DE102006046305B4 - Device for at least partial forming of sheet metal beyond the known shaping limits - Google Patents

Abstract

Apparatus for the partial forming of sheet metal (10) beyond the shaping limits, comprising heated working medium leading mold parts (20, 22) with mold surfaces and a Fluidzuführsystem, characterized in that the active medium leading mold parts (20, 22) are designed such that the active medium locally to a partial surface of the sheet (10) is guided.

Description

The invention relates to a device according to the preamble of claim 1.

Under sheets is understood in the following plate or in any other way three-dimensionally shaped layer.

A typical method for the production of molded parts within the mold boundaries, in particular of formed sheets, is the hot or cold pressing or deep drawing of sheet metal (possibly heated sheet) in molds. Typical suitable presses are hydraulic presses or mechanical presses, such as deep drawing presses.

"Form boundaries" or the "limit shape change" are expressions that describe the forming behavior of sheets under normal conditions and are, for example, in the Kurt Lange "Textbook of Umformtechnik", Springer-Verlag, Berlin defined, to which in order to avoid repetition in full circumference is taken. A correct and rapid forming of sheets, especially steel or aluminum and magnesium alloys for automobile bodies, sheet metal panels u. Like. Is especially in the vehicle industry a long-cherished desire and of great importance for various reasons. Shaped sheets are also important for other applications, such as aluminum facades, furniture panels; Aircraft parts, etc. Important is a fast and precise production. Usually formed from flat, relatively thin sheets by forming in press tools formed sheet metal parts. Most of these can be cold pressed. In order to realize high degrees of deformation, hot sheets are often used, for example. Steel sheets are heated to temperatures above 900 ° C placed in a mold and formed there; Aluminum sheets can be formed even better at 230 ° C, because increased temperatures favor the forming properties of the sheet. Instead of mechanical pressing, it is also possible to form sheets hydrodynamically.

For this purpose, molds are provided with fluid channels and openings, wherein for the forming of the inserted sheet fluid for pressing and thus forming the sheet from the liquid openings of the mold is pressed. Due to the high thermal conductivity of the metal molds occurs during hot forming a rapid cooling of the mold itself and thus the sheet on.

It is also desirable to enable the forming of sheets with complex shapes, such as undercuts, or to make faster and more economical, in particular beyond the deformation limits. Particularly interesting are secondary features and undercuts, beads, tight radii u. Like. In order to transform sheets over the classically defined strain limits, there is, for example, the superplastic forming, in which slowly deformed, the hot forming, in which the sheet is heated externally or heated within the mold - this can be inductively, by introducing warm medium into the shape or by IR emitters in the form; as well as high-speed forming.

The DE 4417460 B4 teaches a method for the production of sheet metal parts by drawing or deep drawing, wherein a pressure medium is passed via an intermediate plate to the effective location of a held between a drawing ring and a hold-down sheet metal blank.

DE 19806761 A1 describes a motor vehicle seat shell or a body part, produced by superplastic forming from a light metal alloy, wherein hot gas forming is used.

DE 19827614 B4 relates to a method and an apparatus for the production of deep-drawn parts, in which a deep-drawn part made of sheet metal with the aid of a punch, hold-down and matrix existing so-called Fluidfom is introduced into the tunnel of a high-pressure tunneling press and in an endverformenden stage the closed fluid form is subjected to a force exceeding the final deformation pressure and is finally shaped by means of the pressure medium in the matrix under appropriate high pressure.

The documents indicate normal sheet metal high pressure forming, but not the production of special extreme individual forms, such as undercuts.

It is therefore an object of the invention to provide a device for forming sheet metal, which avoids the disadvantages of the prior art.

The object is achieved by a device according to claim 1. Advantageous developments emerge from the dependent claims.

• – geringere Kosten, da die aufwendige Umformungen nun in einer Form mit einer Kanalkonstruktion für Fluid durchgeführt werden, anstelle in mehreren Formen.
• – geringere Investitionskosten (es können langsamere Pressen eingesetzt werden), denn durch Isolation der Oberflächen bleibt das Blech und das Fluid länger warm und führt nicht sogleich seine Wärme an das Pressenwerkzeug ab.
• – geringe Taktzeiten, da die Abkühlzeiten durch direkte Erwärmung kurz sind
• – Hinterschneidungen und Nebenformelemente, insbesondere solche, die Umformungen über die Grenzformänderung hinaus ermöglichen, in Blechen sind nun in einer Presse formbar

Advantages of the invention include:

• Lower costs, since the complex transformations are now carried out in a mold with a channel construction for fluid, instead of in several forms.
• - lower investment costs (slower presses can be used), because by insulating the surfaces the sheet metal and the Fluid warm longer and does not immediately dissipate its heat to the press tool.
• - Low cycle times, since the cooling times by direct heating are short
• - Undercuts and secondary features, especially those that allow transformations beyond the limit shape change, in sheets are now malleable in a press

It is thus possible to use presses to produce more complicated shapes in press-forming tools than hitherto possible, since by forming them with fluid, the sheet can also be applied to areas of the engraving which are not mirror images of the punch. The fact that hot fluid or partial heating of the sheet in the forming area can be used, the advantages of a - even partial - hot forming can be achieved, which allows greater degrees of deformation.

The process costs are significantly reduced by the device according to the invention, which makes the process interesting even for small batches.

It is therefore proposed in a preferred embodiment of the invention, a device for combined mechanical and active media-forming of sheet metal, with active medium leading mold parts with mold surfaces and a Fluidzuführsystem, the access of fluid for active media forming at least a partial surface of the mechanically formed sheet metal allows.

It is possible for some applications for the production of sheets with undercuts that a mold engraving has at least one undercut, in the sheet is formed by the active medium.

If the forming is to take place with warm fluid and / or warm sheet metal, it is favorable that at least the surfaces of the forming tool that come into contact with the sheet are in the wstl. consist of thermally poorly conductive or heat-insulating material.

It may be beneficial for better heat formable materials, such as aluminum and magnesium alloys, when the working medium is warm.

It is often sufficient that at least the coming into contact with the sheet surfaces of the mold with thermally poorly conductive or heat-insulating material are coated.

In the device according to the invention, it makes sense that the mold has at least one lower tool and an upper tool.

It is convenient that the fluid delivery system, allowing fluid to be formed into at least one surface of the formed sheet, allows fluid to force forming pressure upon collapse of the movable mold parts while mechanically forming the sheet in direct contact with a portion of the formed sheet surface.

In general, an apparatus according to the invention for sheet metal forming consists of an at least two-part mold, wherein the surface areas coming into contact with hot metal or fluid are preferably thermally insulated, whereby an excessive heat flow of hot liquid or during the forming of the sheet can be avoided. The insulation can also be a faster cooling of the formed sheet, in particular from the other side, take place, since the heat of the tool does not have to be dissipated by cooling. But it can also be a heat source, such as an IR emitter, be provided directly in the tool to partially heat the plate and thereby allow a high degree of deformation in the heated area.

In this case, at least the coming into contact with the hot metal surfaces of the lower tool and the upper tool of the mold in wstl. consist of thermally poorly conductive or heat-insulating material, as well as the Fluidleiteinrichtungen. This can be achieved by coating the lower tool and the upper tool of the mold with thermally poorly conducting or heat-insulating material, at least in the area of the surfaces coming into contact with the hot metal sheet.

But it is also possible that the lower tool and the upper tool of the mold consist of thermally poorly conductive material.

The fluid delivery system, which allows access of fluid for forming to at least one surface of the formed sheet, is designed according to the invention for a high pressure of fluid to effect rapid forming of the sheet. For example, it may include a multi-part tool that retracts movable tool parts for cooling the sheet, wherein fluid supply is provided to allow cold or warm fluid to be injected into the mold portions released by the movable tool parts in contact with the sheet surface Retracting the movable tool parts allows the insertion of fluid in the released tool areas.

According to the invention, the device is used, by
Introducing the sheet into a mold;
Inflowing fluid from the mold into contact with at least a partial surface of the sheet while deforming it against a shape engraving beyond the forming boundaries.

It may be advantageous if the forming tool is also the known mechanical deformation of the sheet by deep drawing od. Like. Within the forming limits and secondary features or undercuts in the same tool that require a transformation beyond the forming beyond, after partial heating of Sheet or under the conditions of superplastic forming or high speed forming.

Due to the fluid pressure for forming over the forming boundaries, it is possible to achieve a transformation even complicated shapes, such as undercuts, in the first, mechanical or Wirkmediums-formed sheet metal, which is also supported by the insulating tool surfaces during hot forming. The thermal management of the system is significantly improved.

It is also possible to partially heat the plate in the mold itself, for example by induction or by means of infrared steels.

Suitable fluids are those selected from the group consisting of water, aqueous solutions, a high temperature resistant liquid, such as high temperature resistant oil or a gas.

Typical plates to be formed, to which the invention is by no means limited, are selected from the group consisting of iron alloys, including steels, aluminum alloys, magnesium alloys.

In the device, it may be beneficial if at least one tool half in wstl. made of thermally insulating material.

It can also be provided that at least one mold half of the mold is coated with thermally insulating material at least in the region of the surface which comes into contact with the metal sheet.

Preferably, the fluid is a liquid, such as water or a temperature-resistant liquid, such as high temperature resistant oils. Water has the advantage of high heat capacity and low price. In some cases, gaseous fluid may also be provided.

It can also be a hot hydroforming in the inventive device used as a deformation step. This is particularly possible if fluids are used for sufficient heating of the sheet to forming temperature - eg. For aluminum sheets can be done with hot oil such a transformation.

By virtue of the fact that, according to the invention, several forming stages can now be carried out in a simple manner, for example in a single mold or system, it is surprisingly possible to achieve a considerable simplification and reduction of expenditure in the production of shaped sheets.

This is even more true if they have mold areas in which the sheet is to be formed beyond the shaping limits.

A suitable apparatus for many applications according to the invention is a classical press for forming within the forming limit - such as a hydraulic press or a mechanical press, to which an aggregate is connected with a control for partial active-medium forming beyond the forming limit. As a result, conventional forming presses can be enabled to previously not possible forming steps in a surprising manner. Preferred embodiments of the invention will now be explained in detail below with reference to the accompanying drawings. It shows:

1 a mold assembly with pickled sheet after mechanical forming;

2a an open mold assembly with pickled sheet metal

2 B the mold assembly of 2a in closed form at the beginning of the pressure build-up of the active medium

2c a detail from the Wirkmediumsumformung subject sheet metal area in the mold;

2d the detail of 2c after the active medium deformation of the sheet metal area

3a an open mold with undercut; and

3b the mold of the 3a in closed form during fluid introduction.

According to the invention, an at least two-part mold arrangement is provided. Preferred are mold parts 20 . 22 for forming at elevated temperatures made of thermally insulating material or coated with such to avoid heat inflow or outflow.

Forming in a device according to the invention is carried out in a first embodiment as follows:
The sheet 10 , for example, from 22MnB5, is placed in a classic hydraulic forming press.

At the in 1 illustrated embodiment, the mold consists of a lower tool 20 and an upper tool 22 , The sheet 10 gets between the mold halves 20 . 22 spent and the mold halves 20 . 22 Now under deep drawing of the sheet 10 moved together. Thereafter, the fluid supply in the upper mold 22 opened for partial further forming beyond the forming limits. The - for example - heated - fluid 24 Presses the partially accessible for it sheet metal surface against the form engraving of the upper tool beyond the forming boundaries by applying the area to the form engraving. The formed sheet metal part can now be removed and the fluid drained.

Another sheet 10 gets between the disjointed mold halves 22 . 20 spent, mechanically deformed, hydrodynamically deformed, etc. Of course, the forming tools can have other and more tool parts, as shown, which are arranged accordingly and can be controlled. Such embodiments are familiar to the person skilled in the art.

It is also possible to design the system for hot sheets, then preferably insulating mold surfaces or completely insulating molds are used and hot fluid directly with the transformed hot sheet 10 pressed in the mold for further forming. As a result, fast forming times, short cooling times, lower energy and tool costs can be achieved.

Instead of hot forming for the over the form boundaries to be reshaped workpiece areas but also appropriately adapted superplastic forming of these areas or partial high speed forming can be used by means of fluid. The person skilled in the art, on the basis of his specialist knowledge, can select the appropriate procedure with a device according to the invention for heavy forming.

Accordingly, the sheet metal forming according to the invention is easier, faster to perform with simpler and slower and therefore cheaper presses than the conventional conventional forming by the inventive device. With pressing thus a shorter cycle time can be achieved than previously customary, since the more important clock timer so far is the transfer of the first sheet metal mold in another mold.

The economic advantages of the device are therefore both in the process costs, as well as in tooling costs, which makes them more attractive for small batches.

In 2a -D is shown as a mechanically formed sheet 10 in an inventive mold 20 . 22 spent there and warm by warm fluid 24 is transformed. For this purpose, the fluid channels are provided with insulation to keep the fluid warm.

In 2 B and 2c you can see the sheet in contact with the fluid supply while in 2d It is shown how warm fluid presses the metal sheet faithfully against the form engraving.

In 3a to 3b is a special embodiment of a forming tool for producing undercuts in the formed sheet metal. It can clearly be seen that the undercut, which would not be producible with a conventional pressing tool, can now be formed by introducing an internal high-pressure part. The device according to the invention thus sheet metal shapes in pressing methods can be achieved, which could not be produced previously.

LIST OF REFERENCE NUMBERS

10

sheet

20

lower tool

22

upper tool

23

thermal insulation

24

fluid

25

air

30

sealing bead

Claims (7)

Device for partially forming sheet metal ( 10 ) beyond the shaping limits, comprising heated working medium-carrying mold parts ( 20 . 22 ) with mold surfaces and a Fluidzuführsystem, characterized in that the active medium leading mold parts ( 20 . 22 ) are configured such that the active medium locally to a partial surface of the sheet ( 10 ) to be led. Apparatus according to claim 1, characterized in that a mold engraving of the mold ( 20 . 22 ) at least one Undercut has, in the sheet metal ( 10 ) is einformbar by the active medium. Apparatus according to claim 1 or 2, wherein at least the with the sheet ( 10 ) coming into contact surfaces of the mold ( 20 . 22 ) in the wstl. consist of thermally poorly conductive or heat-insulating material. Apparatus according to claim 1 to 3, wherein at least the with the sheet ( 10 ) coming into contact surfaces of the mold ( 20 . 22 ) are coated with thermally poorly conductive or heat-insulating material. Device according to one of the preceding claims, wherein the molding tool ( 20 . 22 ) at least one lower tool ( 20 ) and an upper tool ( 22 ) having. Device according to one of the preceding claims, characterized in that the fluid supply system, the access of fluid ( 24 ) for forming at least one surface of the formed sheet ( 10 ) allows fluid ( 24 ) after moving together the movable mold parts ( 20 . 22 ) with mechanical deformation of the sheet in direct contact with a part of the deformed sheet surface can exert forming pressure. Apparatus according to claim 1, characterized in that the tool has means for at least partially heating the sheet in the forming area.

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