Traditional Xbar Charts for PET Preform and Bottle Manufacture Reduce the Effectiveness of the Industry's SPC Efforts - Issues and Solutions

摘要

Traditional Xbar charts, the most popular statistical process control charts in the PET preform and bottle manufacturing industry, are often counterproductive. The typical application ignores the fact that each mold cavity of an injection or blow mold potentially behaves differently due to characteristics of that mold cavity. This paper discusses effective control charting techniques for dealing with blow molding and injection processes. The techniques offer more accurate estimation of when it is necessary to intervene in the process, quicker forecasting of impending defective production, and better visibility of what's going on in individual molds or mold cavities.