Injection molding apparatus control system and method of injection molding
First Claim
1. A process for molding patterns or parts from a fluid molding material using an injection molding apparatus having a source of fluid molding material and an injection ram acting to force said fluid molding material into a molding die under pressure, and a control means for initiating and controlling an injection cycle of said injection molding apparatus, comprising the steps of:
- 1) storing a die recipe in at least one memory means associated with a programmable logic controller forming a part of said control means, said die recipe defining an injection cycle for a particular molding die to be used in the injection molding process, wherein said die recipe includes predetermined values of variable process parameters of said injection cycle,2) selecting a die recipe corresponding to a particular molding die from said memory means, wherein said die recipe is downloaded into said control means with said predetermined values of said variable process parameters being utilized by said programmable logic controller to generate control signals representative of desired values of said variable process parameters,3) initiating an injection cycle wherein operation signals indicative of the actual values of said variable process parameters will be supplied to said control means, and4) controlling said injection cycle by regulating the injection of said fluid molding material with said operation signals being driven toward equilibrium with said control signals such that said variable process parameters of said injection cycle simulate the predetermined values of said die recipe.
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Abstract
There is shown an injection molding apparatus, which comprises a source of a fluid molding material and a molding die into which the molding material is forced under pressure. The apparatus includes a control means for initiating and controlling an injection cycle in which the fluid molding material is injected into the molding die in a particular and predetermined manner. The control means generally comprises a programmable logic controller (PLC) which is programmed to receive signals from sensors adapted to sense variable parameters of the injection cycle. The PLC is programmed to generate control signals based upon the signals from the sensors so as to control the variable parameters of the injection cycle. The output control signals of the PLC are coupled through an interface circuit to a servo-control circuit which in turn is operatively coupled to control various parameters of the injection cycle. The control system allows the user to pre-set multiple flow rates to accomplish desired acceleration/deceleration characteristics during the injection cycle so as to optimize fabrication of high quality patterns while reducing scrap patterns. The control system may also be implemented to prevent a machine operator from making unauthorized changes of injection parameters to assure the integrity of injection parameters on a continuous basis. The use of a high level PLC also enables generation and collection of data relevant to the injection processes to visually monitor the process dynamic parameters, to display an injection profile with tolerances, to facilitate diagnostics as well as other valuable functions.
79 Citations
28 Claims
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1. A process for molding patterns or parts from a fluid molding material using an injection molding apparatus having a source of fluid molding material and an injection ram acting to force said fluid molding material into a molding die under pressure, and a control means for initiating and controlling an injection cycle of said injection molding apparatus, comprising the steps of:
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1) storing a die recipe in at least one memory means associated with a programmable logic controller forming a part of said control means, said die recipe defining an injection cycle for a particular molding die to be used in the injection molding process, wherein said die recipe includes predetermined values of variable process parameters of said injection cycle, 2) selecting a die recipe corresponding to a particular molding die from said memory means, wherein said die recipe is downloaded into said control means with said predetermined values of said variable process parameters being utilized by said programmable logic controller to generate control signals representative of desired values of said variable process parameters, 3) initiating an injection cycle wherein operation signals indicative of the actual values of said variable process parameters will be supplied to said control means, and 4) controlling said injection cycle by regulating the injection of said fluid molding material with said operation signals being driven toward equilibrium with said control signals such that said variable process parameters of said injection cycle simulate the predetermined values of said die recipe.
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- 2. An injection molding apparatus, comprising a source of a fluid molding material and a molding die into which said fluid molding material is forced under pressure by means of a moveable ram during an injection cycle, control means for initiating, monitoring and controlling said injection cycle, said control means comprising a programmable logic controller, PLC, having memory means for storing selected values of a plurality of variable physical parameters associated with said injection cycle, said PLC generating control signals corresponding to said selected values of said variable physical parameters, said control means also including a servo-control circuit operating to control said variable physical parameters of said injection cycle and being coupled to said PLC by means of an interface circuit, wherein said servo-control circuit is supplied with operation signals corresponding to said variable physical parameters during said injection cycle and wherein said servo-control circuit receives at least in part said control signals generated from said PLC and to supply said operation signals to said PLC by means of said interface circuit, said servo-control circuit operating to continuously monitor and control said variable physical parameters during said injection cycle by means of said servo-control circuit which drives said operation signals toward equilibrium with said control signals to regulate the injection of said fluid molding material into said molding die.
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28. An investment pattern molding machine comprising a source of a fluid molding material and a moveable ram, wherein said fluid molding material is forced into a molding die by means of said moveable ram which is caused to move in fluid injection and fluid charging directions as part of an injection cycle, wherein flow of said fluid molding material into said molding die is controlled by movement of said ram in said fluid injection and charging directions, the movement of said ram being controlled by control means including a programmable logic controller, PLC, and a servo-control circuit coupled by means of an interface circuit, with said servo-control circuit acting to sense and control the movement of said ram and the pressure of said fluid molding material as generated by said moveable ram forcing said fluid molding material into said molding die,
said servo-control circuit being responsive to control signals developed by said PLC which is programmed with predetermined parameters correlating to a plurality of variable physical parameters associated with a predetermined injection cycle for a particular molding die to implement said predetermined injection cycle, wherein said control signals include a plurality of signals corresponding to movement of said ram in said fluid injection and charging directions, said plurality of signals implementing multiple flow rates and controlling acceleration or deceleration of the flow of said molding material during an injection cycle, and wherein, said variable physical parameters are continuously monitored and controlled by means of said servo-control circuit during said injection cycle.
Specification