Process Planning and Automation for Additive-Subtractive Solid Freeform Fabrication

Abstract

New additive-subtractive processes promise to enhance SFF capability from prototyping to true low-volume production. However, to maintain the same degree of process automation as in currently available processes like SLA or SLS, more sophisticated planning and execution systems need to be developed. The system we present in this paper consists of two parts. The first is an off-line planner that decomposes a CAD model into 3D manufacturable volumes called "single-step geometries", arranges these geometries into a graph representation called" adjacency graphs", and automatically generates deposition and machining codes for each single-step geometry. The second is an on-line system that handles asynchronous multi-part building, job-shop scheduling, process control and run-time execution. Communication between these two stages is through a "process description language". The goal of this paper is to present a framework for planning and execution for additive/subtractive processes, outline the issues involved in developing such an environment, and report on the progress made in this direction at the Rapid Prototyping Laboratory of Stanford University.