ROTARY FORMING FOR THE STRAIGHTENING OF TUBING

A new straightening method using rotary forming with three rollers is proposed. A helical rolling mill with three rollers is used in the exp eriment. The prebend aluminum seamless pipes are straightened under va rious working conditions. It is clarified that an attainable straighte ning ratio of the product can be determined by the pitch and the nomin al reduction in radius, and there exists a minimum length of rollers t o guarantee the selected straightening ratio. The curved shape can be straightened up to 90% under optimum working conditions. It is also cl arified that there exists an maximum pitch to guarantee a certain stra ightening ratio and the axial feed rate can be selected arbitrarily in practice.