Described in this thesis is an automated NC programming system for the machining of sculptured surfaces defined in the drawing by a set of cross-sectional curves. A cross-section(CS) curve is assumed to be a plane curve consisting of a sequence of line segments and circular arcs.
Each CS curve is coded into a predefined format(part program). The user has to designate one or two CS curves as "basic curves" which define the basic profile of the surface. One of the basic curves becomes the main basic curve(MBC), and the remaining CS curves, they are called drive curves(DC), are specified with respect to the MBC.
The input part program is processed by the CAM system in four steps: 1) the input CS curves are transformed into 3-D space curves, and then each curve element is approximated by a cubic Bezier curve, 2) enough number of intermediate cross-sections are obtained based on the given relation between DC and MBC(only the Bezier control points are transformed), 3) a number of points on the intermediate CS curves are sampled, 4) finally the sampled points are used to obtain a smooth surface by the Ferguson surface fitting method.
The entire procedure except the last step has been implemented during the thesis research. The program is written in FORTRAN77 to be run on an IBM PC/XT.
