Process analysis software for the prediction of elongation with respect to the draw bending of small diameter thin walled tubing

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Process analysis software for the prediction of elongation with respect to the draw bending of small diameter thin walled tubing

Critchley, K.L. / Blount, G.N.

The need for the work described in this paper was identified during the course of a Teaching Company Programme with a company involved with the supply of brake tubes to the automotive industry. The process used for the manufacture of such tubes is draw bending. It was observed that whenever the draw bending machines were reset for a new batch of components, then several trials were necessary before the machine was producing acceptable tubes. This took up valuable production time as well as generating several scrap components. This was found to be a common problem in industries that are concerned with the cold manipulation of tubes. The overall aims of the work were therefore to reduce this setting up time and to enable a reduction in the scrap produced, allowing right first time components to be manufactured. The manipulation of tubular components by draw bending has two principal problems: springback and axial elongation. This paper addresses the problem of axial elongation. For this it was assumed that the majority of the elongation occurs due to a shift in the neutral axis. A program has been produced that allows the position of the neutral axis to be predicted for small sections (elements) of tube. In this way the shift of neutral axis can be traced throughout the complete bending process and the elongation for any bend can be predicted. The results from the program will be used to provide a generic solution for the prediction of elongation in small diameter thin-walled tubes.