Tolerance design in process planning needs to take into account of the operational sequences and variation sources in the process, e.g. datums, machine tools, and fixtures. Tolerance charting was developed in industries and it provides a foundation to bring together both product and process design engineers in a truly concurrent planning approach (Wade, 1967, 1983, Krag, 1997). Tolerance charting is a graphical tool for representing a manufacturing sequence and for checking that tolerance stackup meets the design specifications. As the actual setup scheme and the repeatability of machine tools and fixtures are hard to be incorporated into the analysis, charting approach still suffer the same aforementioned distribution estimation problems