Stretch forming device and stretch forming method

Abstract

A stretch forming device includes a die and gripping portions gripping both end portions of an elongate material. The cross-sectional shape of the die has a curved shape bulging a central side of a forming surface; the length in a longitudinal direction of the elongate material is less than that of the forming surface; a second die having a second forming surface along the forming surface is installed removably on a central portion of the forming surface; and the stretch forming device has a first mode wherein, when the second die is installed on the forming surface, only the second die is pressed against the elongate material while a tensile force is applied to the elongate material, and a second mode wherein, when the second die is removed from the forming surface, the die is pressed against the elongate material while a tensile force is applied to the elongate material.

1 . A stretch forming device comprising:
 a die; and   gripping parts which grip both end portions of a material to be formed having an elongated shape,   wherein a cross-sectional shape of the die has a curved shape in which a center side of a forming surface of the die bulges, and the forming surface is formed so as to give a curved shape to the material to be formed,   a second die having a second forming surface in which a length thereof along a longitudinal direction of the material to be formed is shorter than a length of the forming surface and which is along the forming surface is removably installed at a central portion of the forming surface, and   the stretch forming device has   a first mode in which, when the second die has been installed on the forming surface, only the second die presses the material to be formed while a tensile force is applied to the material to be formed by the gripping parts, and   a second mode in which, when the second die has been removed from the forming surface, the die presses the material to be formed while a tensile force is applied to the material to be formed by the gripping parts.   
     
     
         2 . A stretch forming device comprising:
 a die; and   gripping parts which grip both end portions of a material to be formed having an elongated shape,   wherein the die is divided into a plurality of pieces in a longitudinal direction of a material to be formed to have a plurality of divided dies which can be individually changed in position with respect to a side of the material to be formed, and   the stretch forming device has   a first mode in which, when the divided die installed at a central portion, among the plurality of divided dies, is disposed to protrude to the side of the material to be formed more than the divided dies installed at end portions, only the divided die disposed at the central portion presses the material to be formed while a tensile force is applied to the material to be formed by the gripping parts, and   a second mode in which, when the plurality of divided dies disposed at the central portion and the end portions are disposed so as to give a curved shape to the material to be formed, the plurality of divided dies disposed at the central portion and the end portions press the material to be formed while a tensile force is applied to the material to be formed by the gripping parts.   
     
     
         3 . A stretch forming device comprising:
 a die; and   gripping parts which grip both end portions of a material to be formed having an elongated shape,   wherein a cross-sectional shape of the die has a curved shape in which a center side of a forming surface of the die bulges, and the forming surface is formed so as to give a curved shape to the material to be formed, and   the stretch forming device has   a first mode in which only a central portion of the forming surface of the die presses the material to be formed while a tensile force is applied to the material to be formed by the gripping parts, and   a second mode in which an entire surface of the forming surface of the die presses the material to be formed while a tensile force is applied to the material to be formed by the gripping parts.   
     
     
         4 . A stretch forming method using a stretch forming device,
 the device including   a die, and   gripping parts which grip both end portions of a material to be formed having an elongated shape,   a cross-sectional shape of the die having a curved shape in which a center side of a forming surface of the die bulges, and the forming surface being formed so as to give a curved shape to the material to be formed,   the method comprising:   a step of installing a second die having a second forming surface in which a length thereof along a longitudinal direction of the material to be formed is shorter than a length of the forming surface and which is along the forming surface, at a central portion of the forming surface;   a step of causing, when the second die has been installed on the forming surface, only the second die to press the material to be formed while a tensile force is applied to the material to be formed by the gripping parts; and   a step of causing, when the second die has been removed from the forming surface, the die to press the material to be formed while a tensile force is applied to the material to be formed by the gripping parts.   
     
     
         5 . A stretch forming method using a stretch forming device,
 the device including   a die, and   gripping parts which grip both end portions of a material to be formed having an elongated shape,   the die being divided into a plurality of pieces in a longitudinal direction of a material to be formed to have a plurality of divided dies which can be individually changed in position with respect to a side of the material to be formed,   the method comprising:   a step of disposing the divided die installed at a central portion, among the plurality of divided dies, so as to protrude to the side of the material to be formed more than the divided dies installed at end portions;   a step of causing only the divided die disposed at the central portion to press the material to be formed while a tensile force is applied to the material to be formed by the gripping parts; and   a step of causing, when the plurality of divided dies disposed at the central portion and the end portions are disposed so as to give a curved shape to the material to be formed, the plurality of divided dies disposed at the central portion and the end portions to press the material to be formed while a tensile force is applied to the material to be formed by the gripping parts.   
     
     
         6 . A stretch forming method using a stretch forming device,
 the device including   a die, and   gripping parts which grip both end portions of a material to be formed having an elongated shape,   a cross-sectional shape of the die having a curved shape in which a center side of a forming surface of the die bulges, and the forming surface being formed so as to give a curved shape to the material to be formed,   the method comprising:   a step of causing only a central portion of the forming surface of the die to press the material to be formed while a tensile force is applied to the material to be formed by the gripping parts; and   a step of causing an entire surface of the forming surface of the die to press the material to be formed while a tensile force is applied to the material to be formed by the gripping parts.