JP3328027B2 - Saddle warpage reduction method in bending - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of reducing saddle warpage caused by bending a sheet material by a press brake or the like.

[0002]

2. Description of the Related Art Conventionally, when a plate material is bent by an upper die and a lower die using a bending machine such as a press brake, the resulting product is bent by the influence of residual stress generated when the plate material is cut. A phenomenon that warps inward or outward (generally called saddle warpage) occurs, which causes a problem that product accuracy is deteriorated and appearance is deteriorated.

Generally, when a plate is cut with a shear, the central portion of the bending line p is warped upward as shown in FIG. 1A. When thermally cut using laser, plasma, etc.,
As shown in FIG. 1B, it is known that the central portion of the bending line p is warped downward. As shown in FIG. 2, this saddle warpage does not occur when the ratio l / w of the bending line length (work length) l to the plate width w is equal to or less than a predetermined value. It has been clarified that when / w exceeds a predetermined value, it occurs due to insufficient rigidity of the material. In FIG. 2, the vertical axis represents the amount of saddle warpage (warpage height).
indicates the ratio δ / t between δ and the plate thickness t, the working material is mild steel, black circles are t = 0.8 mm, and white circles are t = 3.2.
mm are shown.

[0004] As means for reducing such saddle warpage, for a saddle warp as shown in FIG. 1 (a) generated in a shear cutting material, an upper metal mold is formed by bending an upper metal mold and a lower metal mold. One in which a pressure in the direction opposite to the pressing direction of the mold is applied to the plate material,
As disclosed in Japanese Patent Application Laid-Open Publication No. H10-209, a punch and a die having a length obtained by appropriately dividing the entire bending width are used, and the punch and the die are warped in the same direction as the saddle warp for each set at the time of pressing. Has been proposed in which a weakly bent portion in the direction opposite to the saddle warp is formed in a portion corresponding to the seam.

[0005]

However, in the case of a cutting material by thermal cutting such as laser or plasma, the direction of saddle warpage is opposite to that of a shear cutting material. There is a problem that the saddle warp reduction method cannot be applied.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to reduce saddle warpage caused by bending of a plate cut by thermal cutting by a simple method. Aim.

[0007]

SUMMARY OF THE INVENTION A method for reducing saddle warpage in bending according to the present invention is a method for reducing saddle warpage caused by bending of a plate material cut by thermal cutting. , particular burn vicinity of the plate bending at the inside bend line using a press brake
This is characterized in that the plate material is thermally yielded .

[0008]

According to the present invention, after thermal cutting of a sheet material, a press is performed.
During the bending process of the plate material using the brake, the position near the inside bending line is burned, so that the plate material is thermally yielded and a residual stress generated in the plate material in a direction opposite to the residual stress generated at the time of cutting, and The material strength can be improved by self-quenching the plate material, and thereby, saddle warpage caused by bending of the plate material can be reduced.

In this case, when the baking position is set to a position several mm away from the bending line on both sides of the bending line and extends over the entire length of the plate material, the effect of reducing the saddle warpage becomes the best.

Further, by performing the baking process using the same cutting machine as that for performing thermal cutting, it is possible to reduce saddle warpage without involving movement of the sheet material between processes and without using a special device. Can be performed.

[0011]

Next, a specific embodiment of the method for reducing saddle warpage in bending according to the present invention will be described with reference to the drawings.

FIG. 3 shows the amount of saddle warpage (warpage height) when an SPC material is cut into a work having a width of 100 mm and a length of 2500 mm by a plasma cutting machine, and the work is bent by a press brake. The measured values are shown. In this case, saddle warpage occurs such that the center of the bending line projects downward (see FIG. 1B), and the amount of saddle warp is
1.6mm thick and 6-7mm at center of bending length
It can be seen that the thickness is 7 to 8 mm when the thickness is 2.3 mm. The bending conditions in FIG. 3 include a gooseneck punch having a tip radius of 0.2 mm and a die width V1.
Two dies were used, and the bending angle was 90 °.

In this embodiment, in order to reduce the above-mentioned saddle warpage, only the cutting conditions are changed while the work after the plasma cutting is mounted on the cutting machine, and the bending line which becomes inside during the bending of the work is formed. At both sides and from the bending line
A position 3 mm apart was burned for the length of the work. Here, as a condition of the plasma cutting machine, when cutting a work (thickness 1.6 mm), an oxygen plasma gas is used, a cutting current is set to 50 A, and a cutting speed is set to 3 m / min. When baking this work after cutting, argon gas was used, the cutting current was set to 30 A, and the cutting speed was set to 1 m / min. In this manner, when no processing is performed, saddle warpage of about 7 to 8 mm occurs due to V bending after cutting the workpiece, whereas in the present embodiment,
The saddle warpage was suppressed to 1 mm or less.

The reason why saddle warpage can be reduced in this way is that thermal yielding of the work causes a residual stress in the work in a direction opposite to the residual stress generated at the time of cutting, and the material strength of the plate material. (Rigidity) is improved by self-quenching.

Table 1 shows the measured data of the amount of saddle warpage when the burning position is changed.

[0016]

[Table 1]

As is clear from this table, the baking position is
As in the present embodiment, positions near both sides of the bending line (2 to 3 mm)
It is understood that setting to is most effective in reducing the saddle warpage.

In this embodiment, the values of the cutting current and the cutting speed of the above-mentioned plasma cutting machine are merely examples, and the combination of the cutting current and the cutting speed can be appropriately changed. Needless to say, these cutting conditions and the like are changed according to the thickness and material of the work. Also, in the above description, plasma cutting was taken as an example, but in the case of laser cutting, by performing the same as above,
The same effect as in plasma cutting can be obtained.

[0019]

As described above, according to the present invention, by burning the position near the bending line after thermal cutting,
It is possible to drastically reduce saddle warpage caused by bending of a plate material. In addition, since the baking process can be performed using the same cutting machine as the one that performs thermal cutting, saddle warpage can be reduced by a simple method without moving the sheet material between processes and without using special equipment. Can be achieved.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a saddle warpage state;

FIG. 2 is a graph illustrating an effect of a sheet width on a saddle warpage amount;

FIG. 3 is a graph showing a measurement result of a saddle warpage amount caused by plasma cutting.

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B21D 1/00 B21D 5/02 B23P 17/00

Claims (3)

(57) [Claims] 1. A method of reducing saddle warpage caused by the bending of the sheet material cut by the thermal cleavage, after thermal <br/> cleavage, and inside during bending of the sheet material using a press brake Plate material by baking near the bending line
A method for reducing saddle warpage in bending, which is characterized by performing thermal yielding . 2. The bending process according to claim 1, wherein the baking position is set at a position separated from the bending line by several mm on both sides of the bending line and extends over the entire length of the plate material. Method of reducing saddle warpage in 3. The method for reducing saddle warpage in bending according to claim 1, wherein the baking process is performed using the same cutting machine as that for performing thermal cutting.