EP2785477B1 - Device and method for machining a workpiece consisting of metal, particularly for producing a cup-shaped component for the automobile industry - Google Patents

Description

The invention relates to the field of machining workpieces of metal, for example of steel or other metals. It relates to a device for forming according to claim 1, a system for forming according to claim 6, and a method for forming according to claim 7.

The machining of a workpiece may include any operations, such as cutting, pressing, pulling, deforming.

Pot-shaped components include a bottom, a pot wall and a drawing edge. Such a component is often used as a spring cup to accommodate the ends of a coil spring. They find particular use in the automotive industry in many ways.

Problematic in the production of such spring pots are high-strength steels. Although these have the advantage that they have extremely high tensile strengths, and therefore steels smaller thickness can be used, and thus also lower weight. However, such steels are relatively brittle and tend to crack. This occurs especially when forming on the highly stressed transition areas. The tearing occurs in particular in the transition region between the bottom of the pot and the pot wall and between the pot wall and the drawing edge.

DE 102 54 103 B3 describes a thermoforming tool for deep drawing of molded parts. This comprises an annular clamping device for clamping a circuit board. The clamping device encloses a space in which a bottom former and a frame former can be moved in the pulling direction. These two can have different speeds. As a result, a higher dimensional accuracy is to be achieved.

DE 27 27 174 C2 describes a method and apparatus for deep-drawing an aluminum container. Two parts are movable against each other, namely a punch and a die. The speed of the upwardly moving punch can be greater than the speed of the moving down die. As a result, a large thermoforming ratio is to be achieved.

DE 10 2007 050 581 A1 describes a method for influencing the thickness of sheet metal during deep drawing of hollow bodies. It is about a multiple buckling (deforming) and back buckling (reforming) of a workpiece. During the reforming phase, the

Relative speed between punch and die increased compared to the speed during the deforming phase. The punch performs a movement against the phase of deforming during the reforming phase. The speeds of the punch during these phases are unequal.

US 2008/0098789 A1 describes a method and an apparatus for forming a sheet metal blank with a two-stage sheet metal posture.

The invention has for its object to make a device, a system, a method and a workpiece such that high-strength steels are deformable without tearing occurs in the edge regions, and that a greater draw depth than previously achieved

This object is achieved by means of the features of the independent claims.

• Es werden in üblicher Weise ein Stempel sowie eine mit diesem zusammenarbeitende Matrize verwendet. Jedoch sind sowohl der Stempel als auch die Matrize zweiteilig. Beide umfassen ein im Wesentlichen zylindrisches Innenteil sowie einen dieses umschließenden Ring.

The basic idea is the following:

• There are used in the usual way a stamp and a cooperating with this die. However, both the stamp and the die in two parts. Both comprise a substantially cylindrical inner part and a ring enclosing this.

All four components mentioned can be moved in the drawing direction for the purpose of forming.

It is crucial that at least two of the parts involved in the drawing process have different speeds, at least during certain stages of forming. In particular, the inner die may have a higher speed than the outer die.

1. I. Während einer Anfangsphase bewegen sich beide Matrizen in derselben Richtung mit gleich großer Geschwindigkeit.
2. II. Während einer mittleren Phase bewegen sich wiederum beide Matrizen in ein und derselben Richtung, die innere Matrize jedoch mit höherer Geschwindigkeit, als die äußere.
3. III. In einer Endphase steht die innere Matrize still, während die äußere sich mit konstanter Geschwindigkeit weiter bewegt.

The following procedures are conceivable:

1. I. During an initial phase, both matrices move in the same direction at the same speed.
2. II. During a middle phase both matrices move in one and the same direction, but the inner matrix moves at a higher speed than the outer one.
3. III. In a final phase, the inner die stops, while the outer moves at a constant speed.

• Die äußere Matrize bewegt sich von Anfang an mit konstanter Geschwindigkeit. Hingegen ist der Bewegungsverlauf der inneren Matrize gleich einer gesteuerten Bewegungskurve, zum Beispiel Sinuskurve, ausgehend von einer Geschwindigkeit unter jener der äußeren Matrize, dann diese übersteigend, und schließlich wieder abnehmend.

Other variants are the following:

• The outer die moves at a constant speed from the beginning. On the other hand, the course of movement of the inner matrix is equal to a controlled movement curve, for example sine curve, starting from a speed below that of the outer matrix, then exceeding it, and finally decreasing again.

The speed differences can be significant. Thus, the speed of the inner die may be 1.5, 2, 2.5, or 3 times the speed of the outer die.

Figur 1

zeigt in schematischer Darstellung und im Aufriss eine Ziehvorrichtung mit bereits vorgeformtem Werkstück in einer ersten Umformphase, des gesamten Umformhubes.

Figur 2

zeigt das Werkstück kurz vor Ende der zweiten Umformphase.

Figur 3

zeigt das Werkstück am Ende des Umformvorganges.

Fig. 4 bis 9

veranschaulichen den Umformvorgang in sechs verschiedenen Umformstationen.

The invention is explained in more detail with reference to the drawing. It details the following:

FIG. 1

shows a schematic representation and in elevation a drawing device with already preformed workpiece in a first forming phase, the entire Umformhubes.

FIG. 2

shows the workpiece shortly before the end of the second forming phase.

FIG. 3

shows the workpiece at the end of the forming process.

Fig. 4 to 9

illustrate the forming process in six different forming stations.

In the FIG. 1 shown pulling device comprises a punch 1 and a blank holder 2. The punch 1 is of slightly conical shape. It has a bottom mold surface 1.1 and a wall mold surface 1.2.

Stamp 1 is surrounded by a blank holder 2. Sheet metal holder 2 has a support surface 2.1. Sheet holder 2 is annular.

Above the punch 1 is an inner die 3. This is at least approximately cylindrical. It is surrounded by an outer die 4. This is ring-shaped.

The inner die 3 in turn has a bottom mold surface 3.1. The outer die 4 is annular. It has a wall mold surface 4.1, further a clamping surface 4.2 for clamping the drawing edge 5.3 of a workpiece 5 on the support surface 2.1 of the sheet holder 2. The workpiece 5 has emerged from a circular disk-shaped board. See also Fig. 2 , It comprises a bottom 5.1, a wall 5.2, and the drawing edge 5.3.

It is initially open, that is, the clamping surface 4.2 of the outer die 4 is located approximately at the height of the bottom mold surface 3.1 of the inner die 3. At about the same height is the support surface 2.1 of the sheet holder. 2

In this phase, a workpiece 5 is inserted into the pulling device and clamped between the support surface 2.1 and the clamping surface 4.2. Now begins the actual work phase of the pulling device. In this case, the inner die 3 and the outer die 4 move together with the preformed workpiece, as well as the sheet holder 2 in the arrow direction down. The parts mentioned (inner die 3, outer die 4, blank holder 2 and preformed workpiece) have the same speed.

This changes according to the invention in a subsequent phase. In this case, the inner die 3 overtakes the outer die 4.

In a subsequent phase, on the other hand, the outer die 4 overtakes the inner die 3.

Note that this may be the other way around.

In the FIG. 1 The drawing apparatus shown is only one station of a series of drawing stations. These are not shown here. In practice, they are connected in series in a workshop.

It only needs a single drawing station to be designed according to the invention, that is provided with drives that can give the inner die 3 on the one hand, the outer die 4 and the blank holder 2 on the other hand, different speeds during the drawing process.

How the workpiece looks after leaving the various drawing stations can be seen from the FIGS. 4 to 9 ,

• Auch Stempel 1 ist auf und ab verfahrbar, und/oder
• In einer kinematischen Umkehrung bewegen sich Blechhalter 2 und äußere Matrize 4 mit eingespanntem Werkstück einerseits, und Stempel 1 andererseits nach oben. Die mittlere Matrize 3 ist ortsfest.
• Während des Ziehvorganges bleibt die mittlere Matrize 3 stehen, und/oder es bleiben der Blechhalter 2 und die äußere Matrize 4 stehen.

The drawing edge 5.3 can also be stamped after the last drawing of the wall 5.2, depending on the use of the finished pot.
Further possibilities for realizing the invention are the following:

• Also stamp 1 is moved up and down, and / or
• In a kinematic reversal plate holder 2 and outer die 4 move with clamped workpiece on the one hand, and stamp 1 on the other hand upwards. The middle die 3 is stationary.
• During the drawing process, the middle die 3 stops, and / or it remain the blank holder 2 and the outer die 4 stand.

The invention is described with regard to the production of a pot-shaped component. It is understood, however, that deviating from the cup shape hollow body can be made with it.

Also, the dies may have shapes that differ from the shapes of a disk and a ring described.

LIST OF REFERENCE NUMBERS

1.

stamp

1.1

Floor molding surface

1.2

Wall molding surface

2

blankholder

2.1

support surface

Third

inner matrix

3.1

Floor molding surface

4

outer die

4.1

Wall molding surface

4.2

chucking

5

workpiece

5.1

ground

5.2

wall

5.3

drawing border

Claims (8)

1. An apparatus for forming a sheet metal blank into a pot (5), having a bottom (5.1), a wall (5.2) and a drawn edge (5.3), said apparatus comprising the following features or components:

   1.1 a punch (1) with a bottom forming area (1.1) forming the bottom (5.1) and a wall forming area (1.2) forming the wall (5.2);

   1.2 an annular blank holder (2) surrounding the punch (1) and having a supporting surface (2.1) for placing the drawn edge (5.3);

   1.3 an inner die (3) with a bottom forming area (3.1);

   1.4 an outer die (4) with a wall forming area (4.1) and a clamping area (4.2) for gripping the drawn edge (5.3) and for pressing said drawn edge against the supporting surface (2.1) of the blank holder (2);

   characterized by the following features:

   1.5 a drive is respectively associated with at least the inner die (3) and the outer die (4), said drive being formed and designed in such a way that it provides said dies (3, 4) simultaneously with different velocities in one and the same direction after clamping and thus at the beginning of the working phase of the forming of the workpiece area within the clamping region.
2. An apparatus according to claim 1, characterized by the following features: a drive is respectively associated with the inner die (3) on the one hand and the outer die (4) as well as the blank holder (2) on the other hand, by means of which the inner die (3) overtakes the outer die (4) in a first phase, or vice versa, and in a subsequent phase the outer die (4) overtakes the inner die (3), or vice versa.
3. An apparatus according to claim 2, characterized in that also the punch (1) is also displaceable by a drive in the drawing direction.
4. An apparatus according to one of the claims 2 or 3, characterized in that the forming area (4.1) of the punch (1) extends conically in the direction towards the bottom forming area (1.1) of the punch (1).
5. An apparatus according to one of the claims 2 to 4, characterized in that the wall forming area (4.1) of the outer die (4) tapers in the drawing direction.
6. An installation for forming a sheet metal blank into a pot (5), having a bottom (5.1), a wall (5.2) and a drawn edge (5.3), comprising a plurality of apparatuses of which at least one comprises the features of one of the claims 1 to 5;

   6.1 the installation comprises a number of drawing stations;

   6.2 at least one of the drawing stations is formed according to one of the claims 1 to 5.
7. A method of forming a sheet metal blank into a pot (5), comprising the following features or components:

   7.1 a punch (1) with a bottom forming area (1.1) forming the bottom (5.1) and a wall forming area (1.2) forming the wall (5.2);

   7.2 an annular blank holder (2) surrounding the punch (1) and having a supporting surface (2.1) for placing the drawn edge (5.3);

   7.3 an inner die (3) with a bottom forming area (3.1);

   7.4 an outer die (4) with a wall forming area (4.1) and a clamping area (4.2) for gripping the drawn edge (5.3) and for pressing said drawn edge against the supporting surface (2.1) of the blank holder (2);

   characterized by the following features:

   7.5 a sheet metal blank or an intermediate product produced therefrom is placed in the drawing apparatus which is opened;

   7.6 during a first forming phase the inner die (3) and the outer die (4) as well as the blank holder (2) together with the clamped sheet metal blank or with the clamped pre-shaped workpiece are moved in the drawing direction;

   7.7 the dies (3, 4) are moved simultaneously at different velocities in one and the same direction after the clamping and thus at the beginning of the work phase of the forming of the workpiece area within the clamping area, and during a phase of the forming process the inner die (3) overtakes the outer die (4), or vice versa.
8. A method according to claim 7, characterized by the following features:

   8.1 during an initial phase the two dies (3, 4) move in the same direction at equal velocity;

   8.2 during a middle phase the two dies (3, 4) move in one and the same direction, but the inner die (3) at higher velocity than the outer die (4);

   8.3 in an end phase the inner die (3) stands still, while the outer die (4) continues to move at constant velocity.

Images