening degree of the nozzle valve 11.

To explain the molding control method, first, the temperature of the mold 5 is heated to a set temperature by a built-in heater, etc., and the nozzle valve 11 is heated to the set opening V5 set by the nozzle valve opening setting device 21. It is controlled so that
Pressure oil is supplied to the extension chamber 7a of the injection cylinder 7, and the screw 2 is rotated and moved forward to compress the molten resin at the tip of the screw and pass through the nozzle 4 and the nozzle valve 11 into the cavity 6 of the mold 5. Ordinary molding is carried out by injection.

At this time, the temperature of the mold 5 is detected by the mold temperature detector 15,
The detected temperature T or the reference temperature T. When it is equal to , the deviation amount ε
Since is zero, the nozzle valve opening is the set opening V, which is either the detected temperature T or the reference temperature T. When it is lower, the deviation amount ε
occurs, and accordingly, a correction value is calculated to reduce the set opening degree V using the correction coefficient k, and a control current for reducing the opening degree is sent to the proportional solenoid 14 from the control amount 22, thereby reducing the opening degree of the nozzle valve 11. .

As a result, the opening area of the nozzle 4 decreases, the flow resistance of the molten resin increases, frictional heat increases, the temperature of the molten resin increases, and the mold temperature becomes the reference temperature.

Further, when the detected temperature is higher than the reference temperature, the opening degree of the nozzle valve 11 is increased in the same manner as described above, and the nozzle 4 is
By increasing the opening area and reducing the flow resistance of the molten resin, frictional heat is reduced and the mold temperature is lowered.

〔Effect of the invention〕

The temperature of the molten resin is controlled by changing the frictional heat of the molten resin by increasing or decreasing the opening area of the nozzle 4 according to changes in the mold temperature, and thereby the mold temperature is set at a preset reference temperature. The mold temperature can be precisely controlled to the set temperature,
It is possible to perform precise and stable molding with continuous stability of molded product quality, and since the pressure of the molten resin is not controlled, the internal stress distribution of the mold does not change and molded product defects do not occur. Control is easy because it is only necessary to change the opening area of the nozzle 4, and there is no need to keep the room temperature in the factory constant, so the cost is low.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention. 2 is a screw, 4 is a nozzle, 5 is a mold, and 6 is a cavity.

Claims (1)

[Claims] In an injection molding machine that moves a screw 2 while rotating to fill a cavity 6 of a mold 5 with molten resin from a nozzle 4, when the temperature of the mold 5 is lower than a preset reference temperature, the nozzle 4 is opened. A molding control method for an injection molding machine, characterized in that the frictional heat of the molten resin flowing through the nozzle 4 is controlled by decreasing the area and increasing it when the area is high.