In-Mold Non-Time Dependent Determination of Injection Molded Part Ejection Readiness

Abstract

Non-time dependent measured variables are used to effectively determine an optimal ejection time of a part from a mold cavity. A system and/or approach may first measure at least one non-time dependent variable during an injection molding cycle. The part is ready to be ejected from the mold upon the measured variable reaching a threshold value indicative of, for example, a part temperature dropping below an activation temperature.

What is claimed is: 
     
         1 . A non-time dependent injection molding system comprising:
 an injection molding machine comprising an injection unit and a mold forming a mold cavity, the injection unit adapted to receive and inject a molten plastic material into the mold cavity to form a molded part;   a controller adapted to control operation of the injection molding machine; and   one or more sensors coupled to the injection molding machine and the controller;   wherein at least one of the one or more sensors is adapted to measure a non-time dependent variable of the injection molding machine and transmit the measured non-time dependent variable to the controller, wherein the controller is adapted to determine whether the measured non-time dependent variable reaches a threshold value indicative of the molded part being structurally sound and is further adapted to cause the molded part to be ejected from the mold cavity upon the measured non-time dependent variable reaching the threshold value.   
     
     
         2 . The system of  claim 1 , wherein at least one of the one or more sensors is adapted to measure the non-time dependent variable at a location inside of the mold cavity. 
     
     
         3 . The system of  claim 1 , wherein at least one of the one or more sensors comprises a temperature sensor adapted to sense at least one of:
 a gate temperature value measured at a gate of the injection mold or mold cavity;   a cavity temperature value measured in the mold cavity; or   a rate of temperature change.   
     
     
         4 . The system of  claim 1 , wherein at least one of the one or more sensors comprises a strain sensor adapted to measure a strain value of the injection mold or mold cavity. 
     
     
         5 . The system of  claim 1 , wherein at least one of the one or more sensors comprises a hardness sensor adapted to measure a hardness value of at least a portion of the molded part. 
     
     
         6 . The system of  claim 1 , wherein at least one of the one or more sensors comprises an optical sensor adapted to measure an optical characteristic of at least a portion of the molded part. 
     
     
         7 . The system of  claim 1 , wherein at least one of the one or more sensors comprises a pressure sensor adapted to measure at least one of:
 a back pressure value of the injection molding unit;   a cavity pressure; or   a rate of pressure change.