Influence of Dimensions of Chip on Roughness of Finished Surface Produced by Hobbing (Fundamental Experiments Using Fly Tool)

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This paper describes the influence of the length and thickness of the uncut chip on roughness of the finished surface using TiN- and (Al,Ti)N-coated tools, for dry and minimal quantity lubrication (MQL) systems in hobbing at different cutting speeds. Experiments were carried out to simulate hobbing by fly tool cutting on a milling machine. The following results were obtained: (1) For dry cutting at a cutting speed of 117m/min, low surface roughness was obtained for chip lengths of 15 to 25mm and thickness of 0.10 to 0.25mm, irrespective of the type of coatings. When the MQL system was used, low surface roughness could also be obtained with longer chip length. (2) When dry cutting was carried out at 159m/min, low surface roughness was obtained with the (Al,Ti)N-coated tool for chip lengths of 13 to 20mm and thickness of 0.09 to 0.18mm; these ranges were wider than those for the TiN-coated tool. For both types of tool, much narrower ranges were obtained with the MQL system. (3) Chatter vibration sometimes occurred under the cutting conditions used, and this is thought to be associated with regenerative chatter. The chatter vibration was found to be more severe in the case of the MQL system.