Verification system for NC programming for quality in milling

The present work outlines the development of a system to examine NC programs and predict the occurrence of chatter in common milling operations such as pocketing. This system plays the role of an off-line tool to ensure chatter-free machining and increased metal removal rates. The NC program, which contains a list of the various tool movements, does not provide explicit information about cutting parameters such as the radial and axial depths of cut, feed directions and the mode of milling (up or down) which are needed for chatter prediction. It is therefore necessary to extract these parameters from models which represent the tool motions contained in the NC program. The algorithms outlined in this paper use previously established databases of the limiting values of axial and radial depths for chatter avoidance. Additionally certain corrective actions that are undertaken when the extracted values exceed these limit values are described. The pockets considered here have simple 2 1/2 dimensional geometries and may include islands. Several examples are used to illustrate the application of the above system using pocketing operations generated by commercial NC packages and generated using special algorithms.