Closed Loop Control for an Injection Unit
A method is provided for improving melt quality in an injection unit. A closed loop control system regulates operation of the injection unit in accordance with a reference value for at least one operating parameter. A sensor measures the present value of a load upon the motor which drives an injection screw during operation of the injection unit. A processor compares the present value of the load to a reference value for the load. If the present value of the load deviates from the reference value of the load by more than a predetermined amount, then the processor adjusting the reference value of the at least one operating parameter. Operating parameters can include barrel temperature, back pressure and screw RPMs.
1 . A method for improving melt quality in an injection unit, comprising:
regulating operation of the injection unit in accordance with a reference value for at least one operating parameter;
measuring a present value of a load upon a motor operable to rotate an injection screw during operation of the injection unit;
comparing the present value of the load to a reference value for the load; and
if the present value of the load deviates from the reference value of the load by more than a predetermined amount, then adjusting the reference value of the at least one operating parameter.
2 . The method of claim 1 , wherein the at least one operating parameter includes barrel temperature.
3 . The method of claim 1 , wherein the at least one operating parameter includes injection back pressure.
4 . The method of claim 1 , wherein the at least one operating parameter includes rotational speed of the injection screw.
5 . The method of claims 2 to 4 , wherein the reference value of the at least one operating parameter is bound between a minimum value and a maximum value.
6 . The method of claim 5 , wherein the at least one operating parameter comprises at least two operating parameters.
7 . The method of claim 6 , wherein the reference value of one of the at least two operating parameters is adjusted and the present value of the load is re-measured prior to adjusting the reference value of another of the at least two operating parameters.
8 . The method of claim 7 , wherein more than one of the at least two operating parameters is adjusted simultaneously.
9 . The method of claim 6 , wherein at least one of the reference value for the load, the minimum value for the load, the maximum value for the load, the reference value for the at least one operating parameter, the minimum value for the at least one operating parameter, and the maximum value for the at least one operating parameter is set by an operator using a human-machine interface.
11 . The method of claim 6 , wherein at least one of the reference value for the load, the minimum value for the load, the maximum value for the load, the reference value for the at least one operating parameter, the minimum value for the at least one operating parameter, and the maximum value for the at least one operating parameter is provided by a database.
12 . The method of claim 11 , wherein the value of any of the at least one of the reference value for the load, the minimum value for the load, the maximum value for the load, the reference value for the at least one operating parameter, the minimum value for the at least one operating parameter, and the maximum value for the at least one operating parameter provided by the database is based upon which material is being processed by the injection unit.
13 . The method of claim 2 , wherein the load on the motor is measured by determining the torque output of the motor.
14 . The method of claim 2 , wherein the load on the motor is measured by determined current drawn by the motor.
15 . The method of claim 1 , wherein regulating operation of the injection unit in accordance with the reference value for the at least one operating parameter includes using closed loop control for the at least one operating parameter.
16 . The method of claim 1 , wherein regulating operation of the injection unit in accordance with the reference value for the at least one operating parameter includes using open loop control for the at least one operating parameter.
17 . An injection unit, operable to:
regulate its operation in accordance with a reference value for at least one operating parameter;
measure a present value of a load upon a motor operable to rotate an injection screw during the operation of the injection unit;
compare the present value of the load to a reference value for the load; and
if the present value of the load deviates from the reference value of the load by more than a predetermined amount, then adjust the reference value of the at least one operating parameter.
18 . The injection unit of claim 17 , wherein the at least one operating parameter includes barrel temperature.
19 . The injection unit of claim 17 , wherein the at least one operating parameter includes injection back pressure.
20 . The injection unit of claim 17 , wherein the at least one operating parameter includes rotational speed of the injection screw.
21 . The injection unit of claims 18 to 20 , wherein the reference value of the at least one operating parameter is bound between a minimum value and a maximum value.
22 . The injection unit of claim 21 , wherein the at least one operating parameter comprises at least two operating parameters.
23 . The injection unit of claim 22 , wherein the reference value of one of the at least two operating parameters is adjusted and the present value of the load is re-measured prior to adjusting the reference value of another of the at least two operating parameters.
24 . The injection unit of claim 22 , wherein more than one of the at least two operating parameters is adjusted simultaneously.
25 . The injection unit of claim 23 , wherein at least one of the reference value for the load, the minimum value for the load, the maximum value for the load, the reference value for the at least one operating parameter, the minimum value for the at least one operating parameter, and the maximum value for the at least one operating parameter is set by an operator using a human-machine interface.
26 . The injection unit of claim 23 , wherein at least one of the reference value for the load, the minimum value for the load, the maximum value for the load, the reference value for the at least one operating parameter, the minimum value for the at least one operating parameter, and the maximum value for the at least one operating parameter is provided by a database.
27 . The injection unit of claim 26 , wherein the value of any of the at least one of the reference value for the load, the minimum value for the load, the maximum value for the load, the reference value for the at least one operating parameter, the minimum value for the at least one operating parameter, and the maximum value for the at least one operating parameter provided by the database is based upon which material is being processed by the injection unit.
28 . The injection unit of claim 18 , wherein the load on the motor is measured by determining the torque output of the motor.
29 . The injection unit of claim 18 , wherein the load on the motor is measured by determining current drawn by the motor.
30 . The injection unit of claim 17 , wherein regulating operation of the injection unit in accordance with the reference value for the at least one operating parameter includes using closed loop control for the at least one operating parameter.
31 . The injection unit of claim 17 , wherein regulating operation of the injection unit in accordance with the reference value for the at least one operating parameter includes using open loop control for the at least one operating parameter.