JPH0330447B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for removing warpage that occurs in a metal plate such as a steel plate due to spring back during press forming, and an apparatus used in the method.

In manufacturing industries such as the automobile industry, when pressing steel plates, etc. by press forming and bending the edges to produce, for example, door outer panels, etc., the flange part is formed by bending and flange processing, which bends the edges of the steel plate. In many cases, it is necessary to perform molding (shrinkage flange molding) in which a pressure is applied to the processed plate in a direction to compress the flange portion.
When the molded plate is removed from the press after this molding, a repulsive force (spring back) against the applied external force acts, causing deformation (warp) such as distortion. This warping causes problems when assembling the final product, such as a car, such as making it difficult to raise and lower the window glass or not following the design line. Conventionally, in order to correct this warpage, recesses are formed at regular intervals in the steel plate (back cutting) in the parts that are hidden inside during the bending process (bending process) following shrinkage flange forming, or recesses are formed in the mold where the warpage occurs. We use methods such as creating unevenness (overcrown) in advance to account for the amount of deformation caused by warping.

However, each of these conventional methods has its own problems. In other words, although the overall warpage can be corrected with the back cutting method, when forming the back cut shape, distortion occurs around the back cut part, causing distortion even to the surface that appears on the surface of the final product (general surface), causing external distortion. A problem arises when it comes to sheet steel. On the other hand, in the case of overcrowning, it is necessary to make corrections in consideration of deformation at the parts of the mold where warpage occurs during all processes leading to the final product, and a large amount of production is required in processing and finishing the mold. This requires a number of steps and costs a huge amount.

The present invention is intended to solve the problems of the prior art described above.

The object thereof is to provide a method for correcting warpage by performing partial back cuts in the bending process, and an apparatus for use in the method.

That is, the method for correcting springback in press forming of the present invention corrects the warpage that occurs in the metal plate flange after shrinkage flange forming by moving the flange from the bending start end toward the open end at regular intervals in the bending process. It has a feature that correction is achieved by forming a recess from a position approximately half the distance from the open end to the open end.

Further, the device of the present invention is biased downward by a deflection processing cam, a deflection member attached to the tip of the cam, and an elastic means mounted vertically movably between the deflection members. A back-cutting curved blade for forming recesses at regular intervals in the flange portion to be bent from a position approximately half the distance between the bending start end and the open end from the bending start end toward the open end. It also includes a fixed cam that is attached to the die and pushes up the curved blade in response to the advance of the processing cam, and has the feature of being able to correct spring back during press molding.

If the curvature of the bent part is constant, the warpage that occurs during the bending process will be the length of the bent flange part (hereinafter abbreviated as a).
It is determined by only that, the shorter a, the less warpage. Furthermore, although the value of a for ordinary molded products handled in the automobile industry varies, it has been empirically known that warpage falls within the allowable range at a length of about a/2 or less. If back-cutting is carried out to the length, warpage will be acceptable overall, and the result will be the same as when tension flange forming is performed. In order to make the back cut on a part of the flange in this way, when using a conventional bending cam, it is necessary to use a bending cam whose part that forms the back cut of the flange has a convex shape. Make a bend to form a recess at the flange end. In this method, it is necessary to adjust the angle of the curvature processing cam in the advancing direction. In order to cut the back of the flange portion without making such adjustments, the apparatus of the present invention is used. For example, this device is equipped with a back cutting curved blade that can be moved up and down at regular intervals at the tip of the curved cam, and is held by a slide plate that is a holding guide member, and the curved blade is usually held by an elastic body such as a coil spring. is pressed downward, and a slope is provided at the bottom of the curved blade. On the other hand, a fixed cam with an inclined surface is attached to the die located on the opposite surface in the forward direction of the curved cam. While the bending processing cam is advanced and the bending is being performed, the back cutting curved blade is pressed down by the coil spring, so that the back cutting portion is not processed. When the bending flange processing is completed, the processing cam should still have a stroke margin of about 5 to 10 mm, and if it continues to move forward, the slopes of the back cutting curved blade and the fixed cam will come into contact with each other, and the curved blade will slide. It rises in the direction determined by the plate and starts cutting out the spine. Then, the back cutting process ends when the movement of the bending process cam stops. To take out the bent flange from the processing die after processing is completed, a pull-out claw attached to the tip of the bent cam is hooked to the end of the flange, and the flange is pulled out when the cam is returned. At this time, since the back-cut shape part forms a negative angle with respect to the drawing direction, a mold relief for side bending corresponding to this part is provided so that the product can be taken out without deforming.

The method and apparatus of the present invention are generally applicable to areas where warpage occurs due to spring back after tightening flange forming. The forming material is usually a steel plate, but may also be other metal plates such as stainless steel, aluminum, brass, etc. The length, width, mutual spacing, number, etc. of the spine cuts are optimally selected so as to minimize warping for each molded member. For this reason, the number of curved blades of the back cutting device and the dimensions and shapes of each part can be changed as desired.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the method of the present invention and a device used therein will be described below with reference to the drawings, while comparing it with a conventional example.

FIG. 1 shows two perspective views at different angles of an automobile door outer panel 1 that has been subjected to the conventional back-cutting process in the bending process.

In the figure, the shaded area indicates the remaining distortion caused by the back cutting process. As described above, in the conventional back-cutting process, although it is possible to remove the warpage of the shrunk portion, the distortion caused by the back-cutting process extends to the surface portion of the panel 1.

FIG. 2 shows a perspective view of a door outer panel 3 that has undergone partial back cutting according to the present invention.

In the figure, the shaded areas represent the same meanings as in FIG. 1. As is clear from a comparison of the shaded areas in FIG. 1 and FIG. 2, in the partial back cutting of the present invention, distortion does not extend to the panel surface. Further, in order to cut the back from the middle of the bent part, the back cut part is further bent inward.

FIG. 3 is a sectional view showing a method of performing the partial back cutting process according to the present invention shown in FIG. 2 by increasing the cam angle and using a bent cam.

The door outer panel 5, which has been subjected to shrinkage flange processing, is held between a die 6 and a pad 7, and is pressed from the direction A in the figure by a bending cam 9 equipped with a back cutting blade 8 having a convex tip shape at regular intervals. At the same time, a partial back cut is performed.

FIG. 4 shows a sectional view at the forward end of the apparatus according to the present invention for performing the above-mentioned partial back cutting process. This device consists of a bending cam 9, a bending member 10, a back cutting blade 11, a coil spring 12, a slide plate 13, and a fixed cam 14. The method of using this device is to sandwich the door outer panel 5 to be partially back-cut between the die part and the pad 7 made up of dies 6 and 15, and insert the bending cam 9 onto the lower mold body 16. All you have to do is move it forward and backward.

FIG. 5 shows a sectional view of the door outer panel 3 immediately after partial back cutting has been performed using the bending cam shown in FIG. 3 and the above-mentioned apparatus.

Since the die 6 is provided with a mold relief 17, it can be easily taken out by simply pulling it out in the direction B in the figure.

By using the method and apparatus of the present invention as described above, the following effects can be obtained.

That is, since it is no longer necessary to perform overcrowning, the number of mold manufacturing steps and the cost required for mold manufacturing in the product production preparation stage can be significantly reduced. In addition, since the warpage correction value of bent members can be controlled by simply adjusting the amount of partial back cuts, it is easy to quickly respond to various changes that increase or decrease warpage and stabilize the quality of the final product. be. Furthermore, by performing partial back-cutting, it is possible to easily remove distortions on the surface of the outer panel parts, which not only makes it possible to make the design lines of the final product (automobile) cleaner throughout the car body. This can be done more smoothly than raising and lowering the glass plate of the door.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an automobile door outer panel with a conventional back-cutting process, and FIG. 2 is a perspective view showing a similar door outer panel with a partial back-cutting process according to the present invention. Further, FIG. 3 is a cross-sectional view showing a method of performing partial back cutting according to the present invention using a conventional bending cam, and FIG. 4 is a cross-sectional view of a similar case using the apparatus of the present invention. FIG. 5 is a sectional view showing how to take out the processed panel. In the figure, 1... door outer panel with back-cutting, 2... back-cutting portion,... location where distortion occurs due to back-cutting or partial back-cutting, 3... door outer panel with partial back-cutting, 4... Partial spine cut part, 5... Door outer panel with shrink flange processing, 6... Die, 7... Padded,
8... Back cutting blade, 9... Bent processing cam, 10
...Bending member, 11...Back cutting curved blade, 12...
...Coil spring, 13...Slide plate, 14
... Fixed cam, 15 ... Die, 16 ... Lower mold body, 17 ... Mold release.

Claims (1)

[Scope of Claims] 1. Warpage that occurs in the metal plate flange after shrinkage flange forming can be avoided by changing the distance between the bending start end and the open end from the bending start end toward the open end at regular intervals in the bending process. A method for correcting springback in press molding, characterized in that correction is performed by forming a recess from a position separated by about half a distance to an open end. 2 The bending processing cam, the bending member attached to the tip of the cam, and the elastic means installed between the bending members so as to be able to move up and down force the flange portion to be bent downward. A back-cutting curved blade is attached to the die to form a recess from a position approximately half the distance between the bending start end and the open end to the open end at regular intervals from the bending start end toward the open end. A working flange device capable of correcting spring back in press forming, characterized in that it comprises a fixed cam that pushes up the curved blade in accordance with the advance of the working cam.