JPH03142020A - Bending method of stretch-flange - Google Patents

Abstract

PURPOSE:To prevent the generation of deformation near by the bend line and irregularity of bend angle of flange by performing bending after performing stretch deformation processing in a part to be flanged before bending. CONSTITUTION:A metallic plate P is placed on a cut bend die 1 and fixed with a pad 2. The cutting edge 1b of the cut bend die 1 is straight, but the cutting edge 3a of a bend punch 3 is corrugation that has mutually peak parts 3a1 and trough parts 3a2 and the height of ridgeline parts 3b following to the peak parts 3a1 is gradually reduced in the thickness direction of the punch 3. When the punch 3 is lowered, the part F0 to be flanged of the metallic plate P is cut and bent into corrugation and given with preliminary deformation. The flange part F is formed by lowering further the punch 3 and holding/ pressing with the clearance between the side wall of the recessed part 1a of the die 1 and the side wall of the punch 3. The deformation such as shear droop and scoop along the bend line L isn't generated.

Description

Detailed Description of the Invention A0 Object of the Invention (1) Industrial Application Field The present invention relates to a method for bending a flange on a metal plate such as aluminum or iron, and in particular, it relates to a method for bending a flange on a metal plate such as aluminum or iron. This invention relates to a stretch flange bending method suitable for bending a flange while stretching it along a bend line, or for bending a flange while stretching it along a bend line of a three-dimensional metal plate after drawing.

(2) Conventional technology A flat metal plate P is bent along an arcuate bend line L using a bend die and a bend punch to form an arcuate stretch flange as shown in No. 5 [1(c)]. If F is formed, elongation stress remains in the vicinity of the flange F and shrinkage occurs in the direction of the bend line L, resulting in sagging D1 as shown in Fig. 6(a) in the vicinity of the bend line L. , as shown in FIG. 6(b), the accuracy of the bend line L is reduced, and the angle of the flange F is not exactly 90', resulting in an error θ.

'In order to avoid such inconvenience, a large number of small holes etc. are continuously drilled in advance along the pen and drain lines to form a stress concentration area, and the stress concentration area is completely plastic deformed by bending. It has been proposed to prevent the occurrence of deformation such as sag or shakiness by causing this (see, for example, Japanese Patent Application Laid-Open No. 189828/1983).

(3) Problems to be Solved by the Invention However, when a large number of small holes etc. are formed along the bend line as described above, not only does the strength of that part decrease significantly, but also the small holes etc. are exposed to the outside. May be exposed and degrade the appearance of the product.

The present invention has been made in view of the above-mentioned circumstances, and provides a stretch flange bending method that can reliably prevent the occurrence of deformation such as sag and shank, and that does not adversely affect the appearance of the product. The purpose is to provide.

B1 Structure of the Invention (1) Means for Solving the Problems In order to achieve the above object, the present invention involves bending the edge of a metal plate such as aluminum or iron while giving it elongation at the flange forming part. A first feature of the stretch flange bending method for forming a flange is that, prior to bending, the flange forming portion is stretched and deformed, and then the flange forming portion is bent.

Further, in addition to the first feature, the present invention performs the elongation deformation process by trimming the flange forming portion of the metal plate with a wavy cutting blade that converges toward the bend line, and then The second feature is that the bending process is performed using a bend punch along the curve.

(2) Effect According to the above-described first feature of the present invention, the flange-forming portion of the metal plate is stretched in advance to a state where it undergoes deformation due to stretch deformation prior to the bending process. When forming the flange, elongation stress is prevented from remaining in the flange, and as a result, deformation does not occur near the bend line.

According to the second feature of the present invention, by using a wave-shaped trimming blade when trimming the edge of the flange-shaped tL portion of the metal plate, the flange-forming portion of the metal plate is stretched into a wave shape. The predeformation is given by Therefore, by bending this flange forming portion with a bend punch, a stretch flange without a defom can be formed.

(3) Examples Hereinafter, the present invention will be explained in detail based on the drawings.

Figures 1 to 5 show one embodiment of the present invention.
The figure is a longitudinal sectional view of a bending mold for carrying out the method of the present invention, FIG. 2 is a sectional view taken along the line ■-■ in FIG. 1, FIG. The figure shows the first part after the bending process is completed.
5(a) to 5(c), which are the same cross-sectional views as in the figure, are diagrams showing the deformation process of the metal plate due to processing.

FIG. 5(a) shows a metal plate P cut into a roughly rectangular shape before bending, and this metal plate P is processed with a cut-bend die to be described later to form a flange forming part F. After the predeformation shown in FIG. 5(b) is applied, the flange F is finally bent by 90° along the bend line as shown in FIG. 5(c).

The bend line L consists of a circular arc, and therefore the length between both ends of the flange F is extended from a length of 1° before machining to a length l after machining by the difference between the straight line and the circular arc.

As shown in FIGS. 1 to 3, this bending mold includes a cut-bending die 1, a pad 2 for fixing a metal plate P as a workpiece on the upper surface of the cut-bending die 1, and It consists of a pend bunch 3 which is fitted from above into a recess ala formed on the upper surface of a cut-bend die l by a hydraulic drive mechanism (not shown) to perform trimming and bending on the metal plate P at the same time. In order to form a flange F having a curved bend line L on the metal plate P, the pend bunch 3 and the recessed portion 1a of the cut bend die 1 are formed into an arc shape in a plan view.

The outer surface in the curved direction of the pend bunch 3 formed in an arc shape (
(left side in Fig. 1) and recess 1 of cut bend die 1
A gap δ between the thickness of the metal plate P and the path is formed between a and a to form a relief for the bent metal plate P. On the other hand, the inner surface of the pend bunch 3 in the bending direction and the recess 1a of the cut-bend die 1 are in sliding contact with each other and the metal plate P
Cutting blades 3a and lb are formed for trimming the edges. As is clear from Fig. 2, cut bend die 1
The cutting blade 1b on the side is formed in a straight line in a side view, whereas the cutting blade 3a on the side of the bend punch 3 is formed in a waveform with alternating peaks 3a+ and valleys 3az, The height of the ridgeline portion 3b following the peak portion 3a+ of the blade 3a is formed so as to gradually decrease in the thickness direction of the pend bunch 3.

Next, the operation of the embodiment of the present invention having the above-described configuration will be explained.

A metal plate P cut into a substantially rectangular shape as shown in FIG. 5(a)
Place it on cut bend die 1 and fix it with pad 2,
When the pend bunch 3 is lowered from above, the flange forming portion F of the metal plate P is first cut by the many peaks 3a+ of the cutting blade 3a of the pend bunch 3 and the cutting blade 1b of the cut bend die 1. is partially sheared at predetermined intervals, and the sheared portions are pressed by the ridgeline portion 3b of the descending pend bunch 3 and bent into a wave shape. When the pend bunch 3 further descends and the valley fB3a2 of the cutting blade 3a engages with the cutting blade 1b of the cut bend die 1, the flange forming portion F of the metal plate P
0 is completely cut and given the predeformation shown in FIG. 5(b). Thus, the metal plate P is plastically deformed in a waveform such that the amount of deformation gradually increases from the vicinity of the bend line L toward the edge of the flange forming portion F0.

After the trimming of the metal plate P is completed as described above, when the bend punch 3 further descends and reaches the position shown in Fig. 4,
A pre-deformed flange forming portion F of the metal plate P. is bent downward and pressed into the gap between the side wall of the recess tffla of the cut-bend die 1 and the side wall of the bend punch 3, and finally a flange F as shown in FIG. 5(C) is formed. This flange F is a flange forming portion F that has been predeformed to a plastic deformation region. As a result, residual elongation stress is avoided, and as a result, deformation such as wobbling or shakiness is prevented from occurring along the bend line L.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the embodiments described above, and various small design changes can be made without departing from the scope of the invention described in the claims. Is possible.

For example, in the embodiment, the trimming process for pre-deforming the flange forming part F0 of the metal plate P and the bending process for forming the flange F are performed simultaneously using the cut-bend die 1, but it is also possible to perform both processes separately. Of course, it is also possible. Moreover, as a means for pre-deforming the metal plate P, instead of making one of the pair of cutting blades corrugated, both of the cutting blades can be made corrugated. Furthermore, the method of the present invention provides a flat metal plate P.
It is applicable not only to forming a flange along a curved bend line, but also to forming a flange on the edge of a three-dimensionally drawn metal plate P.

C3 Effect of the Invention According to the first feature of the present invention described above, the flange forming portion of the metal plate is predeformed to a state where mold deformation occurs prior to the bending process, so that the flange is not easily deformed by the subsequent bending process. Elongation stress is prevented from remaining in the flange during formation. As a result, occurrence of deformation in the vicinity of the bend line due to residual elongation stress and uneven bending angles of the flanges are reliably prevented. Furthermore, according to the method of the present invention, no small holes are formed in the vicinity of the flange after the molding is completed, so there is no risk that its strength will decrease or its appearance will be adversely affected.

According to the second feature of the present invention, by using a wave-shaped trimming blade when trimming the edge of the flange-forming portion of the metal plate, the flange-forming portion of the metal plate is stretched into a wave shape. A predeformation is given. Therefore, by bending this flange forming portion with a bend punch, generation of defom can be prevented.

[Brief explanation of the drawing]

Figures 1 to 5 show one embodiment of the present invention.
The figure is a longitudinal cross-sectional view of a bending mold for carrying out the method of the present invention, Figure 2 is a cross-sectional view taken along the - shore line in Figure 1, Figure 3 is a cross-sectional view taken along the line III--I in Figure 1, and Figure 4 is a cross-sectional view taken along the line III--I in Figure 1. is the same cross-sectional view as FIG. 1 after the bending process is completed, FIGS.
) is a diagram showing the deformation of a flange formed by a conventional bending method. F...Flange, F, o...Flange forming part, L.
...bend line, P...metal plate,

Claims (1)

[Scope of Claims] [1] Stretch flange bending in which a flange (F) is formed by bending the flange forming portion (F_0) at the edge of a metal plate (P) such as aluminum or iron while giving elongation. In the method, the flange forming part (F_0) is stretched and deformed before the bending process, and then the flange forming part (F_0) is
A stretch flange bending method characterized by bending. [2] A wave-shaped cutting blade (
The stretching and deforming process is performed by trimming in step 3a), and then the bending process is performed along the bend line (L) with a bend punch (3),
The method of bending a stretch flange according to claim 1.