Individual cavity flow control methods and systems for co-injection molding

Abstract

Methods and systems for co-extruding multiple polymeric material flow streams into a mold having a plurality of cavities to produce a plurality of multi-layer polymeric articles each having a consistent coverage of an interior core layer are disclosed herein. In an example method, a flow rate of a first skin material into a cavity is individually controlled for each cavity before initiation of co-injection of a second core material into the cavity, which may address inconsistent interior core layer coverage for articles from different cavities.

1 - 6 . (canceled) 
     
     
         7 . A system for co-injection of multilayer plastic articles, the system comprising:
 a mold defining a plurality of cavities, each cavity corresponding to a resulting plastic article; a plurality of nozzle assemblies, each of the plurality of nozzle assemblies corresponding to one of the plurality of cavities, each nozzle assembly configured to inject a first material into a corresponding cavity of the plurality of cavities and configured to co-inject a second material into the corresponding cavity to form an interior layer of the second material between an inner layer of the first material and an outer layer of the first material in each cavity, each nozzle assembly including a flow initiation device for enabling and disabling flow of the first material into the corresponding cavity and for enabling and disabling flow of the second material into the corresponding cavity; and   a processor programmed to   control a first flow initiation device of a first nozzle assembly to initiate flow of the first material into a first cavity of the plurality of cavities at a first time,   control a second flow initiation device of a second nozzle assembly to initiate flow of the first material into a second cavity of the plurality of cavities at a second time,   control the first flow initiation device to initiate flow of the second material into the first cavity after a first specified time delay relative to the first time, and   control the second flow initiation device to initiate the flow of the second material into the second cavity after a second specified time delay relative to the second time.   
     
     
         8 . The system of  claim 7 , wherein each flow initiation device comprises a valve pin associated with one of the plurality of nozzle assemblies and a corresponding one of the plurality of cavities, the valve pin being configured to enable and disable at least flow of the first material. 
     
     
         9 . A system for co-injection of multilayer plastic articles, the system comprising:
 a mold defining a plurality of cavities, each cavity corresponding to a resulting plastic article;   a plurality of nozzle assemblies, each of the plurality of nozzle assemblies corresponding to one of the plurality of cavities, each nozzle assembly configured to inject a first material into a corresponding cavity of the plurality of cavities and configured to co-inject a second material into the corresponding cavity to form an interior layer of the second material between an inner layer of the first material and an outer layer of the first material in the corresponding cavity; and   a co-injection controller configured to execute instructions for:   initiating flow of the first material from a first nozzle assembly of the plurality of nozzle assemblies into a first cavity of the plurality of cavities at a first time;   initiating flow of the first material from a second nozzle assembly of the plurality of nozzle assemblies into a second cavity of the plurality of cavities at a second time;   co-injecting the second material into the first cavity of the plurality of cavities after a first specified time delay relative to the first time; and   co-injecting the second material into the second cavity of the plurality of cavities after a second specified time delay relative to the second time, wherein the second specified time delay is different than the first specified time delay.   
     
     
         10 . The system of  claim 9 , wherein initiating flow of the first material from the first nozzle assembly into the first cavity of the plurality of cavities at the first time comprises displacing a first valve pin of the first nozzle assembly at the first time, and wherein initiating flow of the first material from second nozzle assembly into the second cavity of the plurality of cavities at the second time comprises displacing a second valve pin of the second nozzle assembly at the second time. 
     
     
         11 . The system of  claim 9 , wherein the first time is different than the second time. 
     
     
         12 . The system of  claim 11 , wherein co-injection of the second material into the first cavity of the plurality of cavities occurs simultaneously with co-injection of the second material into the second cavity of the plurality of cavities. 
     
     
         13 . The system of  claim 9 , wherein the first time is the same as the second time. 
     
     
         14 . The system of  claim 9 , wherein the first specified time delay and the second specified time delay are determined from a first article previously formed in the first cavity of the plurality of cavities and a second article previously formed in the second cavity of the plurality of cavities. 
     
     
         15 - 20 . (canceled) 
     
     
         21 . The system of  claim 8 , wherein to control the first flow initiation device to initiate the flow of the first material into the first cavity, the processor is programmed to cause a displacement of a first valve pin of the first flow initiation device, and wherein to control the second flow initiation device to initiate the flow of the first material into the second cavity, the processor is programmed to cause a displacement of a second valve pin of the second flow initiation device. 
     
     
         22 . The system of  claim 8 , wherein each flow initiation device further comprises a valve sleeve associated with one of the plurality of nozzle assemblies and a corresponding one of the plurality of cavities, the valve sleeve being configured to enable and disable flow of the second material. 
     
     
         23 . The system of  claim 22 , wherein to control the first flow initiation device to initiate the flow of the second material into the first cavity, the processor is programmed to cause a displacement of a first valve sleeve of the first flow initiation device, and wherein to control the second flow initiation device to initiate the flow of the second material into the second cavity, the processor is programmed to cause a displacement of a second valve sleeve of the second flow initiation device 
     
     
         24 . The system of  claim 7 , wherein the first specified time delay is different than the second specified time delay. 
     
     
         25 . The system of  claim 24 , wherein the processor is programmed to initiate flow of the second material into the first cavity and to initiate the flow of the second material into the second cavity simultaneously. 
     
     
         26 . The system of  claim 7 , wherein the first time is the same as the second time. 
     
     
         27 . The system of  claim 7 , wherein the first specified time delay and the second specified time delay are determined from a first article previously formed in the first cavity of the plurality of cavities and a second article previously formed in the second cavity of the plurality of cavities. 
     
     
         28 . The system of  claim 7 , wherein the processor is further programmed to control the first flow initiation device to block a flow path of the first material forming the inner layer. 
     
     
         29 . The system of  claim 7 , wherein the processor is further programmed to initiate flow of the first material into the first nozzle assembly and into the second nozzle assembly at the same time. 
     
     
         30 . The system of  claim 7 , wherein the processor is further programmed to initiate flow of the second material into the first nozzle assembly and into the second nozzle assembly at the same time. 
     
     
         31 . The system of  claim 9 , wherein initiating flow of the second material from the first nozzle assembly into the first cavity of the plurality of cavities comprises displacing a first valve sleeve of the first nozzle assembly, and wherein initiating flow of the second material from second nozzle assembly into the second cavity of the plurality of cavities comprises displacing a second valve sleeve. 
     
     
         32 . The system of  claim 9 , wherein the co-injection controller is further programmed to initiate flow of the first material into the first nozzle assembly and into the second nozzle assembly at the same time.