Controller for injection molding machine

• US 3,893,792 A
• Filed: 04/06/1973
• Issued: 07/08/1975
• Est. Priority Date: 04/06/1973
• Status: Expired due to Term

• Current Assignee: Dynisco, Inc. (Roper Technologies, Inc.)
• Original Assignee: Frank Laczko
• Inventors: Laczko, Frank
• Primary Examiner(s): Annear, R. Spencer
• Application Number:
  US05/348,614
• Time in Patent Office: 823 Days
• Field of Search: 425/149 164/4,155 264/40
• US Class Current: 425/149
• CPC Class Codes: B29C 35/0288 Controlling heating or curing of polymers during moulding, e.g. by measuring temperatures or properties of the polymer and regulating the process controlling or regulating chemical, physical or physico- chemical processes in general B01J19/0006
• CPC Class Codes: B29C 45/7646 viscosity
• CPC Class Codes: B29C 45/768 Detecting defective moulding conditions B29C45/84 takes precedence

Abstract

In an injection molding machine there is provided control circuitry for monitoring a number of predetermined process conditions for controlling the quality and consistency of injection molded articles. The system comprises a hydraulic pressure transducer and a cavity pressure transducer employed in concert with the control circuitry which monitors the viscosity of the article presently being formed, provides a corrective adjustment during the present cycle when the measured viscosity deviates from a reference viscosity, compares the applied hydraulic pressure with a hydraulic reference pressure, and measuring the peak cavity pressure during one cycle in order to control the applied pressure during the subsequent cycle as a function of the previously measured peak cavity pressure.

Claims

1. For an injection molding machine having a mold defining a cavity for receiving a plasticized material to form an article during a cycle of operation of the machine, a controller comprising;

variable pressure applying means for forcing the material into the cavity, means associated with the variable pressure applying means for sensing applied pressure, transducer means in or proximate said cavity for sensing cavity pressure, means responsive to the applied and cavity pressures for establishing a time reference viscosity signal, means for establishing a viscosity error signal during an initial portion of the cycle when the time reference viscosity signal deviates from a predetermined reference signal, and means responsive to said viscosity error signal for operating the pressure applying means at a new pressure level during the remainder of the cycle.

2. The controller of claim 1 wherein said means for providing a viscosity error signal comprises means coupled from said applied pressure sensing means for establishing a first circuit condition when the applied pressure reaches a predetermined threshold level, and means coupled from said cavity pressure sensing means for establishing a second circuit condition when the cavity pressure reaches a predetermined threshold level.

3. The controller of claim 2 comprising timer means responsive to said means for establishing the first and second circuit conditions, said timer means defining an output time interval representative of the time difference between the establishing of the first and second circuit conditions. 4. The controller of claim 3 wherein said timer means has an output voltage, upon establishment of said second circuit condition, that is a function of said time difference.

5. The controller of claim 2 wherein each means for establishing a circuit condition includes a digital comparator having one fixed threshold input.

6. The controller of claim 4 comprising means for comparing the output of said timer means with a viscosity reference level to provide said viscosity index error signal.

7. The controller of claim 6 wherein said means for comparing inclues an analog comparator.

8. For an injection molding machine having a mold defining a cavity for receiving a plasticized material to form an article during a cycle of operation of the machine, a controller comprising;

variable pressure applying means for forcing the material into the cavity, means for sensing applied pressure, means for sensing cavity pressure, means responsive to the applied and cavity pressures for establishing a time reference viscosity signal, means for establishing a viscosity error signal during an initial portion of the cycle when the time reference viscosity signal deviates from a predetermined reference signal, means for providing an applied pressure error signal when the applied pressure deviates from a predetermined reference pressure, and means responsive to said viscosity error signal for controlling the applied pressure during the remainder of the cycle.

9. The controller of claim 8 wherein said means for providing an applied pressure error signal includes means coupled from said applied pressure sensing means for comparing the signal therefrom with a pressure reference threshold.

10. The controller of claim 9 including means for inhibiting the applied pressure error signal during the initial portion of the cycle.

11. The controller of claim 10 wherein said means for providing a viscosity error signal comprises means coupled from said cavity pressure sensing means for determining when the cavity pressure reaches a predetermined value to generate an enabling signal, said enabling signal being present only when said predetermined value is attained.

12. The controller of claim 8 comprising means for summing said applied pressure error signal and viscosity error signal to provide a summed error signal.

13. The controller of claim 12 comprising means coupled from said means for sensing cavity pressure for registering the peak cavity pressure during the operating cycle.

14. The controller of claim 13 comprising means for providing a peak cavity pressure error signal when the measured peak cavity pressure deviates from a predetermined peak cavity reference pressure.

15. The controller of claim 14 comprising means for modifying said summed error signal by a cumulative peak cavity pressure error signal to provide a modified error signal.

16. The controller of claim 15 wherein said modifying means comprising a register for storing a code representative of the peak cavity error signal and means responsive to said code for altering in a subsequent cycle summed error signal as a function of said peak cavity error signal.

17. For an injection molding machine having a mold defining a cavity for receiving a plasticized material to form an article during a cycle of operation of the machine, a controller comprising;

means for applying pressure to force the material into the mold cavity, means for sensing applied pressure and providing a signal representative of applied pressure, means for sensing cavity pressure and providing a signal representative of cavity pressure, means responsive to said applied pressure signal and said cavity pressure signal for providing a signal representative of the viscosity of the material, means responsive to said viscosity signal deviating from a predetermined reference signal during an initial portion of the cycle for establishing a viscosity error signal, means responsiVe to said applied pressure signal deviating from a predetermined reference signal for establishing an applied pressure error signal, means for combining said viscosity error signal and said applied pressure error signal, and means responsive to said combining means for controlling the pressure applied during the remainder of the cycle.

18. The controller of claim 17 including means for inhibiting the means for establishing an applied pressure error signal until the cavity pressure signal has reached a predetermined level.

19. The controller of claim 17 comprising means responsive to said cavity pressure signal for registering the peak cavity pressure during the operating cycle.

20. The controller of claim 19 comprising means for providing a peak cavity pressure error signal when the measured peak cavity pressure deviates from a predetermined peak cavity reference pressure.

21. The controller of claim 20 comprising means for modifying the combined error signal by a cumulative peak cavity pressure error signal.

22. For an injection molding machine having a mold defining a cavity for receiving a plasticized material to form an article during a cycle of operation of the machine, a controller comprising;

means responsive to applied pressure and cavity pressure during an initial portion of the operating cycle for providing a signal representative of the viscosity of the material, means responsive to said viscosity signal deviating from a predetermined reference signal during an initial portion of the cycle for establishing a viscosity error signal, means responsive to the applied pressure deviating from a predetermined value for establishing an applied pressure error signal, and means responsive to one or both of said viscosity error signal and applied pressure error signal for controlling the pressure applied during the remainder of the cycle.

23. For an injection molding machine having a mold defining a cavity for receiving a plasticized material to form an article during a cycle of operation of the machine, apparatus for controlling the consistency and quality of the articles, said apparatus comprising, means for applying pressure to force the material into the mold cavity, means for sensing applied pressure and providing a signal representative of applied pressure, means for sensing cavity pressure and providing a signal representative of cavity pressure, means coupled from said means for sensing applied pressure for providing an applied pressure error signal when the applied pressure deviates from a predetermined reference pressure, means coupled from said means for sensing cavity pressure responsive to cavity pressure and coupled to said means for providing an applied pressure error signal for enabling the applied pressure error signal but only after the cavity pressure reaches a predetermined value, and feedback means responsive to said applied pressure error signal for controlling said means for applying pressure.

24. For an injection molding machine having a mold defining a cavity for receiving a plasticized material to form an article during a cycle of operation of the machine, a controller comprising;

means responsive to applied pressure and cavity pressure during an initial portion of the operating cycle for providing a signal representative of the viscosity of the material, means responsive to said viscosity signal deviating from a predetermined reference signal during the initial portion of the cycle for establishing a viscosity error signal, means for detecting the peak cavity pressure and providing a peak cavity pressure error when the peak pressure deviates from a reference pressure, logic means for modifying said viscosity error signal by the peak cavity pressure error signal to provide a modified error signal, and means responsive to said modified error signal for controlling the pressure applied during the remainder of the cycle.