Development of under-cut shape sprocket forming by CNC press

In standard P/M (Press-Sinter) technique, it is difficult to make under-cut shape parts. In this development, the possibility of under-cut forming by a CNC press was investigated in the basic experiment. And an under-cut shape sprocket of whole circumference was made by the CNC press and the newly designed die and tools. This paper describes the features of the CNC press and technical issues encountered in the production of the sprocket of the under-cut shape. These are as follows: Elimination of cracks and burrs in compaction; Achievement of an even density throughout the complex part; Keeping the dimensional tolerance; and Prevention of breakage of the die and tools. These were resolved by using newly designed die and tools. These are described in detail.