Experimental investigation of effective parameters in the tube rotary draw bending process

The rotary draw bending (RDB) process is one of the complex forming processes which is widely used for tube bending. There are different parameters in this process that incorrect selection of them cause the happening of some defects such as thinning and tube ovality. In the present study, the effects of main parameters of the RDB process is investigated on the thinning and ovality of BS 3059 steel tube using the experimental tests. Therefore, a design of experiment (DOE) base on the Taguchi method is used to investigate the effect of mandrel diameter, pressure of pressure die and mandrel position on the thinning of tube outer wall and the tube ovality. Four different values of 7 MPa, 10 MPa, 12 MPa, and 15 MPa are considered for the pressure of pressure die and four values of 7 mm, 15 mm, 20 mm and 34 mm for the mandrel position. The mandrel position is the distance between the mandrel and bending center. Two different chain link mandrels are used with balls diameter of 33.5 mm and 34.5 mm. The results showed that the mandrel position had the most significant effect on the thinning and tube ovality. Although the increase of mandrel position improved the thinning defect in the tube outer wall, the tube ovality increased by the increase of mandrel position from 20 mm to 34 mm. The results showed that the pressure of 7 MPa, mandrel position of 15 mm and the mandrel diameter of 33.5 mm were the best parameters for RDB of BS 3059 steel tube.