| 摘要 |
The present invention relates to a method for manufacturing a hollow hydro-formed product using a multi-tube assembly, which comprises the steps of: (a) stably placing a multi-tube assembly in a mold, the multi-tube assembly including a hollow outer tube and a hollow inner tube inserted in the hollow outer tube, the hollow inner tube having a plurality of fluid channel holes radially formed therethrough; (b) injecting fluid into the inner periphery of the inner tube; (c) applying fluid pressure to the inner periphery of the outer tube by the fluid while the fluid is discharged through the fluid channel holes of the inner tube; and (d) obtaining a formed product having an intended outer peripheral shape completed according to diameter-enlargement and plastic deformation of the outer tube. According to the present invention, the inner periphery of the outer tube is pressed and hydro-formed by discharging the fluid through the fluid channel holes of the inner tube formed through the inner tube of the multi-tube assembly, and it is thus possible to form a hollow multi-tube product regardless of the plasticity of the inner tube and remarkably improve the shape precision. Moreover, only the outer tube can be selectively and plastically deformed without change in the shape of the inner tube, to produce a hollow formed product having an intended outer peripheral shape. |
