Singhal, Subhash C. (1992, ASQC) AT&T Bell Labs, Mesquite, TX 75149
The author has developed a Multi Parameter Analysis Chart that displays and analyzes data for a group of variable parameters. The chart consolidates into a concise graphical summary the testing/inspection results for several different lot parameters.
The chart include an X axis where positive values are lower specification limits (LSL) and negative values are upper specification limits (USL). On the Y axis, positive values are USL while negative values are LSL. A set of contour lines appear in the upper right quadrant (where values fall between the specification limits) with a target line running diagonally at a 45 degree angle through them. A parameter's position on the chart can be used to determine four performance measures: the departure (relative and absolute) of mean from the target value, variability, two capability indices, and expected fallout outside specifications. The chart can also be used to show a parameter's performance within capability zones (Cpk 1.0-3.0 and Cp 1.0-2.0).
The chart can be used to evaluate lot performance with respect to several different parameters, to group parameters into different performance categories for priority-setting, and to illustrate parameter history. A MPAC chart provides a comprehensive summary about a lot's different parameters.
Manufacturing,Control charts,Specification limits,Target