The influence of radial engagement and milling direction for thin wall machining: a semi-analytical study

Abstract

Milling stability prediction of regular milling processes has to be normally carried out by means of complex numerical methods due to the multidimensional nature of the limiting modes, hindering the direct study of the influence of the process parameters on milling stability. However, the dynamics of thin-walled part milling processes, especially flank milling operations, can often be described in a unique direction. Thus, the directional factor matrix is condensed onto a single coefficient whose mean value uniquely depends on the engagement limits and the radial-tangential cutting force ratio. By these means, this paper studies the influence of radial engagement and milling direction on thin wall milling stability. The superior performance of up-milling is demonstrated on account of its special geometric configuration, permitting both positive and negative mean directional factor situations. In addition, the expressions for optimal radial engagement for minimum Hopf chatter likelihood are provided, which serve as excellent tool for process planning regardless of the part dynamics or other process parameters. The obtained results are finally validated through semidiscretisation and initial value time domain simulations.