Abstract

Short runs (in which the production cycle for a product is relatively short) and small runs (in which relatively few products of the same type are produced) require special statistical process control (SPC) techniques. Process capability studies should identify sources of variation before production takes place. If there are less than 50 observations, it is appropriate to have a minimum Cpk process capability index value of 1.5 at the 4-sigma acceptance level. The process audit, control charts, and advanced statistical techniques are good SPC tools, but data collection and analysis for small and short runs may also rely on common sense and experience with the process. Three approaches for handling variables data, such as measurements of weight and temperature are: the exact method; code value charts; and stabilized control charts. When it is not feasible to use continuous variables data, it is acceptable to gather discrete attribute data. Tools for attribute data are stabilized attribute control charts and demerit control charts. The article provides detailed examples covering both types of data.