Polymer raw material, process and production fingerprints in injection moulding

In-process monitoring of polymer melts is found to provide a fingerprint of the: polymer (process-relevant polymer rheometry); the process (injection pressure-time curves which reflect the material-machine-mould combination, including polymer batch to batch variation and machine dynamic repeatability); and production trends, with 'process indices' offering an efficient basis for 100% automatic inspection, Statistical Process Control, and even insight into factory housekeeping. Specific pressure indices in an indentified low noise region of the primary injection stage of injection moulding have been found to provide a sensitive indicator of changes in a polymer, including batch to batch changes and process-induced changes, as such measurements are closely related to the rheology of the polymer melt. The same information has also been found to provide sensitive indications of variation in the processing operation for a given polymer-mould combination, and also consequently to allow meaningful statistical analysis of trends in the injection moulding process. Laboratory and factory data for raw material, process and production trend analysis (the latter involving data from substantial production runs) are presented.