Experimental and numerical investigation on metal tubes forming with a novel reconfigurable hydroforming die based on multi-point forming

It is necessary to fabricate individual dies in conventional hydroforming, to produce different tubular parts. This procedure is costly and time-consuming. Tube multi-point hydroforming is a new flexible forming technology which facilitates producing various tubular products by only one die. In this study, a new reconfigurable hydroforming die was designed and fabricated. The main difference of this die with conventional types is substitution of the rigid surface with a set of spaced pins. Different tubular sections could be produced by adjusting the pins position. Due to the low cost of changing the tool into a new die, this process is appropriate for producing small batch numbers of a tubular product. Numerical simulations were employed to determine the effects of pin diameter and polyurethane layer thickness on the characteristics of final products. Increasing the number of pins was found out to improve dimensional accuracy and surface quality. On the other hand, while using a thicker polyurethane layer reduced dimpling, it led to a poor dimensional accuracy. A bulged and a square brass 70/30 tube were produced with an initial thickness of 2 mm. Thereafter, experimental tests were performed to compare distribution of the thickness and variation of dimensions with the numerical results.