EP3027335B1 - Device for forming metals - Google Patents

Description

The invention relates to a device for forming metals, in particular the molding of parts, such as the shaping of a collar.

An important area is the molding of a collar on a workpiece made of steel, for example a sheet steel plate made of the material of the plate. See for example DE 10 2006 029 124 B4 such as DE 1 916 826 , The workpiece is placed on a die. The die has a bore adjacent to the workpiece. Then, with a sharpened punch, a hole is pressed into the workpiece, thereby pulling material out of the sheet plane and into the hole in the die. This creates a collar that remains part of the workpiece. This principle is used particularly in the automotive industry.

In the described forming process, it comes within the forming zone to stresses the workpiece. Thus, when installing the collar in the sheet edge substantially tensile stresses are effective. The achievable collar height is limited. The smaller the ratio of collar diameter to collar height, the higher the risk of tearing of the material in the collar region.

The failure of reshaping is a big problem. It occasionally becomes recognizable only during use. In such a case, the removal of defective parts and the replacement by flawless parts is particularly complex.

It has already been tried to optimize the drawing process by applying heat. For example, the stamp has already been heated to apply heat to the forming zone of the workpiece, for example the sheet metal plate. However, this has the disadvantage that the stamp loses its strength due to its heating and thus has only a short service life. JP-A-2009262184 discloses a device according to the preamble of claim 1. With this device, a pot-like object is heated prior to a forming operation. For this purpose, electrodes must be moved up to the workpiece and then driven off again to make room for bringing a ram with punch.

The machining process is thus divided into two phases, which means time expenditure.

JP-A-2007260761 describes a device comprising two electrodes for heating a steel sheet. When heating the sheet, a plunger must first be raised, and lowered again after heating. Again, this is time consuming.

The invention has for its object to provide a device for molding a collar to a workpiece made of sheet metal, especially to a metal plate or the like, whereby the forming process is improved and the risk of tearing of the collar is reduced, but at the same time retain the tool elements involved their strength , The device should in particular comprise fewer components and perform the machining operations more quickly than known devices.

This object is solved by the features of claim 1.

The inventors have recognized that they must search for a solution in which, although the forming area of the workpiece is heated, but not the tool, in particular the stamp. It was therefore necessary to search for a system based on the principle of "hot workpiece, cold tool".

• Es wird eine Hülse vorgesehen, die den Stempel umgibt und aus elektrisch gut leitendem Material besteht.
• Es wird ein in die Matrizenbohrung einsetzbarer Gegenhalter aus einem Material vorgesehen, das ebenfalls elektrisch gut leitet.
• Der Gegenhalter ist entsprechend der Abwärtsbewegung des Stempels nach unten verfahrbar.
• Die Hülse dient als Niederhalter und zugleich als Elektrode.

The solution according to the invention lies in the following:

• It is provided a sleeve which surrounds the stamp and consists of electrically good conductive material.
• It is provided an insertable in the die bore counter-holder of a material that also conducts good electrical.
• The anvil can be moved downwards in accordance with the downward movement of the punch.
• The sleeve serves as a hold-down and at the same time as an electrode.

In such a device, no heating of the stamp takes place, since the current is not passed through the stamp, but by the hold-down and the counter-holder.

• Es wird im Wesentlichen nur das Werkstück erwärmt, und auch nur im Umformbereich, somit auf einen engen Bereich fokussiert. Das Werkzeug hingegen bleibt im Wesentlichen kalt.
• Es lassen sich auch Zuschnitte oder Formteile aus hochfestem, dünnem Blech verwenden, weil aufgrund der Erfindung die Gefahr des Ausreißens beim Umformen (Ziehen) von Kragen verringert wird. Hierdurch wird an Gewicht gespart, aber auch an Kosten.

The invention solves this problem in an outstanding way:

• Essentially, only the workpiece is heated, and also focused only in the forming area, thus on a narrow range. The tool, on the other hand, remains essentially cold.
• It can also blanks or moldings of high-strength, thin sheet metal use, because due to the invention, the risk of tearing when forming (pulling) of collar is reduced. This saves weight, but also costs.

Interesting embodiments emerge from the subclaims and from the description of the figures.

Figur 1

zeigt eine Vorrichtung mit Stempel, Matrize und Werkstück, ferner eine den Stempel umgebende Hülse, sowie einen Gegenhalter in der Matrize.

Figur 2

zeigt eine zweite Ausführungsform.

Figur 3

zeigt eine weitere Ausführungsform.

Figur 4

veranschaulicht die Ausführungsform von Figur 3 nach dem Umformen des Kragens.

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

FIG. 1

shows a device with punch, die and workpiece, also a sleeve surrounding the stamp, and a counter-holder in the die.

FIG. 2

shows a second embodiment.

FIG. 3

shows a further embodiment.

FIG. 4

illustrates the embodiment of FIG FIG. 3 after forming the collar.

• Die dargestellte Vorrichtung umfasst einen Stempel 1 sowie eine Matrize 2, ferner eine konduktive elektrische Heizeinrichtung mit einer Stromquelle 3. Stempel 1 ist von einem hülsenförmigen Niederhalter 5 umgeben.

Out FIG. 1 In particular, one recognizes the following:

• The device shown comprises a punch 1 and a die 2, further a conductive electric heater with a power source 3. Stamp 1 is surrounded by a sleeve-shaped hold-5.

On the die 2, a metal plate 4 made of high-strength steel is placed.

Stamp 1 is made of high-strength material. Stamp 1 has a tip 1.1. This penetrates into a bore 4.1 in the metal plate 4. The bore can already be introduced into the metal plate 4 before the forming process. However, the metal plate 4 can also have no bore, so that the punch 1 creates the hole when pressed into the metal plate 4 only. The stamp 1 can also be blunt. Also, the shape of the front end of the punch can be adapted to the requirements of the forming process. Stamp 1 is surrounded by a sleeve 5. This is traversed by electricity during operation.

As illustrated, there is a current flow 3.1, starting from the electric current source 3 through the electrically good conductive hold-down 5 through, further through a certain deformation region of the metal plate 4, and then to die 2. Die 2 is made of electrically highly conductive material, such as copper.

In the presentation according to FIG. 1 the forming process is currently in an initial phase. If the forming process is completed, the bore 4.1 is widened to the shape of the desired collar - not shown here. The collar then has a clear width which is equal to the diameter of the punch 1. How this looks, can be seen from Figure 5.

Sleeve 5 has three functions. On the one hand, it serves as a hold-down, on the other hand as a current conductor, and finally as a scraper.

It also recognizes a counter-holder. 6

The flow of current passes through the hold-down device 5 through the metal plate 4 and through the counter-holder 6.

Stamp 1 is completely free of current flow and is therefore not actively heated. It may therefore be a tool steel of conventional quality, or a heat-working steel.

There may be an air gap between the punch 1 and the hold-down 5. But this does not have to be this way.

The hold-down 5 does not need to have great strength. It can be made of copper. In any case, it should consist of a material with good electrical conductivity. The same applies to the counter-holder 6.

The material of the die 2 is irrelevant in this case. It can be any material - steel or copper, better but a little heat-conducting material, so that the heat generated by the electricity is limited to the actual forming area.

In the embodiment according to FIG. 2 again one sees stamp 1, die 2, sheet metal plate 3. The representation and effect of an electric heater is hereby omitted. Nevertheless, such is available.

at FIG. 2 the relevant component is an insulating coating 7. This may be a sleeve or a covering.

• Die Blechplatte 4 liegt zunächst auf der Matrize 2 auf. Niederhalter 5 bewegt sich nach unten und setzt auf die Blechplatte 4 auf, sodass ein Stromfluss aktiviert und die Umformzone erwärmt wird. Der Stempel bewegt sich sodann weiter nach unten, und der Niederhalter 5 federt ein. Kurz vor Berührung des Stempels an der Blechplatte 4 wird der Strom abgeschaltet, und der Gegenhalter 6 weggesteuert. Der Kragen wird durchgestellt.

The forming process is as follows:

• The metal plate 4 is initially on the die 2. Hold-down device 5 moves downwards and sits on the metal plate 4, so that a current flow is activated and the forming zone is heated. The punch then moves further down, and the hold-down 5 springs. Shortly before touching the stamp on the metal plate 4, the power is turned off, and the counter-holder 6 away. The collar is put through.

The particular to the embodiment according to FIG. 3 is a thread former 1.2 on stamp 1. Stamp 1 is equipped with a rotary drive, not shown here. If he wanders down, so stamp 1 and thus thread former 1.2 is put into circulation. Thus, the resulting collar (not shown) formed a thread through which a screw can be passed.

In the embodiment according to FIG. 4 you can see for the first time the collar 4.2 - in one piece with the rest of the metal plate. 4

In this figure, one again sees a thread former 1.2, as in the embodiment according to FIG FIG. 3 , and an insulating coating 7, as in the embodiment according to FIG FIG. 2 ,

If the forming capacity of an existing collar for thread forming is insufficient, it can also be actively heated.

For all of the mentioned embodiments, direct current or low frequency alternating current can be used for heating.

In all representations, individual elements of the device can be interchanged with each other, such as punch and die. Also, the working direction of the punch may differ from the vertical.

The essence of the invention is that exclusively or predominantly the workpiece is heated.

The tool, however, is not heated, or only to a small extent, so that its strength is only slightly reduced.

LIST OF REFERENCE NUMBERS

1

stamp

1.1

punch tip

1.2

thread former

2

die

2.1

die bore

3

power source

3.1

current flow

4

sheet metal plate

4.1

drilling

4.2

collar

5

Stripper plate

6

backstop

7

insulating coating

Claims (4)

1. A device for processing a workpiece (4), comprising the following features:

   1.1 a punch (1) on the one side of the workpiece (4);

   1.2 a die (2) on the opposite site of the workpiece (4);

   1.3 a conductive electric heating system (3) for generating an electric current, which completely or predominantly flows through the workpiece (4) starting from a component situated on the one side of the workpiece outside of the punch (1) to a component situated on the other side of the workpiece outside the die (2),

   characterized by the following features:

   1.4 the one component is a sleeve (5) made of an electrically well-conducting material surrounding the punch (1) and can be placed on the workpiece (4);

   1.5 the other component is a counterholder (6) made of an electrically well-conducting material insertable into the die bore (2.1);

   1.6 the counterholder (6) can be displaced downward corresponding to the downward movement of the punch;

   1.7 the sleeve (5) serves as a blank holder and at the same time as an electrode.
2. The device according to claim 1, characterized in that the soffit of the die bore (2.1) is lined with electrically insulating and/or heat insulating material (7).
3. The device according to any one of the claims 1 or 2, characterized in that the soffit of the sleeve (5) is lined with heat-insulating or electrically insulating material.
4. The device according to any one of the claims 1 to 3, characterized in that the punch (1) can be driven around its longitudinal axis and comprises a thread molder (1.2) for forming a thread in the soffit of the collar (4.2).

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