OPERATION SEQUENCING IN AN AUTOMATED PROCESS PLANNING SYSTEM

One of the most difficult tasks we face in automated process planning is determination of operation sequencing. In this paper we present an approach to automatic generation of machining sequences in an object-oriented automated process planning system. Sequencing of machining operations is carried out in three phases of planning: initial planning, set-up planning, and final planning. The initial planning generates general plans including the required operations and machine cells. Two types of information are used at this stage, manufacturing process knowledge and component information, including features and associated dimensions, tolerances, surface finish, and material conditions. Based on process requirements decided in the initial planning, the set-up planning selects machines and fixtures, decides the clamping surfaces and feature accessibility, and sequences the set-ups. The final planning determines all the detailed sequences of operations based on the set-ups using the built-in manufacturing logic and heuristics. We introduce the set-up planning, the core of the planning system, to link the part model, initial planning and final detailed planning. The strategy has been implemented in an object-oriented process planning system. An example is provided to demonstrate the approach.