Patent ID: 8720247

Claim:
A method for bending a material of a thin metal plate using a bending machine, the method comprising: providing the bending machine with a first die unit including multiple first die portions, each of which has a forward end for a bending process and is neighboring to each other in a direction of movement of the material, the first die unit having an upstream-side first die portion and a downstream-side first die portion, providing the bending machine with a second die unit including multiple second die portions, each of which has a forward end for the bending process and is neighboring to each other in the direction of movement of the material, the second die unit having an upstream-side second die portion and a downstream-side second die portion, each of the first die portions being opposed to each of the second die portions to form an upstream-side pair of the first and second die portions and a downstream-side pair of the first and second die portions in the direction of movement of the material, each of the upstream-side and downstream-side pairs of the first and second die portions being sequentially operated so that at least one of the first and second die portions is relatively moved toward the other die portion, in order to continuously carry out the bending method so as to form the material in a corrugated shape, a first step feeding the material toward a press work area between the first and second die units; a second step relatively moving the downstream-side second die portion toward the downstream-side first die portion to a lower-most position of the downstream-side second die portion in order to carry out the bending process to the material, which is fed to a press-work operating position between the downstream-side first and second die portions, a third step relatively moving the upstream-side second die portion toward the upstream-side first die portion to an intermediate position of the upstream-side second die portion and holding the upstream-side second die portion at the intermediate position during the second step, so as to form a clearance between the forward end of the downstream-side first die portion and the forward end of the upstream-side second die portion, so that the clearance is located at a position before the press-work operating position for the bending method, wherein the material is in contact with the forward end of the upstream-side second die portion but distanced from the forward end of the downstream-side first die portion and the clearance is larger than a thickness of the material; and a pulling force of the material during the second and third steps is controlled by the clearance.