EP1526931B1 - Method for controlling the material flow during the deep-drawing of sheet metal, and deep-drawing tool - Google Patents

Abstract

A method for controlling the material flow during the deep-drawing of sheet metal involves compressing the edges of the sheet metal ( 1 ) between at least one upper stopper ( 13 ) and at least one lower stopper ( 6, 7 ) during the deep-drawing process, with a controllable elastic force ( 8, 9 ). A corresponding deep-drawing tool is also provided. A Z-shaped blocking step ( 11 ) is stamped into the edge ( 1 a) of the sheet metal when the upper and lower stoppers ( 13, 6, 7 ) are closed, the basic shape is then produced by deep-drawing, maintaining the blocking step ( 11 ) and completely blocking the sheet metal between the stoppers. The sheet metal ( 1 ) is outwardly stretched, and the blocking step ( 11 ) is then reduced in terms of height, facilitating the outward displacement of the sheet metal towards the outside. The deep-drawing tool has a lower stopper including an inner stopper ( 6 ) and an outer stopper ( 7 ). The stoppers are arranged in an annular manner on the edge of the sheet metal ( 1 ) and can be displaced in relation to each other in the holding direction.

Description

The invention relates to a method for material flow control during deep drawing of sheets, preferably of higher strength steels and / or multi-phase steels or aluminum according to the preamble of claim 1 and to a deep-drawing tool according to the preamble of claim 4.

As part of the development of lighter and lighter motor vehicles, the use of higher-strength steels in the body shop is becoming increasingly important. For example, plates made of polyphase steels are increasingly being proposed for the cladding parts. In particular, for paneling made of thermoforming materials with high solidification values, it is important that the metal sheet is stretched as "large area" as possible. For this purpose, it is state of the art that the sheet trailing is inhibited from the outside by a stopper or blocking bead located on the sheet holder. It may be disadvantageous here if the sheet metal inhibition is maintained constant throughout the drawing process, in particular if the sheet is stretched beyond the critical elongation of 20% in strongly deformed regions and towards the end of the drawing process. In an article by S. Beck under the title "Control of the drawing process by active drawing beads in the book" Recent developments in sheet metal forming ", editor Klaus Siegert, May 2000, the use of height-adjustable drawing rods is described to the stresses during forming and thus the material flow The structural solutions relate exclusively to a relatively complex height adjustment of the drawing rods.

From EP 806 256 B1, moreover, a method for material flow control when pulling workpieces such as sheet metal parts known, using a friction force sensor, the frictional force between the workpiece and hold-down is measured and used as a control variable for a hold-down force. A segmented downholder is also used to regulate the holding force of individual distributed on the circumference segments of the blank holder. This solution is also relatively complicated.

The invention is therefore based on the object to propose a generic method for controlling the deep drawing of sheets and a corresponding thermoforming tool, can be dispensed with the height adjustment by pulling rods and the complex friction force sensors.

The solution to this problem is described in claims 1, 3 and 4. The dependent claims 2 and 5 to 7 contain useful additional measures or embodiments.

According to claim 1, this is done first, i. Prior to the actual drawing process with the closing of the upper and lower plate holder in the sheet edge a Z-shaped shut-off marked (see feature a), which is then maintained during the final drawing of the basic shape, wherein by the compressed blank holder a complete shut-off is effected and the Sheet metal is stretched out from inside to outside (see feature b). During the further drawing process, the shut-off stage is finally reduced in height, thereby facilitating the lead-back from outside (cf feature c). The Z-shaped shut-off according to the invention, the sheet metal escapement can be increased from the outside and the end of the deep-drawing process by reducing the height of Absperrstufe by mechanical Wegsteuem the drawing stage, the sheet metal inhibition reduced and even completely canceled, so that the sheet tracing is done exclusively from the outside in.

The inventive method can also be found by reversing the stage for the opposite case, as described in claim 3, pulled at the beginning of the process without a blocking stage and only during the thermoforming process a locking stage is embossed using the blank holder. It is therefore only at the end of the lead tracking inhibited by means of the locking stage. This can be advantageous both in thermoforming operations with locally strong deformation, where material must be "submitted", as well as in sheet metal materials with low elongation at break, such as aluminum.

The constructive solution provides a thermoforming tool according to claim 4, wherein at least one sheet holder, preferably the lower sheet holder along the locking stage is divided into an inner and an outer ring and at least one of the rings is movable relative to the other in the holding direction. The two sheet metal holders arranged side by side can form an adjustable shut-off stage for the edge of the sheet and be pressed against a corresponding fixed stage of the counter-holder to achieve the desired sheet metal inhibition. By operating the outer ring in the holding direction relative to the inner ring, the level can be reduced from the initial height with maximum blocking effect to any desired depth of draw in extreme cases to zero. According to the method of claim 3, this process can also be reversed by first working virtually without locking step between the inner and outer plate holder and then turned on by increasing the level between the two rings, the effect of the blocking stage and is increased to maximum effect to the end.

By means of the two-part sheet metal holder according to the invention and the relative movement of the outer ring relative to the inner ring, a deep-drawing tool having controllable locking level is achieved. In contrast to single-acting tools, the die and the upper sheet holder are movable relative to each other. This drawing tool can be used in virtually all conventional presses with controlled or delayed trailing die cushion.

Fig. 1

einen Schnitt durch das erfindungsgemäße Tiefziehwerkzeug zwischen Kopfplatte 2 und Grundplatte 3 einer Presse,

Fig. 2

eine vergrößerte Darstellung des zentralen Bereiches in Fig. 1 und

Fig. 3

entsprechend zu der Darstellung nach Fig. 1 die steuerbare Sperrstufe in fünf verschiedenen Phasen.

The invention will be explained in more detail with reference to the accompanying figures 1 to 3, for example. Show it

Fig. 1

a section through the deep-drawing tool according to the invention between the top plate 2 and the base plate 3 of a press,

Fig. 2

an enlarged view of the central region in Fig. 1 and

Fig. 3

corresponding to the illustration of FIG. 1, the controllable locking stage in five different phases.

In Fig. 1, the sheet 1 is shown before the deep drawing process with the sheet edge la as a dashed line with the shut-off stage 11. After the deep-drawing process, the sheet edge 1b is drawn by a solid line. The sheet 1 is located between the thermoforming punch 4 and the die 5, which are arranged between the top plate 2 and the base plate 3 of a conventional press. The base plate 3 is stationary fixed in the usual way, while the top plate 2 is vertically movable for the deep drawing process. The movable relative to the die 5 upper plate holder 13 has on its underside a step 16 which corresponds to the shut-off stage 11 of the plate edge la. The upper sheet metal holder 13 is acted upon during the deep drawing process by the spring force 9, which is also referred to as upper air, and pressed against the sheet edge. As a counter-holder, the two lower sheet holders 6 and 7, which are shown in its upper position 6a, 7a, before the deep-drawing process with dashed border. In the lower position 6b, 7b, these two plate holder are drawn hatched. The inner sheet holder 6 is pressed by the spring force 8 and the outer sheet holder 7 of the stroke-dependent counterforce 10 from below against the edge of the sheet 1. To form a molding stage, the punch 4 has a bead 12 and the die 5 a corresponding nose 14, which is shown in Fig. 2, in particular in the upper (dashed line) and the lower position.

Phase 1:

Blechhalter schließen
Über den mit Oberluft 9 beaufschlagten oberen Blechhalter 13 und die mit Unterluft 8 wirkenden unteren Blechhalter 6, 7 wird eine Absperrstufe 11 mit maximaler Stufenhöhe 11.1 in den Blechrand 1a geprägt. Der äußere Blechhalter 7a liegt mit der Unterseite auf der Auflagefläche 15 des inneren Blechhalters 6a auf.

Phase 2:

Streckziehen der Grundform
Unter komplettem Absperren und Beibehaltung der maximalen Stufenhöhe 11.2 wird die Grundform fertiggezogen, wobei das Blech ausschließlich von innen nach außen ausgereckt wird. Diese Fließrichtung des Materials wird durch die Pfeile P1 angedeutet.

Phase 3:

Beginn der Formung der Formstufe auf dem Stempel
Durch das Einwirken der hubabhängigen Gegenkraft 10 auf den äußeren unteren Blechhalter 7 wird die Sperrstufe in ihrer Stufenhöhe 11.3 reduziert und der Blechnachlauf von außen erleichtert (vgl. Pfeil P2).

Phase 4:

Weitere Verformung der Formstufe
Durch das weitere Reduzieren der Sperrstufenhöhe 11.4 erfolgt der erforderliche Blechnachlauf verstärkt von außen.

Phase 5:

Fertigformen
Durch die nicht mehr vorhandene Stufenhöhe 11.5 und die praktisch weggefallene Sperrstufe erfolgt der Blechnachlauf ausschließlich von außen (vgl. Pfeil P3).

In Fig. 3 in particular five different phases for the position of the two lower, inner and outer plate holder 6 and 7 are shown:

Phase 1:

Close sheet holder
About the acted upon with upper air 9 upper plate holder 13 and the lower air 8 acting lower plate holder 6, 7 a shut-off 11 is embossed with maximum step height 11.1 in the sheet edge 1a. The outer sheet holder 7a rests with the underside on the support surface 15 of the inner plate holder 6a.

Phase 2:

Stretching the basic shape
With complete shut-off and maintenance of the maximum step height 11.2, the basic shape is finished, whereby the sheet metal is only stretched out from inside to outside. This flow direction of the material is indicated by the arrows P1.

Phase 3:

Start of molding of the molding step on the stamp
By the action of the stroke-dependent counterforce 10 on the outer lower sheet holder 7, the locking level is reduced in its step height 11.3 and the sheet trailing facilitated from the outside (see, arrow P2).

Phase 4:

Further deformation of the molding stage
Due to the further reduction of the locking step height 11.4, the required sheet metal run-off is reinforced from the outside.

Phase 5:

finish forming
Due to the no longer existing step height 11.5 and the virtually eliminated blocking stage, the sheet tracing is carried out exclusively from the outside (see arrow P3).

LIST OF REFERENCE NUMBERS

1

sheet

1a

Sheet edge (dashed line, before the deep drawing process)

1b

Sheet edge (solid line, after the deep drawing process)

2

Head plate (vertically movable)

3

Base plate (fixed)

4

Thermoforming stamp on 3

5

Die at 2

6

Sheet holder (down, inside)

6a

Sheet holder (bottom, inside, before the deep drawing process, shown in dashed lines)

6b

Sheet holder (bottom, inside, after the deep-drawing process, shown hatched in FIG. 1)

7

Sheet holder (bottom, outside)

7a

Sheet holder (bottom, outside, before the deep-drawing process, shown in dashed lines)

7b

Sheet holder (below, outside, after the deep-drawing process, shown hatched in FIG. 1)

8th

Spring force (under-air)

9

Spring force (upper air)

10

stroke dependent counterforce to 9

11

Shut-off stage in 1a

11.1

maximum step height

11.2

maximum step height

11.3

reduced step height

11.4

reduced step height

11.5

no step height

12

Bead on 4

13

Sheet holder above

14

Nose at 5

15

bearing surface

16

Step at the bottom of 13

P1, P2, P3

Arrow for flow direction of the material

Claims (7)

1. A method for controlling the material flow during the deep-drawing of sheet metal plates, preferably made of high-strength steels and/or multiple-phase steels or aluminum, wherein

   - the sheet metal plate (1) is formed in a press between a die stamp (4) arranged at a base plate (3) and a matrix (5) arranged at a top plate (2),

   - the die stamp (4) and the matrix (5) have adapted profiled sections (12, 14) for the formation of die beads at the edges of said sheet metal plate (1) and

   - the edges of said sheet metal plate (1) are compressed between at least one upper sheet metal stopper (13) and at least one lower sheet metal stopper (6, 7) during the deep-drawing process, applying a controllable spring load (8, 9),

   characterized in that

   a) initially, as the upper and lower sheet metal stoppers (13,6,7) are closed, a Z-shaped blocking step (11) is stamped into the sheet metal plate edge (1a),

   b) then, by maintaining the blocking step (11) and a complete blocking between said sheet metal stoppers, the drawing of the base form is completed, with said sheet metal plate (1) being stretched-out from inside to outside, and

   c) finally, the blocking step (11) is reduced in its height, thus facilitating the sheet metal trailing from outside.
2. A method pursuant to Claim 1, characterized in that by the end, through complete abandonment of the blocking step (11), the sheet metal trailing takes place exclusively from outside to inside.
3. A method for controlling the material flow during the deep-drawing of sheet metal plates, preferably made of high-strength steels and/or multiple-phase steels or aluminum, wherein

   - the sheet metal plate (1) is formed in a press between a die stamp (4) arranged at a base plate (3) and a matrix (5) arranged at a top plate (2),

   - the die stamp (4) and the matrix (5) have adapted profiled sections (12, 14) for the formation of die beads at the edges of said sheet metal plate (1) and

   - the edges of said sheet metal plate (1) are compressed between at least one upper sheet metal stopper (13) and at least one lower sheet metal stopper (6, 7) during the deep-drawing process, applying a controllable spring load (8, 9),

   characterized in that

   a) initially, mainly without any bead effect, the base form is drawn, while the upper and lower sheet metal stoppers (13, 6, 7) rest upon each other mainly evenly, and

   b) then a blocking step is stamped into the sheet metal plate edge in order to impede the sheet metal trailing from outside to inside.
4. A deep-drawing tool for the deep-drawing of sheet metal plates, preferably for executing the method according to the preceding claims, said tool being comprised of

   - a die stamp (4) arranged in a press at a base plate (3) and a matrix (5) arranged oppositely at a top plate (2),

   - profiled sections (12, 14) arranged at the die stamp (4) and at the matrix (5) for the formation of die beads at the edges of the sheet metal plate (1) to be deformed, and

   - at least one upper sheet metal stopper (13) and at least one lower sheet metal stopper (6, 7),

   characterized in that the lower sheet metal stopper consists of an inner sheet metal stopper (6) and an outer sheet metal stopper (7), said stoppers being annularly arranged at the edge of said sheet metal plate (1) and being movable relative to each other in the direction of holding.
5. A deep-drawing tool pursuant to Claim 4, characterized in that the lower inner sheet metal stopper (6) has a support surface (15) onto which the outer sheet metal stopper (7) comes to rest in the lower relative position as compared with the inner sheet metal stopper (6).
6. A deep-drawing tool pursuant to any of the preceding claims 4 or 5, characterized in that the two lower sheet metal stoppers (6, 7) with their upper sides create an adjustable blocking step (11) for the edge of said sheet metal plate (1).
7. A deep-drawing tool pursuant to any of the preceding claims 4 to 6, characterized in that a step (20) corresponding to the maximal step height (11.1) of said blocking step (11) is arranged at the underside of the upper sheet metal stopper (13).

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