JPH0639890A - Apparatus for controlling injection process in motordriven injection molding machine - Google Patents

Abstract

PURPOSE:To make content of the process of an injection process variable and to stop an injection screw at a specified position. CONSTITUTION:A necessary control among speed control, positioning control and dwelling control is set in a selective setting device 31 and control switching position or the position and pressure is set in a switching position (pressure) setting device 32 and furthermore, stopping time of an injection screw 13 is set in a temporary stopping time setting device 33 respectively. A motion selection control circuit 30 switches a speed control circuit 21, a dwelling control circuit 26 and a positioning control circuit 28 in accordance with the setting contents of the setting devices 31, 32 and 33. When the speed control and the positioning control are set in the setting device 31 and it is switched to the positioning control circuit 28, a motor 6 is stopped and an injection process is finished. When the pressure control is set in addition to the above ones, the positioning control circuit 28 starts the motor 6 again at the same time when set time of the setting device 33 is over and the dwelling control is started.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection process control device for an electric injection molding machine in which an injection screw is axially moved back and forth by an electric motor.

[0002]

2. Description of the Related Art The injection process of an injection molding machine is roughly divided into a filling process of advancing an injection screw to fill a cavity of a mold with resin and a pressure holding process of holding the filled resin at a set pressure. . Switching between the filling process and the pressure-holding process is performed by switching the filling process to the pressure-holding process when the injection screw advances to a predetermined position, and the injection screw moves forward to the predetermined position and the filling resin has a pressure higher than a predetermined pressure. In such a case, a method of switching from the filling step to the pressure holding step is adopted.

[0003]

However, the injection process control device in the conventional electric injection molding machine has a structure in which the pressure-holding process is started immediately after the filling process in any of the switching methods described above. The injection screw comes to stop past a predetermined position, which causes inconveniences such as variations in the amount of filled resin and the occurrence of burrs.

According to the present invention, the contents of the injection process can be changed, the injection screw can be correctly stopped at a predetermined position, and a predetermined amount of resin can be accurately filled in the mold cavity. An object of the present invention is to provide an injection process control device for an electric injection molding machine, which can prevent the occurrence of the occurrence.

[0005]

In order to achieve the above object, the present invention provides an injection screw inserted in a heating cylinder,
In an electric injection molding machine that is moved in the axial direction by a motor through a screw mechanism, a speed setter that sets the injection speed of the injection screw in the filling process of the injection process and a speed conversion circuit from a position sensor attached to the motor Speed control circuit that controls the electric motor so that the injection speed of the injection screw that is output as a result becomes the injection speed set in the speed setter, and the holding pressure that sets the injection pressure of the injection screw in the pressure holding process of the injection process. A setter, a holding pressure control circuit that controls the electric motor so that the injection pressure of the injection screw output from the load cell attached to the injection screw becomes the injection pressure set by the holding pressure setter, and the injection by the electric motor Positioning control circuit that controls stop and start of the screw, and two or more of speed control, pressure holding control and positioning control are selected and their order is set. Selective setting device for setting the control position, switching position setting device for setting the control switching position, and temporary stop time for setting the stop time when the forward movement of the injection screw by the electric motor is temporarily stopped by the positioning control circuit. Operation selection that receives the output signal of the setting device and the position sensor, and selects the speed control circuit, the pressure holding control circuit, and the positioning control circuit according to the setting contents of the selection setting device, the switching position setting device, and the pause time setting device. It is configured to include a control circuit.

[0006]

The function of the injection process can be changed by the selection setting device, the switching position setting device and the temporary stop time setting device. For example, if the speed setting and then the positioning control are set in the selective setting device and the holding pressure control setting is omitted and the switching position is set in the switching position setting device, the injection screw is set to the switching position setting device. When it advances to the position, it stops and the injection process ends only by the filling process without performing the pressure holding process.

In the above description, when the holding pressure control is set in the selection setter after the positioning control and the time is set in the temporary stop time setter, the injection screw stops when it reaches the switching position, and then the temporary stop. When the time set in the time setting device has elapsed, the operation is resumed and the pressure holding process starts. In the above two injection steps, the injection screw stops correctly at the set position, so that the amount of resin filled is accurate and burrs and other inconveniences can be prevented.

If the speed control and then the pressure holding control are set in the selective setting device and the positioning control is not set, the pressure holding process is immediately performed after the filling process as in the conventional case.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of an injection process control device for an electric injection molding machine according to the present invention. In these drawings, reference numeral 1 is a front plate. A heating cylinder 2 is fixed to the front plate 1. A rear plate 3 is provided behind the front plate 1 (on the right side in FIG. 1) in parallel with the front plate 1, and a pair of identical ball screw shafts 4 and 4 rotate between the plates 1 and 3. It is supported and provided freely. Pulleys 5 having the same diameter are attached to the ends of the ball screw shafts 4, respectively.

An electric motor (servo motor) 6 is fixed to the rear plate 3, and an endless timing belt 9 is wound between a drive pulley 8 and a pulley 5, 5 provided on an output shaft 7 of the electric motor 6. It is hung. Electric motor 6
Rotates the ball screw shafts 4 and 4 in the same direction in synchronization with each other via the drive pulley 8, the timing belt 9, and the pulleys 5 and 5.

A ball nut 1 is attached to each of the ball screw shafts 4 and 4.
1 are screwed together, and the pair of ball nuts 1
A pressure plate 12 is installed between 1 and 11. The pressure plate 12 has each ball screw shaft 4, 4
When is rotated, it moves in the front-back direction (left-right direction in FIG. 1) together with the ball nuts 11, 11. An injection screw 13 is attached to the front surface of the pressure plate 12 on the heating cylinder 2 side via a load cell 14. The injection screw 13 is inserted into the heating cylinder 2, and advances in the axial direction together with the pressure plate 12 to inject the resin from the nozzle 15 into the cavities of the molds 16, 16. The electric motor 6 is provided with a position sensor 17 such as a pulse encoder.

Reference numeral 20 is a speed setting device. The speed setter 20 sets the injection speed of the injection screw 13 in the filling process, and is connected to the speed control circuit 21. The output signal of the position sensor 17 is converted into the forward speed of the injection screw 13 by the speed conversion circuit 22 and input to the speed control circuit 21. The speed control circuit 21 receives the output signal of the position sensor 17 via the speed conversion circuit 22, and switches the switching circuit 2 so that the injection (forward) speed of the injection screw 13 becomes the injection speed set in the speed setter 20.
It outputs to the output circuit 24 via 3 and controls the electric motor 6.

A pressure holding control circuit 26 is connected to the load cell 14 via a pressure conversion circuit 25. A holding pressure setting device 27 that sets the injection pressure of the injection screw 13 in the holding pressure process is connected to the holding pressure control circuit 26. The holding pressure control circuit 26 receives the output signal of the load cell 14 via the pressure converting circuit 25, and outputs the output circuit through the switching circuit 23 so that the injection pressure of the injection screw 13 becomes the injection pressure set in the holding pressure setting device 27. It outputs to 24 and controls the electric motor 6.

The output circuit 24 includes the control circuits 21 and 2 described above.
In addition to 6, the positioning control circuit 28 is connected via the switching circuit 23. The positioning control circuit 28 uses the switching circuit 2
3 to output to the output circuit 24 to stop the electric motor 6 in operation or to operate the electric motor 6 in stop.

Reference numeral 30 is an operation selection control circuit. The operation selection control circuit 30 includes a selection setting device 31, a switching position setting device 32, a pause time setting device 33, a position sensor 17,
And the pressure conversion circuit 25 are connected. Selection setting device 3
1 selects two or more of the speed control, the pressure holding control, and the positioning control in the injection process and sets them together with the order. The switching position setting device 32 sets a switching position A (FIGS. 3 to 5) for controlling the filling process, the pressure holding process, and the like, and the switching position setting device 32 fills the switching position setting device 32 as needed. The final pressure of the process can also be set.

Further, the temporary stop time setting device 33 sets the stop time when the forward movement of the injection screw 13 is temporarily stopped. The operation selection control circuit 30 receives the output signals of the position sensor 17 and the pressure conversion circuit 25, and switches the switching circuit 23 according to the setting contents of the selection setting device 31, the switching position setting device 32, and the pause time setting device 33. The control circuits 21, 26 and 28 are selectively connected to the output circuit 24.

Next, the operation of the injection process control device in the electric injection molding machine of the present invention constructed as described above will be described. There are the following three types of methods for setting each control of the injection process with respect to the selection setting device 31. (1) Speed control and holding pressure control. (2) Speed control, positioning control, and pressure holding control. (3) Speed control and positioning control. In addition, the order of each control is the above order.

The injection screw 13 is moved to the left in FIG. 1 by the electric motor 6 via the screw mechanism composed of the ball screw shaft 4 and the ball nut 11 as in the conventional case, and the resin is injected from the nozzle 15 into the cavity of the mold 16. To do. Selection setting device 31
In the case of (1) in which the speed control and then the pressure holding control are set, the operation selection control circuit 30 first switches the switching circuit 23 to the speed control circuit 21. Therefore, as soon as the injection process is started, the speed control circuit 21 operates and the injection screw 13 sent from the position sensor 17 through the speed conversion circuit 22.
The electric motor 6 is controlled so that the injection speed of the motor becomes the injection speed preset in the speed setting device 20 (step S in FIG. 2).
1 and FIG. 3).

In this way, when the injection screw 13 reaches the switching position A preset in the switching position setting unit 32, it is judged whether or not the setting for the selection setting unit 31 is the above (1) ( Step S2), here (1)
Therefore, the operation selection control circuit 30 immediately switches to the switching circuit 2
3 is switched to the holding pressure control circuit 26. Holding pressure control circuit 26
Controls the electric motor 6 so that the injection pressure of the injection screw 13 sent from the load cell 14 via the pressure conversion circuit 25 becomes the pressure set in advance by the holding pressure setting device 27 (step S6, FIG. 3). ), And ends the injection process.

The above is the case where the filling process is switched to the pressure holding process only by the position of the injection screw 13, but the filling process can be switched to the pressure holding process by both the position and pressure of the injection screw 13. In this case, the switching pressure is set in the switching position setter 32 together with the switching position. With such a setting, the injection screw 13 reaches the setting switching position and the pressure reaches the setting pressure before the filling process is switched to the pressure holding process.

In the case of (2) in which the speed control, the positioning control and the pressure holding control are set in this order in the selection setting device 31,
The operation selection control circuit 30 switches the switching circuit 23 to the speed control circuit 2
Switching to 1 and the speed control of the injection screw 13 is performed by the speed control circuit 21 as in the case of (1) above.

When the injection screw 13 reaches the switching position A set in the switching position setter 32, it is determined in step S2 whether or not (1), and in this case (2), the operation selection control is performed. The circuit 30 immediately switches to the switching circuit 23.
To the positioning control circuit 28. The positioning control circuit 28 immediately outputs to the output circuit 24 to stop the electric motor 6 (step S3). After that, it is judged whether or not the setting for the selection setting device 31 is the above (3) (step S4). In this case, since it is not (3), until the time set in the pause time setting device 33 elapses. The stop state is maintained, and after a set time has passed, the positioning control circuit 28 outputs the output circuit 24 again to start the electric motor 6.

At the same time when the electric motor 6 is restarted, the operation selection control circuit 30 switches the switching circuit 23 to the pressure holding control circuit 26, so that the pressure holding control is performed in the same manner as described above (step S).
6, FIG. 4). When the injection screw 13 is stopped by the positioning control, not only the position of the injection screw 13 but also the pressure can be used in the same manner as (1).

In the case of (3) in which the speed control and then the positioning control are set in the selection setter 31, the same as (2) up to step S3. However, since the result of the determination in step S4 is "Y (YES)", the injection process is terminated without performing the pressure holding control (FIG. 5).

The control contents of the injection process are (2) or (3)
In this case, the position A of the injection screw 13 is fixed.
Since it stops properly, the cavity of the mold 16 can be accurately filled with a predetermined amount of resin. Further, in the case of (2), since the skin layering is formed on the surface of the molded product due to the progress of solidification, the holding pressure is applied, and in combination with the above, burrs and sink marks are further prevented in the molded product having a large projected area. Will be done.

[0026]

As described above, since the injection process control device in the electric injection molding machine of the present invention has the above-mentioned configuration, the process content of the injection process is adjusted to the type of molded product or resin. The injection screw can be properly stopped at a predetermined position by selecting the positioning control. Therefore, a predetermined amount of resin can be accurately filled in the mold cavity, and burrs and the like can be prevented.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an injection process control device in an electric injection molding machine of the present invention.

FIG. 2 is likewise a flow chart.

FIG. 3 is a diagram showing an example of process details of an injection process when speed control and pressure holding control are set in a selection setting device.

FIG. 4 is a diagram showing an example of the content of an injection process when speed control, positioning control, and pressure holding control are set in a selection setting device.

FIG. 5 is a diagram showing an example of process details of an injection process when speed control and positioning control are set in a selection setting device.

[Explanation of symbols]

 2 heating cylinder 6 electric motor 13 injection screw 14 load cell 17 position sensor 20 speed setting device 21 speed control circuit 22 speed conversion circuit 26 pressure holding control circuit 27 pressure holding setter 28 positioning control circuit 30 operation selection control circuit 31 selection setting device 32 switching Position setter 33 Pause time setter

Claims (1)

[Claims] 1. A speed setter for setting an injection speed of an injection screw in a filling step of an injection step in an electric injection molding machine in which an injection screw inserted in a heating cylinder is axially moved by a motor via a screw mechanism. And a speed control circuit for controlling the electric motor so that the injection speed of the injection screw output from the position sensor attached to the electric motor through the speed conversion circuit becomes the injection speed set in the speed setter, and the injection process So that the injection pressure of the injection pressure of the injection screw output from the load cell attached to the injection screw and the injection pressure of the injection screw in the pressure-holding process of the A holding pressure control circuit for controlling the electric motor, a positioning control circuit for controlling stop and start of the injection screw by the electric motor, a speed control and a pressure holding control, A selection setter that selects two or more of the positioning controls and sets them together with their order, a switching position setter that sets the control switching position, and the positioning control circuit that temporarily stops the forward movement of the injection screw by the electric motor. In the case where the speed control circuit is set, the stop time setting device for setting the stop time and the output signal from the position sensor are received and the speed control circuit is maintained according to the setting contents of the selection setting device, the switching position setting device and the pause time setting device. An injection process control device in an electric injection molding machine, comprising an operation selection control circuit for selecting a pressure control circuit and a positioning control circuit.