A System for Automated Fixture Planning with Modular Fixtures

Abstract

This thesis describes a system to advance the automation of the fixture planning process with modular fixture components. Algorithms consider both physical constraints of metal cutting principles and geometric constraints. These algorithms automatically generate fixture plans with a minimal number of machined test parts. In order to generate practical fixture plans, the system considers actual fixture components available in the fixture library. The system considers fixture requirements such as geometric, kinematic, and force constraints in order to automate the generation of fixture plans with little or no human assistance. Since the number of clamps in a fixture plan is often related to the cost, candidate fixture plans with a small number of clamps are first generated by placing clamps on discretized candidate clamp locations on the part. In each candidate fixture plan with known clamp locations, the algorithm checks the interference between part/fixture/cutter paths and fixtures, and estimates the minimal clamping force to hold the part rigidly. A locating plan and a supporting plan are made considering the clamping plan and locating/supporting principles. The algorithm to generate fixture plans using a vise determines various valid candidate jaws?positions and the parallel bars?heights using extensive geometric reasoning on cutter paths, the part, and the vise geometry. The necessary clamping force is estimated in consideration of the contact area between the jaw and the part. The system has been integrated and tested with the other intelligent modules necessary for the automation of various metal cutting processes. The system typically generates multiple fixture plans for a setup within a few CPU seconds. The result shows that the system can be incorporated into a setup planning system to quickly generate a metal cutting setup sequence.