Abstract
It is important in tube bending to prevent both decrease in the tube strength by the reduction of its outer thickness and decrease in its cross sectional area by the flattening of the tube. The effect of the bending conditions such as the pressure of clamp die, pressure die, booster, the booster speed and bending speed on changes in the thickness and the degree of flatness of tubes bended by a rotary draw bender was investigated using A6063 alloy tubes. It was found that the effect of the booster speed was biggest and the effects of pressure of the pressure die and the bending speed were small, and then that the pressure of the clamp die and the booster had no effect. In order to gain the little decrease of the outer thickness and the degree of flatness of the bended tubes, the pressure of the pressure die, the booster speed and the bending speed have to be low, fast and slow, respectively. These are related to the decrease of axial tension in tube bending.
