JPS61189915A - Injection controlling method in injection molding machine - Google Patents

Abstract

PURPOSE:To prevent molten resin sufficiently from leaking by drawing a screw in the direction opposite to the direction in an injection molding time and at the same time rotating the screw in the direction opposite to the direction in an plasticizer metering time. CONSTITUTION:When the screw 1 is drawn and sucked back at the end of plasticizer metering by the screw 1, the molten of the barrel 2 to the screw 1 is shown by a vector 11, and when the screw 1 is rotated in the direction opposite to the direction in the plasticizer matering time, the rotation of the screw 1 is shown by a vector 12, and the partial forces of a vector 13 obtained by synthesizing the vectors 11 and 12 are given by 13a and 13b. The partial force 13a acts along the screw flight 1a. When this is compared with the partial force 10a or 10b, that direction is clearly opposite to each other. Therefore, the pressure of the molten resin around the screw 1 is lowered by the back-flow valve 3, the entry of resin through the back-flow valve 3 is reduced remarkably, therefore, the leakage can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial Application Field" The present invention relates to an injection control method for improving molding accuracy during injection molding of a molded product in an injection molding machine.

"Conventional technology" Conventionally, when injection molding a molded product using an injection molding machine,
Various measures have been taken to improve the molding accuracy of injection molded products.

Here, molding accuracy refers to molded product dimensions, warpage, short shots, etc. as criteria for judgment.

Therefore, one of the important items is the measurement accuracy of the molten resin.

The measurement accuracy of molten resin refers to whether the amount of molten resin stored at the tip of the screw for injection is accurate.

In the general process of injection molding, after one shot is injected into the mold cavity, the screw is rotated to plasticize and measure the molten resin for the next shot.

When this plasticization measurement is completed, the rotation of the screw is stopped. If a method is used to hydraulically or mechanically stop the screw from retracting after measurement is complete,
The metering completion position of the screw is accurately maintained.

However, in this case, especially when the plasticization back pressure is high,
Since the pressure of the molten resin at the tip of the screw remains as residual pressure, it is necessary to prevent so-called nasal drip from the nozzle, and a special nozzle such as a needle nozzle must be used.

When using a normal open nozzle, in order to prevent dripping from the nozzle, there is a step of forcibly pulling out the screw after metering is completed, in order to remove the residual pressure of the molten resin stored at the tip of the screw. A process called suckback is used.

This will be explained in more detail. Figure 4 shows the relative movement of barrel 2 with respect to screw 1, showing how the screw rotates during plasticization and metering with the screw ■ expanded. moves in the direction shown by vector IO, and its component force 10a
serves to transport the molten resin toward the nozzle along the screw flight 1a.

Also, when suckback is performed after the rotation of screw 1 is completed, screw 1 is pulled out, so the movement of barrel 2 with respect to screw 1 is indicated by vector 1■, as shown in Figure 5. The component force 1.1a serves to transport the molten resin along the screw flight 1a toward the nozzle.

When the suckback is completed, as shown in FIG. 2, the molten resin pressure P0 of the four screw heads is lower, and the molten resin pressure P1 around the screw 1 is lower than that of the check valve 3. The component force 10a in FIG. 4 and the component force ILa in FIG. 5 create a high pressure state.

This high pressure cannot easily escape to the hopper 6 side because the groove of the screw 1 is filled with molten resin and semi-molten resin up to the hopper 6 side.

That is, in such a state, the molten resin will flow into the nozzle 4 side through the check valve 3 even after the rotation of the screw l is stopped and the suckback is completed.

Therefore, even if you perform suckback after weighing,
In terms of control, even in the stopped state after completion of suckback, the measured value of the resin actually changes, which is not preferable in terms of precision molding.

Furthermore, as another method, after completing screw metering, screw 1 is slightly advanced in the nozzle direction by rotating screw 1 several times in the opposite direction to that during plasticization metering. , the molten resin pressure P on the screw 1 side, and the check valve 3 on the screw 1 side.
By sticking it closely to the side and sealing the flow of molten resin in the turning part,
There is also a method to improve measurement accuracy.

However, in this case, as the screw 1 moves forward slightly, the molten resin pressure P on the screw head 4 side increases. rises and causes nasal drip, making it impossible to use the oven nozzle.

Also, after rotating the screw l in the reverse direction, the molten resin pressure P. If the above-mentioned suckback is performed in order to reduce the The flow of molten resin from the 1 side to the screw head 4 side cannot be prevented.

``Problems to be Solved by the Invention'' The present invention solves the problem of suck-back, which is carried out for the purpose of preventing the so-called nose dripping of molten resin, or by screwing, in order to improve the measurement accuracy of injection molding. We attempted to improve the measurement accuracy by reversing the plasticization measurement several times, but we were unable to sufficiently prevent this nasal drip. It is something to do.

``Means for Solving the Problems'' In the present invention, during the injection molding of a molded product, the screw is pulled out in the opposite direction to the injection during plasticization and metering of the molten resin, and is stored at the tip of the screw. The residual pressure of the molten resin is removed, and at the same time, the screw is rotated in the opposite direction to that during plasticization measurement to reduce the molten resin pressure around the screw, thereby increasing the measurement accuracy of the molten 51J! resin. An injection control method for an injection molding machine that aims to improve

``Function'' When the plasticization measurement by the screw 1 is completed, when the screw 1 is pulled out and sucked back, the movement of the barrel 2 with respect to the screw 1 is as a vector 11, as shown in Fig. 3. shown.

Further, when the screw 1 is rotated in the opposite direction to that during plasticization measurement, the rotation of the screw 1 is represented by a vector 12, as shown in the figure.

The combination of both vectors 11 and 12 becomes a vector 13, and when the component forces of this vector 13 are determined, they become a component force 13a and a component force 13b.

The component force 13a is along the screw flight 1a, and can be expressed as the component force 10a or ll in FIGS. 4 and 5.
Compared to a, the direction is clearly opposite.

Therefore, the molten resin pressure P around the screw 1 is lowered by the backflow prevention valve 3, and the flow of molten resin through the backflow prevention valve 3 is greatly reduced, thereby preventing nasal drip.

"Effects of the Invention" In the present invention, after the molten resin is plasticized and measured, the residual pressure of the molten resin stored at the tip of the screw is removed by pulling the screw in the opposite direction to that during injection. At the same time, the screw is rotated in the opposite direction to the plasticization metering direction to reduce the resin pressure around the screw, and by performing both processes at the same time, the residual pressure at the screw tip is removed by suckback. By doing so, it is possible to prevent the increase in pressure on the nozzle head side of the molten resin due to rotation of the screw in the opposite direction to the plasticization metering, and to reduce the deviation between the control value and the actual value of the metering value, improving metering accuracy. can improve molding accuracy.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional side view of an injection molding machine, Fig. 2 is a longitudinal sectional view of a part of the screw to explain how the screw rotates during plasticization and metering, and Fig. 3 is the relative relationship between the screw and barrel according to the method of the present invention. Figure 4 is a diagram showing the rotation of the screw and relative movement of the barrel during plasticization measurement, and Figure 5 is a diagram showing the relative movement of the screw and barrel during suckback. be. 1. Molten resin pressure on the screw head side Molten resin pressure around the P screw Patent applicant Japan Steel Works Co., Ltd. Patent attorney Haruo Kuwa★ 3 Colored large La White 9 Mud Iα

Claims (1)

[Claims] During injection molding of molded products, after plasticizing and measuring the molten resin,
The screw is pulled out in the opposite direction to that used during injection to remove the residual pressure of the molten resin stored at the tip of the screw, and at the same time, the screw is rotated in the opposite direction to that used during plasticization and metering. An injection control method for an injection molding machine that reduces the pressure of molten resin around the screw, thereby improving the accuracy of measuring molten resin.