Selection of manufacturing tolerances for open-chain mechanisms

Flexible manufacturing systems play an important role in modern industries. The equipment used in flexible manufacturing systems such as industrial robots, NC machines, conveyors etc. demand high performance and accuracies. The selection of manufacturing tolerances is critical in deciding the accuracy of the mechanism and the manufacturing cost. In the present work a new kinematic model for open-chain mechanism is proposed which will help the designer in selecting the manufacturing tolerances. The model allows the designer to estimate the manufacturing cost for the required accuracy. By using the model and the cost function, a set of tolerances can be estimated to achieve the required accuracy and/or manufacturing cost. The end point location and the manufacturing cost of the mechanism are expressed as a functions of tolerances and major dimensions. By using these expressions one can optimize the tolerances based on (1) optimizing accuracy under the cost constraint, (2) optimizing cost under the accuracy constraint.