Contouring Accuracy Assessment Of CNC MachineTools - A User's View

The methods used at AWE Aldermaston to assess the contouring accuracy of computer numerically controlled (CNC) machine tools procured by AWE are discussed.

Abstract

The purpose of this paper is to discuss the methods used at AWE Aldermaston to assess the contouring accuracy of computer numerically controlled (CNC) machine tools procured by AWE. It will also explain how the measurement and evaluation techniques have been developed over the years for this purpose. Aldermaston has been involved with precision machine tools for the past thirty years, although mostly lathes, they have ranged from copying to the present day computer controlled machines. As a result, most of the techniques explained in this paper originated from the need to assess the contouring accuracy of lathes although the present techniques can be used just as effectively on CNC milling machines. The importance of contouring assessment for CNC machine tools is now widely established by the work of Knapp [3] and Kakino 4] who proved that contouring profiles can be used to diagnose the various error components within the system. These can provide information on the geometry, control system and drive mechanisms as well as any thermal distortions between tool and workpiece zones. No attempt will be made to describe in detail the various analysis techniques used to evaluate contouring assessment as that is now widely documented. Equally, only those test methods actually used at AWE will be discussed.