| 摘要 |
<p>An improved drawing die apparatus is disclosed for reducing the wall thickness of a thin wall metal tube in cooperation with a floating pin or a fixed mandrel. At least three, and preferably four, wall thickness sensors are positioned in the die body in angular relationship around the outer periphery of a carbide draw die nib for indicating the wall thickness, and thus the eccentricity, of the tubing as it is being produced. Preferably, the sensors are contact type ultrasonic transducers which are acoustically coupled with a viscous couplant to flats formed on the draw nib in regions overlying a land region of the die. The acoustic coupling between the draw nib and tube is achieved through the O.D. drawing lubricant.</p> |
