Automatic Tool Selection for Finish Turning

This paper describes a procedure to select tools for finish turning operations performed on a CNC (computer numerically controlled) turning centre. The finishing tools considered herein consist of a holder and an indexable tungsten carbide insert. The finishing profiles may be stepped or even contain a recess/shoulder. In the former case, only one tool is selected but in the latter a pair of tools, forming a unit, is selected. In both cases, several alternative solutions are evaluated and presented, in increasing order of normalized machining cost, to the user who then makes the final decision. Rather than make extensive calculations to determine a precise machining cost, the approximate cost of machining with a tool is based on a nominal length and an average profile diameter, and on cutting parameters which, although approximate, are realistic because the procedure takes into consideration constraints such as chipbreaking, surface finish required and diametral tolerance. Extensive graphic facilities are provided so that the user can visually verify that a tool selected by the system does not collide with the workpiece or the work-holding device. Three examples are included and the tools selected for them demonstrate the considerable reduction in machining cost that is possible when compared with non-optimal solutions.