Design and chatter prediction analysis of a duplex face turning machine for manufacturing disk-like workpieces

Simultaneous, parallel or double-sided machining can increase the metal-removal-rate (MRR) of hard-to-cut materials. This paper presents a direct-drive duplex-face-turning (DFT) machine for manufacturing thin-walled disk-like components characterized by a very large diameter-to-thick ratio, which allows simultaneous cutting of opposite sides to improve productivity and mitigate workpiece deformations/vibrations during machining. The unique dynamic characteristics on the cutting interface between the thin-walled disk and the two cutters, however, present some challenges in chatter prediction and process parameter optimization. To address these challenges, a multi-dimensional chatter stability analysis method based on a conceptually straightforward modeling approach in terms of the major oblique cutting parameters is presented, where the dynamic effects of both the workpiece and two cutters in addition to the insert geometries are taken into considerations in the formulation of the DFT process. The proposed chatter stability analysis is numerically illustrated and experimentally validated. The relative merit of the direct-drive DFT process has been experimentally evaluated for machining thin-walled hard-to-machine compressor disks by comparing symmetric and non-symmetric DFT operations with single-sided face-turning, along with an example that illustrates a quick guide for nonsymmetrical DFT in the specified speed range.