JPH04298317A - Mold protect method of injection molding machine with servomotor - Google Patents

Abstract

PURPOSE:To protect a mold in a mold clamping mechanism for clamping a mold using a servomotor as a drive source. CONSTITUTION:A mold clamping mechanism is driven by means of a servomotor. Upon reaching a mold protection start position, torque limit is outputted to drive the servomotor with low torque (S2,S3). When, even with low torque, a mold moves and a mold touch is produced, the torque limit is released to perform mold clamping (S5, S6, S7). When foreign matters are present between the molds and the molds driven with low torque are not moved and the servomotor does not rotate, error (position deviation) being differences of feedback signals detected by movement command and a position detector increases, thereby causing a NC device to stop the servomotor. Even if foreign matters are present between the molds, since the molds are driven only with low torque, large forces are not exerted on the molds, so that the molds are protected.

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, and more particularly to mold protection in an injection molding machine that uses a servo motor as a drive source for driving a mold clamping mechanism.

0002

2. Description of the Related Art Hydraulic pressure has been used as the drive source for the mold clamping mechanism of conventional injection molding machines. In order to prevent the mold from being damaged due to foreign matter if the mold is clamped with a foreign object inside the mold, the mold clamping mechanism is driven at the lowest hydraulic level and the mold is moved. When the mold comes into contact with a foreign object, so-called mold protection is used to protect the mold from further movement.

0003

[Problems to be Solved by the Invention] The present invention provides the following advantages even when the mold clamping mechanism of an injection molding machine is driven by a servo motor.
The purpose is to enable the above-mentioned mold protection.

0004

[Means for solving the problem] In an injection molding machine, a servo motor is used as a drive source for a mold clamping mechanism that moves a mold, and a position detector for detecting the position of the mold is attached to the servo motor, An NC control device is provided to control the servo motor, and during the mold closing operation, when the mold comes to the mold protection start position, the NC control device outputs a torque limit command and moves the mold with low torque. When the difference between the movement command and the feedback signal of the position detected by the position detector exceeds a predetermined value, the drive of the servo motor is stopped to protect the mold.

[0005]

[Operation] When the mold protection start position is reached, the NC control device outputs a torque limit command and moves the mold with low torque. If there is no foreign object between the molds, there is no load on the mold other than friction, so the mold moves, and the difference between the movement command and the position feedback signal detected by the position detector does not increase. . Then, the molds come into contact and when the mold protection period ends, the torque limit is released and mold clamping is performed. On the other hand, if there is a foreign object between the molds, the mold is being driven with low torque, so the movement of the mold is blocked by the foreign object and does not move, and the servo motor does not rotate. The difference between the detected position and the feedback signal increases. When the difference reaches a predetermined value, the NC control device stops driving the servo motor. As a result, the force exerted on the mold by the foreign matter is small and does not damage the mold, so that the mold is protected.

[0006]

[Embodiment] Fig. 1 is a block diagram of an embodiment of the present invention, in which 1 and 1' are molds, 2 is a mold clamping mechanism that opens and closes the mold, and M is a drive for the mold clamping mechanism 2. , a servo motor that opens and closes the mold and clamps the mold; P is a position detector provided on the servo motor M; 3 is a servo circuit that drives and controls the servo motor M; 4 is an NC control device; 1 is a central processing unit (hereinafter referred to as CPU), and 6 is an input/output circuit, which is connected to the servo circuit 3 and the position detector P.

7 is a ROM in which a control program for controlling the injection molding machine is stored; 8 is a RAM for temporary data storage and arithmetic processing; and 9 is a torque limit command for various commands and mold protection to be described later. A manual input device 10 is a display device used for setting the torque limit value and the torque limit value. Note that 11 is a bus.

Next, the operation of this embodiment will be explained along with the operation processing flow shown in FIG.

First, the manual input device 9 is used to set the mold protection start position, that is, the position where the torque limit command of the NC control device 4 is to be sent, the torque limit value, etc. This torque limit command clamps the output torque of the servo motor M so that it does not output more than a certain torque, and as a result, the mold clamping mechanism and mold are moved with low torque. .

Then, when the servo motor M is driven and the mold clamping operation starts (step S1), the CPU 5 judges based on the signal from the position detector P whether or not the mold has reached the mold protection start setting position. When the torque limit is reached (step S2), the timer T is started and a torque limit command is output (step S3). As a result, the servo motor M is driven with low torque, and the mold 1 is moved forward with a weak force. Then, whether the timer T has timed up (step S4) or whether the mold has come to the touch position (step S4).
5) is determined, and when the mold comes to the mold touch position, the torque limit is released (step S6), the mold is clamped (step S7), and mold clamping is completed. However, step S4,
When the timer T times out before the mold comes to the mold touch position in S5, the display device 10 generates an alarm to display that a foreign object is present between the molds. In other words, when a foreign object is present between the molds, the mold 1 is driven with low torque, so when the molds 1, 1' come into contact with the foreign object, the mold 1 moves further (the molds 1, 1' The mold 1 stops at that position, and as a result, the timer T times out and generates an alarm as described above. In addition, since the mold 1 does not reach the movement command position commanded by the NC control device 4 when the mold 1 stops, errors that are the difference between the feedback signal from the position detector and the movement command value accumulate. , when the error reaches a predetermined value, the NC control device stops driving the servo motor M.

[0011]

As described above, the present invention utilizes the torque limit function of the NC control device to limit the output torque of the servo motor in the mold protection zone and drive the servo motor to prevent foreign matter from occurring between the molds. However, if the mold cannot be moved with this limited output torque, the error (position deviation), which is the difference between the movement command to the servo motor and the position feedback signal detected by the position detector, will increase. Since the servo motor is stopped when the predetermined value is reached, only a low torque force is applied to the mold and the foreign matter between the molds, thereby protecting the mold.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment implementing the present invention.

FIG. 2 is an operational processing flow of the same embodiment.

[Explanation of symbols]

1,1' Mold M Servo motor P Position detector 4 NC control device

Claims (1)

[Claims] 1. A mold clamping mechanism that moves and clamps a mold, a servo motor that drives the mold clamping mechanism, and a position detector attached to the servo motor that detects the position of the mold. An NC control device that controls the servo motor is provided, and when the mold comes to the mold protection start position during mold closing operation, the NC control device outputs a torque limit command and moves the mold with low torque. an injection molding machine using a servo motor, wherein the servo motor stops driving when a difference between a movement command and a position feedback signal detected by the position detector exceeds a predetermined value. Protection method.