JPH0516189A - Method for controlling mold clamping in motor-driven injection molding machine - Google Patents

Abstract

PURPOSE:To make it possible to control a clamping force wherein a fine change is needed by providing a clamping force just as set torques in a plurality of stages. CONSTITUTION:A clamping force at the first stage is generated by rotating a motor 16 for clamping based on a set torque at the first stage for a specified time. Then, after a molten resin is injected in a cavity 3 by means of an injection cylinder 15, the torque is changed to a set torque of the second stage and at the beginning of changing to the set torque of the second stage, a speed command for a specified time is output from a speed control part 19B and a torque based on this speed command is added to the above described set torque of the second stage and the motor 16 for clamping is started to rotate. When this rotation is detected by means of a rotation detector 17, it is changed to the set torque of the second stage and rotation for a specified time is performed to generate a clamping force of the second stage. Thereafter, in a similar way, a clasping force of each stage is generated to complete one molding cycle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold clamping force of an electric injection molding machine having a so-called injection compression function of injecting a molten resin into a cavity of a mold which has been clamped and then compressing it by further applying a mold clamping force. It relates to a control method.

[0002]

2. Description of the Related Art Conventionally, there is the following method for controlling a mold clamping force of an electric injection molding machine having an injection compression function.

The one used for carrying out the present invention which will be described later,
Using an electric injection molding machine having the same structure except for the control device, the movable platen is moved forward through the ball screw mechanism by the driving force of the mold clamping motor to perform mold clamping with a predetermined mold clamping force, After the molten resin is injected into the mold cavity that has been clamped, the torque is changed by changing the current flowing through the mold clamping motor according to the set value to change the mold clamping force.

[0004]

SUMMARY OF THE INVENTION In the above conventional method,
Since there is static friction force due to mechanical static friction of the ball screw mechanism, each bearing, movable plate and other operating members that compose the mold clamping mechanism, the difference in the set value of the mold clamping force is commensurate with the static friction force. Otherwise, the mold clamping force will not change according to the set value.
As a result, with respect to a molded product that requires a minute change in the mold clamping force, there is a problem in that the mold clamping force cannot be controlled with the required accuracy and a defective product occurs.

The present invention has been made in view of the problems of the above-mentioned conventional techniques, and the mold clamping force of an electric injection molding machine capable of controlling the mold clamping force that requires a minute change. It is intended to provide a control method.

[0006]

In order to achieve the above object, a method of controlling a mold clamping force of an electric injection molding machine according to the present invention is an electric injection molding provided with a mold clamping device driven by a mold clamping motor. In the machine, when changing the torque of the mold clamping motor with a plurality of preset torques corresponding to preset mold clamping forces set in advance, for each stage, the set torque of each of the plurality of stages Before changing, a speed command is given to the mold clamping electric motor for a predetermined time to start rotation of the mold clamping electric motor, and then the mold clamping electric motor is rotated by the set torque of each stage. It is characterized by.

[0007]

When the speed command is given to the mold clamping motor for a predetermined time before the mold clamping motor is rotated at the set torque at each stage, the mold clamping motor is rotated. Since the start, the influence of the static frictional force of the mold clamping device is eliminated, and thereafter, the mold clamping force according to the set mold clamping force can be obtained even if the mold clamping motor is rotated at each set torque.

[0008]

First, an example of an electric injection molding machine used for carrying out the present invention will be described.

As shown in FIG. 1, a fixed platen 4 to which a fixed mold 1 is attached is fixed to the center of the bed 20, and a mold clamping housing 6 is fixed to one side of the bed 20. Has been done. The fixed platen 4 and the mold clamping housing 6 are connected by four tie bars 7. The fixed platen 4 and the mold clamping housing 6 are guided by the tie bar 7 and reciprocally movable in the axial direction. A movable board 5 to which the movable mold 2 is attached is arranged. The mold clamping housing 6 has a stepped cylindrical rotary shaft 10 via a pair of bearings 11a and 11b.
Is rotatable but is provided so as not to move in the axial direction. A ball screw 8 is screwed into a ball nut 9 fitted to the tip of the rotary shaft 10 on the movable plate 5 side, and the tip of the ball screw 9 is joined to the movable plate 5 by appropriate means so as not to rotate. Has been done.

A pulley 12 is integrally provided at the other end of the rotary shaft 10, and the pulley 12 and an output shaft of a mold clamping motor 16 mounted on the bed 20 are integrally formed. A timing belt 13 is wound around between the provided pulley 14 with a collar. As a result, the mold clamping motor 1
The torque at the time of forward rotation of 6 is the flanged pulley 14,
The ball nut 9 is rotated by being transmitted to the ball nut 9 via the timing belt 13, the pulley 12, and the rotary shaft 10, and as a result, the ball screw 8 advances toward the fixed platen 4 side to move the movable platen. A mold clamping force is generated by advancing 5 and pressing the movable mold 2 against the fixed mold 1. On the contrary, when the mold clamping motor 16 is rotated in the reverse direction, the ball screw 8 retracts to the side opposite to the fixed platen 4 and the movable platen 5 retracts to open the mold. In addition,
The injection cylinder 15 provided on the other end side of the bed 20 is
Cavity 3 of clamped fixed mold 1 and movable mold 2
It is for injecting molten resin into.

The mold clamping motor 16 has a rotation detector 1 including a rotary encoder for detecting the rotation thereof.
7 is provided, and the rotation detector 17 detects the rotation of the mold clamping electric motor 16 and sends the signal to the control device 19 via the driver amplifier 18. The torque control unit 19A of the control device 19 has a function of setting a plurality of set torques corresponding to a set mold clamping force of a plurality of two or more stages. The mold outputs to the driver amplifier 18 to change the torque of the mold clamping electric motor 16, and at the same time, it also has the function described below.

The controller 19 gives a preset speed command for a predetermined time, preferably 0.01-, in synchronism with the timing at which the output of the set torque of each stage is started.
The speed control unit 19B is provided so as to be able to output to the driver-amplifier 18 within a range of 0.5 seconds. By this speed command, the mold clamping motor 16
The torque generated in the above is set to a magnitude excluding the influence of the static friction force described above. Next, an embodiment of the method of the present invention using the above-mentioned electric injection molding machine will be described.

Prior to the start of molding, the torque control unit 19A of the control device 19 is set with a plurality of stages of set torque, and the speed control unit 19B is supplied with a speed command selected in the range of 0.01 to 0.5 seconds. Is set.

When molding is started, a command from the control device 19 is transmitted to the mold clamping electric motor 16 via the driver-amplifier 18, and the mold clamping electric motor 16 is rotated as described below.

The mold clamping motor 16 starts to rotate via the driver amplifier 18 by the first stage set torque output from the torque control section 19A, and the first stage set mold clamping force is generated. Next, after the molten resin is injected into the cavity 3 by the injection cylinder 15, the setting torque of the second stage is changed, but at the start of the change to the setting torque of the second stage, a predetermined time (0.01 to 0.5) is reached. Range of seconds)
Then, the speed command H is output from the speed controller 19B to the driver amplifier 18, and the mold clamping electric motor 16 starts rotating. That is, the influence of the static friction force described above is removed, and the mold clamping electric motor 16 starts rotating. When the rotation detector 17 detects this rotation, a signal is output from the torque control unit 19A to the mold clamping electric motor 16 via the driver amplifier 18 so as to generate the mold clamping force with the set torque. Thereafter, similarly, the speed command H is given for each stage, and when the mold clamping motor 16 starts rotating, the mold clamping force is generated at each set torque.

[0016]

According to the present invention, the static friction force of the mold clamping device of the electric injection molding machine used is rotated before the mold clamping motor is rotated at the set torque of each of the plurality of stages of set torque. Since the influence is eliminated, it is possible to obtain the mold clamping force according to the set torque corresponding to the set mold clamping force at each stage, and when the torque difference between the set torques is small, that is, a slight change in the mold clamping force. Even when it is required, since it is possible to control the mold clamping force according to the set torque of a plurality of stages corresponding to the set mold clamping force of a plurality of stages, it is possible to prevent defective products from being generated.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an electric injection molding machine used for implementing the present invention.

[Explanation of symbols]

 1 fixed mold 2 movable mold 3 cavity 4 fixed plate 5 movable plate 6 mold clamping housing 7 diver 8 ball screw 9 ball nut 10 rotating shaft 11a, 11b bearing 12 pulley 13 timing belt 14 flanged flange -Re 15 Injection cylinder 16 Electric motor for mold clamping 17 Rotation detector 18 Driver-Amplifier 19 Controller 19A Torque controller 19B Speed controller 20 Bed

Claims (1)

Claim: What is claimed is: 1. An electric injection molding machine equipped with a mold clamping device driven by a mold clamping motor, wherein a plurality of preset torques corresponding to preset preset mold clamping forces are set. When changing the torque of the mold clamping electric motor, a speed command is given to the electric motor of the mold clamping device for a predetermined time before changing to the set torque of each of the plurality of stages for each step. A mold clamping control method for an electric injection molding machine, comprising: starting rotation of the mold clamping electric motor, and then rotating the mold clamping electric motor at a set torque in each of the stages.