Design of irregular pitch end mills to attain robust suppression of regenerative chatter

This paper presents a design method of irregular pitch end mills, which ensures robust suppression of total regeneration in milling. Firstly, general formulation of irregular pitch angles is explained for simultaneous suppression of multi-mode regenerations. An index named “Regeneration Factor (RF)” is introduced to quantify regenerative effect. Minimizing the mean value of the |RF| within a certain frequency range, suppression frequencies are distributed in the proposed method, resulting in robust suppression of regeneration regardless of chatter frequency and/or spindle speed variations. Experimental investigations verified significant robustness of the end mill with the proposed design against the spindle speed variation.