Method and device for spin forming

Abstract

A method and a device for spin forming includes a workpiece set in rotation with 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. At least one inner roller is positioned at an inner side of the workpiece with an inner support, which is displaceable axially and radially relative to the axis of rotation independently of the outer roller. The inner support with the inner roller and an outer support with the outer roller are displaced individually with a CNC control unit, forming 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 a vehicle wheel, comprising: setting a workpiece about an axis of rotation using a spindle; positioning at least one outer roller at an outer side of the workpiece, and shaping an axially extending lateral region of the workpiece by thinning the material of the workpiece, and wherein at least one inner roller is positioned at an inner side of the workpiece using an inner support, which is displaceable axially and radially relative to the axis of rotation and independently of the at least one outer roller, each of the at least one inner roller is associated with a respective one of the at least one outer roller, a defined shaping gap is formed between the outer roller and the associated inner roller, the at least one outer roller and the inner support with the at least one inner roller are displaced individually, a relative adjustment between the at least one outer roller and the associated at least one inner roller and thus of the shaping gap takes place, wherein a defined wall thickness profile with different wall thicknesses between the at least one outer roller and the associated at least one inner roller is formed at the lateral region, the at least one inner roller and the associated at least one outer roller are displaced radially and axially relative to one another in order to shape the lateral region, the lateral region is shaped as a rim base of a vehicle wheel with at least one hump, the at least one hump formed as a thickening in the wall thickness profile, in order to form the at least one hump, the at least one inner roller and the associated at least one outer roller are simultaneously displaced relative to one another in the radial direction and in the axial direction, and the at least one inner roller and the at least one outer roller are moved axially along the lateral region to form the rim base.

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

3. The method according to claim 1, wherein the workpiece is clamped at a part-region of an outer circumference of the workpiece.

4. The method according to claim 1, wherein an internal clamp is provided to cover a hub region of the workpiece.

5. A device according to the method of claim 1 for spin forming, wherein the spindle can be driven in rotation via a drive about an axis of rotation and is configured to hold a workpiece.

6. The device according to claim 5, wherein a clamp for clamping the workpiece is arranged on the spindle, and a free space remains in a central region radially inside the lateral region of the workpiece.

7. The device according to claim 5, wherein there is provided a control device having a data memory, in which data sets for the displacement of the at least one inner roller and the at least one outer roller for different workpiece shapes are stored.

Description

(1) The invention will be described in greater detail hereinbelow by means of preferred exemplary embodiments, which are shown schematically in the drawings, in which:

(2) 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;

(3) 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;

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

(5) 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.

(6) 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.

(7) 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.

(8) 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.

(9) 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).

(10) 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.

(11) 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.

(12) 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.

(13) 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 (internal clamp) which is adapted to a contouring of the hub region 6 of the workpiece 5.

(14) 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.

(15) 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.

(16) Preferably spin forming of cast wheels at temperatures up to 400° C. Heat treatment of the wheels can immediately follow the spin forming operation.

(17) In addition, the method can also be used for the cold forming of forged aluminum wheels as well as for steel wheels.

(18) 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.

(19) Alternatively, a combination of flexible inner rollers with a partially acting short mandrel is also possible.