Automated microplanning for 2.5-D pocket machining
Journal of Manufacturing Systems

Abstract

Microplanning, as defined in this research, consists of the decomposition of machining features generated by the macroplanner into sub-features, selection of appropriate tools to machine these sub features, and the selection of appropriate cutting parameters. This paper describes the implementation of a microplanner that is capable of optimally accomplishing the abovementioned tasks, either minimizing time or cost.

Keywords: Pocket Machining, Feature Decomposition, Process Planning, Optimal Tool Sequence Selection

Introduction

Process planning (Sarma 1997) is the act of generating a plan for manufacturing a part from a given design. This research concentrates on manufacturing using the three-axis milling process. In previous research (Sarma 1997, Stori 1998, Sundararajan and Wright 1998), process planning has been subdivided into three distinct tasks, namely, macroplanning, microplanning, and tool path planning. Macroplanning is concerned with generating machining features (Sundararajan and Wright 1998) from a given CAD model and sequencing the order in which these features are manufactured. Microplanning is concerned with the decomposition of features generated by the macroplanner into subfeatures depending on feature geometry and on the tools available, the selection of appropriate tools, and the selection of appropriate cutting parameters. Tool path planning is concerned with the generation of actual NC codes for the three-axis milling machine.

Features generated by the macroplanner can either be pockets or holes. Holes of a given diameter can be machined with drills of the same diameter. On the other hand, different milling tools can be used to machine a pocket. To reduce the time needed to machine a given pocket, it is necessary that large tools be used to remove large amounts of material quickly. Subsequently, smaller tools have to be used to clean up areas where large tools cannot enter. It is therefore necessary to subdivide a given pocket into subpockets to be removed by different tools. Overall, there is the issue of selecting a combination of tools that will result in the minimum total machining time or cost. Significant time savings in the manufacturing cycle can be achieved by automating the process of pocket subdivision, tool selection, and selection of cutting parameters.