Micro form rolling: Imprinting ability of microgrooves on metal shafts

This study aims at clarifying the conditions necessary for form rolling microgrooves a few μm deep uniformly onto the surface of a metal shaft. A new testing apparatus for form rolling microgrooves on a surface of a metal shaft is designed and built. The gap between the flat dies inserted in the machine can be determined with micrometer resolution. Two kinds of flat dies which have different projection patterns are used: spline patterns and dimple patterns. The height of projection is commonly 10 μm in both patterns. The materials used in this study are austenitic stainless steel, SUS303, and aluminum alloy, A5056, 9 ± 0.0005 mm in diameter. The effects of the amount of die indentation and the projection pattern on the performance of micro form rolling are experimentally investigated; the transcription ratio (the ratio of the depth of formed grooves to the height of projection) and the oblateness of specimens after form rolling are measured in detail. The transcription ratio of dimple microgrooves reaches 100% for A5056. Increasing the reduction improves the transcription ratio, but worsens the oblateness of specimens.