ABSTRACT
Process capability studies had been performed on the entire product line, by part number, for the key product characteristic “slug weight” long before the current problem had reached its current, serious stage. Each process capability study had generated a statistical product control chart for each of the extruded part numbers studied, resulting in dozens of statistical product control charts-one for each product. Each time the extruder was set up to accommodate a particular part number, an X Bar and R product control chart with preprinted centerlines and control chart limits specific to that part number was posted at the extruder. Operators were required to select five samples during a 30-minute period, weigh each sample on a gram scale, calculate the average and range of the subgroup of five samples, and record the results on the respective X Bar and R charts.
