We are a first and second tier supplier of Automotive Components, with the majority of of parts being produced by injection moulding. Historically, we have carried out capability studies on each cavity of multi- cavity tools. Due to some tools having in excess of 24 cavities, this results in a time consuming exercise, and 24 seperate cpk values. We are led to believe that it is more relevant to conduct a study taking random samples from all cavities, resulting in one cpk value. Does this represent an acceptable method of achieving process capability for multi-cavity tools?