Blown Film Extrusion Optimization - Control and Screws, 1990 Polymers, Laminations & Coatings Conference Proceedings

We live in a wonderful age of emerging technological developments which are making it possible to automate portions of the extrusion process, improve extrusion accuracy, and give constant supervision to the process. Acquisition of process data and film parameters make SPC and SQC practical tools of quality and cost reduction. There are some smoke and mirrors in some SPC programs and devices the later which need to be sorted out to achieve valid extrusion science.

Microprocessor controls, electronic data presentation and acquisition have been with us for a number of years but not fully utilized in every day practice. Recent improvements in data handling, on-line film gauging, innovations in automatic blown film dies are initiating new standards in blown film quality, cost reduction and effective material utilization. The combination of microprocessor control, automatic film dies and gravimetric feeding are surely the leading edge developments which are and will set the standards for production quality and manufacturing costs.

As a polyethylene polymer supplier we are keenly interested in accurately determining the process and property performance levels of our polymers in typical production applications. To be a good Quality Partner with our customers, we must have practical tools for evaluating the constancy of our polymer production, box to box, car to car, lot to lot and plant to plant, through time.

Precision small production size film test lines can be a good quality audit device for attaining and maintaining a high level of performance with a maximum of constancy.

This paper discusses some aspects of improving the accuracy of the film production process to achieve a level of reproducible extruder operation that can accurately separate machine variations from polymer variations and become a polymer test device.

Microprocessor control sensitive instrumentation, electronic data presentation, acquisition and handling, screw characterization and selection, rigid operating protocol and statistical testing of machine operation are some of the key factors to precise polymer performance evaluation.