Abstract
Numerical and experimental investigations were carried out on the excessive decrease in outside diameter occurring on a tube cold extruded through two conventional types of die, a taper die and an R die. Wide ranges of the parameters of die profile were adopted in order to precisely examine the influence of die geometry on the undershooting phenomenon, and appropriate die geometries for the suppression of the undershooting phenomenon were shown. The R die is more practical in the manufacturing operation compared with the taper die. Bending was also investigated, and it was shown that the bending intensity becomes lower as the undershooting intensity decreases. However, it is not necessary to suppress bending sufficiently, even if the undershooting is suppressed to zero in the case of adopting the ordinary types of die – there seemed to be another governing factor for the occurrence of bending and this is a remaining problem.
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