Method for controlling measurement in injection molding machine, and injection molding machine

Abstract

A method for controlling measurement in a motor-driven in-line screw type injection molding machine using servo-motors as a measurement driving source and an injection driving source. Control is made so that all of a measured value of back pressure controlled by the measurement servo-motor, a measured value of an astern speed of a screw controlled by the injection servo-motor, and a measured rotational speed of the screw turn zero concurrently at timing when the screw reaches a measurement completion position. Thus, suck-back can be made dispensable.

1 . A method for controlling measurement in an in-line screw type injection molding machine using servo-motors as a measurement driving source and an injection driving source, said method comprising the steps of: 
 controlling driving of said measurement servo-motor by open control with a constant set rotational velocity of a screw and controlling driving of said injection servo-motor by back pressure feedback control in which an astern speed of said screw is controlled to follow a set value of back pressure set in advance, in a period between a measurement start position and a measurement control changeover position on a measuring stroke; and    controlling driving of said injection servo-motor by open control following an astern speed setting pattern and controlling driving of said measurement servo-motor by back pressure feedback control in which said rotational velocity of said screw is controlled, in a period between said measurement control changeover position and a measurement completion position;    wherein control is made so that all of a measured value of said back pressure controlled by said measurement servo-motor, a measured value of said astern speed of said screw controlled by said injection servo-motor, and a measured rotational speed of said screw turn zero concurrently at timing when said screw reaches said measurement completion position.    
     
     
         2 . A method for controlling measurement in an in-line screw type injection molding machine according to  claim 1 , wherein: 
 in said period between said measurement control changeover position and said measurement completion position, driving of said injection servo-motor is controlled by open control following an astern speed setting pattern having a region of a constant astern speed calculated from a measured astern speed in a position short of said measurement control changeover position, while driving of said measurement servo-motor is controlled initially by back pressure feedback control in which said rotational velocity of said screw is controlled to follow said set back pressure value set in advance, and next controlled by back pressure feedback control in which said rotational velocity of said screw is controlled to follow a back pressure decompression setting pattern calculated into a value proportional to a deceleration pattern in said astern speed setting pattern for said open control; and    said deceleration pattern between a position where said astern speed is constant and a position where said astern speed is zero in said astern speed setting pattern between said measurement control changeover position and said measurement completion position is set so that said position where said astern speed is zero coincides with only said measurement completion position, and a position where a rotation number is zero in a deceleration pattern of a measured rotational speed of said screw with respect to a time axis coincides with only timing when said screw reaches said measurement completion position.    
     
     
         3 . An in-line screw type injection molding machine using servo-motors as a measurement driving source and an injection driving source, comprising: 
 means for controlling driving of said measurement servo-motor by open control with a constant set rotational velocity of a screw and controlling driving of said injection servo-motor by back pressure feedback control in which an astern speed of said screw is controlled to follow a set value of back pressure set in advance, in a period between a measurement start position and a measurement control changeover position on a measuring stroke;    means for controlling driving of said injection servo-motor by open control following an astern speed setting pattern and controlling driving of said measurement servo-motor by back pressure feedback control in which said rotational velocity of said screw is controlled, in a period between said measurement control changeover position and a measurement completion position;    wherein control is made so that all of a measured value of said back pressure controlled by said measurement servo-motor, a measured value of said astern speed of said screw controlled by said injection servo-motor, and a measured rotational speed of said screw turn zero concurrently at timing when said screw reaches said measurement completion position.