Capability Analysis & Statistical Process Control Applied to Photochemical Machining

Using the concepts of Cp and CPk this paper demonstrates, with the aid of worked examples, that Capability Analysis may be usefully applied to PCM. It is shown that the Capability Index, for any stage of the process, may be calculated from the process data and compared to the “target” values. The variation of the Index with process mean levels, standard deviation and specification limits is clearly shown. In part 2, Statistical Process Control, as applied to the etching process will be considered in depth and the derivation of control limits discussed.