NC machining of free form surfaces

The continuation of a trend towards more user-friendly, interactive CADCAM systems, prompted the creation of a prototype software package called CISPA (Computer Interactive Surfaces Pre-APT). This system uses a menu-driven front end with graphical feedback to guide a user through curve and free form surface definition resulting in a mathematical model which may be used to generate NC machine CLSF. This front end was built upon the curve and surface complex taken from CAM-I's CASPA (Computer-Aided Sculptured Pre-APT). This complex is part of the execution phase of APT 4. Improvements were made in the definition and calculation of step size basing the input on geometric attributes such as chordal deviation and scallop height rather than on abstract algebraic quantities. Further additions include increased flexibility in milling surfaces, by roughing to depth.