Improvement of Local Decrease in Material Thickness on Fuel Filler Tube

Abstract

A growing demand for lightweight products has been brought about by the rapid development of new automobiles in order to reduce fuel consumption, since the global environment conservation meeting at Kyoto. One of the keys to reduced fuel consumption is to utilize high-strength, light materials like stainless-steel, high-tensile strength steels and magnesium alloys, which are difficult to form due to their material characteristics compared to normal steel tubes. The purpose of this paper discuses the development of our new pressing technology that forms a relatively high-strength and light weight stainless-steel tube which is SUS436 with surface screw threads. Our new press-forming process was tested in order to obtain accurate screw threads on stainless-steel tubes. Finite element simulation and a 3-D digitizer were used to measure the accuracy of tubes manufactured by the proposed pressing method. It was proved from FEM simulation and a 3-D digitizer measurement that the proposed press-forming method decrease tube thickness more effectively than conventional roll-forming technology. As a result, the maximum decrease in material thickness produced by conventional roll-forming process was 40%, but the maximum decrease in material thickness produced by our press-forming process was 20%. Especially the processing by four outer dies and two inner dies is better as for material thickness than the processing by six outer dies and three inner dies.