METHOD AND DEVICE FOR SPIN FORMING

Abstract

The invention relates to a method and a device for spin forming, wherein a workpiece is set in rotation by means of a spindle and at least one outer roller is positioned at an outer side of the workpiece. With material thinning, an axially extending lateral region of the workpiece is shaped. According to the invention, it is provided that at least one inner roller is positioned at an inner side of the workpiece by means of an inner support, which is displaceable axially and radially relative to the axis of rotation independently of the outer roller. By means of a CNC control unit, the inner support with the inner roller and an outer support with the outer roller are displaced individually, wherein there is formed at the lateral region a defined wall thickness profile with different wall thicknesses between the at least one outer roller and the at least one inner roller.

Claims

1. A method for spin forming, in particular for spin forming a vehicle wheel, wherein a workpiece is set in rotation about an axis of rotation by means of a spindle, and at least one outer roller is positioned by means of an outer support at an outer side of the workpiece, wherein, with material thinning, an axially extending lateral region of the workpiece is shaped, and wherein at least one inner roller is positioned at an inner side of the workpiece by means of an inner support, which is displaceable axially and radially relative to the axis of rotation independently of the outer support, wherein at least one outer roller is positioned, wherein an inner roller is associated with each outer roller, in that a defined shaping gap is formed between the outer roller and the associated inner roller, and in that the inner support with the inner roller and the outer support with the outer roller are displaced individually by means of a CNC control unit, wherein a relative adjustment between the outer roller and the associated inner roller and thus of the shaping gap takes place, wherein there is formed at the lateral region a defined wall thickness profile with different wall thicknesses between the outer rollers and the associated inner rollers.

2. The method according to claim 1 wherein the at least one inner roller and the at least one associated outer roller are displaced radially and axially relative to one another in order to shape the lateral region.

3. The method according to claim 1, wherein the workpiece is clamped on the spindle, wherein a free space remains in a central region radially inside the lateral region.

4. The method according to claim 1, wherein clamping of the workpiece takes place at a part-region of the outer circumference.

5. The method according to claim 1, wherein the workpiece is provided with a clamping and/or centering aid before spin forming.

6. The method according to claim 5, wherein the clamping and/or centering aid is removed from the workpiece after spin forming.

7. The method according to claim 1, wherein an internal clamping device is provided, by which a hub region of the workpiece is covered.

8. The method according to claim 1, wherein the lateral region is shaped as a rim base of a vehicle wheel with at least one hump, which is formed as a thickening in the wall thickness profile.

9. The method according to claim 8, wherein in order to form a hump and/or flange region, the inner roller and the associated outer roller are simultaneously displaced relative to one another in the radial and in the axial direction.

10. A device for spin forming by the method according to claim 1, having a spindle which can be driven in rotation via a drive about an axis of rotation and is configured to hold a workpiece, at least one outer roller, which is rotatably mounted on an outer support, which is displaceable axially and radially relative to the axis of rotation in order to position it at the workpiece, and at least one inner roller, which can be positioned at an inner side of the workpiece opposite the outer roller, and wherein the at least one inner roller is rotatably mounted on an inner support, which is mounted to be displaceable axially and radially relative to the axis of rotation independently of the outer support, wherein at least one outer roller is provided, wherein an inner roller is associated with each outer roller, in that a defined shaping gap is formed between the outer roller and the associated inner roller, and in that a CNC control unit for individually displacing the at least one inner support with the inner roller and the at least one outer support with the outer roller is provided, wherein, in order to form a defined wall thickness profile with different wall thicknesses at a lateral region of the workpiece, a relative adjustment between the outer roller and the associated inner roller and of the shaping gap can take place.

11. The device according to claim 10, wherein a clamping device for clamping the workpiece is arranged on the spindle, wherein a free space remains in a central region radially inside the lateral region of the workpiece.

12. The device according to claim 10, wherein there is provided a control device having a data memory, in which data sets for the displacement of the inner roller and the outer roller for different workpiece shapes are stored.

13. The device according to claim 10, wherein at least one of the rollers is provided with an auxiliary drive for driving the roller in rotation.

Description

[0031] The invention will be described in greater detail hereinbelow by means of preferred exemplary embodiments, which are shown schematically in the drawings, in which:

[0032] FIG. 1: is a partial cross-sectional view of a device according to the invention during the shaping of a vehicle wheel in an initial stage;

[0033] FIG. 2: is a partial cross-sectional view of the device of FIG. 1 during the production of a vehicle wheel in an end stage;

[0034] FIG. 3: is a partial cross-sectional view of a further device during the production of a vehicle wheel in an initial stage; and

[0035] FIG. 4: is a partial cross-sectional view of the device of FIG. 3 during the production of a vehicle wheel in an end stage.

[0036] A device 10 according to the invention for spin forming according to FIG. 1 has a spindle 12 which is driven in rotation via a drive (not shown). The spindle 12 rotates about a central axis of rotation 13, which in the example shown extends horizontally. The spindle 12 can likewise be oriented with the axis of rotation 13 vertical, a workpiece 5 then resting on the spindle 12 or, in the case of a suspended spindle arrangement, being clamped on a spindle 12 located at the top.

[0037] Via a plate-shaped clamping device 14 which is attached to the spindle 12 and has axially acting clamping claws 16, a workpiece 5 can be connected to the spindle 12 releasably and in a rotationally secure manner as well as centrally relative to the axis of rotation 13. In the exemplary embodiment shown, the workpiece 5 is a preform of a vehicle wheel. The preform is preferably manufactured from a metal material by casting or forging. The rotationally symmetrical workpiece 5 has a hub region 6 which extends substantially radially and has a central opening 4, and a drum-shaped lateral region 7 extending substantially axially. By means of the clamping claws 16, the workpiece 5 is fixed on one side at its outer circumference to the spindle 12.

[0038] After clamping, the spindle 12 with the workpiece 5 is set in rotation. Preferably three outer rollers 20, of which only one outer roller 20 is shown, are positioned radially at the outer side of the lateral region 7 of the workpiece 5 by means of outer supports (not shown). At the same time, an inner support 40 having three inner rollers 30 arranged offset by 120 relative to one another is positioned in a central free space inside the drum-shaped lateral region 7. The inner rollers 30 are thereby first applied to an inner side of the lateral region 7 adjoining the radial hub region 6.

[0039] The inner support 40 has a central and conical central carrier 42 on the outer side of which there are arranged linear guides 44 for slides 46. Roller holders 48 are pivotably mounted on the linearly displaceable slides 46. The inner rollers 30 are rotatably mounted in the cup-like roller holders 48 via roller bearings. The inner rollers 30 can be pivoted via the pivotable roller holders 48 during the spin forming operation and also displaced radially and/or axially by means of the slide 46 and the inner support 40. In a corresponding manner, the outer rollers can be mounted pivotably and also radially and axially displaceably on an outer support (not shown).

[0040] The displacement of the outer roller 20 and the inner roller 30 takes place via a CNC control unit (not shown) and actuating drives, on the basis of stored data for the shaping of the desired workpiece 5. As can be seen in FIG. 2, the lateral region 7 of the workpiece 5 can be shaped into a rim base with a hump 8, which represents a thickening in the wall thickness profile of the lateral region 7. The finished shaped lateral region 7 is lengthened compared with the lateral region 7 of the starting workpiece 5 and thinned in terms of wall thickness. It is possible to produce virtually any desired outer contour and also an inner contour using the device 10 according to the invention.

[0041] The second embodiment according to FIGS. 3 and 4 corresponds substantially to the construction of the first device 10 according to the invention according to FIGS. 1 and 2.

[0042] In contrast to the first embodiment, in the device 10 according to FIG. 3 a changed inner roller 30 having an annular radial projection 32 and an adjoining counter bearing portion 34 in the front region is provided. The radially protruding radial projection 32 on the inner roller 30, in conjunction with the outer roller 20 acting radially on the outside, can serve to shape an inner contour along the inner side of a lateral region 7 of the workpiece 5. The front counter bearing portion 34 can be used to form a rim flange at the free end of the shaped rim base, as is clearly shown in FIG. 4. The counter bearing portion 34 can in particular be a negative form of the inner contour of the rim flange and be designed to accommodate the shaping forces of the outer roller 20. In a corresponding manner, different outer rollers 20 having an adapted outer contour can be positioned at the lateral region 7. In particular, an outer roller 20 can have an outer contour corresponding to the desired shaping of the rim flange that is to be formed.

[0043] In the second embodiment according to FIGS. 3 and 4, an axially displaceable counter holder 18 is also additionally provided for clamping the workpiece 5, in addition to the clamping device 14 already described above having axially displaceable clamping claws 16 for clamping the workpiece 5 at the radial outer side. In particular after initial contouring of the lateral region 7, the counter holder 18 can be pushed axially against the hub region 6 of the workpiece 5 into the central free space of the drum-shaped lateral region 7. Additional axial clamping and centering of the workpiece can thereby take place at least during an end stage of the spin forming process. The counter holder 18 can have a plate-shaped contact element 19 which is adapted to a contouring of the hub region 6 of the workpiece 5.

[0044] With the device 10 according to the invention and the method which can be carried out therewith, workpieces 5 can be formed with a wide variety of shapes of a wall region 7 without modification measures.

[0045] This method for the first time allows spin forming to be carried out multiple times and stepwise until the final geometry or complete structural change has been achieved.

[0046] Preferably spin forming of cast wheels at temperatures up to 400 C. Heat treatment of the wheels can immediately follow the spin forming operation.

[0047] In addition, the method can also be used for the cold forming of forged aluminum wheels as well as for steel wheels.

[0048] The use of a special programming interface or the use of offline programming support software is also preferred in order to allow the complex programs to be prepared more simply and quickly, as well as to test and optimize them by simulation prior to use.

[0049] Alternatively, a combination of flexible inner rollers with a partially acting short mandrel is also possible.