||Generalized design method of highly-varied-helix end mills for suppression of regenerative chatter in peripheral milling
Hayasaka, Takehiro ,
Ito, AtsushiShamoto, Eiji
59 , 2017-04 , Elsevier
Peripheral finishing of hardened steel by milling has recently been introduced to the machining field, but often causes severe chatter vibration due to high specific cutting force and low stiffness of slender end mills. It was shown in the previous papers that highly-varied-helix end mills were effective for the suppression of regenerative chatter, and a low radial immersion was applied to avoid the effect of mode coupling. Especially for the highly-varied-helix end mills, it was proved experimentally that they were effective across a wide range of cutting conditions, making it possible for cutting with a relatively large axial depth of cut to be carried out and thus realizing a high surface generation rate in peripheral milling of hard materials. However, the milling tests were carried out under just one specific condition, i.e., tool diameter 8 [mm], projection length 36 [mm], and workpiece of 60 HRC hardened steel, etc., and the helix angles of the tool were varied large enough to suppress regenerative chatter but with no quantitative discussion for their determination. In this paper, a generalized design method for varied-helix end mills to suppress regenerative chatter is proposed. Namely a design index ap/alim, in which ap is the distance between 2 adjacent regenerative effect cancellation lines and alim is the asymptotic stability limit in the targeted cutting process, is introduced to design the helix angle difference of a tool, and milling experiments are carried out in several conditions to verify the validity of the proposed index.