Automated design of machining fixtures: tolerance and sequential operations

The long lead time for jig and fixture design is a serious bottle-neck in modern manufacturing. Efforts to automate the fixture design process using intelligent CAD systems have not been taken beyond the prototype stage, mainly because of impediments which include the requirement of complex data structures to represent the workpiece and its attributes. Two deficiencies in existing systems for fixture design are addressed; design for a sequence of operations and design with tolerance considerations. Tolerance and process specifications are obtained from the user during an interactive session. A knowledge-based design system, AutoFix II, designs a fixture for the workpiece. The fixture is optimised for a particular datum specification and sequence of operations. It is analysed and presented via the CAD system. AutoFix II is automated to minimise user-induced errors.