EP0974411B1 - Engraved forming tool for forming by means of a pressure medium - Google Patents

Abstract

The mold has a micro-surface structure at the mold wall to prevent distortion and surface damage at the workpiece when being shaped under pressure. The mold to shape a workpiece by inner pressure which forces it against the mold wall, has a pressure medium feed to press the workpiece (W) against the wall surface (2) which has a surface microstructure. The wall microstructure surface does not affect the workpiece (W) surface, and prevents a buildup between the workpiece and the wall, holds the workpiece in place, and can hold a lubricant. The microstructure also acts on the workpiece material flow during the shaping action. The microstructure is formed by a laser, electro-erosion, ultrasonic erosion, scraping or etching. The microstructures are about equal to the dimensions of the molecules of the pressure medium, with a width of 100 mu m and a depth/height of 100 mu m.

Description

The invention relates to a tool engraving Forming tool for forming by means of active medium, according to the Preamble of the first claim, the tool a pressure medium supply for the active medium and a Engraving according to the desired final contour of the Has workpiece and liquid or as the active medium gaseous pressure media are used. The invention can for the internal high pressure forming of tubular workpieces as well from adjacent to one another and possibly with one another connected double plates as well as in the hydroforming of Single or double boards or with hydromechanical Thermoforming application.

With the generic tool engraving takes place at Hyroforming (e.g. DE 44 34 799 A1) and at Hydroforming (see e.g. DE 195 35 870 A1 and Notrott, A .: Recent developments in sheet metal forming; Siegert, K .; Recent developments in hydroforming ..., 1998, publisher MAT-INFO Materials Information Society mbH, pp. 365-377) by printing of the pressure medium forming the wall of the workpiece to the engraving of the tool. When removing the The print medium can be engraved on the workpiece Tool arrive, whereby when the subsequent workpieces in the area in which Pressure medium adheres to the engraving, no contact between Engraving and workpiece wall comes about undesirable deformations occur on the workpiece. These deformations cause restrictions in the Evaluation of the surface quality of the workpiece. Also at gaseous active media can form bubbles between Sheet metal or thin foils to be formed and engraving occur, which also causes undesirable deformations of the Workpieces are generated.

The object of the invention is to deform the To prevent the workpiece by the active medium and the Improve surface quality and at the same time defined To achieve surface properties of the workpiece.

This object is achieved with the features of first claim solved in that in the engraving microstructures are incorporated into the tool. This Microstructures should improve the surface quality of the Do not negatively influence the workpiece and be suitable for this be while the workpiece is pressed against the engraving to take up the printing medium sticking in the engraving and a deformation due to local build-up of the pressure medium counteract between engraving and workpiece. Farther there is a possibility through the microstructures (Microstructures) the surface structure of the workpiece to influence them in a targeted manner so that e.g. a more even Forming takes place and better adhesive properties for one subsequent coating can be guaranteed.

The microstructures should have a dimension in the Order of magnitude from one molecule of the printing medium to approx. Have 100µm width and 100µm depth / or height. The Microstructures can have any shape and in equal or different distances from each other be arranged or merge and e.g. Line structures, meandering structures or form punctiform structures. According to the spec of the component, the microstructures on the engraving over the whole area or only at defined positions (e.g. in Radii elements), if only on these There is a risk of deformation, or if only on certain surface areas of the workpiece special surface properties (e.g. adhesive and Friction properties) are desired.

The invention is based on exemplary embodiments and associated drawings explained in more detail.

Fig. 1:

Prinzipdarstellung eines Innenhochdruckumformwerkzeuges

Fig. 2:

Prinzipdarstellung eines Hydroumformwerkzeuges

Fig. 3:

Schnittdarstellung durch eine Gravur mit Mikrostrukturen in den Eckbereichen

Fig. 4:

Gravur mit meanderförmigem Linienverlauf der Mikrostrukturen

Fig. 5:

Gravur mit kreisförmigen Linienverlauf der Mikrostrukturen

Show it:

Fig. 1:

Schematic diagram of a hydroforming tool

Fig. 2:

Schematic diagram of a hydroforming tool

Fig. 3:

Sectional view through an engraving with microstructures in the corner areas

Fig. 4:

Engraving with meandering lines of the microstructures

Fig. 5:

Engraving with circular lines of the microstructures

Figure 1 shows an internal high pressure forming tool with an upper tool half 1a and a lower tool half 1b, which are movable relative to each other for loading and removing the workpiece. In the example shown, both tool halves 1a, 1b are closed and have an engraving 2. In the internal high-pressure forming tool is the not yet formed tubular workpiece W. Feed cylinders 3 act on both pipe ends of the workpiece, which ensure that the material continues to flow during the internal high-pressure forming and at the same time seal the workpiece W. A pressure medium feed line 4 leads to the feed cylinder 3 shown on the left in FIG. 1, via which the pressure medium is fed to the workpiece W, for example by means of a hydraulic unit 5. During hydroforming, the wall of the workpiece then presses against the inner contour of the tool and thus against the engraving 2 of the hydroforming tool. The engraving is complete or only provided with microstructures in the areas in which the liquid pressure medium can collect before inserting the next workpiece (marked separately).
When forming single or double blanks using the active medium, the tool also has a split shape (see FIG. 2). The upper tool half 1a has, for example, the engraving 2 and the lower tool half 1b has a pressure chamber 6, in which the pressure medium supply 4 opens. The workpiece W is clamped in the form of a single blank between the closed tool halves 1a and 1b. As a result of the subsequent pressure supply of the active medium into the pressure chamber and the pressurization, the sheet (workpiece W) lies against the engraving 2 of the upper tool half 1a. In this case, too, the engraving can be provided with microstructures which either avoid an unwanted deformation of the workpiece due to the active medium enclosed between the engraving and the workpiece and / or specifically influence the surface quality of the workpiece.

In Fig. 3 is a tool part 1a with an engraving 2 acc. Fig. 2 shown, in which in the corner areas Microstructures M are arranged.

4 shows a further variant of the line course of the microstructures M shown. The surface of the engraving 2 has the smallest depressions in the form of Microstructures M into which the engraving 2 pent active medium can escape during the forming process, so that a perfect surface of the workpiece W is guaranteed. The microstructures are here lined up in a meandering pattern.

5 is a circular arrangement of the Microstructures M are shown which e.g. at a deepest Point of an engraving 2 may lie.

The production of these microstructures M can for example by laser machining, electroerosive Machining, ultrasonic erosion, scoring, etching or by other suitable ablation procedures. In equivalent shape can also be engraved on particles applied (e.g. by lithography) through which the microstructures arise. The shape, the size and the Microstructure spacing can be selected as required become.

The arrangement of the microstructures can take the form of a cross, a line, a circle, a meander or in other structures or shapes.
4 shows two variants with meandering and circular lines of the microstructures.
When forming thin foils with air, for example, the microstructures avoid the formation of bubbles, since the active medium can escape into the microstructures.
It is also possible for the first time to create a lubricant depot with these microstructures in areas of high wear and thus to significantly reduce wear.
In the case of very lubricated workpieces, this lubricant depot is filled up, for example, and if the parts are not lubricated enough, the lubricant is released by the pressure when the component wall is pressed against the engraving. The emergency running properties of the tool are thus surprisingly significantly improved. Furthermore, lubricants can be saved on the workpiece.
A defined influence on the material flow is also possible, for example, by roughening the engraving with the microstructures.
The microstructures can be used to produce a workpiece surface with more favorable adhesive properties for a subsequent coating of the workpiece.

The size of the microstructures should preferably be between 10 and 100 microns are around this not to the To make the workpiece surface visible.

Claims (9)

1. Tool engraving of a forming tool for forming by means of active medium, whereby the tool exhibits a pressure medium supply (4) for the active medium and an engraving (2) corresponding to the desired final contour of the workpiece (W), characterised in that the engraving (2) is provided with microstructures (M).
2. Tool engraving according to claim 1, characterised in that the microstructures (M) do not affect the surface quality of the workpiece (W) adversely and are suitable

   for absorbing the active medium while the workpiece (W) is pressed against the engraving (2) during the internal high pressure forming and for counteracting deformation due to local trapping of the active medium between the engraving (2) and the workpiece (W) and/or

   for systematically influencing the adhesive properties of the workpiece and/or

   for accommodating lubricant and serving as a lubricant depot and/or

   for influencing the material flow of the workpiece during forming.
3. Tool engraving according to claim 1 or 2, characterised in that the microstructures (M) exhibit a defined size, shape and arrangement.
4. Tool engraving according to one of claims 1 to 3, characterised in that the microstructures (M) exhibit a size in the order of magnitude from one molecule of the active medium to approximately 100 µm in width and 100 µm in depth or 100 µm in height.
5. Tool engraving according to one of claims 1 to 4, characterised in that the microstructures (M) are arranged over the entire area of the engraving (2) or in defined positions.
6. Tool engraving according to claim 5, characterised in that the microstructures (M) are arranged

   in engraving areas in which the active medium is trapped and in which as a result deformation of the workpiece (W) can occur and/or

   in engraving areas with which the surface structure of the workpiece (W) is to be systematically influenced and/or

   in engraving areas in which a high level of wear occurs and/or

   in engraving areas with which the flow of material is to be influenced.
7. Tool engraving according to one of claims 1 to 6, characterised in that the microstructures (M) are arranged in rows in the form of lines, circles, undulations or in other forms.
8. Tool engraving according to one of claims 1 to 7, characterised in that it is provided with microstructures (M) produced by laser cutting, electroerosion, ultrasound erosion, scribing, etching or other material-removing methods.
9. Tool engraving according to one of claims 1 to 6, characterised in that it exhibits microstructures (M) produced by lithography or other coating methods.

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