OO control for injection molding machine

• US 20030090018A1
• Filed: 09/25/2002
• Published: 05/15/2003
• Est. Priority Date: 09/29/2001
• Status: Active Grant

• Current Assignee: Van Dorn Demag Corp. (Sumitomo Heavy Industries Limited)
• Original Assignee: Van Dorn Demag Corp. (Sumitomo Heavy Industries Limited)
• Inventors: Bulgrin, Thomas C.
• Granted Patent: US 7,031,800 B2
• Time in Patent Office: Days
• US Class Current: 264/40.1
• CPC Class Codes: B29C 2945/76006 Pressure
• CPC Class Codes: B29C 2945/76083 Position
• CPC Class Codes: B29C 2945/7612 rotational movement
• CPC Class Codes: B29C 2945/76187 screw
• CPC Class Codes: B29C 2945/76224 Closure or clamping unit
• CPC Class Codes: B29C 2945/76307 hydraulic fluids
• CPC Class Codes: B29C 2945/76498 Pressure
• CPC Class Codes: B29C 2945/76531 Temperature
• CPC Class Codes: B29C 2945/76595 Velocity
• CPC Class Codes: B29C 2945/76692 drive means
• CPC Class Codes: B29C 2945/76702 Closure or clamping device
• CPC Class Codes: B29C 2945/76866 Mould closing
• CPC Class Codes: B29C 2945/76872 Mould opening
• CPC Class Codes: B29C 2945/76933 The operating conditions are corrected immediately, during the same phase or cycle
• CPC Class Codes: B29C 45/76 Measuring, controlling or regulating measuring in general G01; controlling or regulating in general G05
• CPC Class Codes: B29C 45/766 the setting or resetting of moulding conditions, e.g. before starting a cycle
• CPC Class Codes: G05B 2219/34246 OOC object oriented control
• CPC Class Codes: G05B 2219/45244 Injection molding

Abstract

A plastic injection molding machine has an object oriented programmed routine to control the molding cycle of the machine. The programmed routine implements the inter-related molding cycle of clamp, inject, hold, eject and recover by development of classes corresponding to machine structure performing basic molding cycle steps. The basic classes use object oriented concepts of data encapsulation, inheritance, polymorphism, abstraction and the like that are linked together to produce objects during run time. The classes in turn include controller, observer and actuators classes. The controller class functions as a state machine. The observer class functions to determine the current state and the actuator class produces command signals controlling class related machine hardware. A modeling system is also disclosed for constructing the OO programmed routine for any injection molding machine using existing classes, principally by difference.

Claims

3-1. ) The molding machine of claim 2 wherein each aggregate class includes as components thereof a plurality of classes in a multi-level, parent-child hierarchical arrangement.

15. ) A method for controlling the operation of an injection molding machine having a screw axially translatable in a barrel by a screw injector to cause injection of a shot of melt into a mold and a clamp operable to open, close and clamp said mold contained therein by clamp hardware associated with said clamp, said method comprising the steps of:

generating an object oriented, computerized, programmed routine in source code controlling the sequence and implementation of injection and clamping functions of said machine by command signals produced during run time, said object oriented routine including i) a master sequence class defining behavior of said machine through the machine cycle in accordance with a machine control law, ii) a clamp class defining behavior and attributes of said clamp mechanism and owning a plurality of constituent classes and iii) a base screw injector class defining screw attributes and behavior of said screw during injection and owning a plurality of constituent classes;

instantiating said classes when said routine is run to produce from said source code at any instance i) a base clamp object having attributes and defining behavior of said clamp hardware and ii) a screw injector object having attributes and defining behavior of said screw hardware; and

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compiling and linking or interpreting or assembling said source code from said base clamp object and said screw inject object into object code processed by the microprocessor in said control system to produce command signals outputted by said system to actuators associated with said screw and said clamp and controlling the behavior thereof.

16. ) The method of claim 15 wherein said machine has a mechanism for rotating said screw and said program generates command signals controlling rotation of said screw and said method additionally includes the steps of providing an object oriented rotator class defining rotational screw attributes and behavior and instantiating said rotator class to produce from said source code a rotator object controlling rotational behavior of said screw.

17. ) The method of claim 16 wherein said machine has an eject mechanism for ejecting the molded part from the mold and said program generates command signals controlling the ejection mechanism, said method additionally includes the steps of providing an object oriented ejector class to produce from said source code an ejector object controlling behavior of said ejection mechanism.

18. ) The method of claim 17 wherein said machine has a die height mechanism for setting the die height of the mold halves in the mold held by said clamp and said program generates command signals controlling said die height mechanism, said method additionally includes the steps of providing a die height class to produce from said source code an object oriented die height object controlling behavior of said die height mechanism.

19. ) The method of claim 18 wherein at least one of said screw inject, clamp, rotate, eject and die height classes further includes as an aggregation and constituents thereof a controller class, an observer class and an actuator class with said controller class in relationship with at least said actuator class, and said observer class at least in relationship with said actuator class, and instantiating a) said controller class to produce a controller object indicating when a change in state or behavior of the machine element being controlled is to occur;

b) said observer class to produce at least one observer object indicative of the current state or behavior of the machine element being controlled by the object of said at least one of said classes; and

, c) said actuator class to produce at least one actuator object indicative of the command signal regulating the state or behavior of the machine component being controlled by said at least one of said classes.

20. ) The method of claim 19 wherein said controller object changes state prior to the time said state change is to occur on the machine hardware regulated by said controller.

21. ) In a plastic injection molding machine having hardware and associated actuators permitting said machine to mold parts in a sequenced cycle including clamp, inject, hold, recover and eject and having a microprocessor control system controlling the operation of said actuators to produce a molding cycle meeting set points established by an operator of said machine, said microprocessor control system including at least one controller regulating specific machine hardware to meet the set points for a sequence in the cycle, the improvement comprising:

said controller being programmed as an object-oriented programmed sequence having a controller class instantiated as a controller object with behavior transitioning from at least a first state to a second state in advance of the time a state transition is to occur and said controller class having attributes related to the hardware and machine actuator controlled by said controller.

22. ) The machine of claim 21 wherein said controller object is an aggregated object owning a plurality of constituent objects, each constituent object having behavior for preparing the transition of said controller object from one state to the other in advance of the time at which said transition occurs.

23. ) The machine of claim 22 wherein said object oriented program sequence further includes an actuator class in relationship to said controller class and instantiated to produce an actuator object controlling the behavior of said actuator regulated by said controller in accordance with state instructions from said controller object.

24. ) The machine of claim 23 wherein said object oriented program sequence further includes an observer class in relationship to at least said actuator class and instantiated to produce an observer object indicative of the behavior of the machine hardware and its associated actuator(s).

25. ) The machine of claim 24 wherein said observer class and said actuator classes are aggregations of a plurality of constituent classes, one of said constituent classes of said observer class including a digital filter class for producing, as an instance thereof, a digital filter object indicative of the current motion of the hardware being controlled by said controller.

26. ) A method for controlling molding of parts by an injection molding machine having hardware performing a sequence of clamp, inject, hold, recover and eject through a computerized control system having an operator station setting set points for the sequence and including at least one controller generating control signals for regulating performance of machine hardware through a machine actuator(s) for performing at least one of said sequences pursuant to sequence instructions received from said control system, said method comprising the steps of:

generating i) an object-oriented controller class having behavioral characteristics of said machine hardware performing one of said controlled sequences, said behavior characteristics including transitioning said controller from a first state to a second state and ii) an object oriented actuator class in relationship with said controller class and having behavioral characteristics indicative of move instructions for said machine actuator to implement for controlling said machine hardware performing one of said controlled sequences;

instantiating said controller class to produce a controller object and said actuator class to produce an actuator object, said controller object sending messages to said actuator object and said actuator object containing source code for generating move commands to its associated machine actuator(s); and

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compiling and linking or assembling or interpreting said source code to produce object code acted upon by said microprocessor to produce command signals for controlling said machine actuator(s) of said machine hardware performing one of said controlled sequences.

1. ) A plastic injection molding machine comprising:

a screw within a barrel and a screw injector mechanism for axially translating said screw within said barrel to inject a shot of melt into a mold;

a clamp containing a mold separable along a parting line and a clamp mechanism for opening, closing and clamping said mold within said clamp;

a computerized control system having an object-oriented program for controlling the operation of said clamp and translation of said screw during the molding cycle, said program including i) a clamp class corresponding to said clamp mechanism which, when instantiated, produces a composite clamp object effective to control said clamp and ii) a screw injector class corresponding to said screw injector mechanism which, when instantiated, produces a composite injector object effective to control the injection performed by said screw.

2. ) The molding machine of claim 1 wherein at least one of the classes is an aggregate class having a plurality of constituent classes.

3. ) The molding machine of claim 2 wherein each aggregate class is a child of a parent abstract class.

4. ) The molding machine of claim 1 wherein said machine further includes rotation hardware for rotating said screw and said control system further includes a rotator class effective to cause rotation of said screw when instantiated as a rotator object.

5. ) The molding machine of claim 4 wherein at least one of the classes is an aggregate class having a plurality of constituent classes.

6. ) The molding machine of claim 4 wherein said machine further includes ejector hardware for ejecting a molded part from said mold and said control system further includes an ejector class and an ejector object as an instance of said ejector class effective to cause ejection of said molded part.

7. ) The molding machine of claim 6 wherein at least one of the classes is an aggregate class having a plurality of constituent classes.

8. ) The molding machine of claim 6 wherein at least one of said injector, ejector, clamp and rotator classes include,

a) a controller class which when instantiated forms a controller object receiving instructions from a programmed sequence object and functioning as a state machine;

b) an observer class in a relationship with sensors on said machine such that when instantiated an observer object determines the current state of said machine; and

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c) an actuator class in relationship with at least said controller class generating as an instance thereof an actuator object for controlling an actuator associated with the related hardware of said at least one class.

9. ) The molding machine of claim 8 wherein said controller class is an aggregation of classes including a transition class, a compartment class and a state class, an instance of said state class being a state object indicative of the state of the machine component being controlled by objects of said actuator class, an instance of said transition class being a transition object indicative of an impending change in state of the machine component being controlled by objects of said actuator class and an instance of said compartment class being a compartment object indicative of the various states that the machine component can transition to.

10. ) The molding machine of claim 8 wherein said actuator class is an aggregation of a number of classes including a move class indicative of the motion of the machine component which is actuated.

11. ) The molding machine of claim 8 wherein said observer class is an aggregation of a number of classes including a sensor class and a digital filter class, an instance of said sensor class being a read object indicative of the state of a sensor monitoring an observed machine component, an instance of said digital filter class being a digital filter object linked to said read object indicative of the state of current or future motion of the machine component being observed.

12. ) The molding machine of claim 11 wherein said controller class is an aggregation of classes including a transition class, a compartment class and a state class, an instance of said state class being a state object indicative of the state of the machine component being controlled by objects of said actuator class, an instance of said transition class being a transition object indicative of an impending change in state of the machine component being controlled by objects of said actuator class and an instance of said compartment class being a compartment object indicative of the various states that the machine component can transition to.

13. ) The molding machine of claim 9 wherein said actuator class is an aggregation of a number of classes including a move class indicative of the motion of the machine component which is actuated.

14. ) The molding machine of claim 12 wherein said actuator class is an aggregation of a number of classes including a move class indicative of the motion of the machine component which is actuated.

27. ) The method of claim 26 wherein said generating step produces an aggregate controller class owning component classes having behavior that prepares said controller class to ready a transition from one state to another in advance of the actual time said transition is to occur.

28. ) The method of claim 26 further including the step of generating an observer class with behavior producing as an observer object a triggering signal indicative of the current state of the machine hardware being controlled by said controller object.

29. ) The method of claim 28 wherein said observer class is an aggregate observer class owning a plurality of constituent classes, one of said constituent observer classes including a digital filter class producing when said source code is run a digital filter object indicative of the current motion of the machine hardware being regulated by said controller class.

27-2. ) The modeling method of claim 26 further including the step of identifying a specific machine variant with its source code and storing the information in a machine project file for future use.

28-3. ) The modeling method of claim 27 wherein said additional classes added to said variant are related to the size of a desired machine if a subsystem for such machine size does not exist and includes limits of shot size, injection stroke and related matter used to program classes, by difference, whose behavioral function is affected by such parameters.

30. ) A modeling method for assembling source code into an object oriented programmed routine for controlling any specific injection molding machine having hardware actuators controlling hardware machine components performing an interrelated machine molding cycle of close, inject, hold, recover and eject pursuant to a general, sequence control law common to all injection molding machines, said method comprising the steps of:

a) building an object oriented class library collection by modeling as general classes therein a class corresponding to attributes and behavior of major machine components necessary to perform each step of said molding cycle including at least the general, abstract classes of a clamp class, an inject class, a rotate class and an eject class and relations therebetween;

specifying for each general class a plurality of more specific child classes, each child class inheriting the attributes and behavior of its parent class and adding thereto additional attributes and behavior more specific to different hardware components used in injection molding machines for performing the function controlled by said general abstract class and optionally specifying additional descendants until all different types of molding machine hardware performing the behavior of the realizable descendants have been modeled, principally by difference;

b) building a component library including i) a collection of primitive components corresponding to the assembled classes including usage relations, associations and aggregations for the realizable and selective abstract classes, ii) a subsystem collection of related primitive components is specified and iii) a machine variant component in which desired subsystems for a specific machine and making up the control system for a desired machine are selected; and

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c) adding additional objects of classes depending from classes in said subsystem for any specific machine, principally by difference, to account for any specific requirements of the specific machine not accounted for in the subsystem collection whereby any injection molding machine using existing hardware components can be programmed to produce a molding machine cycle.