| 摘要 |
PROBLEM TO BE SOLVED: To manufacture a variety of U-bend pipes economically by setting the trench dimensions regulating the outside diameter of all bending tools for manufacturing U-bend pipes of different bending radius at the outside diameter of an original pipe or above according to a specified formula and limiting the outside diameter at the bend below an upper limit thereby suppressing fluctuation of the outside diameter. SOLUTION: Trench dimensions M1-Mn regulating the outside diameter, in the direction perpendicular to the bending plane, of all bending tools (ring dice) 10 for manufacturing a variety of U-bend pipes of different bending radius is set at the outside diameter D0 of an original pipe, shown by formulas, or above and the outside diameter, in the direction perpendicular to the bending plane, at the bend of the U-pipe is limited below an upper limit Dmax thus suppressing fluctuation of the outside diameter. In the formulas, M1-Mn represent the trench dimensions of respective bending tools 10 in the ascending order of the bending radius.ΔD1-ΔDn represent increments in the outside diameter in the direction perpendicular to the bending plane determined by performing bending work previously with respective bending radius in the ascending order of the bending radius. DMAX represents upper limit outside diameter in the direction perpendicular to the bending plane. |
