AUTOMATED PROCESS PLANNING FOR CNC MACHINING OF SPHERICAL SPACE-FRAMENODES

Space-frame nodes are joints connecting linear members in complex spac e frames. Each spherical node has a particular hole configuration that defines the orientation of the bolt holes used to connect the space-f rame members. The hole configurations are determined by CAD software f or space-frame design. Nodes with the same hole configuration vary in number depending on the design of the space frame. A computer-automate d machining cell has been implemented to batch manufacture the spheric al nodes. The machining cell consists of a three-axis vertical machini ng center interfaced with a two-axis CNC rotary table. To reduce chang eover time between the machining of batches, produce consistent and re liable NC programs, and minimize manpower required to run the cell, a PC-based computer-automated process planning system has been developed to directly translate geometric data from the CAD software to NC prog rams, without intervention by the operator. An important consideration in the process plan for the machining of the space-frame node is the transformation of the CAD-defined bolt hole configuration to a mountin g-hole-referenced configuration that minimizes setup and mounting hole requirements. Based on the optimal mounting-hole-referenced configura tion, NC toolpaths are derived and corresponding NC programs are gener ated. This paper presents the approach to determine the optimal mounti ng-hole-referenced configuration and the operation of the automated pr ocess planning system that is suitable for the machining of spherical parts.