JPH07214614A - Injection control method in injection molding machine - Google Patents

Abstract

(57) [Summary] [Purpose] Correct the injection conditions to realize the optimum injection process. [Structure] A resin sensor is attached during the resin flow in the mold, and the subsequent speed switching target position is corrected based on the difference between the measured screw position and the theoretical screw position at the time when the resin flow front passes. .. Further, the target value of the speed switching time thereafter is corrected by the time difference.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding machine for molding plastic products, and more particularly to an injection control method for controlling the injection process with high accuracy.

[0002]

2. Description of the Related Art In an injection process of an injection molding machine, it is possible to obtain a desired high quality molded product by setting and controlling a resin speed and a resin pressure to optimum conditions in a process of injecting and filling a molten resin in a mold. Is very important for.

In order to obtain the optimum injection speed and pressure of the molten resin, depending on the experience of a skilled person, or by using CAE (Computer Assisted Technology) calculation, the ideal molding conditions are set and the set values are set. It was controlled based on.

[0004]

By the way, in the actual injection process, due to the backflow of the resin due to the closing delay of the check ring or the gap generated at the nozzle tip by the suck back operation, the injection process starts, that is, the screw advance starts. There is a difference between the time and the start time of inflow of the resin into the mold, which causes a problem that the injection process as set cannot be realized no matter how the optimum injection conditions are set.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide an injection control method in an injection molding machine for correcting an injection condition to realize an optimum injection process. is there.

[0006]

In order to achieve the above object, in the first aspect of the present invention, a resin sensor for detecting the presence / absence of resin is attached in the middle of a resin flow path in a mold to remove the resin. The time when the flow front passes is detected, and the difference between the measured screw position and the theoretical screw position at that time is used as a reference,
The control target position of the speed switching thereafter is corrected and controlled, and in the second invention, the control of the speed switching thereafter is based on the difference between the time of claim 1 and the theoretical time. The target time was corrected and controlled.

[0007]

[Function] By detecting the delay in closing the check ring and the filling delay at the start of injection caused by the space in the nozzle tip portion caused by the suck back operation, the time is detected by the resin sensor provided in the middle of the resin flow path in the mold. Based on, the difference between the measured screw position and the theoretical screw position is reflected in the target position, and further, the difference between the measured time and the theoretical time is reflected in the target value of the speed switching time thereafter. It is possible to realize a nearly ideal injection process.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A concrete embodiment of an injection control method in an injection molding machine according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic diagram showing a simplified structure of a main part of an injection molding machine, FIG. 2 is an explanatory diagram showing a state immediately before the start of an injection process, and FIG. 3 is a flow front of a molten resin passed through a resin sensor. FIG. 4 is an explanatory diagram showing an instantaneous state, FIG. 4 is a diagram for correcting the screw position and the theoretical position at the time when the flow front has passed the resin sensor, and FIG. 5 is a diagram for correcting the speed switching time at the time of injection.

In FIG. 1, a screw 1 is inserted in a heating cylinder 3 which constitutes an injection device 20 so as to be able to move forward and backward with respect to rotation, a nozzle 4 is attached to the tip of the heating cylinder 3, and a rear end of the heating cylinder 3 is attached. An injection cylinder 16 in which a piston 14 in which the screw 1 is axially movable and is rotatably attached is inserted is attached to the.

A resin sensor 6 is disposed so as to face the resin passage 11 of the fixed mold 10a at the tip of the nozzle 4. This resin sensor 6 has a screw head front portion 2 after the start of the injection process.
It is provided in order to confirm whether or not the flow front of the molten resin stored in 2 has passed over the resin sensor 6. It should be noted that the installation position of the resin sensor 6 is as close to the nozzle 4 as possible in consideration of the fact that the feedback control has better response when the time difference between the start of the injection process and the passage of the flow sensor through the resin sensor 6 is smaller. Is preferable. The resin sensor 6 may be, for example, an ultrasonic sensor that detects the presence or absence of sound wave propagation, or an optical sensor that detects the light transmission state.

A check sheet 1a is attached to the tip of the screw 1.
The screw head 18 is screwed on, and the screw head 18 has a substantially conical shape toward the tip, and the rear side (right side in the figure) of the conical shape is stepped to have a small diameter. A check ring 2 which is slidable in the axial direction is inserted. Reference numeral 12 is a hopper, 12a is a pellet, and 8 is a cavity formed between the fixed mold 10a and the movable mold 10b when the mold is closed.

Next, the operation of the present invention will be described. At the start of the weighing process, the screw 1 is on the left side of the position shown in FIG. 2, and when the screw 1 is rotated, the pellets 12a are supplied from the hopper 12 to the right end side of the screw 1, and the pellets 12a are moved to the left side by the screw 1. While being sent to, the resin becomes molten resin and is stored in the front portion 22 of the screw head.

The screw 1 retracts as it is stored in the front portion 22 of the screw head. For example, when a limit switch (not shown) detects this, the rotation of the screw 1 is stopped and the measurement of the molten resin is completed.

After that, when the screw 1 is further retracted and a suck back operation is performed, a gap 9 is formed at the tip of the nozzle 4. When the injection process is started from this state, as shown in FIG. 2, the check ring 2 is in contact with the screw head 18 side, and the check ring 2 is in contact with the check sheet 1a side as the screw 1 advances. Due to the closing, the molten resin stored in the screw head front portion 22 is injected to the mold 10 side.

When the flow front of the injected molten resin passes through the resin sensor 6 (FIG. 3), the resin sensor 6 detects this and transmits a signal to the controller of the injection molding machine.

When the control device of the injection molding machine receives the signal,
The screw forward position was measured from the start of injection until the molten resin passed through the resin sensor 6, and the actual measurement values obtained were compared with the theoretical values when these operating conditions for injection were calculated, and there was a difference. For example, it is aimed to realize a stable injection process operation by appropriately correcting the subsequent set value from the difference.

The theoretical value described above is such that the reverse flow rate due to the closing delay of the check ring 2 accompanying the advance of the screw 1 at the start of the injection process and the void 9 generated at the tip of the nozzle 4 due to the suck back operation at the completion of the metering process are zero. The injection conditions under the theoretical conditions are shown.

On the other hand, the actually measured value is a value obtained by adding the void 9 caused by the back flow rate and the suck back operation due to the closing delay of the check ring 2 contained at the start of the actual injection process.

Thus, the above-mentioned theoretical values and actual measured values are
It depends on the reverse flow rate due to the delay in closing the check ring 2 at the start of injection and the presence or absence of the void 9 at the tip of the nozzle 4.

Further, as shown by the solid line in FIG.
When the injection speed is set and controlled based on the position, the screw 1 position X _AO at the theoretical time t _A is calculated. Next, actually perform the injection process, measure the screw 1 moving position X _A at the time t _A actually measured, calculate the difference _ΔX between X _AO and X _A , and change the theoretical speed after t _A time. Points X _{1 to} X ₄ (shown by solid lines in FIG. 7) are each ΔX.
The correction is made to X ₁ ′ to X ₄ ′ indicated by dotted lines in FIG.

Further, as shown by the solid line in FIG. 5, when the injection speed of the screw 1 is set and controlled as a target value with respect to the elapsed time after the start of injection, the theoretical resin passage time t _AO of the resin sensor 6 is calculated. The difference Δt is calculated from the measured value t _A of the actually measured resin passage time. Then, the subsequent speed switching times t ₁ to t ₄ are corrected by Δt to be speed switching times t ₁ ′ to t ₄ ′ shown by the dotted line, and the target value is corrected and controlled as shown by the dotted line in FIG.

[0023]

As is apparent from the above description, in the first aspect of the invention, a resin sensor for detecting the presence / absence of resin is mounted in the middle of the resin flow path in the mold and the resin flow front end passes through. The time is detected, and the control target position for speed switching thereafter is corrected and controlled based on the difference between the actually measured screw position and the theoretical screw position at that time. Based on the difference between the time and the theoretical time, the control target time of the speed switching thereafter is corrected and controlled, so that a nearly ideal injection process can be realized and a desired non-defective product can be stably obtained. be able to.

[Brief description of drawings]

FIG. 1 is a schematic view showing a simplified configuration of a main part of an injection molding machine.

FIG. 2 is an explanatory diagram showing a state immediately before the start of an injection process.

FIG. 3 is an explanatory diagram showing a state at a moment when a flow front of a molten resin passes a resin sensor.

FIG. 4 is a diagram for correcting the screw position and the theoretical position at the time when the flow front passes through the resin sensor.

FIG. 5 is a diagram for correcting a speed switching time at the time of injection.

[Explanation of symbols]

 1 Screw 1a Check Sheet 2 Check Ring 3 Heating Cylinder 4 Nozzle 6 Resin Sensor 8 Cavity 9 Gap 10 Mold 10a Fixed Mold 10b Movable Mold 11 Resin Passage 12 Hopper 14 Piston 16 Injection Cylinder 16a Injection Cylinder Head Side Hydraulic Chamber 18 Screw Head 20 Injection device 22 Screw head front part

Claims (2)

[Claims] 1. A resin sensor for detecting the presence / absence of resin is mounted in the middle of a resin flow path in a mold to detect the time when the resin flow front passes, and the measured screw position and theoretical screw position at that time are detected. An injection control method in an injection molding machine, characterized in that a position to be controlled for speed switching thereafter is corrected and controlled on the basis of a difference between the two. 2. A resin sensor for detecting the presence / absence of resin is mounted in the middle of the resin flow path in the mold to detect the time when the flow front of the resin passes, and the difference between the time and the theoretical time is used as a reference. In addition, an injection control method in an injection molding machine, characterized in that the control target time of speed switching thereafter is corrected and controlled.