In this study, a novel load cell embedded small ball-burnishing tool with a double spring mechanism was designed and fabricated to conduct the burnishing process on STAVAX material. The influences of process parameters, namely burnishing lubricant, burnishing force, step-over, burnishing speed, and number of passes, on the surface roughness and superficial hardness of the workpiece were investigated. The hybrid grey-based Taguchi method with the weighting coefficients estimated by principal component analysis and grey entropy was employed for experimental design and data analysis. After conducting two sets of experiments, the optimal small ball-burnishing condition on STAVAX material was determined.

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The smoothing ball-burnishing process has commonly been used as a post-processing method to reduce the irregularities of machined surfaces. However, the mechanism of this process has rarely been examined. In this study, a simulation procedure is proposed to predict the surface roughness of a burnished workpiece under varying burnishing forces. The roughness of the workpiece surface was firstly approximated by parabolic functions. The burnishing process was then numerically simulated through two steps, namely the elastic–plastic indentation of the burnishing ball on the workpiece’s surface, and the sliding movement of the burnishing tool. The results of the simulation were verified by conducting small ball-burnishing experiments on oxygen-free copper (OFC) and Polmax materials using a load cell-embedded small ball-burnishing tool. For the OFC material, the optimal burnishing force was 3 N. The obtained experimental surface roughness was 0.18 μm, and the simulated roughness value was 0.14 μm. For the Polmax material, when the burnishing force was set at its optimal value—12 N, the best experimental and simulated surface roughness were 0.12 μm and 0.10 μm, respectively.

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