Advanced Interpolation Techniques for N.C. Machines

This paper describes two methods for curve and surface interpolation. The layout of the machine and the implementation of these methods on an N.C. machine are discussed. The requirement for additional computational power to implement these interpolation methods is addressed by a network of computers called transputers. The interface between the controller and the network is described. This network also provides the ability to do interference checking in real time using the subdivision technique. The advantage of this implementation is that it enhances the ability of the conventional controller and avoids problems such as communication errors, jerky motion, gouging, and closed architecture. The method used to determine the accuracy of the interpolator is described and some results are given. Curved surfaces described as a series of B-spline curves can be machined using the curve interpolator, whereas a B-spline surface can be machined with the surface interpolator. Sample surfaces are machined to show the ability of the controller in both the curve interpolation and surface interpolation modes.