US 2004/0071809 A1 · Force detecting controlling device of a screw for an injection molding machine

Abstract

The present invention is a force detecting controlling device of a screw for an injection molding machine, which adopts a load cell to be as a force sensor for injection, holding pressure and back pressure. The load cell arranged on a rear fixed plate directly detects a force applied onto a ball screw nut. Because the ball screw nut is fastened on the load cell, and the load cell is fixed on the rear fixed plate, further, force on a ball screw is directly transmitted to the ball screw nut, therefore, a total value of the force on the ball screw, force produced by back pressure and friction among mechanical parts are equal to a force value of the ball screw nut applying onto the load cell. To accurately control the injection pressure is the basic requirement for precision injection, that is, the injection force may be very truthful. To avoid that the friction among mechanical parts becomes a key reason of a setting injection force not equal to a detected injection force, to compensate instantly to the ball screw is really necessary. Hence, to detect the injection force via the load cell for instant compensation can reach a close loop control; procedures of holding pressure and back pressure are specifically controlled as well.

Claims20

Dependent claims

A force detecting controlling device of a screw for an injection molding machine, which being installed on an injection unit, the injection unit comprising:

at least one front fixed plate having a penetrating hole center of the front fixed plate;
at least one rear fixed plate installed parallel to front fixed plate, and a center of the rear fixed plate having another penetrating hole to contain a force detecting component and a ball screw nut;
at least two guiding rods installed between front fixed plate and rear fixed plate, and the two guiding rods being parallel each other;
a moving plate being capable of sliding on two guiding rods and, a side of the moving p late connecting to a screw via a metering driving device and another side connecting to a ball screw via an injection driving device;
a force detecting component as a load cell which outside ring fixed on the rear fixed plate by a set of bolts, and an inner ring of the load cell fixed on a ball screw nut by another set of bolts;
wherein the injection driving device rotates said ball screw relative to the ball screw nut fixed on said force detecting component and drives said moving plate and said screw reciprocating in the injection and holding process;
besides the metering driving device drives said screw rotating in the metering process.

4 more elements

A force detecting controlling method of a screw for an injection molding machine comprising:

(a) initially receiving at least one related pre-setting parameter signal for injection, metering and other parameters of an injection molding machine and at least one position signal for the screw captured by the screw position detecting device, continuously a position/force transformer outputs a pre-setting injection pressure signal;
(b) a value of the pre-setting injection pressure signal and a first detecting value output from a load cell are imported into a comparator simultaneously;
(c) the comparator computes a difference between the value for the pre-setting injection pressure signal and the detecting value, and outputs the difference to a controller;
(d) the controller outputs a compensation signal to an injection servomotor to adjust an output injection force from the injection servomotor;
(e) while the injection servomotor driving the injection screw to move forward or back, the load cell detects a second detecting value compensated by the injection servomotor, if the second detecting value differs with the value of the pre-setting injection pressure signal, steps (b) to (d) are repeated to continuously amend forces output from the injection servomotor, after a force value accepted by the load cell being equal to the value of the pre-setting injection pressure signal, an execution of a closed loop control of the injection screw is completed.

2 more elements

Dependencies are inferred from the claim text.

Force detecting controlling device of a screw for an injection molding machine

Life of this patent

Force detecting controlling device of a screw for an injection molding machine

Life of this patent

Abstract

Claims20