Modeling of positional variability of a fixtured workpiece due to locating errors

In manufacturing practice, fixtures play an important role in locating and restraining a workpiece. It is clear that locating error is one of the factors that significantly contribute to workpiece quality in the early stage of machining. In this study, we develop a mathematical model that is able to predict geometric variation of a resultant-machined surface when the tolerance of a datum feature is given. A model for a 2-D scheme was initially established that subsequently expanded to a more realistic case in a 3-D scenario. Results from the model show that when variability of a datum feature is allowed, a paraboloid-shaped variational function of a machined surface is detected.