JPH072358B2 - Mold clamping control method for electric injection molding machine - Google Patents

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 further compressing it by applying a mold clamping force. It relates to a control method.

[0002]

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

The one used for carrying out the invention of the present application described later,
Using an electric injection molding machine with the same structure except for the control device, the movable platen is advanced through the ball screw mechanism by the driving force of the mold clamping motor, and the mold is clamped with a predetermined mold clamping force. After injecting the molten resin into the cavity of the mold, 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 a 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 not larger than the static friction force. Then, the mold clamping force does 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 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 prior art, and the mold clamping force of an electric injection molding machine capable of controlling the mold clamping force which requires a minute change. It is intended to provide a control method.

[0006]

In order to achieve the above object, a method for controlling a mold clamping force of an electric injection molding machine of 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 set torques corresponding to preset mold clamping forces set in advance, the set torque of each of the plurality of stages is changed for each step. Before changing, after starting the rotation of the mold clamping motor with a correction torque obtained by adding a torque difference of a magnitude that eliminates the influence of the static friction force of the mold clamping device to the setting torque of each stage, It is characterized in that the mold clamping electric motor is rotated at a set torque at each stage.

[0007]

Before the mold clamping motor is rotated at the set torque in each step, the torque difference of a magnitude that eliminates the influence of the static friction force of the mold clamping device is set in the set torque in each step. Since the rotation is started by the correction torque added to the above, a torque difference sufficiently larger than the set torque difference in each of the stages is given, and the mold clamping motor surely starts rotation. When the rotation is started, the influence of the static friction force of the mold clamping device disappears,
After that, even if the mold clamping electric motor is rotated at each set torque, the mold clamping force according to the set mold clamping force can be obtained.

[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 the 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. Between the fixed platen 4 and the mold clamping housing 6, a movable metal which is guided by the tie bar 7 and is reciprocally movable in its axial direction. A movable platen 9 to which the mold 2 is attached is arranged. The mold clamping housing 6 has a stepped cylindrical rotating 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. . Further, a pulley 12 is integrally provided on the other end of the rotary shaft 10, and a pulley 14 with a flange is integrally provided on the output shaft of the mold clamping motor 16 mounted on the pulley 12 and the bed 20. A timing belt 13 is laid between the and. As a result, the torque of the mold clamping motor 16 is sequentially transmitted to the ball nut 9 via the flanged pulley 14, the timing belt 13, the pulley 12, and the rotary shaft 10 to rotate the ball nut 9, resulting in the ball screw. 8 moves forward to the fixed platen 4 side and moves to the movable platen 5
The mold clamping force is generated by advancing and moving the movable mold 2 against the fixed mold 1. The injection cylinder 15 provided on the other end side of the bed 20 is for injecting the molten resin into the cavities 3 of the fixed mold 1 and the movable mold 2 that are clamped.

The mold clamping electric motor 16 has a rotation detector 1 including a rotary encoder for detecting the rotation thereof.
7 is provided, 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 control device 19 is
It has a function of setting a plurality of stages of setting torque corresponding to a plurality of stages or more of a plurality of stages of setting mold clamping force.
Is output to change the torque of the mold clamping motor 16, and at the same time, it also has the function described below.

The control device 19 has a function of setting a torque difference of a magnitude that excludes the influence of the static friction force of the mold clamping device of the electric injection molding machine, which has been obtained in advance by experiments, and the controller 19 of the mold clamping motor 16 has a function of setting the torque difference. When changing the torque with a set torque of multiple stages, before changing to each set torque for each stage,
After starting the rotation of the mold clamping motor 16 with a correction torque obtained by adding the preset torque difference to the set torque of each stage, a command to rotate the mold clamping motor 16 with the set torque of each stage is output. It is possible.

Next, one 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 control device 19 is set with a plurality of stages of set torque, and a torque difference of a magnitude is set so as to eliminate the influence of the static friction force of the mold clamping device described above.

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.

When the rotation of the mold clamping motor 16 is started by the first stage correction torque obtained by adding the torque difference to the first stage set torque and the rotation detector 17 detects this rotation, the first
Change to the set torque of the stage and rotate for a predetermined time,
Generate the set mold clamping force of the stage. Then, after injecting the molten resin into the cavity 3 by the injection cylinder 15,
The rotation of the mold clamping motor 16 is started by the second stage correction torque obtained by adding the torque difference to the second stage set torque, and when this rotation is detected by the rotation detector 17, the set torque is changed to the second stage set torque. And rotate for a predetermined time. Thereafter, similarly, the mold clamping electric motor 16 is rotated with the correction torque and the set torque in the remaining stages to complete one molding cycle.

[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 if it is necessary 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.

[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 reference symbols] 1 fixed mold 2 movable mold 3 cavity 4 fixed plate 5 movable plate 6 mold clamping housing 7 tie bar 8 ball screw 9 ball nut 10 rotary shaft 11a, 11b bearing 12 pulley 13 timing belt 14 flanged pulley 15 Injection cylinder 16 Electric motor for mold clamping 17 Rotation detector 18 Driver amplifier 19 Controller 20 Bed

Claims (1)

[Claims] 1. An electric injection molding machine equipped with a mold clamping device driven by a mold clamping motor, wherein the mold clamping motor has a plurality of preset torques corresponding to preset preset mold clamping forces. When changing the torque of each step, before changing to the set torque of each step of the plurality of steps, the torque difference of a magnitude that eliminates the influence of the static friction force of the mold clamping device of each step. After the rotation of the mold clamping electric motor is started by the correction torque added to the set torque, the mold clamping electric motor is rotated by the set torque of each of the stages, and the mold clamping of the electric injection molding machine is characterized. Control method.