Method and system for thermally monitoring process for forming plastic blow-molded containers

Abstract

The present invention provides a method of measuring the placement of material forming a blow-molded plastic container after the container is released from a mold of a blow molder having a plurality of molds, wherein each plastic container comprises a continuous sidewall and a base, the method comprising the steps of: detecting with an infrared camera infrared light emitted from the container after the container is released from a mold; converting the detected infrared light into corresponding electrical signals; transmitting the electrical signals to a microprocessor; comparing in the microprocessor the electrical signals with stored data regarding desired material distribution forming the plastic container; and producing output information regarding the placement of material forming the container.

1 . A method of controlling a blow molding production line based on measuring the placement of material forming a blow-molded plastic container produced on the production line, the method comprises the steps of:
 providing an extrusion blow molding machine having a plurality of molding stations each comprising a mold and a parison extruding system, wherein the extrusion blow molding machine provides an output of plastic blow-molded containers, wherein each plastic container has a continuous sidewall and a base;   measuring the placement of material in the sidewall and base of the containers by:
 detecting with an infrared camera infrared light emitted from the container; 
 converting the detected infrared light into corresponding electrical signals; 
 transmitting the electrical signals to a microprocessor; 
 comparing in the microprocessor the electrical signals with stored data regarding desired material distribution forming the plastic container; and 
 producing output information regarding the placement of material forming the plastic container and, if the output information indicates that a container has a material distribution that is a deviation from the stored data regarding desired material distribution, performing in the microprocessor at least one of the following steps:
 i. activating a rejection chute to reject the deviant container; 
 ii. adjusting at least one parameter of the extrusion blow molding machine to bring material placement within the desired material distribution; and 
 iii. stopping the production line. 
 
   
     
     
         2 . The method of  claim 1  wherein the measuring step further comprises the steps of:
 comparing in the microprocessor the electrical signals of the plastic blow-molded containers from each of the stations in the blow molding machine with stored reference data regarding desired material distribution forming the plastic blow-molded container; and 
 determining whether there is a station-to-station and/or a cycle-to-cycle variation. 
 
     
     
         3 . The method of  claim 1  wherein the blow molder is an extrusion blow molder. 
     
     
         4 . The method of  claim 3  wherein the extrusion blow molder comprises a plurality of blow mold stations. 
     
     
         5 . The method of  claim 3  wherein the material comprises a plastic selected from the group consisting of: polyethylene (PE), such as high-density polyethylene (HDPE), medium-density polyethylene; low-density polyethylene (LDPE), cross-linked high-density polyethylene (XLPE), linear low-density polyethylene (LLDPE), ultra low-density polyethylene, and very low-density polyethylene; polycarbonate (PC); polypropylene (PP); polypropylene copolymer (PPCO); polyallomer (PA); polymethylpentene (PMP or TPX); polyketone (PK); polyethylene terephthalates (PET), including polyethylene terephthalate G copolymer (PETG) and oriented PET; polystyrene (PS); polyvinylchloride (PVC); naphthalate; polybutylene terephthalate; thermoplastic elastomer (TPE); and mixtures thereof. 
     
     
         6 . The method of  claim 5  wherein the material is selected from the group consisting of: HDPE, PVC, PC, PP, LDPE, EPET, and PETG. 
     
     
         7 . The method of  claim 5  wherein the material further comprises a colorant such that the container is substantially opaque to light. 
     
     
         8 . An apparatus for measuring the placement of material forming a plastic blow-molded container, the apparatus comprising:
 a blow molder having a plurality of molds used to form a plurality of plastic containers, wherein each plastic container has a continuous sidewall and a base;   an infrared camera that detects infrared light emitted from each of the plurality of plastic containers; and   a microprocessor that receives electrical signals from the infrared camera and determines whether material distribution in the sidewall and base of the containers are within desired reference limits stored in the microprocessor.