EP2420330A1 - Method for moulding a piece of sheet metal and piece of sheet metal - Google Patents

Abstract

The method involves forming an output part on a sheet metal part (10) by forming motion in axial hub direction. An intermediate mold is formed with an outlet (14) and an axial bar by using a tool part with a projection part that is transversely directed to hub direction. A material bead (16) is formed in transverse direction of the projection part of the tool part for forming an axial rear section (12), and the axial bar is axially compressed. The sheet metal part is axially removed from the tool part and elastically deformed for detaching the axial rear section. An independent claim is also included for a sheet metal part with an axial rear section, comprising a deflection point.

Description

The invention relates to a method for forming a sheet metal part with an axial undercut by means of a press tool, wherein by a forming movement in an axial stroke direction, an output part is formed into the sheet metal part. The invention further relates to a sheet metal part with an axial undercut, wherein the axial undercut is formed by means of a tool part on a press.

One of the most common types of sheet metal forming is by pressing tool on presses. Thermoforming, bending, upsetting or punching operations can be performed with such press tools, so that a sheet metal part having a complex structure can be formed. In this case, the press tool on an upper tool part and a lower tool part, which are movable in an axial stroke direction to each other.

However, the problem with this forming by means of a press tool is the formation of an axial undercut in the stroke direction. For forming such undercuts, it is known to provide movable slide elements on one of the tool parts. These are extended to form the undercut transversely to the axial stroke direction in a protruding position. To this extended slide element then the undercut can be formed. Subsequently, the slider element is retracted again in the transverse direction, so that the sheet metal part can be removed in the axial direction of the press tool.

However, press tools with such movable slide elements cause relatively high tooling costs. In addition, the movably mounted slide elements are due to the high forming forces within the press tool one exposed to relatively high wear, so that there is a correspondingly high maintenance. In addition, in the formation of rotationally symmetrical body with an axially encircling axial undercut there is the need to provide a plurality of such slide elements on the press tool to produce an annular axial undercut. When using several co-operating slide elements small burrs occur due to the resulting butt joints on the sheet metal part. For some applications, such as the inclusion of sensitive elastomer seals, such burrs are disturbing and may need to be removed in a separate processing step.

The invention has for its object to provide a method for forming a sheet metal part with an axial undercut and a correspondingly produced sheet metal part, in which despite production by means of pressing tools a particularly well-formed axial undercut is achieved.

According to the invention, the object is achieved on the one hand by a method for molding a sheet metal part with the features of claim 1 and on the other hand by a sheet metal part having the features of claim 10. Preferred embodiments of the invention are indicated in the dependent claims.

The method according to the invention is characterized in that by means of a first tool part with a transversely directed to the stroke direction projection an intermediate shape with a shoulder and an axial web is formed and then axially compressed the axial web and the projection of the first tool part to form the axial undercut a bead of material is formed in the transverse direction. The axial undercut is thus generated in two stages. First, a transverse shoulder and an axial web are formed, which form a first part of the axial undercut. Subsequently, on the projection which is fixedly arranged on the first tool part, by upsetting the axial web, a bead of material is formed as a second step for completing the axial undercut in the transverse direction corresponding to the first step.

In particular, in the case of annular parts, in particular rotationally symmetrical parts, the undercut region can thus be produced without a burr, in particular at the base of the groove-like axial undercut.

It is particularly advantageous according to the invention that the sheet metal part is pulled axially from the first tool part, wherein the sheet metal part is axially deformed for releasing the molded undercut. In this way, complex movable slide elements can be omitted on the press tool.

According to the invention, it is particularly preferred that at least one deflection point with defined reduced bending stiffness is formed on the sheet metal part to form the elastic deformability. In this way it is ensured that no uncontrolled deformation or even damage of the sheet metal part takes place when loosening from the press tool. Rather, a deflection point is provided at a suitable position of the sheet metal part, on which the flexural rigidity is given in relation to an axial withdrawal of the sheet metal part with the axial undercut of the first tool part with a projection. This reduced flexural rigidity relates to the adjacent further regions of the sheet-metal part, which have a higher, in particular substantially constant, flexural rigidity in relation to the deflection point. Compared with these ranges, the reduction in flexural rigidity is preferably between 30% and 70%.

The deflection point is preferably formed at a position of the sheet metal part to which the reduction of the strength for the function of the component is not essential. This can be, in particular, an area of the component which is supported at a later assembly at this point by other components and thus reinforced.

In principle, the deflection point can be formed, for example, by the structural design of a shoulder with a relatively long lever arm. According to the invention, it is particularly expedient that the deflection point is formed by a reduction in wall thickness. Here, a very precise hinge point or a hinge line can be defined, so that the ridge of the elastic deformation when releasing the sheet metal part is very well determined.

Here, a preferred embodiment is that the deflection point is formed by impressing a groove with rounded groove bottom. Although the material thickness and thus the local bending stiffness is reduced by the non-cutting shaping of a groove with rounded groove bottom, however, takes place by the chipless molding a surface hardening and reducing the surface roughness, so that at this point the risk of stress cracking along surface roughness is reduced.

Furthermore, it is preferred according to the invention that the axial web is formed with a material fold. The axial web, which adjoins the first step formed and forms part of the bottom of the axial undercut, is thus at least partially formed by the material fold with a double wall thickness. Thus, sufficient material at the axial web is also available for the subsequent swaging operation in order to form the bead of material for closing the axial undercut. Of course, the material folding can also be provided several times, so that correspondingly more material is present at the axial web.

It is further provided according to the invention that the axial compression of the axial web is performed by a second tool part, which is movable relative to the first tool part. The mobility is also given parallel to the stroke direction, so that this can be achieved without major design effort in a press. By this second tool part, which may be stored in particular between the first tool part and a third tool part, there is a defined compression and thus displacement of the material of the axial web against the projection of the first tool part, so that the material bead terminates as the second paragraph the axial undercut.

A further preferred variant of the invention consists in that a strength of the deflection point is increased again after the release of the sheet metal part from the first tool part. The increase can be, for example, by the additional introduction of indentations in the vicinity of the deflection. This results in a defined strain hardening of the entire area around the deflection point, so that overall the strength and thus also the bending strength in the region of the deflection point is increased again. In principle, other means and methods for increasing the strength are possible. For example, an increase in strength could take place by build-up welding or by shot peening.

Furthermore, it is preferred that a bevel is formed at least on the bead of material to the bottom of the axial undercut and / or that the bead of material protrudes in the transverse direction by an amount relative to the bottom of the undercut, the smaller than the wall thickness of the starting sheet is. In particular, the amount by which the bead of material projects transversely may be between 0.1 mm to 2 mm, preferably between 0.4 mm and 0.8 mm. The slope preferably has an angle of between 15 ° and 75 ° with respect to the axial direction. The edge transitions are preferably rounded.

Furthermore, it is preferred that the sheet metal part is formed rotationally symmetrical to a center axis. In this way, a rotationally symmetrical sheet metal part can be formed with an axial undercut on a conventional press. The output part may be a flat piece of sheet metal or a preformed sheet metal body. The sheet metal is a metal forming, especially forming steel, provided.

The sheet metal part according to the invention is characterized in that the axial undercut is formed by pressing tool on a projection of a first tool part and that on the sheet metal part a deflection with defined reduced bending stiffness is formed on which the sheet metal part for axial removal of a transverse projection of the tool part elastically deflectable is.

The sheet metal part with axial undercut can be made on a press in a particularly cost-effective manner, with burrs, as caused by slide elements on press tools, are avoided.

Further embodiments of the sheet metal part will become apparent from the foregoing description of the method.

Fig. 1

eine vergrößerte Teilquerschnittsansicht eines Blechteiles vor dem Anformen des Hinterschnitts;

Fig. 2

eine Ansicht gemäß Fig. 1 nach dem Anformen des axialen Hinterschnitts;

Fig. 3

eine Teilquerschnittsansicht gemäß Fig. 2 mit Werkzeugteilen beim Anformen des axialen Hinterschnitts; und

Fig. 4

eine vergrößerte Teilquerschnittsansicht eines weiteren erfindungsgemäßen Blechteiles.

The invention will be further described by means of preferred embodiments, which are shown schematically in the accompanying drawings. In the drawings show:

Fig. 1

an enlarged partial cross-sectional view of a sheet metal part before molding the undercut;

Fig. 2

a view according to Fig. 1 after molding the axial undercut;

Fig. 3

a partial cross-sectional view according to Fig. 2 with tool parts when forming the axial undercut; and

Fig. 4

an enlarged partial cross-sectional view of another sheet metal part according to the invention.

For forming a sheet metal part 10 according to the invention Fig. 1 an intermediate mold 5, which has been manufactured from a starting sheet with the wall thickness 6 in one or more punching and bending steps on a press. The intermediate mold 5 is rotationally symmetrical to a center axis 11, around which a drum-shaped peripheral wall 25 extends. On the peripheral wall 25, a first shoulder 14 and an axial web 6 are formed in addition to other folds. The axial web 6 extends cylindrical and coaxial with the center axis 11, wherein a part of the outer surface of the axial web 6 represents the base of the axial undercut 12 to be formed. To increase the material density at the axial web 6, a material fold 7 is formed by an everting. Subsequently, a hub 26 directed radially to the center axis 11 extends.

Furthermore, a radially outwardly directed beveled outer web 27 is provided on the intermediate mold 5 at the lower end of the peripheral wall 25. In the transition region between the peripheral wall 25 and the radial outer web 27 an annular groove 22 is embossed. The annular groove 22 forms a deflection point 20 for the sheet metal part 10 according to the invention. To avoid stress peaks during the deflection, a groove base 23 of the groove 22 is formed rounded.

The final shaping of the axial undercut 12 in a second stage is associated with Fig. 2 recognizable. The free end of the axial web 6 is compressed in the axial direction, so that the material in a transverse direction, ie radially to the center axis 11 to the side of the first paragraph 14 is formed into a bead of material 16. The material bead 16 forms a second shoulder 15, so that the axial undercut 12 is now closed to both axial sides. Between the lower first shoulder 14 and the upper second shoulder 15 of the axial undercut 12, the circumferential base 18 extends.

At the second shoulder 15, a slope 17 is formed, which is arranged approximately at a 45 ° angle to the center axis 11. A corresponding slope may also be provided on the first paragraph 14, but this need not necessarily be the case.

On the sheet metal part 10 allows the annular deflection point 20 between the peripheral wall 25 and the outer web 27 a certain elastic deflection or deformation of the peripheral wall 25 with respect to the outer web 27 in the direction of arrow P. In this way, an efficient production of the sheet metal part 10 on a Press done as related to Fig. 3 is explained.

In this case, the intermediate mold 5 is moved with a first tool part 30 and a third tool part 60 of a press tool shell on a press in a known manner by moving in a stroke direction H against a not shown press tool lower part. The stroke direction H runs parallel to the center axis 11 of the sheet metal part 10.

The first tool part 30 has a radially inwardly projecting projection 32. The projection 32 comprises a lower corner region 33 for forming the first shoulder 14 and an upper corner region 34 for shaping the second shoulder 15. In the first stage, however, this second shoulder 15 is not yet formed, but it becomes the intermediate mold 5 according to FIG Fig. 1 formed with a material fold 7 on the web 6. Furthermore, the first tool part 30 has on its underside an axially projecting embossing attachment 36 for forming the groove 22.

After this first forming step, a second annular tool part 50 is delivered in the stroke direction H between the annular first tool part 30 and the third tool part 60. The lower end face of the second tool part 50 has an arcuate upsetting surface 52. The arcuate compression surface 52 contacts the axially projecting web 6 and compresses its axial length. In this case, material is displaced radially outward in a transverse direction to form a bead of material 16. In this case, the displaced material is formed against the upper corner region 34 of the radially inwardly directed projection 32, so that the second shoulder 15 forms with a defined slope 17. In this case, the height of the second shoulder 15 extends radially outwards in relation to the base 18 by the amount a.

To release the thus formed sheet metal part 10 with the axial undercut 12, the second tool part 50 is first moved away in the stroke direction H from the sheet metal part 10. The same is done with the third tool part 60. Now, the sheet metal part 10 remains due to the molded axial undercut 12 on the projection 32nd However, the sheet metal part 10 can be deducted according to the invention, since by means of the annular groove 22 shown in the exemplary embodiment as a deflection 20, the peripheral wall 25 with respect to the radial outer web 27 elastically can dodge radially inwardly. The removal is supported by the integrally formed bevel 17 on the second shoulder 15 of the sheet metal part 10. After the material bead 16 has passed the lower corner region 33 of the transverse projection 32, the peripheral wall 25 returns to its original starting position and the sheet metal part 10 can now be easily removed from the press tool. For pulling an ejection may be provided on the press tool.

While the sheet metal part 10 according to the Figures 2 and 3 having an axial undercut, which is arranged on a radial outer side, shows Fig. 4 another possible embodiment of a sheet metal part 10 'according to the invention. In the sheet-metal part 10 ', an axial undercut 12' is formed on a radially inner side on a drum-shaped wall 25 'between a first shoulder 14' and a second shoulder 15 '. The shoulder 15 'is bent radially inwardly by an axial compression movement and thus constitutes the transverse material bead or material projection. A deflection point 20' is likewise formed in the transition region between the drum-shaped peripheral wall 25 'and a radially extending disc-shaped hub 26'. Due to the deflectability about the deflection point 20 ', the sheet metal part 10' formed in this way can be pulled off elastically deformable by a press tool, not shown here, in spite of the radially inwardly projecting second shoulder 15 '.

According to the invention, a variety of different shapes of sheet metal parts according to the invention are possible.

Claims (10)

Method of forming a sheet-metal part (10) with an axial undercut (12) by means of a pressing tool, in which a starting part is converted to the sheet-metal part (10) by a forming movement in an axial stroke direction,
characterized,
that by means of a first tool part (30) with a transversely directed to the stroke direction projection (32) is formed an intermediate mold (5) with a shoulder (14) and an axial web (7) and
in that subsequently the axial web (7) is axially compressed and a material bead (16) is transversely formed on the projection (32) of the first tool part (30) to form the axial undercut (12). Method according to claim 1,
characterized,
in that the sheet-metal part (10) is pulled off axially from the first tool part (30), wherein the sheet-metal part (10) is elastically deformed for releasing the integrally formed undercut (12). Method according to claim 2,
characterized,
in that at least one deflection point (20) with a defined reduced bending stiffness is formed on the sheet metal part (10) to form the elastic deformability. Method according to claim 3,
characterized,
that the deflection point (20) is formed by a reduction in wall thickness. Method according to claim 3 or 4,
characterized,
that the inflection point (20) by impressing a groove (22) with a rounded groove bottom (23) is formed. Method according to one of claims 1 to 5,
characterized,
that the axial web (7) is formed with a material fold (8). Method according to one of claims 1 to 6,
characterized,
in that the axial compression of the axial web (7) is performed by a second tool part (50), which is movable relative to the first tool part (30). Method according to one of claims 3 to 7,
characterized,
that the strength of the inflection point (20) after release of the sheet metal part (10) of the first tool part (30) is increased again. Method according to one of claims 1 to 8,
characterized,
in that at least on the bead of material (16) a bevel (17) to the base (18) of the axial undercut (12) is formed and / or
in that the bead of material (16) protrudes transversely with respect to the base (18) of the undercut (12) by an amount which is smaller than the wall thickness (6) of an output sheet of the starting part. Sheet metal part with an axial undercut (12), in particular produced by a method according to one of claims 1 to 9,
in which the axial undercut (12) is formed on a press by means of a tool part,
characterized,
in that a deflecting point (20) with a defined reduced bending stiffness is formed on the sheet metal part (10), on which the sheet metal part (10) for axial withdrawal from a transverse projection (32) of the tool part (30) is elastically deflectable.

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