US 5,997,778 A · Auto-tuned, adaptive process controlled, injection molding machine

Abstract

An injection molding machine uses a summed, multi-term control law to control ram velocity during the injection stroke of a molding cycle to emulate a user set velocity profile. An automatic calibration method sets no load ram speeds to duplicate user set ram speeds. Finite impulse response filters produce open loop, no load control signals at advanced positions on the velocity profile to account for lag in system response. An adaptive, error term indicative of load disturbance, observed from a preceding cycle is added at the advanced travel position predicted by the finite impulse response filter to produce a predictive open loop, load compensated control signal. Finally, an auto tuned PID controller develops a real time, feedback load disturbance signal summed with the open loop control signal to produce a drive signal for the machine's proportioning valve.

Claims35

Dependent claims

A method for controlling the speed of a ram in an injection molding machine during the injection step of the molding cycle after the operator has set a plurality of velocity set points, said method comprising the steps of:

a. machine generating a second, larger plurality of set point signals from said operator set points, each set point signal indicative of a set ram velocity at a set ram travel position in a sequence defining a velocity profile said ram is to emulate during said injection step;
b. automatically adjusting selected set point signals for processing by a machine generated calibrated factor so that any selected set point signal of a given speed will cause said ram to move at approximately the same speed when the machine is not under load;
c. modifying the selected set point signals to account for the load imposed on the machine by the molding material being injected to produce velocity control signals at set ram positions corresponding to said velocity profile;
and
d. applying said control signals as a drive signal to the machine for controlling the speed of the ram.

2 more elements

A system for variably controlling the speed of the ram of an injection molding machine during the injection stroke of a molding cycle comprising:

means for selecting a plurality of user set points specifying set ram velocities at set ram travel positions which said ram is to achieve during said injection stroke,
means for automatically establishing a second larger plurality of machine set point signals from said user set points indicative of set ram velocities at set tram travel positions and defining a locus of set travel and velocity points in turn defining a velocity profile which said ram is to emulate during said injection stroke;
means for determining a load compensated velocity control signal for each machine set point signal at a set time during the injection stroke, said determining means including means for sensing the real time position of said ram during said injection stroke and means for applying an automatically established calibrated factor to each set point signal causing said ram to move at approximately the speed of a set point signal when the machine is not under load;
means to apply said velocity control signals as a variable drive signal to said machine to cause said ram to variably move during said injection stroke at speeds corresponding to said velocity profile.

1 more element

A system for variably controlling the speed of the ram of an injection molding machine during the injection stroke of a molding cycle comprising:

means for selecting a plurality of user set points specifying desired ram velocities at specified ram travel positions,
means for automatically establishing, from said user at points a second larger plurality of set point signals indicative of a user set velocity profile having a plurality of set ram speeds at set ram travel positions which said ram is to emulate during said injection stroke;
means to modify said set point signals selected from said velocity profile at specified ram positions to produce velocity control signals;
said means to modify including predictive means for selecting set point signals at advanced ram travel positions which have not been traversed at the time the set point signal is selected for precessing as said velocity control signal, said selected set point signals being predictive control signals;
and
means to apply said velocity control signals as a drive signal to said machine to cause said ram to variably move during said injection stroke at speeds corresponding to said velocity profile.

3 more elements

Dependencies are inferred from the claim text.

Auto-tuned, adaptive process controlled, injection molding machine

Life of this patent

Auto-tuned, adaptive process controlled, injection molding machine

Life of this patent

Abstract

Claims35