| 摘要 |
PROBLEM TO BE SOLVED: To provide an apparatus to suppress thinning of a back face side in a simple constitution in the case of bending a metal tube having a low mechanical elongation in a small radius. SOLUTION: By controlling start timing of side bending for pull-bending and its working speed, the neutral axis of a bending section is moved at 5-10% toward a back face side than the geometrical axis, while metal thinning of the back face side is suppressed, small radius bending of the tube is conducted. A side bending apparatus to a pull-bending apparatus generally used in tube bending are combined, by controlling a pull-bending speed and a side bending speed, small radius bending of a tube having a low mechanical elongation is achieved in a thinning rate of <=20%.
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