Apparatus for controlling a plastic extruder

In an extruder apparatus having a barrel including a rotatable screw for moving extrusion material from an inlet to an outlet of the barrel and means for controlling the temperature of the extrusion material in response to temperature control signals, a temperature control signals generating means comprising:

• means for generating a signal representing the actual melt temperature of the extrusion material adjacent the barrel outlet;
• means for generating a melt temperature set point signal;
• means for generating a melt temperature error signal representing the difference between said actual melt temperature signal and said melt temperature set point signal;
• a first controller means responsive to said melt temperature set point signal for generating a first melt temperature control signal;
• a second controller means responsive to said melt temperature error signal and said first melt temperature control signal for generating a second melt temperature control signal;
• a third controller means responsive to said second melt temperature control signal for generating a first zone temperature control signal;
• means for generating a signal representing the actual temperature of the extrusion material at a zone along the barrel;
• means for generating a zone temperature error signal representing the difference between said second melt temperature control signal and said actual zone temperature signal;
• and
• a fourth controller means responsive to said zone temperature error signal and said first zone temperature control signal for generating a second zone temperature control signal as one of the temperature control signals whereby said zone temperature is controlled to maintain said actual melt temperature at said melt temperature set point.

In an extruder apparatus having a barrel including a rotatable screw for moving extrusion material from an inlet to an outlet of the barrel, means for controlling the speed of the screw in response to a speed control signal, and means for controlling the melt temperature of the material in response to a temperature control signal, a control means comprising:

• means for generating a signal representing the actual melt pressure of the extrusion material;
• means for generating a melt pressure set point signal;
• means responsive to said actual melt pressure signal and said melt pressure set point signal for generating a melt pressure control signal;
• means for generating a signal representing the actual melt temperature of the extrusion material;
• means for generating a melt temperature set point signal;
• means responsive to said actual melt temperature signal and said melt temperature set point signal for generating a melt temperature control signal;
• means responsive to said melt pressure control signal and said melt temperature control signal for generating the speed control signal;
• and
• means responsive to said melt temperature control signal and said melt pressure control signal for generating the temperature control signal.

In an extruder apparatus having a barrel including a rotatable screw for moving extrusion material from an inlet to an outlet of the barrel and through a die attached to the barrel at the outlet;

• means for controlling the speed of the extruder screw in response to a speed control signal;
• at least one temperature controlling means individual to a zone defined along the barrel being responsive to a zone temperature control signal for controlling the temperature in the respective zone;
• means for generating a signal representing the actual melt pressure of the extrusion material adjacent the barrel outlet;
• means for generating a melt pressure set point signal;
• means responsive to the actual melt pressure signal and the melt pressure set point signal for generating the speed control signal;
• means for generating a signal representing actual temperature in the zone;
• means for generating a zone temperature set point signal and means responsive to the actual zone temperature signal and the zone temperature set point signal for generating the zone temperature control signal, the zone temperature control signal generating means comprising:
• a zone temperature feedforward controller responsive to the zone temperature set point signal for generating an output signal;
• means for generating a zone temperature error signal representing the difference between the zone temperature set point signal and the actual zone temperature signal;
• and
• a zone temperature feedback controller responsive to said feedforward controller output signal and said error signal for generating the zone temperature control signal.