Abstract:The machining of complex parts typically involves a sequence of n operations on m machine tools. Conventional tolerance control specifies a fixed set point for each such operation and permissible variation about this set point to insure compliance with tolerance specifications. However, this approach may be inadequate for complex, low-volume, highvalue added parts. This paper introduces the concept of Sequential Tolerance Control (STC), an approach that uses real-time measurement information at the completion of a stage to exploit available space inside a dynamic feasible zone and reposition the set point for subsequent operations so as to optimize the production of an acceptable part. It is also demonstrated that the measurement information acquired during STC can be used to compensate for systematic variation such as tool wear. STC is then used in the context of an implicit enumeration approach to select an optimal subset of technological processes required to execute a process plan. Finally, a probabilistic approach to the problem of optimal selection of technological processes under conventional tolerance control is presented and the First Order Second Moment Method (FOSMM) is used to estimate yield.Introduction: Interchangeability in mechanical assemblies and satisfactory functional aptitude of parts and products are only possible when component dimensions and other geometric features are produced inside prescribed tolerance zones. The drawing or print of a part translates the above requirement into a sketch of exact part geometry augmented by dimensional and geometric tolerance information; tolerance information specifies permissible deviations from perfect geometry. In machining, final specifications of a mechanical part are arrived at via a logical, chronological sequence of material removal operations. This sequence may involve several machine tools with each machine tool performing one or more material removal operations, under one or more distinct set-ups. During the processing of a complex part, design specification datums and manufacturing operations datums do not always coincide. This leads to the commonly encountered situation where, even under the best of manufacturing plans, a large subset of part specifications are satisfied by the combination of two or more manufactured dimensions. Knowing that the output of each manufacturing operation (dimension produced) x j will fall within a certain tolerance range such that ] , [