Abstract
This paper presents a pragmatic approach for automating set-up and fixture planning for 3-axis machining on CNC machines. Although the larger project encompasses automation and integration of all aspects of machining feature recognition, tolerance charting, high level (macro) planning, and detailed (micro) planning, this paper focuses only on set-up and fixture planning. Only standard modular fixtures are considered (tooling plates, rest pads, pin locators, strap clamps, and vises). In set-up planning we consider not only similar tool approach directions and processes for feature grouping, but also spatial constraints in machines, tools and fixtures. The approach presented here for fixture planning combines elements of both geometric reasoning and feature-based approaches. Set-ups are automatically planned based on the volumes to be removed in each workpiece orientation and the instantaneous state of the stock is tracked at the different stages of the proposed plan. Also verification techniques use feature information to estimate possible collisions between fixtures and volumes to be removed. The fixture planning algorithm is based on both the 3-2-1 locating principle and Vise clamping methods. The overall system architecture is modular, allowing the possibility of selective use of the modules by other developers of CAPP systems. The process planning system exploits the capabilities of commercial toolkits for geometric modeling (ACIS) and NC toolpath generation (STRATA).
