Process Capability Studies. Before performing a process capability study the process must be stable. The natural behavior of a process is termed its process capability. Once the process capability study is completed, process improvement studies can start (PDSA) cycle.
Upper Natural Limit (UNL) = process centerline + 3(process standard deviation)
Lower Natural Limit (LNL) = process centerline - 3(process standard deviation)
Note: it is assumed that the measurements follow a normal distribution
The ABC Co. produces steel tubes. The steel tube process is a stable cut-to-length operation that generates tubes that are distributed normally with a mean of 12.00 inches and a standard deviation of 0.10 inch.
The LMN Co. wishes to but tubes from the ABC Co. The LMN Co. requires steel tubes 11.95 inches long with a tolerance of ± .30 inches.
Compute Cp, CPU, CPL and Cpk