Development and characterization of diamond tip burnishing with a rotary tool

The effectiveness of a diamond tip burnishing method with a rotary tool, which is proposed by the authors and can be applied to the flat and curved surfaces of cuboid workpieces, is investigated. A proposed hybrid-type parallel mechanism with spherical 5-degree-of-freedom range and force control system was used as a burnishing machine. A diamond tipped tool, rotated by a high-speed motor spindle, was used as a burnishing tool. A stainless steel and a hardened cold work tool steel surface were targeted, respectively. The burnishing characteristics of the proposed method were evaluated in terms of the appearance and profile of burnishing marks, surface profile, residual stress and hardness of the burnished surface layer, surface roughness, and glossiness of the burnished surface. The advantages of the proposed method were clarified by comparing its performance with that of the conventional method, which does not rely on the tool rotation. The burnishing marks on the stainless steel workpiece, obtained using a single tool feed (without the cross feed) using the proposed method were wider and deeper than those obtained using the conventional method, and the convex profiles generated by the cutter marks were satisfactorily smoothed using the proposed method. The compressive residual stress and higher hardness of the burnished surface layer of the stainless steel workpiece could be obtained as well. In the case of the hardened cold work tool steel workpiece, the burnishing marks obtained using the proposed method were also not similar to those obtained using the conventional method. The feed rate of the burnishing tool affected the burnished surface profile only when using the proposed method, and the burnished surface profile could be controlled by the tool feed rate. The burnishing force, too, strongly affected the burnished surface profile. The proposed method allows obtaining high-quality burnished surfaces, with smooth profiles, low surface roughness, and high glossiness, even for relatively hard materials.