EP2208551B1 - Method for producing a complex sheet metal part - Google Patents

Description

The invention relates to a method for producing a complex sheet metal part, as well as a complex sheet metal part produced by this method, (see, eg DE-A-19524235 ).

Under a complex sheet metal part is understood in the context of this invention, due to its spatial shape or shape only consuming writable sheet metal part. For example, a complex sheet-metal shaped part can be composed or formed from many individual, even curved, surface sections. Due to its complex shape, such a complex sheet metal part according to the current state of the art can only be produced in a complex manner. The complex sheet metal parts are simply shaped sheet metal parts opposite, which can be easily described and produced in a simple manner, for example. By simple bending operations or the like.

Body parts for motor vehicles, in particular body panels and structural parts, are often complex sheet metal parts.

Complex sheet-metal shaped parts, in particular body parts, are typically produced in today's state of the art in multi-stage forming processes and in particular deep-drawing processes. For this purpose, for example, press lines or transfer step presses are known from the prior art, in which the sheet material to be formed is passed from one forming step to the next and finally punched and / or cut in the finished molded state.

This disadvantageous are the high investment costs for equipment and tools that are in small numbers in an unfavorable ratio. To remedy this disadvantage, various proposals have been made. The US 4,212,188 proposes an adjustable forming tool, in which both in the lower tool and in the upper tool, a plurality of height-adjustable pressure punches is arranged like a matrix, with which a shaping contour are set changeable can. A similar procedure using a CAD program is from the younger one DE 100 65 142 A1 known. In the current GB 2 444 574 A a method is proposed in which a sheet material is converted by means of attached blocks along defined bending lines to form a complex sheet metal part. The blocks are moved, for example, by robot arms. A disadvantage of this method, however, is that a high quality level of the sheet metal parts, in particular for exterior skin parts, is not achieved.

An object of the invention is to provide a comparatively favorable possibility to be able to provide complex sheet-metal shaped parts with a high quality level.

This object is achieved by an inventive method having the features of claim 1. This object is further achieved by an inventive complex sheet metal part having the features of claim 10 Advantageous and preferred developments are the subject of the respective dependent claims. The use of a complex shaped sheet metal part according to the invention as a body part for a motor vehicle is the subject matter of claim 12.

• Zuschneiden einer ebenen Ausgangsplatine, deren Kontur einer exakten Abwicklung des einbaufertigen Blechformteils in der Ebene entspricht;
• Positionieren der Ausgangsplatine in einem Umformwerkzeug, das wenigstens zwei axial zueinander bewegbare Werkzeugteile umfasst; und
• axiales Bewegen dieser Werkzeugteile zueinander, wobei ein Umformen der Ausgangsplatine zu einem einbaufertigen Blechformteil derart erfolgt, dass wenigstens zwei Freiformflächen ausgebildet werden, welche durch wenigstens eine Konturlinie zumindest abschnittsweise voneinander abgegrenzt sind, wobei beim Umformen keine Streckung oder Stauchung des Blechmaterials erfolgt, so dass die Blechdicke der Ausgangsplatine über das gesamte Blechformteil erhalten bleibt.

The method according to the invention serves to produce a complex sheet metal part which is essentially ready to be molded from the shape of a sheet material. It includes the following steps:

• Cutting a flat output board whose contour corresponds to an exact settlement of the ready-to-install sheet metal part in the plane;
• Positioning the output board in a forming tool comprising at least two axially movable tool parts; and
• axial movement of these tool parts to each other, wherein a reshaping of the output board to a ready-to-install sheet metal part takes place such that at least two free-form surfaces are formed, which are delimited by at least one contour line at least partially from each other, during the forming no stretching or compression of the sheet material takes place, so that the Sheet thickness of the output board over the entire sheet metal part is retained.

It is preferred that more than two free-form surfaces and a plurality of contour lines are formed. Particularly preferably, a plurality of free-form surfaces is formed. In particular, however, at least one free-form surface is formed, which is delimited at least in sections by at least one contour line.

The term "ruled surface" can be understood to mean a surface or a surface section which can be described in a mathematically simple manner. Ruled surfaces can in particular be planes, one-dimensionally curved surfaces with constant radii of curvature, lateral surfaces of cylinders, cones and the like.

In the context of the invention, the term "free-form surface" can be understood to mean a complex, preferably multi-curved surface which, in particular, can not be mathematically described by simple geometric basic forms such as straight line, circle and conic section. A free-form surface can, for example, have complex concave and / or convex sections.

A ruled surface and a free-form surface are characterized in particular by the fact that they have only a slight change in shape (comparative shape change). In the case of work hardening sheet metal materials, this change in shape is particularly so small that no appreciable cold work hardening occurs during forming.

In the context of the invention, a "contour line" is understood to mean a bending line or a bending edge. Such a contour line is defined essentially by its spatial course, its bending angle and / or its bending radius. A contour line preferably has a curved and in particular a spatially multiply curved course. The bend radius and / or the bend angle may vary along the course. The bending contour can deviate from a circle segment. The bending angle is chosen so that a crack-free forming is guaranteed. Preferably, the bending radius is at least partially selected so that when forming a cold work hardening sheet material, a work hardening occurs.

The output board essentially corresponds to a precise development of the ready-to-install sheet metal part. This implies that during the forming no stretching or compression of the sheet material takes place, so that the starting sheet thickness is maintained in an advantageous manner over the entire sheet metal part. An exception form the areas of the contour lines, in which in particular a bending shortening can occur, which can be considered in the development of the sheet metal part quite well, which is indicated by the wording "essentially". The blank determination is preferably carried out by means of CAD systems.

The invention is based on the idea of designing a complex sheet metal part such that it comprises free-form surfaces which are separated from one another by means of at least one contour line or subdivided by means of this contour line. The free-form surfaces are defined here by the spatial progression of an adjacent contour line or of all contiguous contour lines. That The spatial shape or the shape of the adjacent surfaces or surface sections is predetermined or determined by the spatial progression of a contour line. In the previous design process and in particular in the 3D geometry determination for the sheet metal part is about to divide the overall geometry into individual free-form surfaces and based on the spatial shape of these individual surfaces or surface sections suitable gradients for the contour lines, and to define suitable bending angle and / or bending radii , whereby the reverse sequence is possible. The shape of the sheet metal part must also be developable in the plane, as explained above.

The invention has many advantages. The forming takes place essentially in only one main forming stage, for which only one forming tool and only one forming press are required. Due to the resulting low investment costs, the invention is therefore particularly suitable for small quantities and small batches. However, this does not preclude the fact that the Hauptumformstufe follow other Umformstufen or may be upstream. On the other hand, the sheet metal parts produced by the process according to the invention to a high level of quality, which is quite close to the quality of deep-drawn metal parts, although in the production of sheet metal parts according to the invention explicitly no deep-drawing process is performed. But that does not contradict that the method according to the invention can be combined with a deep drawing process. Furthermore arise for the design process of the sheet metal part new degrees of freedom. For example, the production of one-piece large components is possible, such as. A front flap with integrated side walls or a complete floor assembly for a motor vehicle, which is usually realized in the art by a plurality of sheet metal parts joined together and thus is correspondingly complex and costly.

According to a preferred development, it is provided that the forming takes place between a substantially rigid lower and a substantially rigid upper tool part, which are arranged in a forming press, wherein at least one of these tool parts has at least one closed shaping tool contour. Preferably, all tool parts that are directly involved in forming have a closed shaping tool contour. According to their arrangement, the tool parts can also be referred to as upper tool and lower tool. These can each be constructed in several parts. By using rigid tool parts, the quality of the produced sheet metal parts can be improved.

According to a preferred development, it is provided that, during the forming along a contour line, at least in sections, a bend (of the sheet metal material) takes place with a small bending radius. The term "small" here refers in particular to the relationship between the bending radius and the starting sheet thickness. Preferably, this ratio is in the range between 5 and 10 and in particular in the range between 2 and 5. Furthermore, the above statements on the contour line apply. The inventive method advantageously offers the possibility of defined formation of small radii and very small radii despite large depths of form, and this in particular even at high forming speeds.

According to a preferred development, it is provided that the sheet metal material during forming successively and / or in sections applied to the closed forming tool contour of at least one tool part and as a result a relative movement between the adjacent sheet material and Tool part is largely avoided. The application can be done, for example, by means of the upper tool to a shaping tool contour in the lower tool, or vice versa. A movement of the adjacent sheet material relative to a tool part, as for example, is given in deep-drawing processes, is not provided. Advantageously, the use of lubricant can thus largely be dispensed with; in addition, sheet metal materials with coated, pretreated and / or ready-to-install surfaces, in particular painted surfaces, can be used. Also, a hold-down is not required, so that a Ziehflansch deleted and sheet material is saved.

According to a preferred development, it is provided that at the end of the forming, a pressing operation is carried out, in which at least one contour line (of the sheet metal part) is finally formed or pronounced. In this way, both the course of the contour line and its bending radius and / or the bending angle can be accurately formed. This pressing operation is preferably carried out in the same forming tool and with high pressing forces, which are a multiple of the previous forming forces.

According to a preferred embodiment, it is provided that at least one free-form surface of the sheet metal part is provided with a structuring of rigidity at least in sections during a pressing operation. Such structuring may be, for example, an embossed honeycomb structure or the like.

According to a preferred development, it is provided that the positioning of the output board in the forming tool takes place by means of at least one locking device. Such a locking device may, for example, be a simple locking pin or locking bolt. Alternatively and / or additionally, a suction device may be included in the forming tool.

According to a preferred embodiment, it is provided that openings in the sheet metal part are formed by pre-apertures in the output board. Such openings may be bores, contoured recesses and the like. Starting from their position in the sheet metal part takes place through the plane Processing their positioning on the output board. This makes it possible to dispense with subsequent expensive cutting tools.

According to a preferred development, it is provided that the final formation of at least one contour line (of the sheet metal part) or a folding or edging by means of a separately movable tool part of the same Umformwerkzeugs done in a similar manner, undercuts on the sheet metal part can be produced. As a result, the complexity of the sheet metal part can be increased without the need for another forming step. The separate tool part can be actuated, for example, by means of an auxiliary ram or a die cushion of the forming press.

A complex shaped sheet metal part according to the invention is produced by the process according to the invention. This comprises at least two free-form surfaces, which are delimited from one another by at least one contour line, wherein the F formiform surfaces have a relatively small change in shape over their entire extent and a rigidity of the sheet metal part results to a significant extent from the at least one contour line.

The rigidity can be, for example, the overall stiffness (for example, relevant to the crash case), the torsional stiffness or the average buckling stiffness. The rigidity of the sheet metal part results in particular from the prevailing stresses in the free-form surfaces, from a possible structuring of these surfaces, from the bending resistance of all contour lines, from the stress distribution of the upper side of the sheet to the underside of sheet metal in particular in the region of these contour lines and from a work hardening along these contour lines. According to the invention, however, the rigidity of the sheet metal part is to result in a substantial proportion from at least one contour line and preferably from the totality of all contour lines insofar as the free-form surfaces are stabilized by the adjacent contour lines. Incidentally, a contour line in particular also prevents an elastic return of an adjacent free-form surface.

For the complex sheet-metal shaped part according to the invention, mutatis mutandis, the advantages and further development possibilities given above in connection with the method according to the invention apply.

According to a preferred development, it is provided that the complex sheet-metal shaped part according to the invention has, in the region of at least one contour line, at least in sections, a locally high change in shape (comparative shape change). The change in shape is preferably so great that a clear work hardening occurs in the sheet material, as already explained above in connection with the term "contour line".

Fig. 1

das erfindungsgemäße Verfahren in einer schematischen Übersicht;

Fig. 2

das Umformen nach dem erfindungsgemäßen Verfahren in einer schematischen Ansicht;

Fig. 3

die beim Umformen nach der Fig. 2 verwendete Ausgangsplatine in einer Draufsicht und das hieraus geformte Blechformteil in einer perspektivischen Ansicht;

Fig. 4

das beim Umformen nach den Fig. 2 und 3 verwendete Umformwerkzeug in einer perspektivischer Ansicht; und

Fig. 5

einen zusätzlichen Verfahrensschritt beim Umformen nach dem erfindungsgemäßen Verfahren in einer schematischen Ansicht.

The invention will be explained in more detail with reference to the figures. Show it:

Fig. 1

the inventive method in a schematic overview;

Fig. 2

the forming according to the inventive method in a schematic view;

Fig. 3

when reshaping after Fig. 2 used output board in a plan view and the formed therefrom sheet metal part in a perspective view;

Fig. 4

that when forming after the FIGS. 2 and 3 used forming tool in a perspective view; and

Fig. 5

an additional process step during forming by the method according to the invention in a schematic view.

Fig. 1 shows the inventive method for producing a complex sheet metal part in a schematic overview. The sequence of the process takes place according to the illustration from bottom left to top right, which is symbolized by the arrows.

The method comprises first providing a finished trimmed output board 10 made of a sheet metal material. The contour of the output board 10 essentially corresponds to a precise development of the product to be produced Sheet metal part. The output board 10 comprises pre-punched openings in the form of contoured recesses 12 and holes 14. The output board 10 is positioned in a forming tool 20 with an upper tool 22 and a lower tool 25. The forming tool 20 is installed in a forming press, not shown.

By closing the forming die 20, i. by an axial movement of the upper tool 22 in the direction of the lower tool 25 (or vice versa), there is a forming of the output board 10 to a sheet metal part 30 such that in this case free-form surfaces 32 are formed, which delimited by at least one contour line 34 from each other, limited or limited are. A contour line 34 is a spatially extending bending line or bending edge. The illustrated sheet metal part 30 is an example of a front flap of a motor vehicle. The transformation from the output board 10 to the sheet metal part 30 takes place in only one forming stage (Hauptumformstufe). After this transformation, no trimming of the sheet metal part 30 is required. The sheet metal part 30 is as it were ready to install, subject to any cleaning and / or painting or the like.

The forming of the output board 10 to the sheet metal part 30 by the forming tool 20 is shown schematically in the Fig. 2a and 2b shown.

Fig. 2a shows the inserted between upper tool 22 and lower tool 25 output board 10. This is smaller in size than the shaping tool contours 23 and 26 of the upper tool 22 and the lower tool 25. By closing the forming tool 20, the output board 10 is formed. The reshaping takes place in such a way that the sheet material of the output board 10 successively and / or in sections starting from at least one eg. Highest contact point to the closed forming tool contours 23 and / or 26, wherein in the following a relative movement between the adjacent sheet material and the forming tool 20 is largely avoided. As a result, in particular a thinning or stretching of the sheet material is prevented. The output sheet thickness of the output board 10 is maintained over the entire sheet metal molding 30. Consequently also have the introduced into the output board 10 openings 12 and 14 in the finished molded sheet metal part 30 their exact position and geometry, as in Fig. 1 indicated.

Fig. 2b shows the closed forming tool 20. The output board 10 has been here converted in the manner described above to the sheet metal molding 30. In the illustrated closed state, a pressing operation can be carried out with high pressing forces in order to finally form at least one contour line 34 and / or to provide at least one free-form surface 32 with a stabilizing and rigidity-increasing structuring. This structuring is introduced by the shaping tool contours 23 and / or 26 in the sheet metal molding 30.

Fig. 3a shows the output board 10 in a plan view, which when forming after the Fig. 2 is used. Shown here are the forming during forming contour lines 34th Fig. 3b shows the produced sheet metal part 30 in a perspective view with the freeform surfaces 32, which are delimited by the contour lines 34 to each other.

Fig. 4a shows the lower tool 25 of the forming tool 20 in a perspective view. This includes a closed shaping tool contour 26 and three tool guides 27 for the upper tool 22. Also shown is a resting on the tool contour 26 finished molded sheet metal part 30, which in the manner described above from the output board 10 by successive and / or sectional application of the sheet material was made to the shaping tool contour 26 and can be removed from the forming tool 20 in the state shown.

Fig. 4b shows that to Fig. 4a corresponding, turned upper tool 22 in a perspective view. This comprises a shaping tool contour 23, which is formed as a negative contour to the shaping tool contour 26 of the lower tool 25 with an offset. The application of the sheet material to the tool contour 26 of the lower tool 25 by means of the shaping tool contour 23 in the upper tool 22 (or vice versa), without a Relative movement between the sheet material and the shaping tool contours 23 and 26 is given. To form the contour lines 34, the shaping tool contours 23 and 26 comprise corresponding shaping sections, which are shown schematically in the upper tool 22 shown and designated by the reference numeral 24 and which the sheet material during closing and in particular compression of the forming tool 20 against corresponding shaping sections of the shaping tool contour 26 in Press lower tool 25 (or vice versa) to thereby form a contour line 34 exactly.

Fig. 5 shows an alternative or supplementary possibility for forming at least one contour line. The same components are designated by the same reference numerals but with the addition "a". The forming tool 20a comprises, in addition to the upper tool 22a and the lower tool 25a, a tool part 29a which is movable separately and parallel to the upper tool 22a. First of all, free-form surfaces 32a are formed between the shaping tool contours of the upper tool 22a and the lower tool 25a. Then, preferably, while the upper tool 22a remains in its end position shown, a formation of contour lines 34a, by the tool part 29a is moved downward as shown, wherein initially a folding or stopping the sheet material down. The separate tool part 29a can be moved by the auxiliary ram of a forming press. Alternatively and / or additionally, a separate tool part can also be moved from below, for example by means of the drawing cushion of the forming press. In the same way, undercut can also be produced on the sheet-metal shaped part 30a, for example by means of a laterally displaceable separate tool part.

LIST OF REFERENCE NUMBERS

10 (a)

Output board (sheet material)

12

contoured recess

14

drilling

20 (a)

forming tool

22 (a)

Upper tool; upper tool part

23

Shaping tool contour of the upper tool

24

Shaping section for a contour line in the upper tool

25 (a)

Lower tool; lower tool part

26

Shaping tool contour of the lower tool

27

tool guide

29 (a)

separately movable tool part

30 (a)

complex, ready-to-install sheet metal part

32 (a)

Ruled surface or free-form surface

34 (a)

contour line

Claims (12)

1. A method for producing a complex sheet metal formed part (30) which is ready for installation after forming, from a sheet metal material, the method comprising the following steps:

   - cutting to size a planar starting blank (10), the contour of which substantially corresponds to an exact unfolding of the ready-to-install sheet metal formed part (30) in the plane;

   - positioning the starting blank (10) in a forming die (20) which comprises at least two die parts which are axially movable relative to one another; and

   - axially moving these die parts relative to one another, wherein the starting blank (10) is formed into a ready-to-install sheet metal formed part (30) such that at least two free-form surfaces (32) are formed which are delimited from one another at least in portions by at least one contour line (34), wherein during forming, the sheet metal material is not stretched or compressed so that the sheet metal thickness of the starting blank (10) is retained over the entire sheet metal formed part (30).
2. A method according to claim 1,
   characterised in that
   forming takes place between a rigid lower die part (22) and a rigid upper die part (25) which are arranged in a forming press, at least one of these die parts (22, 25) having at least one closed forming die contour (23, 26).
3. A method according to claim 1 or claim 2,
   characterised in that
   during forming, a bend with a small bend radius occurs at least in portions along a contour line (34).
4. A method according to claim 2 or claim 3,
   characterised in that
   during forming, the sheet metal material rests successively and/or in portions on the closed forming die contour (23, 26) of at least one die part (22, 25) and consequently, a relative movement between the applied sheet metal material and the die part (22, 25) is substantially avoided.
5. A method according to any one of the preceding claims,
   characterised in that
   at the end of forming, a pressing procedure is carried out in which especially at least one contour line (34) is finally formed.
6. A method according to claim 5,
   characterised in that
   during the pressing procedure, at least one free-form surface (32) is provided at least in portions with a rigidity-increasing structuring.
7. A method according to any one of the preceding claims,
   characterised in that
   the starting blank (10) is positioned in the forming die (20) by at least one locking device.
8. A method according to any one of the preceding claims,
   characterised in that
   openings in the sheet metal formed part are formed by pre-punched openings (12, 14) in the starting blank (10).
9. A method according to any one of the preceding claims,
   characterised in that
   the final formation of at least one contour line (34a) or a bending procedure is carried out by means of a separately movable die part (29a) of the same forming die (20a).
10. A complex sheet metal formed part (30), produced by a method according to any one of the preceding claims,
    characterised in that
    it comprises at least two free-form surfaces (32) which are delimited from one another at least in portions by at least one contour line (34), wherein the free-form surfaces (32) exhibit a relatively small change in form over their entire expanse and the stiffness of the sheet metal formed part (30) substantially results from the at least one contour line (34).
11. A complex sheet metal formed part (30) according to claim 10,
    characterised in that
    it exhibits a locally great change in form at least in portions in the region of at least one contour line (34).
12. Use of a complex sheet metal formed part (30) according to either one of claims 10 or 11 as a bodywork part for a motor vehicle.

Images