METHOD AND DEVICE FOR FORMING A COLLAR ON A WORKPIECE

Abstract

The problem of achieving great collar lengths with good quality and even when using high-strength metals, in particular high-strength steels, in a simple manner is solved by the disclosed methods and devices. One such method for producing a collar on a workpiece may involve preforming a region of the workpiece to form a material reserve for a collar drawing operation and drawing the workpiece to form a collar such that the drawn workpiece comprises a flange region and a drawn region adjoining the flange region, with the drawn region including a wall region and an adjoining drawn base. At least some material from a region of the material reserve may be used to form the wall region. The method may further involve punching the drawn base such that an opening is made in the drawn base and the wall region is adjoined by a drawn base sub-region, as well as widening the drawn base sub-region.

Claims

1.-16. (canceled)

17. A method for producing a collar on a workpiece, the method comprising: preforming a region of the workpiece to have a material reserve for a collar drawing operation; drawing the workpiece to form the collar, wherein the drawn workpiece comprises a flange region and a drawn region that adjoins the flange region, wherein the drawn region comprises a wall region and a drawn base that adjoins the wall region, wherein at least some material from the region of the material reserve is used to form the wall region; punching the drawn base in the drawn region such that an opening is made in the drawn base and the wall region adjoins a sub-region of the drawn base; and widening the sub-region of the drawn base.

18. The method of claim 17 wherein the region of the material reserve lies at least partly outside a region of the workpiece to be drawn.

19. The method of claim 17 wherein the preforming comprises forming in the workpiece at least one elevation configured as a bead.

20. The method of claim 17 wherein the preforming of the region of the workpiece to form the material reserve is performed in a way that depends on properties of at least one of the workpiece or the collar to be produced.

21. The method of claim 17 wherein the preforming of the region of the workpiece to form the material reserve comprises pre-stretching at least a portion of the workpiece to at most a yield limit of the workpiece.

22. The method of claim 17 wherein the region of the material reserve corresponds substantially to a collar drawing length of the workpiece.

23. The method of claim 17 further comprising subjecting at least a portion of the workpiece to a force in the region of the material reserve during the drawing of the workpiece to form the collar.

24. The method of claim 17 wherein the preforming of the region of the workpiece to form the material reserve occurs in a first die or first die portion, wherein the drawing of the workpiece to form the collar occurs in a second die or second die portion.

25. A device for producing a collar on a workpiece, the device comprising: preforming means for preforming a region of the workpiece to have a material reserve for a collar drawing operation; collar drawing means for drawing the workpiece so that the workpiece comprises a drawn region that adjoins a flange region, the drawn region comprising a wall region and a drawn base that adjoins the wall region; punching means for punching the drawn base to produce a sub-region of the drawn base that adjoins the wall region; and widening means for widening the sub-region of the drawn base.

26. The device of claim 25 further comprising: a first die or first die portion that comprises the preforming means; and a second die or second die portion that comprises the collar drawing means, the punching means, and the widening means.

27. The device of claim 25 wherein the preforming means and the collar drawing means are adapted to each other so that the region of the material reserve lies outside a region of the workpiece to be drawn.

28. The device of claim 25 wherein the preforming means include surfaces having a shape that corresponds to an elevation to be formed as part of the material reserve in the workpiece.

29. The device of claim 28 wherein the shape of the surfaces of the preforming means is bead-like.

30. The device of claim 25 further comprising means for applying force to at least a portion of the flange region of the workpiece during the collar drawing operation.

31. The device of claim 25 wherein the collar drawing means comprises a drawing die, wherein the punching means comprises a cutting edge disposed on a bottom of the drawing die, and a punching die disposed opposite the drawing die and adapted to the cutting edge.

32. The device of claim 31 wherein the cutting edge is rounded and the punching die is sharp-edged.

33. The device of claim 31 further comprising an inhibiting member for applying force to the punching die in response to a force exerted by the drawing die in a collar drawing direction.

34. The device of claim 33 configured such that a defined inhibiting force of the punching die exceeds a cutting force needed for the punching of the drawn base.

Description

[0049] In the following, the invention shall be explained more closely with the aid of sample embodiments in connection with the drawing. The drawing shows:

[0050] FIG. 1 a schematic view of a sample embodiment of a first die or die portion of a device prior to the forming of a material reserve;

[0051] FIG. 2 a schematic view of the first die or die portion from FIG. 1 after the forming of a material reserve;

[0052] FIG. 3 a schematic view of a sample embodiment of a second die or die portion of a device prior to the collar drawing;

[0053] FIG. 4, 5 a schematic view of the second die or die portion of FIG. 3 during the collar drawing;

[0054] FIG. 6 a schematic view of the second die or die portion of FIG. 3 after the punching;

[0055] FIG. 7 a schematic view of the second die or die portion of FIG. 3 after the widening an

[0056] FIG. 8 a schematic view of the second die or die portion of FIG. 3 after the ejecting.

[0057] FIG. 1 shows a schematic view of a sample embodiment of a first die or die portion 1 of a device prior to the forming of a material reserve. The die or die portion 1 is shown in a partial longitudinal section, and is constructed symmetrically about the axis A. The die or the die portion 1 is installed in a suitable press, not represented here, and comprises with an upper forging die 1a and an adapted lower forging die or die 1b preforming means for forming a region 4 of a workpiece or workpiece section 2. The workpiece or the workpiece section 2 in the form of a billet or a metal sheet is placed between the forging dies 1a, 1b in the opened press. Thanks to the geometry of the pressing surfaces, a region 4 of the workpiece 2 can be shaped by the die 1 so that a material reserve is formed in the region 4 for a later collar drawing operation. For this, the upper forging die 1a for example is moved onto the lower forging die for the closing of the die 1 in the direction of the arrow 6.

[0058] FIG. 2 shows a schematic view of the first die 1 from FIG. 1 after the forming of a material reserve in the region 4 of the die 2. Thanks to the forming/preforming of the region 4, elevations have been formed in the depicted sample embodiment in the form of two concentric encircling beads 6a, 6b. The forming/preforming with the die 1 has caused a prestretching of the material in the region 4 of the beads 6a, 6b and the adjoining regions, resulting in a lengthening of the cross-sectional length in the region 4 of the workpiece or workpiece section 2. As a result, the region 4 with the beads 6a, 6b may serve as a material reserve for a later collar drawing operation.

[0059] Since the die 1 may also constitute a die portion of a more complex die, not represented, it is basically possible for it to undertake further machining steps, such as further forming, of the workpiece 2, during the closing of the press.

[0060] FIG. 3 shows a schematic view of a sample embodiment of a second die 10 of a device prior to the collar drawing. The device 10 is likewise formed symmetrically about the axis A. It comprises means of drawing the workpiece 2 to form a collar with a drawing die or drawing and blanking die 12 able to move in the collar drawing direction 8. The drawing die has a rounded cutting edge 16 arranged on the drawing die bottom 14. The cutting edge 16 protrudes from the drawing die bottom 14 in the collar drawing direction 8. This avoids the danger of a premature damaging or punching of the workpiece 2.

[0061] The die 10 furthermore comprises, with the hold-down clamp 18, means of fixation of the workpiece 2. As shown by the arrow 9, the hold-down clamp can apply a controlled force to the workpiece 2 in a flange region 20 in the collar drawing direction 8. In this way, the workpiece 2 can be secured and material can be brought up from the region 4 of the material reserve.

[0062] The die 10 furthermore comprises a forging die 26, whose cross-sectional contour represents the necking contour 28 and is adapted to the drawing die 12. In the lower region of the forging die, a punching die 30 is spring-loaded and adapted to the cutting edge 16 in order to enable a punching of the drawn base portion 42. In addition, a spring element 32 is provided, which can apply a force to the punching die contrary to the collar drawing direction 8. Furthermore, an inhibiting member in the form of a shoving wedge 34 is mounted in the forging die 26. The shoving wedge braces the punching die 30 so that the movement of the punching die 30 is at first inhibited in the collar drawing direction 8. For this, the shoving wedge 34 presses with a spring element 36 under the punching die 30. The punching die 30 and the shoving wedge 34 comprise mutually adapted sliding surfaces 38, 40, enabling the punching die 30 to slide along the shoving wedge 34.

[0063] FIGS. 4 and 5 show a schematic view of the second die 10 from FIG. 3 during the collar drawing. The drawing die 12 here is moved in the collar drawing direction 8. In this way, a drawn region is formed in the workpiece 2 with a wall region 44 adjoining the flange region 20 and with a drawn base 42 adjoining the wall region. During the collar drawing, material is made available by the region 4 for the collar drawing operation and drawn into the wall region 44. At the same time, thanks to the application of force to the region 4 with the hold-down clamp 18, material of the material reserve is shoved into the wall region 44. In this way, the wall region 44 may be formed longer than with the conventional methods, while the drawn base 42 substantially does not become thinner. As can be seen in FIG. 5, the beads 6a, 6b are substantially smoothed out during the collar drawing.

[0064] Thanks to the providing of a rounded cutting edge 16, the drawn base 42 is not damaged or prematurely punched during the collar drawing and a thinning out of the drawn base 42 can be reduced or prevented by the substantially flat drawing die bottom 14 running transversely to the collar drawing direction 8.

[0065] During the progressive collar drawing operation, either further material is brought in from the flange region 20 to the wall region 44 and/or the wall region 44 is ironed out until the drawing die 12 has reached the punching die 30. Because of the counter force produced by the shoving wedge 34, the punching die 30 initially cannot move away and the cutting edge 16 of the combined drawing and blanking die 12 punches the drawn base 42, cutting or punching a slug 46 from the drawn base 42, which can drop out from the die 10 through the punching die and does not need to be manually removed.

[0066] FIG. 6 shows for this a schematic view of the second die or die portion 10 from FIG. 3 after the punching. The wall region 44 is now adjoined by a drawn base subregion 45. The counter pressure of the punching die 30 on the drawing die 12, however, is limited by the providing of the sliding surfaces 38, 40 on the punching die 30 and the shoving wedge 34 and by the spring loading of the shoving wedge 34 to the cutting force needed for the punching of the drawn base portion. If the force limit is surpassed, the shoving wedge 34 moves outward transversely to the collar drawing direction 8 in the direction of the arrow 48. The punching die 30 is further displaced downward in the collar drawing direction 8, as shown by the arrow 50, by the drawing die 12 and the drawing die 12 can bring about a widening of the drawn base subregion 45 by further advancement in the collar drawing direction 8.

[0067] FIG. 7 shows a schematic view of the second die or die portion 10 of FIG. 3 after the widening of the drawn base subregion 45. Because the collar contains length portions of the wall region 44 and the widened drawn base subregion 45, a longer collar can be formed, with no material failure, from the region 4 of the material reserve and the rounded cutting edge 16.

[0068] With this, the formation of the collar is completed. By a lifting of the drawing die 12 and the hold-down clamp 18, the punching die 30 can again travel to the starting position against the collar drawing direction 8, whereupon the workpiece is ejected. FIG. 8 shows a schematic view of the second die or die portion 10 of FIG. 3 after the ejecting. The workpiece 2 here has been transported from the forging die 26 by the spring-loaded punching die 30 for removal from the die 10.