EP2490835A1

EP2490835A1 - Method and device for shaping flat workpieces

Info

Publication number: EP2490835A1
Application number: EP11804921A
Authority: EP
Inventors: Walter Hommel
Original assignee: GIW Verwaltungs- und Vertriebs GmbH
Current assignee: GIW Verwaltungs- und Vertriebs GmbH
Priority date: 2010-09-21
Filing date: 2011-07-26
Publication date: 2012-08-29
Also published as: WO2012037914A1; DE102010048589A1

Abstract

The invention relates to a method for shaping flat workpieces, in particular for shaping and folding sheet metal parts, preferably external parts in the body construction, wherein the workpiece is subjected to compressive and/or tensile stresses during folding. The method is characterized by measures according to which excess material of the workpiece is used in compression areas and/or material of the workpiece is stretched in expansion areas. The invention relates to an appropriately designed device.

Description

METHOD AND DEVICE FOR MOLDING FLOOR

COMPONENTS

The invention relates to a method for forming flat workpieces, in particular for molding and folding of sheet metal parts, preferably of external parts in the bodywork, wherein the workpiece when folding compressive stresses and / or tensile stresses are mediated. Likewise, the invention relates to a corresponding device which uses the method according to the invention.

Basically, this is about the forming or forming / deformation of workpieces, in particular the deep drawing of sheets.

Body components are usually formed from sheet metal. The basic shape of such body parts is regularly produced by a drawing process. The actual drawing process is followed by further work steps in which the so-called drawing edge is cut off and the part shape is finished.

The function and connection of the finished part to other body parts specify the effort to be operated. So it is usually necessary that a board must be folded after the actual shaping. For outer panels such as bonnets, doors or tailgates is made by folding an intermediate form, which is further formed later. More specifically, the outer panel is mortared or roll-folded against the inner panel. In other outer panels, the bent board serves as a welding or riveting flange for connecting the respective sheet metal parts in the body.

For a better understanding of the teaching according to the invention, FIGS. 1 to 3 show the example of a bonnet the respectively required sequence of operations with reference to a simplified sectional representation.

Figures 1 to 3 relate to a principle section on a hood and show the required sequence of operations.

Specifically, Figure 1 shows a schematic plan view of a hood.

CONFIRMATION COPY Figure 2 shows a simplified sectional view of the section AA through the hood in the connection area to the fender. The outer panel is connected to the inner panel via a flanging flange.

FIG. 3 shows the production steps to be carried out on the outer panel for producing the flanging flange. After the actual drawing, the outer panel is trimmed. There is a folding. After bending, pre-flanging and finally finish flanging up to the flare flange.

Figures 4 and 5 relate to a principle section through a side wall in the connection to the bumper and show the required sequence of operations.

More precisely, Figures 4 and 5 show a simplified sectional view of a side wall in the connection to the bumper and the required sequence of operations for generating the fold, which serves for welding to the inner panel. After pulling, the outer panel or sidewall is trimmed. This is followed by the fold at which the side wall is welded to the inner panel.

Usually, i. Normally, body parts are three-dimensionally shaped and therefore have correspondingly shaped or curved connection boards. This is the figures 6, 7 and 9 to 10 can be removed. When folding the board is stretched or compressed, as shown in detail in the aforementioned figures.

Likewise, the bent edge of the component can be curved. The designed after the drawing board is stretched or dipped accordingly when folding. In that regard, reference is made to FIGS. 8 and 11.

With regard to the strains and compressions that occur, it is essential that these result from the component and edge curvature - forcibly -, whereby stretching and compression can be superimposed. Resultant tensile and / or compressive stresses produce a problematic elastic resilience of the material, which can deform the component. Such an unwanted deformation is to be avoided or compensated. From practice, different process steps are known to substantially eliminate such - unwanted - deformations. These methods include conventional folding, also called free folding (Figures 12, 13). Furthermore, the folding with over-arched shape according to FIGS. 14, 15 is known. The known bending with waves from the drawing is shown in FIGS. 16, 17. For the known folding with preferred shape or preform reference is made to Figures 18, 19. A controlled folding with sheet holder, also known from practice, the figures 20, 21. Finally, from the practice of a folding with an interrupted Abkantlinie is known, as shown in Figures 22, 23 and 24.

For the problem basically occurring during bending, reference is made to FIGS. 6 to 11. In detail the following:

If the workpiece or sheet metal is formed by a positively curved bending line during bending, the sheet is subjected to pressure in the board. The board is compressed. There are considerable compressive stresses.

A positive bending line can result from a positive component curvature or a positively curved component edge. After moving apart of the tool, the sheet springs back by the elastic amount and there is a so-called spring-back. This can be seen in detail in the illustrations from FIGS. 6 and 7.

FIG. 8 shows the folding of a positively curved component edge, according to which the edge of the cut-out edge of the component is longer than the bending line. As clearly shown in FIG. 8, each element of the board during folding is compressed in its outer area by the difference in length shown in FIG. Here, too, compressive stresses occur, which lead to an elastic springing of the sheet.

Figures 9 and 10 relate to the springback of the material during bending due to tensile stresses. If the sheet is formed by a negatively curved bending line during bending, a tensile load is created in the board. The board is stretched, resulting in tensile stresses in the board. A negative bending line can result from a negative component crumple or a negatively curved component edge. After moving apart of the tool, the sheet springs back by the elastic amount of deformation. It creates a so-called deflection.

FIG. 11 shows the folding of a negatively curved component edge, according to which the edge of the cut edge of the board is shorter than the bending line. When folding, each element of the board in its outer area is stretched by the length difference shown in FIG. Again, tensile stresses that result in an elastic deflection according to the preceding statements. As already stated, it has already been the case in the prior art to implement methods for springback compensation.

The free bending shown in FIGS. 12 and 13 is suitable for relatively straight folds in which the expansion or compression is small. Likewise, the free folding in parts with stiff geometry is conceivable, namely, namely, the component is so stiff in itself that the stresses in the board hardly lead to deformation. When free bending no Vorhaltemaßnahmen are required. This is - as far as the free bending possible - of particular advantage. The disadvantage is that the free folding is only applicable if compressive or tensile stresses are extremely low and / or if the component has a sufficient rigidity.

The folding over arched shape according to Figures 14 and 15 is a further measure to compensate for and avoid springback, in which case the part form as far as arc and biased it is that after the compression or compression a dimensionally stable part is obtained. For precise tool design, the degree of deflection or deflection must be determined precisely in advance, for example by complex calculation or simulation. This applies both to the positive partial form shown in FIGS. 14 and 15 and to negative partial forms which are not described in more detail here.

The bending over-arched shape has the disadvantage that the correct Vormaßemaße are complex and difficult to determine. Usually, despite repeated simulation, several manual correction loops are required on the tool. A bending with waves from the pulling is used when the board is stretched during bending, namely at negative curvature of the component surface and / or the component edge. As shown in FIGS. 16 and 17, during the pulling operation, shafts are formed in the board area. This leads to an elongation of the material in this area. The additional material length thus produced is available when folding. By this measure, an elongation can be completely compensated. This is an advantage. The disadvantage, however, is that the board holds a strong mark, causing the board is wavy. In addition, a considerable effort in the incorporation of the tools.

The folding with a preform is used for compression and expansion in the board. When preferred, the board is drawn to a large extent on a stamp, then cropped and then folded. The stresses during bending can be reduced considerably. However, it is disadvantageous that the board after folding regularly has a circumferential constriction and thus marking in the region of the bending radius. FIGS. 18 and 19 show this method and the problem associated therewith.

Figures 20 and 21 relate to controlled forming with blank holder, after which the laid board is formed in an additional drawing operation with a sheet holder controlled. During this forming, the microstructure of the sheet is regularly changed by work hardening, whereby the jumping size is considerably reduced. This method is mainly used for compression. A disadvantage is the tooling complexity, whereby the process is expensive. In addition, the onboard end tends to spring something, resulting in another disadvantage of this method.

Figures 22, 23 and 24 relate to the folding with an interrupted Abkantlinie, after which the board when folding one or more beads is impressed on the board height / are. The beads "consume" excess material and serve to stiffen the board, but they reduce the jumping distance.This method is usually used for upsetting in the board.A disadvantage of this method is the fact that not infrequently surface defects occur as a result of bead embossing, and surface defects on or in the Component surface. Therefore, this method is only suitable for use in interior parts in the body shop.

In light of the foregoing, the invention has for its object to improve the methods known from practice. In particular, a method for forming sheet-like workpieces, in particular for forming and folding of sheet metal parts should be specified, after which by simple means a Aufbzw. Compression is avoided or compensated. A corresponding device should be specified.

In accordance with the invention, it is ultimately about the realization of a Abkantkonzeptes, according to which the jumping size of the component or the elastic recoil can be selectively adjusted when folding.

According to the invention the above object is achieved by the features of the independent claims 1 and 7.

According to claim 1, the method according to the invention is characterized by measures, according to which consumes excess material in compression areas of the workpiece and / or the material is elongated in Dehnbereichen of the workpiece. Specifically, the "consumption" of the material in compression areas serves to eliminate, but at least to reduce, the compressive stresses which normally occur there in stretching areas, additional materal is required, which is provided by lengths of the sheet, namely to eliminate or at least increase tensile stresses to reduce.

The inventive method solves the above problem by the features of the independent claim 7. Thereafter, a device is provided which comprises a special bending tool, which is preferably adjustable. Measures can be implemented by the tool, according to which excess material of the workpiece can be consumed in compression areas and / or material of the workpiece can be elongated in expansion areas. The provision of a so far adjustable tool is advantageous. At this point it should be noted that in accordance with the invention an elimination, but at least a compensation of deflection or rebound is realized. Different variants can be combined to a corresponding compensation. Above all, it is possible to realize compensation measures without interrupting punch and Abkantlinie when folding.

With regard to the teaching according to the invention, it is important that it can be used for exterior parts in body construction, namely for molded parts where no surface problems due to interruptions of the bending line are tolerable. The method according to the invention and the device according to the invention are based thereon in particular.

With regard to the teaching according to the invention, there are several approaches which are explained below with reference to the FIGS. 25 to 48, which describe the invention.

While FIGS. 1 to 24 show the underlying problems and approaches known from practice, FIGS. 25 to 48 relate to embodiments of the teaching according to the invention, namely using the method according to the invention and using the device according to the invention. In concrete, the show

1 to 24 in schematic views known from the prior art,

Fig. 25 to 31 a first variant of a method according to the invention under

Use of a device according to the invention using the example of a car roof,

32 to 39 another variant of a method according to the invention using a device according to the invention using the example of a car bonnet, 40 to 43 a further alternative embodiment of the method according to the invention using a device according to the invention,

FIGS. 44 to 46 show a further alternative embodiment of the invention

Method using a device according to the invention,

Fig. 47 shows a further alternative embodiment of the invention

Method using a device according to the invention and

Fig. 48 shows a further alternative embodiment of the invention

Method using a device according to the invention.

As part of a first embodiment of a method according to the invention, using a device according to the invention, compression areas are compensated for vertical or approximately vertical bends. The consumption of excess material takes place by applying Raffsicken, whereby a reduction / compensation of the compressive stresses is achieved.

Figure 25 shows a plan view and a side view, schematically, a car roof.

According to the illustration in FIG. 25, the laterally bent board has obtained a finished shape after folding and will not be deformed any further. The component remains in the bending tool. The bending bar is at this Zettpunkt in its bottom dead center. The board is under compressive stress over its entire height.

In order to reduce the compression, shirring beads are formed in the lower region of the folded board, as shown clearly in FIGS. 26 to 28. The beads consume the excess material. By partially removing the compressive stress can reduce the springing. The development of the beads not only consumes the excess sheet, but places the board partially under tension with sufficient number of beads and sufficient depth of form. The tensile stresses generated in this way can be compensate for the remaining compressive stresses, which results in another positive effect.

Referring to Figures 29 to 31, the tool design can be explained with Raffsicken stamping running through the bending bar. In the embodiment chosen here, the punches are driven by wedge drive.

The shaping punches for the Raffsicken run through the bending strip and form the beads only after the folding edge has run over the board. As a result, a uniform immersion of the bending bar is possible without interrupting the Abkantlinie. The Raffsicken stamps are driven by a wedge drive.

Advantageously, the number as well as the shape depth of the beads depends on the board length and the deflection to be avoided. The mold depth can be adjusted via a slider mechanism. It is also conceivable that individual Raffsicken-stamp activated or shut down, as needed. To minimize the training effort, the Raffsicken stamp can - vary as needed - in their depth of form, activate and / or shut down.

Figures 32 to 36 serve to discuss a second approach for Dehnbereiche at vertical or approximately vertical bends. The required elongation of the material is done by embossing fields. As a result, a reduction or compensation of tensile stresses can be realized. An interruption of the bending line is avoided according to Figures 32 to 36.

FIG. 32 shows the problem underlying the example of a bonnet. The folded board at the rear of the hood (section P-P) is only a preform and is formed only when crimping or Rollfalzen against the inner panel finished. In that regard, reference is made to the initially discussed FIGS. 2 and 3. Nevertheless, a component in tolerance is required after folding.

When folding the board is stretched, with a negative curved bending line. Therefore, the board is under tension over its entire height. The result resulting deflection leads to excessive over-buckling, whereby the component is out of tolerance.

Due to the introduction of embossed fields, the sheet is - in the inventive manner - placed locally in the thickness direction under pressure. Material is displaced sideways, which leads to an elongation of the board. This counteracts the over-arching.

The embossing fields not only lengthen the sheet, but rather set the sheet under compressive stresses with a sufficient number of embossing fields and sufficient depth of form. These compressive stresses are suitable for compensating for the tensile stresses remaining in the upper region of the board. The necessary number of embossments and the embossing depth result from the board length and the springback to be compensated.

FIGS. 37 to 39 show a tool design with embossing dies running through the bending bar. The drive is effected by wedge drive.

The bending bar is at bottom dead center. The stamping dies for the embossing fields run through the bending strip and form the embossing fields only when the folding edge has crossed the board. As a result, a uniform immersion of the bending bar is possible without interrupting the Abkantlinie. Again, the wedge drive is a preferred drive. The mold depth can be adjusted via a slider mechanism. To minimize the training effort, the dies can be varied in shape as required or - optionally - activated or shut down.

Figures 40 to 43 show another - alternative - tool design with embossing fields sitting on tunable inserts in the essay.

In contrast to the previously discussed variant, no stamping dies are used here in the bending strip. Instead, inserts sit in the attachment and form the embossed fields. When roaming the edging strip is by the used here - above - inserts thinned the sheet at least slightly. The effect achieved thereby can be seen in the illustration in FIG. 35.

About the board length a predetermined number of inserts is provided, which can be adapted by means of the thickness of tuning plates in their embossing depth on the size and spring. Here, too, can be achieved a very significant reduction of the training effort.

In the context of a further variant, in contrast to the embodiment discussed above, fixed embossed fields are provided in the attachment. A tunability is not given.

FIGS. 44 to 48 show a further approach of the teaching according to the invention, which is suitable for stretching areas with undercut shapes with slide tools. The stretching and thus elongation of the material is done by embossing fields. It is possible to reduce or compensate for tensile stresses.

Figure 44 shows a basic illustration of a hood. The laterally folded and reshaped with sliders connection flange is used for attachment to the inner panel of the hood. Section V-V is shown in FIG.

In order to reduce the elongation, embossing fields are introduced during finish-forming of the flange, as FIG. 46 clearly shows. Tensions are converted into compressive stresses. The introduction of the embossed fields in the tool has already been described two preceding variants.

Figures 47 and 48 show further advantageous embodiments, wherein in Figure 47, the basic slide structure is shown. A tunable embossing insert sits on the slider. Figure 47 is self-explanatory, so that further explanations are unnecessary.

FIG. 48 likewise shows a schematic slider construction, with the embossing insert sitting there on the filling slide. With regard to the embodiments shown in FIGS. 47 and 48, it should be noted that it is possible, within the scope of further variants, to insert embossing inserts directly into the slides, but without the possibility of a matching, namely in the absence of inserts and tuning plates in this case a simplified embodiment.

With regard to further advantageous embodiments of both the method according to the invention and the device according to the invention, reference is made to the general part of the description and to the appended claims in order to avoid repetition.

Finally, it should be expressly understood that the above-described embodiments of the teaching of the invention are only for the purpose of discussion of the claimed teaching, but do not limit these to the embodiments.

Claims

1. A method for forming flat workpieces, in particular for molding and folding of sheet metal parts, preferably of outer parts in the body construction, wherein the workpiece when folding compressive stresses and / or tensile stresses are taught,

Measures according to which excess material of the workpiece is consumed in compression areas and / or material of the workpiece is elongated in expansion areas.

2. The method according to claim 1, characterized in that the consumption of the excess material takes place by generating Raffsicken.

3. The method according to claim 1 or 2, characterized in that the elongation of the material takes place by generating embossments or embossing fields.

4. The method according to any one of claims 1 to 3, characterized in that the Raffsicken or embossing or embossing fields are formed only after a folding bar or the like. Has run over the workpiece or the board.

5. The method according to any one of claims 1 to 3, characterized in that the Raffsicken or embossing or embossing fields are formed by protruding tool inserts when roughening a bending strip.

6. The method according to any one of claims 1 to 5, characterized in that the number and shape depth or embossing depth of the beads or embossing or embossing fields are set depending on board length and springing.

7. An apparatus for forming flat workpieces, in particular for forming and folding of sheet metal parts, preferably of outer parts in the bodywork, wherein the workpiece when folding compressive stresses and / or tensile stresses are mediated, in particular using a method according to one of claims 1 to 6, characterized by a preferably adjustable tool, whereby measures can be implemented, according to which excess material of the workpiece can be consumed in compression areas and / or material of the workpiece can be elongated in expansion areas.

8. The device according to claim 7, characterized in that the tool by a folding bar running Raffsicken stamp and / or embossing stamp summarizes.

9. The device according to claim 7, characterized in that provided directly on a tool attachment, slide, Füllschieber, etc. or on preferably tunable inserts in the essay, slide, Füllschieber, etc. tools or tool parts for producing the beads and / or embossing / embossing fields are.

10. Device according to one of claims 7 to 9, characterized in that the Raffsicken punch and / or dies are activatable, deactivatable and / or adjustable via a slide mechanism.

11. Device according to one of claims 7 to 10, characterized in that the tool for generating the Raffsicken and / or embossments can be driven by a wedge drive.