Dynamics modeling and stability analysis of five-axis ball-end milling system with variable pitch tools

•A comprehensive dynamic model for five-axis variable pitch ball-end milling is established.•Stability of the system is solved by an extended 2nd SDM considering multiple modes.•The effects of tool orientation on the stability of variable pitch milling are investigated.•The model is verified by experiments with a variable pitch ball-end cutter being used. Chatter has become a major obstacle in realizing high efficiency milling under the premise of ensuring structure integrity, as it creates violent vibration to the milling system and in turn results in poor surface finish and accelerated tool wear. Although some promising methods have been applied to the avoidance and suppression of chatter, and among them variable pitch tools play a critically important role, few studies focus on the stability prediction of five-axis ball-end milling with variable pitch tools. In this paper, a comprehensive dynamic model characterized by multiple delays is first built for five-axis ball-end milling system with variable pitch tools, and the milling stability lobe diagrams (SLDs) are predicted with an extended second-order semi-discretization method (2nd SDM) by taking the multiple modes of cutter into account. Then, the effects of tool orientation on the stability prediction of five-axis ball-end milling with variable pitch tools and regular tools are analyzed. The optimal cutter pitch angle can be obtained by comparing the SLDs for the stability improvement. Finally, the effectiveness of the proposed method is verified by experiments with a variable pitch ball-end cutter in five-axis machining center. [Display omitted]