Study for polygonal deformation phenomenon of borehole in reaming process

Abstract

Reaming is a finishing process to be performed in order to improve the accuracy of the prepared hole drilled. In this process, a chatter vibration often occurs and the drilled hole is deformed in a polygonal shape. This polygonal deformation phenomenon becomes a problem in quality control of products, because of decrease in the precision of the borehole. Although a countermeasure by irregular tooth spacing is proposed and the prevention effect is confirmed, the mechanism has not been clarified yet. In this paper, the generating mechanism of the polygonal deformation is considered to be a self-excited vibration caused by time delay. A simple analytical model is proposed, and the stability of the self-excited vibration is analyzed numerically. The numerical result agrees well with the actual phenomenon qualitatively. Furthermore, the effect of irregular tooth spacing on the stability of the self-excited vibration is evaluated numerically.