Synchronized temperature contol of plastic processing equipment
View Patent ↗A system for processing plastic feed material includes a machine having a barrel and a screw that rotates in a repetitive cycle in the barrel. An induction winding encircles and extends along an outer surface of the barrel. A control system includes a controller that determines a duty cycle referenced to a length of the machine cycle in response to an error between a desired barrel temperature and a current barrel temperature. The controller electrically connects the power supply to the induction winding at least once during each cycle for a period whose length corresponds to the duty cycle.
1. An apparatus for processing plastic feed material comprising:
a machine that includes a barrel and a screw that rotates in the barrel during repetitive machine cycles;
an induction winding encircling and extending along an outer surface of the barrel; an electric power supply; and
a controller measuring a barrel temperature that synchronizes a heating cycle including having a supply of energy from the electric power supply to the induction winding with each machine cycle, and controls a magnitude of the electric power supplied during one of the machine cycles in response to a barrel temperature error.
2. The apparatus of claim 1 , wherein the controller is further configured to determine a duty cycle in response to the barrel temperature error comprising a difference between a desired barrel temperature and the barrel temperature.
3. The apparatus of claim 1 , wherein the controller is further configured to initiate said supply of electric energy to the induction winding at a beginning of the machine cycle.
4. The apparatus of claim 1 , wherein the controller is further configured to initiate said supply of electric energy to the induction winding while the screw is not rotating.
5. The apparatus of claim 1 , wherein the controller is further configured to initiate said supply of electric energy to the induction winding following a delay that begins when the screw begins to rotate.
6. The apparatus of claim 1 , wherein the controller is further configured to supply electric energy to the induction winding for a period during which the screw rotates.
7. The apparatus of claim 1 , wherein the controller is further configured to supply electric energy to the induction winding for a period during which feed material is injected into the barrel.
8. The apparatus of claim 1 , wherein the controller is further configured to:
determine a duty cycle in response to the barrel temperature error; and
initiate said supply of power to the induction winding for a period whose length corresponds to the duty cycle.
9. The apparatus of claim 1 , further comprising a thermal insulation that is interposed between the induction winding and the barrel.
10. The apparatus of claim 1 , further comprising:
a thermal insulation interposed between the induction winding and the barrel; and
a band heater extending along an outer surface of the barrel and located downstream from the induction winding.
11. The apparatus of claim 10 further comprising a second thermal insulation that covers the band heater.
12. A system for processing plastic feed material comprising:
a machine that includes a barrel and a screw that rotates in the barrel during at least a portion of a repetitive machine cycle;
an induction winding encircling and extending along an outer surface of the barrel;
an electric power supply; and
a controller that synchronizes a heating cycle including having a supply of electric energy from the electric power supply to the induction winding with a machine cycle, an initiation of said supply of power being delayed relative to a beginning of the machine cycle, and controls a magnitude of said power supplied during the machine cycle in response to a barrel temperature error.
13. The system of claim 12 , wherein the controller is further configured to initiate said supply of electric energy at a desired magnitude to the induction winding during a duty cycle which begins with the start of an interval of a mechanical operation of the machine cycle.
14. The system of claim 12 , wherein the controller is further configured to initiate said supply of electric energy to the induction winding at a beginning of an interval of operation that begins when the screw begins to rotate during the machine cycle.
15. The system of claim 12 , wherein the controller is further configured to initiate said supply of electric energy to the induction winding at a beginning of an interval that follows a delay that begins when the screw begins to rotate.
16. The system of claim 12 , wherein the controller is further configured to supply electric energy to the induction winding for a period during which the screw rotates.
17. The system of claim 12 , wherein the controller is further configured to supply electric energy to the induction winding while feed material is injected into the barrel.
18. The system of claim 12 , further comprising:
a thermal insulation interposed between the induction winding and the barrel; and
a band heater extending along an outer surface of the barrel and located downstream from the induction winding.
19. A method for controlling the application of electric power to an induction winding of a machine for processing plastic feed material that includes a barrel and a screw that rotates in a repetitive machine cycles in the barrel, comprising the steps of:
determining a barrel temperature error;
synchronizing a heating cycle including having a supply of electric energy from the electric power supply to the induction winding with each machine cycle; and
reducing the barrel temperature error by controlling a magnitude of said electric energy supplied during one of the machine cycles.
20. The method of claim 19 further comprising the step of:
initiating said supply of electric energy when the screw begins to rotate during the machine cycle.
21. The method of claim 19 further comprising the step of:
initiating said supply of electric energy following a delay period that begins when the screw begins to rotate during the machine cycle.
22. An apparatus for processing plastic feed material comprising:
a machine that includes a barrel and a screw that rotates in the barrel during repetitive machine cycles;
a heating element encircling and extending along an outer surface of the barrel;
an electric power supply; and
a control system operatively connected to the heating element, the power supply and the machine, and including a controller that synchronizes a heating cycle including having a supply of electric energy from the electric power supply to the heating element with a start of each of the machine cycles, and controls a magnitude of said electric energy supplied to the heating element during each machine cycle, said magnitude of electric energy varying with a barrel temperature error.
23. The apparatus of claim 22 , wherein the controller initiates said supply of electric energy to the heating element in-phase with the start of each machine cycle.
24. The apparatus of claim 22 , wherein the controller supplies said electric energy to the heating element during a period whose start is delayed relative to the start of each machine cycle.
25. The apparatus of claim 1 , wherein a magnitude of said electric energy supplied to the induction winding during a machine cycle varies with a magnitude of the barrel temperature error.