Forming press and method for forming a sheet-like blank composed of metal with two frame parts that are movable towards one another

Abstract

A forming press for forming a sheet-like blank has a first thermally insulated frame part having a die with a negative engraving and a second thermally insulated frame part defining a chamber and having a punch movably disposed in the chamber. The sheet-like blank rests in a sealing manner on the second frame part and covers the punch so as to define a pressure chamber with the punch therein. A pressure generator provides a pressurized gas to the pressure chamber during a forming process.

Claims

1. A method for forming a sheet-like blank with a press, comprising: providing a forming press for forming a sheet-like blank, comprising: a first thermally insulated frame part having a die with a negative engraving; a second thermally insulated frame part defining a chamber and having a punch movably disposed in the chamber; a sheet-like blank resting in a sealing manner on the second frame part and covering the punch so as to define a pressure chamber with the punch therein; and a pressure generator providing a pressurized gas to the pressure chamber during a forming process; placing the sheet-like blank onto the second thermally insulated frame part; moving the frame parts toward each other; heating the sheet-like blank to a forming temperature that is specific to the material of the sheet-like blank; pressurizing the pressure chamber with the pressurized gas; moving the punch into the negative engraving of the die; releasing the gas pressure at least to a level that allows opening the frame parts; moving the frame parts apart after forming the sheet-like blank; removing a completed work piece; moving the punch into an initial position, wherein the punch rests on a bottom side of the sheet-like blank prior to forming.

2. The method according to claim 1, further comprising a step of holding the frame parts closed with such a force that the sheet-like blank is held between the frame parts in a sealed manner, without the material of the blank being able to flow out laterally.

3. The method according to claim 1, further comprising a step of holding the frame parts closed with a force that allows forming the blank, the material of the blank being able to flow into the negative engraving of the die from an outside.

4. The method of claim 1, wherein the punch has an at least partially complementary positive engraving that corresponds to the negative engraving of the die.

5. The method of claim 1, wherein a forming process, the punch is movable upwardly from a bottom of the chamber of the second frame part.

6. The method of claim 1, wherein the punch is movably guided in the chamber of the second frame part in a pressure-tight manner.

7. The method of claim 6, further comprising at least one radially circumferential piston seal movably guiding the punch in a pressure-tight manner.

8. The method of claim 1, further comprising at least one temperature control unit operable to control a temperature of the die of the first frame part and/or the punch of the second frame part, the at least one temperature control unit being an open-loop or closed-loop controller.

9. The method of claim 8, wherein the at least one temperature control unit comprises a plurality of temperature control units, each temperature control unit individually being an open-loop or closed-loop controller.

10. The method of claim 8, wherein the at least one temperature control unit comprises a temperature control unit in an area supported on the second frame part.

11. The method of claim 10, wherein the at least one temperature control unit further comprises a temperature control unit in an area of support of the sheet-like blank.

12. The method of claim 1, wherein the sheet-like blank is held between the first and second frame parts in a sealed-off manner.

13. The method of claim 1, wherein: the chamber in the second frame part is a cylindrical chamber; the punch has an initial position in the cylindrical chamber such that the punch is located immediately adjacent the sheet-like blank without forming the sheet-like blank.

14. The method of claim 1, further comprising a pressure equalizing pipe connecting a portion of the chamber in the second frame part under a piston with a chamber formed by the negative engraving of the die of the first frame part.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following the invention will be exemplarily described in more detail based on the drawings.

(2) FIG. 1 is an overview drawing of the invention for explaining the components of the forming press;

(3) FIG. 2 is a drawing showing the initial state of the press after insertion of the sheet-like blank made of metal;

(4) FIG. 3 is a drawing showing the closed state of the two press parts before the forming process;

(5) FIG. 4 is a drawing showing a state in which the punch with the positive engraving is driven into the negative engraving of the die; and

(6) FIG. 5 is a drawing showing the work piece having fallen out or having been ejected out of the opened frame parts.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(7) According to FIGS. 1 to 5, the thermally insulated upper frame part 6 is fastened to the upper press part 2 of the forming press 1 and the bottom frame part 7 is fastened to the bottom press part 3. Both frame parts are heatable, as has been described earlier. The insulation has the reference number 9. The upper frame part 6 comprises the die with the reference number 8, which is also thermally insulated and which features the negative engraving 10, which is disposed in the upper frame part, in such a manner that it can be exchanged depending on the project. Correspondingly, the bottom frame part features the punch labelled 12 with the positive engraving 14, which is formed so that it complements the negative engraving 10 of the die 8. This means that the positive engraving 14 of the punch 12 corresponds to the shape of the negative engraving 10 of the die 8 for forming the work piece 42 from the sheet-like blank 26. The punch 12, which is displaceably mounted in the cylindrical chamber 16 formed by the bottom frame part 7, features several piston rings 18. The piston rings 18 primarily serve to seal off the punch 12 from the cylindrical chamber 16. As has already been mentioned earlier, the piston rings also ensure that, even at temperatures of the punch 12 of up to 1100 C. for heating the positive engraving 14 with the aim of heating the blank 26, the punch 12 is still moveable in the cylindrical chamber 16; indeed, the piston rings 18 allow compensating for a different thermal expansion of the punch 12 on the one hand and the cylindrical chamber 16 formed by the bottom frame part on the other hand. This means that a fretting of the two components is highly unlikely even at highly different temperatures and with different materials. This is in contrast with the prior art, which does not feature such piston rings.

(8) As can be gathered in particular from the figures, the heating of the sheet-like blank 26 takes place in different places, as has already been explained earlier. On the one hand, a temperature control unit is provided as a heater, labelled 20, in the punch 12. The heater 20 is located at the bottom of the punch below the positive engraving 14 of the punch. Another temperature control unit in the form of a heater 23 is disposed in or at the bottom frame part, namely where the die 8 rests on the bottom frame part 7. Correspondingly, the die 8 also comprises a temperature control unit in the form of a heater 22 in this area, in order to at least partially heat up the sheet-like blank 26 in this area, if necessary on both sides, or to generate a heat profile. An additional temperature control device in the form of a heater 25 is provided in the bottom area of the negative engraving 10 of the die 8 between the upper frame part 6 and the negative engraving 10 for heating the negative engraving 10 of the die 8.

(9) The pressure chamber 24 is formed by the bottom side of the sheet-like blank 26, the upper side of the positive engraving 14 of the punch 12 and by the bottom frame part 7.

(10) The pressure chamber 24 is connected with a pressure generator 30 by way of a connection pipe 28. This means that the pressure generator 30, for example a compressor, ensures an increase of the gas pressure of the pressure chamber 24.

(11) The punch 12 comprises a piston cylinder drive 32, which serves for displacing the punch 12 in the cylindrical chamber 16 formed by the bottom frame part 7.

(12) FIGS. 2 to 5 show the forming process. Based on FIG. 2, in its initial position, the positive engraving 14 is located immediately at the bottom side of the sheet-like blank 26, which is to be formed. The two frame parts 6 and 7 are in the opened state.

(13) FIG. 3 shows the state, in which the two frame parts 6 and 7 are closed and now ensure, together with the blank 26, that the pressure chamber 24 is sealed. In this state, the gas pressure in the pressure chamber 24 is now increased by the pressure generator 30. In a first step of this process, the sheet-like blank 26 is formed in the negative engraving 10 of the die 8 by the gas pressure. Once the blank 26 has reached a certain state of deformation, the punch 12 follows, i.e. the punch 12 follows in parallel with the forming process using the gas pressure, wherein the gas pressure increases due to the reduction of the gas volume, in order to then carry out the mechanical final forming in the boundary areas, in particular in the boundary areas with a small radius, if applicable by means of the positive engraving 14 of the punch 12 together with the negative engraving 10 of the die 8. This means that immediately before reaching the final formed state, the remaining forming process substantially takes place purely mechanically due to the positive engraving 14 of the punch 12 running into the negative engraving 10 of the die 8, in particular when small form radiuses must be precisely formed, for example in the boundary area. However, the invention also includes a displacement of the punch simultaneously with the forming process using the gas pressure. Before the mechanical forming process following the gas forming process, it is advisable to at least partially release the now harmful gas pressure between the punch and the almost completely formed work piece.

(14) In order to prevent a counter-pressure from building up within the negative engraving 10 of the die 8, during the forming process, a pressure equalising pipe 36 in the form of a flexible tube is provided between the sealed space 40 below the punch 12 and the space formed by the negative engraving 10 of the die 8. The final formed state can be seen in the representation according to FIG. 4. FIG. 5 shows a representation, in which the blank 26 has been formed into a completed work piece 42. When the pressure equalising pipe 36 in the form of a flexible tube is connected with a pressure generator (not shown), if the pressure within the space formed by the negative engraving 10 of the die 8 increases, a corresponding pressure can be built up for ejecting the work piece 42, i.e. the completely shaped blank. The work piece 42 is then ejected sideways out of the forming press 1. In this context, reference is again made to the prior art according to DE 10 2010 106 299 A1, which does not show how the completed work piece is to get out of the pressure-tight press housing after the frame parts have opened, or how the blank is to be inserted into it.

LIST OF REFERENCE NUMBERS

(15) 1 Forming press 2 Upper press part 3 Bottom press part 6 First frame part (upper frame part) 7 Second frame part (bottom frame part) 8 Die 9 Insulation 10 Negative engraving 12 Punch 14 Positive engraving 16 Chamber (cylindrical) 18 Piston ring 20 Heater at the bottom of the punch 22 Heater in the boundary area of the die 23 Heater in the boundary area of the bottom frame part 24 Pressure chamber 25 Heater of the negative engraving 26 Sheet-like blank 28 Connection pipe 30 Pressure generator 32 Piston cylinder drive 36 Pressure equalising pipe 40 Space below the punch 42 Work piece