Multipass synchronous spinning is a combination of synchronous spinning, in which the roller is synchronized with the rotation of the noncircular mandrel, and multipass spinning, in which the work is gradually deformed from a flat blank into its final shape after multiple passes. When a square cup is formed from a circular blank by multipass synchronous spinning, material accumulates at the side edges. The wall thickness locally increases at the edges and ears are formed at the corners. The calculation method for the tool trajectory is improved so as to equalize the thickness and strain distribution and to suppress ear formation. Considering noncircular spinning of a square pipe from a circular pipe, an intermediate circular section is introduced into the interpolation between the blank shape and the final shape. The experimental results show that the proposed method can decrease the difference in the thickness and strain distributions between the edge and the center of the side wall and can reduce ear formation.

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The characteristics of the surface profile of cemented tungsten carbide dies after either shot peening (SP) or conventional mechanical polishing (MP) surfaces were investigated with a surface roughness tester. The relationship between arithmetic and ten-point mean roughness was almost the same in the MP and SP dies. The mean period of the surface roughness profile of the SP die was approximately 1/3 times shorter that of the MP die. The distribution of the peaks and valleys of the surface profile was symmetric in the SP die, whereas it was skewed toward the peaks in the MP die. The lubrication performance of the MP and SP dies in cold forging of a titanium workpiece was measured by the ring compression test. The SP die with a mirror surface reduced the friction at a high reduction in height range because the die holds liquid lubricant in the micro valleys on its surface during the ring compression test.

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This study was aimed at developing a new prehole shearing process to promote excellent formability of the subsequent hole- expansion process for manufacturing automobile wheel disks made of high-tensile-stress steel. A “simplified opposed-dies shearing process” was newly proposed for forming a prehole for the hole-expansion process, since the original opposed-dies shearing process requires relatively complicated tool sets regardless of its excellent properties for hole expansion. As a result of the series of experiments with the simplified opposed-dies shearing process as the prehole forming process for the hole expansion process, the simplified opposed-dies shearing process was found to show an improvement of 0.3 in the expansion ratio over that in the case of the conventional shearing process.

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