Vrednotenje stabilnosti pri struženju v trdo
Evaluation of the stability during hard turning

english
slovenian

2006

volume 52, issue 11

Univerza v Ljubljani, Fakulteta za strojništvo

This paper deals with the lack of cutting stability during hard turning (appearing due to cutting-depth variation, unfavorable ratio of forces, Fc/Fp,a small tool-nose radius, and a non-uniform stress distribution over the tool/workpiece contact), which is possible to evaluate with process sensing(e.g., forces, vibrations, sound measurements) or after the process hasfinished (e.g., roughness, wear measurements). If the cutting process is unstable, the cutting force can become large and the machined surface quality can be poor or the tool can quickly become broken. Therefore, it is desirable to avoid unstable cutting conditions. Numerical calculations and experimental tests were made to evaluate the rate of cutting instability while using and comparing different process monitoring sensors and acquisition techniques based on the PC platform. It was found that the cutting depth varies by a value of some 60% if the tool/workpiece (T/W) contact geometry is analyzed, and even more if the Fp force signal is analyzed when the machine tool has inadequate stiffness. The results and findings presented in this paper are qualitative and might be slightly different under other cutting condition (e.g., if wiper inserts are used). Assuming that the hard turning is a semi-finishing or finishing process, the surface finish is very relevant, because it is a direct consequence of both the cutting stability and of the tool/workpiece non-uniform loading distribution. The results of the test indicate an optimum cutting depth for the final pass when the minimum surface roughness can be achieved, which can be valuable for the cutting-regime determination.

16.09.2009