Die friction and redundant deformation cause working stresses in drawing to be greater than simple homogeneous deformation would demand. At small die angles, frictional effects are large but the influence of redundant deformation is negligible; as die angles increase, the relative effects of these two factors reverse. Because of this interaction, an optimum angle exists for each combination of reduction and coefficient of friction where the drawing stress becomes a minimum. By modifying the normal Sachs equation to include redundant deformation, minima in the curves of drawing stress versus die angle are demonstrated. Additionally, some theoretical considerations of the maximum possible reduction per pass are presented.

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