JPH09155942A - Metering method in injection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To coincide a metering finishing position with the injection starting position and contrive to rationalize the injection starting position by a method wherein a plasticization stopping position is distinguished from the metering finishing position. SOLUTION: Through the backward movement of an injection screw 2 by the pressure of a material, a molding material is plasticized and metered in the tip part of an injection cylinder 1. A plasticization stopping position STP is set at this side of a metering finishing position SM in anticipation of the amount of backward movement of the injection screw 2 after the finishing of metering. The allowable range of the retreat position is set on the basis of the metering finishing position SM. Only when the retreat position at the starting of injection lies within an allowable range, the injection is judged to be under normal state and is processed to the injection process of an injection device. When the retreat position lies outside the allowable range, the injection is judged to be under abnormal state and is processed to its running stopping process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring a material in an in-line screw type injection device or a pre-plastic type injection device.

[0002]

2. Description of the Related Art In an in-line screw type injection device, an injection screw in an injection cylinder is rotated to plasticize a molding material,
The material pressure generated by the plasticization causes the injection screw to move backward to measure the plasticized material in the tip portion of the injection cylinder.

Further, in a pre-plastic injection device in which a plasticizing device having a screw inside the heating cylinder and an injection device having a plunger inside are installed side by side, and the two devices communicate with each other at the tip, a molding material is generated by rotation of the screw. The plasticized material is metered into the tip portion of the injection cylinder while being plasticized and pressure-fed to the injection device side to move the plunger backward.

The above-described metering is stopped in the in-line screw type injection device by stopping the rotation when the injection screw moves backward to the metering stop position, and in the pre-plastic type injection device when the plunger moves backward to the set position. In addition, the supply of the plasticizing material from the plasticizing device side is stopped. Then, the injection operation is performed with the metering stop position as the plasticization stop and injection start position.

[0005]

Since the backward movement of the injection screw and the plunger depends on the material pressure acting on the tips of the injection screw and the plunger, the residual pressure in the screw, etc., the rotation is stopped or the material is supplied to stop the measurement. Even if the injection is stopped, the injection screw or the plunger retreat, although slightly, due to the influence of the material pressure, the back pressure, the number of revolutions, etc., and the amount of measurement increases in proportion to the retreat amount. The amount of retreat varies depending on the physical properties of the molding material, molding conditions such as screw diameter, shape, temperature, back pressure, and the waiting time from the completion of measurement to the start of injection.

The conventional weighing method employs a system for determining a weighing value based on the screw rotation stop position or the plunger stop position detected by the position setter. Therefore, the weighing fluctuation after the weighing is stopped is not taken into consideration, and even if the fluctuation is actual, it is assumed that the measurement of the set amount has been completed by inputting the information based on the detected stop position at the site and the injection is started. It is transitioning. For this reason, there is a lack of accuracy in determining the injection amount of the molding material in the field, and it is hardly noticed that the injection start position changes due to a change in the molding conditions, so that inconvenience often occurs in the molding especially in the automatic operation.

The present invention was conceived in order to solve the above-mentioned conventional problems, and an object thereof is to shift the measurement completion position from the injection start position without significantly changing the conventional measuring means. It is to provide a new weighing method capable of preventing the occurrence of a measurement error and improving the weighing accuracy and the injection accuracy, and checking the position of the injection screw or the plunger after the completion of the weighing to shift to the processing of the weighing abnormality. .

According to the present invention having the above object, the injection screw or the plunger is moved backward by the material pressure or the like to plasticize and measure the molding material into the tip portion of the injection cylinder, and the injection screw or the plunger is advanced with the measurement stop position as the injection start position. When injecting the weighing material into the mold by moving, the weighing stop position is set separately for the weighing completion position and the plasticization stop position, and the plasticization stop position is set back by the amount of retreat of the injection screw or plunger after the weighing is stopped. In consideration of this, the metering material is set before the metering completion position, and the metering material is injected with the metering completion position as the injection start position.

Further, according to the present invention, the position of the injection screw or the plunger after the plasticization is stopped is confirmed on the basis of the above-mentioned measuring completion position, and only when the position is within the set value range at the time of injection start, the measuring material is normal. It is also the case that the operation shifts to injection, and if it is out of the range, the operation is stopped as an abnormal condition.

In such a construction, the metering completion position and the injection start position are always within the same set value, and there is no change even if the molding conditions are changed, so that the metering error is reduced even in continuous molding by automatic operation. Also, by checking the position of the injection screw or plunger after stopping plasticization,
Since abnormal processing can be performed automatically, even if there is a fluctuation in the weighing due to some reason during the injection standby from the completion of weighing to the start of injection, it will be treated as a weighing error. Molding defects are prevented, and it is possible to mold a molded product with stable molding accuracy.

When the hydraulic control circuit includes a servo valve, the servo valve is used to position the metering completion position. In the case of an open loop, it can be easily carried out by blocking with a hydraulic valve or attaching a mechanical stopper.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view of a measuring method in the case of an in-line screw type injection device, in which 1 is an injection cylinder,
2 is an injection screw. The injection cylinder 1 has a nozzle at its tip, and a heating means (not shown in the figure) is provided on the outer periphery except for the rear portion where the supply port 3 is provided. The injection screw 2 is provided inside the injection cylinder 1 so as to be rotatable and movable back and forth. The rear end portion of the injection screw 2 is connected to a rotary drive device and an injection hydraulic device, although not shown.

When the injection screw 2 is rotated to feed the molding material from the supply port 3 into the injection cylinder, the molding material is plasticized while being sent forward by the screw, and is injected into the front end of the injection cylinder at the front of the injection screw. It will collect. Further, as the amount increases, the material pressure acts on the injection screw 2, and the injection screw 2 moves backward while rotating.

The plasticizing and measuring of the molding material is carried out until the injection screw 2 reaches the preset measuring completion position SM, but the measuring completion position SM is reached.
Even if you stop the rotation of the injection screw 2 and stop the plasticization,
Since the injection screw 2 moves backward, the backward movement amount (0.
3 mm to 2.0 mm), the screw rotation stop position is set in front of the measurement completion position SM, and this is set as the plasticization stop position STP.

As shown in FIG. 1A, when the injection screw 2 moves backward to the plasticizing stop position STP, the rotation of the injection screw 2 is stopped by the operation of the setting device (not shown). This also stops the plasticization of the molding material. Even after the plasticization is stopped, the injection screw 2 naturally retracts by the expected amount and reaches the measurement completion position SM as shown in FIG. 1 (B). At this position, the measurement shifts to the injection, and the injection completion of the measurement material into the mold 4 is started with the measurement completion position SM as the injection start position.

When suck-back is required, the injection screw 2 is forcibly moved backward to the suck-back position SD set based on the measurement completion position SM. The material pressure acting on the injection screw 2 is temporarily reduced by this forced movement, so that the injection screw 2 does not spontaneously retreat from the suck back position SD during the transition to the injection start.

Therefore, even if the injection is started from the suck back position SD, the measurement is substantially the same as the case where the injection is started from the measurement completion position SM, and the measurement value is determined at the measurement completion position SM. As long as the injection is started from that position every time, the injection amount does not change even in the automatic operation.

However, if the retreat speed of the injection screw 2 suddenly changes for some reason, the injection amount also changes.
If the retracted position deviates back or forth from the set measurement completion position SM even at the start of injection due to the backward movement of the injection screw 2, it causes a deviation of the injection start position and affects the injection amount. It causes short shots and overpacking.

The retreat speed of the injection screw 2 is not uniform every time, and there are subtle differences, but if it is within the range of variation measured in advance, the measurement completion position S
It can be determined by setting an allowable range based on M and confirming the position of the injection screw 2 after the plasticization is stopped. If the retracted position is within the range of the set value at the start of injection, it is regarded as normal and the metering material injection starts, and if it is outside the range, the operation is stopped due to an abnormal condition. Can be prevented.

Table 1 below shows an example of the display on the panel of the weighing setting in the in-line screw type injection device.

[0021]

[Table 1]

FIG. 2 shows a pre-plastic injection device.
The difference from the case shown in FIG. 1 is that an injection device in which an injection plunger 12 is housed in an injection cylinder 11 so as to be able to move back and forth, and a heating cylinder 1
3, a plasticizing device having a plasticizing screw 14 rotatably mounted therein is connected by a supply passage 16 at a tip end portion provided with a valve 15, and the molding material plasticized by the rotation of the screw 14 is injected into an injection cylinder. The rotation stop of the screw 14 becomes the plasticization stop because the screw 12 is pumped into the tip end portion of the injection pipe 11 and the plunger 12 is moved backward, and is stored and measured in the tip end portion of the injection cylinder 11.

Even after the plasticization is stopped, the plunger 12 moves backward by an expected amount to reach the measurement completion position SM due to the material pressure or the like, and reaches the measurement completion position SM, which is the injection start position. When the weighing completion position SM is reached,
The valve device 15 closes the supply passage 16 to prevent backflow of the plasticized material during injection.

Also in this pre-plastic type injection device,
It is needless to say that the suck back position SD can be set, and that by setting the allowable range based on the measurement completion position SM, it is possible to check the measurement abnormality from the position determination at the start of injection and to perform the subsequent processing.

Table 2 below shows an example of the display on the panel of the weighing setting in the pre-plastic injection device.

[0026]

[Table 2]

In this way, the plasticizing stop position STP is set in anticipation of the amount of retreat of the injection screw 2 or the plunger 12 after the completion of the measurement before the measurement completion position SM, and the allowable range is set on the basis of the measurement completion position SM. According to the present invention in which the retreat position is confirmed at the start of injection by setting, the measurement error is reduced and the injection accuracy is improved as well as the measurement accuracy, regardless of changes in molding conditions.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram when a measuring method of the present invention is applied to an in-line screw type injection device.

FIG. 2 is an explanatory view of the case of a pre-plastic injection device.

[Explanation of symbols]

 1 Injection Cylinder 2 Injection Screw 11 Injection Cylinder 12 Injection Plunger 13 Heating Cylinder 14 Plasticizing Screw 15 Valve 16 Supply Path

Claims (2)

[Claims] 1. A molding material is plasticized and measured in the front end portion of the injection cylinder by the backward movement of the injection screw or the plunger due to material pressure and the like, and the measurement material is moved forward by the injection screw or the plunger with the measurement stop position as the injection start position. When injecting into the mold, the measurement stop position is set separately for the measurement completion position and the plasticization stop position, and the plasticization stop position is set in consideration of the amount of retreat of the injection screw or plunger after the measurement is stopped. A weighing method in an injection device, characterized in that the weighing material is injected before the completion position and the weighing completion position is set as the injection start position. 2. The position of the injection screw or the plunger after the plasticization is stopped is confirmed with reference to the measurement completion position, and only when the position is within a set value range at the time of injection start, it is determined that the measurement material is to be injected. 2. The measuring method in the injection device according to claim 1, wherein the measuring apparatus shifts to an operation state and, if outside the range, the operation state is changed to an operation stop.