JPH05154888A - Controlling method for injection start timing - Google Patents

Abstract

PURPOSE:To avoid waste resulting from a time lag generated from the start of injection until a clamping force is required by the increase of an in-mold pressure. CONSTITUTION:A pressure (a real claming force) of pressurized fluid in a clamping-side chamber of a clamping cylinder 1 is detected by a pressure sensor 2 to be transmitted to a controller 3. The controller 3 stores a set clamping force arbitrarily determined and an injection start clamping force operated based on the set clamping force and a factor and transmits the both to a comparator 4. The comparator 4 compares the real clamping force with the injection start clamping force. When the real clamping force reaches the injection start clamping force, the comparator 4 outputs an injection start signal to change over a solenoid valve 6 through the controller 3, thereby supplying pressurized fluid to an injection cylinder 5. In this manner, an injection start timing is controlled.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, a method of controlling the injection start timing of an injection molding machine is to confirm the generation of a set mold clamping force by a mold clamping device,
It was supposed to start injection.

However, there is a time delay from the start of injection until the molten resin is actually press-fitted into the mold cavity where the mold is clamped and the original set mold clamping force is required due to the resin pressure increase in the cavity. Therefore, the mold clamping force at the start of injection may be a mold clamping force large enough to oppose the force to open the mold generated by the resin pressure in the cavity. Clamping consumes power wastefully and shortens the life of the mold and the injection molding machine.

Therefore, the minimum required mold clamping force is set in advance at a predetermined position of the screw or plunger during the injection stroke or at an arbitrary time from the start of injection, and the screw or plunger of the injection molding machine performs the injection. When passing an arbitrarily determined position during the stroke, or when an arbitrarily determined time has elapsed from the start of injection,
There is a method of controlling the mold clamping force so that the required minimum mold clamping force is obtained (see Japanese Patent Publication No. 61-50767).

[0005]

SUMMARY OF THE INVENTION In the above conventional technique,
Controlling the magnitude of mold clamping force, that is, mold clamping is performed with the required minimum mold clamping force from the start of injection until the preset time elapses, thus saving power consumption and increasing the life of hydraulic equipment. Although it has the advantage of being made, the waste due to the time delay from the start of injection to the time when the mold clamping force is required due to the rise of the resin pressure in the cavity (hereinafter, referred to as “mold pressure”) is not eliminated. Therefore, power is still wasted and the life of the mold and injection molding machine is shortened.

The present invention has been made in view of the above problems of the prior art, and is wasteful due to a time delay from the start of injection to the time when mold clamping force is required due to the increase of the mold internal pressure. It is an object of the present invention to realize an injection start timing control method that solves the above problem.

[0007]

In order to achieve the above object, the injection start timing control method of the present invention detects an actual mold clamping force generated by a mold clamping device in a method of controlling an injection process of an injection molding machine. However, when the detected actual mold clamping force reaches a preset injection start mold clamping force, the injection start timing is controlled so as to start the injection.

[0008]

Operation: By setting the injection start timing to the time when the preset injection start mold clamping force is reached, from the start of injection of the prior art described above to the time when the mold clamping force is required due to the increase of the mold internal pressure. The time delay of is eliminated.

[0009]

An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic partial cross-sectional view of an injection start timing control device used for carrying out the present invention, and FIG. 2 is a flow chart thereof.

The mold clamping device shown in FIG. 1 comprises a fixed platen 8 and a movable platen 11, and the movable platen 11 is locked to a tie bar 9 also serving as a piston rod of the mold clamping cylinder 1 fixed to the fixed platen 8, The movable platen 11 is fixed to the stationary platen 8 via the piston 10 and the tie bar 9 by supplying a pressurized fluid from a pressurized fluid generation source (not shown) to the mold clamping side chamber of the mold clamping cylinder 1.
It is configured so that the mold 14 can be clamped with a predetermined mold clamping force by moving the mold 14 toward.

A pressure sensor 2 for detecting the pressure of the pressurized fluid at the time of mold clamping, that is, the actual mold clamping force is provided in the mold clamping side chamber (the chamber on the left side in the drawing) of the mold clamping cylinder 1.
The actual mold clamping force detected by the pressure sensor 2 is sent to the controller 3. The controller 3 can set an arbitrary set mold clamping force, calculates and stores an injection start mold clamping force based on the set mold clamping force and a coefficient described later, and also sets the mold clamping force and the injection start. The mold clamping force is output to the comparator 4.

On the other hand, the comparator 4 has two channels, a first comparator and a second comparator, and is sent from the set mold clamping force and the injection start mold clamping force output from the controller 3 and the pressure sensor 2. Compare with the actual mold clamping force.

Then, when the actual mold clamping force reaches the injection start mold clamping force, an injection start signal is sent to the solenoid valve 6 via the controller 3 to switch the solenoid valve 6 and the pump 12 to the injection cylinder 5.
Injection screw 1 by supplying pressurized fluid generated by
3 is moved forward to start injection, and thereafter, when the actual mold clamping force reaches or exceeds the set mold clamping force, the mold clamping completion signal is output. The mold clamping completion signal is used for other than the injection start signal, for example, for confirmation of mold clamping force generation (abnormal output), output signal to peripheral equipment, and the like.

Here, an example of a method of setting the set mold clamping force and the injection start mold clamping force will be described.

The set mold clamping force is arbitrarily set according to the injection pressure, the molding area of the mold, and the like.

On the other hand, the injection starting mold clamping force is predicted by a time delay from the start of injection until the resin pressure in the cavity rises to reach the set mold clamping force, and is determined by an experiment for each mold type and molding condition. The coefficient is obtained in advance, and the coefficient is calculated by multiplying the coefficient with the set mold clamping force. That is, this injection start mold clamping force can also be set to an arbitrary magnitude in advance.

In the above embodiment, the actual mold clamping force is detected by the pressure sensor of the pressurized fluid in the mold clamping side chamber of the mold clamping cylinder.
The invention is not limited to this, and the encoder 7 may detect the amount of change in the length of the tie bar 9 due to the mold clamping force, or the amount of deformation of the mold may be detected by appropriate means.

[0019]

Since the present invention is configured as described above, it has the following effects.

The injection starting mold clamping force is separated from the set mold clamping force and is arbitrarily determined. When the actual mold clamping force reaches the injection starting mold clamping force, the injection is started. Increased internal pressure eliminates unnecessary mold clamping force generation time due to time delay when mold clamping force is required, reducing power consumption,
The life of the mold and the injection molding machine can be increased.

[Brief description of drawings]

FIG. 1 is a schematic partial cross-sectional view of an injection start timing control device used for implementing the present invention.

FIG. 2 is a flowchart of an injection start timing control method of the present invention.

[Explanation of symbols]

 1 Clamping cylinder 2 Pressure sensor 3 Controller 4 Comparator 5 Injection cylinder 6 Solenoid valve 7 Encoder 8 Fixed plate 9 Tie bar 10 Piston 11 Movable plate 12 Pump 13 Injection screw 14 Mold

Claims (1)

[Claims] 1. A method for controlling an injection process of an injection molding machine, wherein an actual mold clamping force generated by a mold clamping device is detected, and the detected actual mold clamping force reaches a preset injection start mold clamping force. When I did
An injection start timing control method characterized in that the injection start timing is controlled so as to start injection.