| 摘要 |
A method of forming butted tubing comprises drawing a tube through a die 52 held in a holder and over a plug 54 attached to a bar. The die holder and plug bar are each independently moveable in the direction in which the tube is drawn through the die and in the opposite direction. Movement of the holder and bar occurs while the tube is being drawn to vary spacing between them and so vary a wall thickness of the tube. In one aspect the holder is moved in the same direction that the tube is drawn through the die, increasing tube wall thickness. In another aspect, movement of the die holder and of the plug bar are at different speeds in the same direction while the tube is being drawn to vary spacing between the die and plug, so varying a wall thickness. Since the plug and die may be moved in the same direction as the movement of the tube, the large friction forces associated with tube drawing do not have to be overcome to vary the spacing between the die and plug bar which allows for lower powered actuators such as stepper motors (62, 72, Figures 5 and 6). |
