TABLE OF CONTENTS In the majority of CNC programming applications, there are only two types of tool motions related to contouring. One is the Linear Interpolation, discussed earlier, the other one is the Circular Interpolation, discussed in this chapter. The programming method of controlling a tool path along an arc is similar to the method of programming a tool path along a line. The method of circular contouring is called circular interpolation. It is commonly used in profiling on CNC vertical and horizontal machining centers, as well as on lathes and many other CNC machines, such as simple milling machines, routers, burners, water jet and laser profilers, wire EDM, and others.
Circular interpolation is used for programming arcs or complete circles in such applications as outside and inside radii (blend and partial), circular pockets, spherical or conical shapes, radial recesses, grooves, corner breaks, helical cutting, even large counterbores, etc. The CNC unit will interpolate a defined arc with a very high precision, if the necessary information is given in the program.
To understand the principles of programming various circular motions, it helps to know something about the basic geometrical entity known as the circle. As an entity that is quite common in everyday life, a circle has various properties that are strictly mathematical, only considered in specialized disciplines, such as Computerized Numerical Control, motion control and automation.
The following definition of a circle and several other definitions that are related to a circle are...
