Chatter avoidance in the milling of thin floors with bull-nose end mills: Model and stability diagrams

Abstract

The milling of thin parts is a high added value operation where the machinist has to face the chatter problem. The study of the stability of these operations is a complex task due to the changing modal parameters as the part losses mass during the machining and the complex shape of the tools that are used. The present work proposes a methodology for chatter avoidance in the milling of flexible thin floors with a bull-nose end mill. First, a stability model for the milling of compliant systems in the tool axis direction with bullnose end mills is presented. The contribution is the averaging method used to be able to use a linear model to predict the stability of the operation. Then, the procedure for the calculation of stability diagrams for the milling of thin floors is presented. The method is based on the estimation of the modal parameters of the part and the corresponding stability lobes during the machining. As in thin floor milling the depth of cut is already defined by the floor thickness previous to milling, it is proposed the use of stability diagrams that relate the tool position along the tool-path with the spindle speed. Hence, the sequence of spindle speeds that the tool must have during the milling can be selected. Finally, this methodology has been validated by means of experimental tests.

Optimisation of variable helix tool geometry for regenerative chatter mitigation

“…In contrast, the productivity of machining aluminium alloys can be enhanced considerably by properly understanding regenerative chatter issues [25], and this has motivated many recent studies that have also focussed purely on aluminium alloys (e.g. [24,26,27,28]). The present study provides a new tool for this approach which allows the regions of chatter stability to be tailored, by adjustment of the tool helix geometry, to suit a particular application.…”

A growth-based topology optimizer for stiffness design of continuum structures under harmonic force excitation

“…As a consequence, growth material in each growth iteration is fully utilized and allocated only to the most suitable growth orientations, which more closely resembles the growth of leaf venation in nature. Possible applications of the proposed approach could be the vibration-proof design of stiffened structures in machine tools (Whalley et al, 2011), rib layout of flexible thin walls (Herranz et al, 2005;Campa et al, 2011), or cable structures in engineering structures .…”

Chatter stability prediction in four-axis milling of aero-engine casings with bull-nose end mill

“…Chatter is one of the main machining problems, which leads to poor surface finish and low production efficiency. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] In order to avoid chatter, the milling process must be conducted in a stable state. Thus, the machining stability prediction becomes very important in achieving good machining quality and high productivity.…”

“…[8][9][10][11][12][13][14][15][16] Altintas 8 extended the two dimensional chatter stability theory to a three-dimensional chatter problem by adding the dynamics in the tool-axis direction. Based on this work, Seguy et al 9 , Campa et al 10,11 and Adetoro et al 12,13 calculated the stability lobe diagrams in bull-nose end milling of thin floors and thin walls by considering the nonlinearities of the axial immersion angle and the cutting force coefficients. For multi-axis milling, the effects of tool positions on the process geometry, mechanics and dynamics cannot be ignored.…”