Electricity: motive power systems – Positional servo systems – Program- or pattern-controlled systems
Patent
1987-07-09
1989-06-20
Ro, Bentsu
Electricity: motive power systems
Positional servo systems
Program- or pattern-controlled systems
318560, 318434, G05B 1918
Patent
active
048412112
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a metering method of an injection molding machine and, more particularly, to a metering method for an injection molding machine which uses a servo motor to drive a screw in a direction of a screw shaft, to perform injection, and to supply a back pressure.
In a conventional injection molding machine, hydraulic pressure is used as a source to drive a screw in an axial direction. In this conventional case, during metering, a predetermined pressure is supplied by a hydraulic pressure to the screw in the axial direction, with the screw being rotated. As the resin is melted, the molten resin is stocked in the distal end portion of the screw and the screw is then moved backward. When the screw backward movement position reaches a metering point, the rotation of the screw and application of the back pressure to the screw are stopped. However, even if rotation of the screw and application of the back pressure are stopped when the metering is completed, the screw is moved backward by the molten pressure of the resin and so on, resulting in a metering error. When the metering is incorrect and the injection amount is large, a burr may occur in a molded product. When the injection amount is insufficient, the resin cannot easily flow in a thin portion. As a result, a high-quality molded product cannot be obtained.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a metering method in which the drawbacks of the above prior art technique are eliminated and which can perform high-precision metering.
In order to achieve the above object, according to the present invention, a servo motor is used for driving a screw in an axial direction, thus performing injection and supplying a back pressure. The servo motor is driven even after a screw position has reached a metering point and the rotation of a screw is stopped, thereby holding the screw position at the position of the metering point. In this manner, after the backward movement position of the screw has reached the metering point, the rotation of the screw is stopped, and the metering process is ended. The servo motor for driving the screw in the axial direction is driven and positioned so as to hold the screw at the exact position of the metering point. Therefore, any metering error is small, and high-precision metering can be performed. Thus, factors causing a burr or a sink mark in the molded product are eliminated, and a high-quality molded product is obtained.
BRIEF DESCRIPTION OF THE DRAWING
The accompanying drawing is a block diagram of a metering control system of an injection molding machine for implementing the method of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The accompanying drawing shows a metering control system of an injection molding machine according to an embodiment of the present invention. The injection molding machine 41 has a numerical controller 1, incorporating a microcomputer (CPU) 10 for controlling the injection molding machine. The controller 1 is connected to a servo circuit 2 of a servo motor M1, for rotating a screw 40, and a servo circuit 3, of an injection servo motor M2, for applying a back pressure during injection and metering. The servo motors M1 and M2 are, respectively, provided with pulse encoders P1 and P2 for detecting the position and speed thereof. Reference numeral 4 denotes a D/A converter for converting a torque limit command supplied from the numerical controller 1 into an analog voltage.
In the numerical controller 1, the microcomputer (CPU) 10 is connected to: a memory 11 including a ROM for storing a control program, for controlling the injection molding machine, and a RAM utilized for temporarily storing data; a nonvolatile RAM 12, for storing various preset values; a manual data input unit (to be referred to as a CRT/MDi hereinafter) 13 having a CRT display; a pulse distributor 14, for driving the servo motors M1 and M2; and an input/output circuit 15 through a bus 16.
The servo circuit 3 has
REFERENCES:
patent: 3860801 (1975-01-01), Hunkar
patent: 4094940 (1978-06-01), Hold
patent: 4326255 (1982-04-01), Fujita
patent: 4601653 (1986-07-01), Inaba
patent: 4695237 (1987-09-01), Inaba
Fanuc Ltd.
Ro Bentsu
LandOfFree
Metering method of injection molding machine does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Metering method of injection molding machine, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Metering method of injection molding machine will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-527293