Determining Rotational Setups from Visibility of Slice Files for Rapid CNC Machining

A method for Rapid CNC machining is being developed in an effort to automatically create functional prototypes and parts in a wide array of materials. The method uses a plurality of simple 21⁄2-D toolpaths from various orientations about an axis of rotation in order to machine the entire surface of a part without refixturing. It is our goal to automatically create these tool paths for machining, and eliminate the complex planning traditionally associated with CNC machining. In this paper, we consider the problem of visibility to the surface of a model that is rotated about a 4 th axis. Our approach involves slicing the CAD model orthogonal to the axis of rotation. The slice geometry is used to calculate 2-D visibility maps for the set of polygons on each slice plane. The visibility data provides critical information for determining the minimum number and orientation of 21⁄2-D toolpaths required to machine the entire surface of a part.