| 摘要 |
PURPOSE: To eliminate cutting after bending or trial bending before actual working by detecting the deviation between a tube stock length during the bending and the planed value and adding the control operation for adjusting the thickness of a deformation progressing part in the direction to reduce the deviation. CONSTITUTION: A turning angleθof an arm 2 and an actual travel quantity of a tube 1 sent in for turning of the angleθ, that is, a length of a straight tube sent in are measured, in order to generate the actual travel quantity and the turning angleθ, the deviation to a planned value of the travel quantity L set beforehand based on the equation: L=R.θ(1+ρ) is operated, a thickness of the bending part is adjusted so as to reduce the deviation. (in equation, R is a bending radius,ρis a compression rate). That is, in normal bending, by advancing or retreating a guide pieces 4 in the longitudinal direction of the tube 1 and by controlling a compression rate, the tube length of a tube stock sent in for forming the bent part of the prescribed bent angle is controlled so as to be the planned length.
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