Clamp control for injection molding machine

In a control system using a programmable controller for an injection molding machine having a stationary mold member, a moving mold member, pump means for moving said moving mold member into contact with said stationary mold member, said controller evaluating a first set of equations to generate an output signal controlling said pump means in response to a continuously generated sensor signal from a sensor indicative of the position of said moving mold member whereby the speed of said moving mold member is reduced when said moving mold member reaches a first crossover position set by a command signal, the improvement comprising:

• buffer means for storing said sensor signal as a plurality of sensor signals, each sensor signal corresponding to the position of said moving mold member at selected time intervals;
• finite impulse response filter means for establishing a predictive sensor signal at a set time in advance of the current position of said moving mold member by periodically evaluating a plurality of said sensor signals to determine the current speed of said moving mold;
• comparing means for comparing said predictive sensor signal to said command signal to indicate a state of comparison;
• and
• means for transmitting said predictive sensor signal to said controller when said comparing means senses a change in the status of said state of comparison indicative of when said moving mold member reaches said crossover position at said set advance time whereby said moving mold member changes speed when said moving mold member physically reaches said first crossover position without substantial overtravel.

A control system regulating at least one output device by an output signal produced in response to a sensor sensing measurements indicative of when an actual event programmed into a programmable controller as a command signal occurs, said sensor generating prior sensor signals before said actual event occurs and an actuating sensor signal when said actual event occurs, said control system comprising:

• said programmable controller periodically evaluating a first set of normal equations to produce at least said output signal in response to said actuating sensor signal;
• FIR means for establishing a predictive sensor signal indicative of the occurrence of said event prior to the time said actuating sensor signal is generated by periodically evaluating a second set of equations utilizing certain prior sensor signals;
• means comparing said predictive sensor signal with one of i) said prior sensor signals and ii) said command signal to determine a state of comparison;
• and
• transmitting means actuated when said comparing means indicates a change in the state of comparison to transmit said predictive sensor signal as said actuating signal to said programmable controller at a set time prior to the occurrence of said actual event which substantially coincides with the time expended by said programmable controller in evaluating said first set of equations whereby the response latency of said controller is substantially eliminated.

A method for controlling the molding cycle of an injection molding machine comprising the steps of:

• a. sensing a plurality of events occurring during a molding cycle and generating sensor signals for said events, at least one specific sensor signal continuously generated before and during a specific event by a continuous sensor;
• b. inputting said sensor signals and command signals which define said events into a programmable controller;
• c. periodically evaluating a set of normal equations during a scan time of said programmable controller to produce at least a first output signal for a specific physical device associated with said molding machine for controlling a portion of said molding cycle affected by said specific event;
• d. periodically evaluating a second set of equations utilizing said specific sensor signals to produce a predictive sensor signal indicative of an event estimated to occur at a future set time in place of said specific sensor signal;
• e. comparing said predictive sensor signal with a command signal indicative of said specific event;
• and
• f. transmitting to said programmable controller said predictive sensor signal, when a change in the status of comparison has occurred in step (e), at said set time prior to the occurrence of said specific event to cause said controller to generate said first output signal at the time said specific event occurs.

A method for controlling a molding cycle in which mold members are closed, molding material injected into the closed mold, recovered and the mold is opened whereat the molded part is ejected, said method comprising the steps of:

• generating at least one input sensor signal;
• periodically evaluating a first set of normal equations indicative of any given state of said molding cycle by a programmable controller scanning said first set of normal equations to develop, at the completion of a scan, at least one output signal resulting from said input sensor signal;
• said output signal causing said programmer to stop evaluating said first set of normal equations and to start evaluating a second set of normal equations indicative of a successive state of said molding cycle;
• and
• during said successive state and prior to starting the scan of said second set of equations by said programmable controller, reading said output signal out to control said output device.