EP0075599A1 - Process for manufacturing round objects - Google Patents

Abstract

The process for producing round bodies, e.g. wheel rims for motor vehicles, is designed and the apparatus chosen such that an extruded profile with overlength, i.e. with an addition, is used, as would be required by the development of the rim, and these deforming and stress-absorbing pieces are chosen by an appropriate choice of the process steps and apparatus such that they are located at the beginning and end of the extruded profile and can then be cut to length after the appropriate process steps. Thus, in the first two process steps, use is made of a core mould around which the extruded profile is bent, while in the following step rolling is carried out, i.e. an apparatus is used which is suitable for rolling operations. When welding the transverse joint a procedure is also adopted such that stresses are avoided by clamping in a given order. <IMAGE>

Description

The invention relates to a process for the production of round bodies, e.g. Wheel rims for motor vehicles, the rim in particular made of an aluminum alloy as an elongated extruded profile with a final cross-sectional shape rounded to the wheel shape and connected in a transverse joint by a weld.

In the previous processes, heat treatments had to be switched on between the individual shaping processes in order to keep the material largely free of tension.

With aluminum alloys in particular, recrystallization phenomena can occur during cold working, which then occur during later stresses, e.g. by temperature and / or vibrations, as they are unavoidable in motor vehicle rims, can lead to deformation. Constant concentricity must be guaranteed, especially in the manufacture of motor vehicle rims. In the previously known methods, in which extruded aluminum profiles were used, these profiles then had to be subsequently treated or reformed, so that a relatively large amount of scrap was incurred, and otherwise the known methods were expensive, lengthy and cumbersome, so that they were just for mass production were not suitable.

The object of the invention is to select the method steps in this way and to use known, easy-to-use devices, so that it is possible in mass production, production lines according to the new Establishing processes without the need to introduce heat treatments in between, or the need to have stations to rework the profile.

• a) Das mit Zugabe versehene Strangpreßprofil wird an seinem vorderen Ende eingespannt und auf einer, das Fertigprofil aufweisenden Kernform, mit zu kleinem Durchmesser gegenüber dem Fertigdurchmesser der Radfelge, vorgebegen bzw. gerundet.
• b) Nach Ablängen des Einspannstückes wird das vorgebogene Strangpreßprofil auf einer das Fertigprofil aufweisenden Kernform mit zu großem Durchmesser gegenüber dem Fertigdurchmesser der Radfelge auf ca. 360 Grad gebogen bzw. gerundet.
• c) Anschließend wird auf einer Rollbiegemaschine mit einer das Fertigprpfil aufweisenden Kernformrolle und Gegenrollen nach Festlegung des hinteren Endes des kreisförmig gebogenen Strangpreßprofiles dieses auf den Fertigdurchmesser gerollt bzw. gebogen.
• d) Nach Ablängen des Endstückes wird,der Roll- bzw. Biegevorgang mit einer das Fertigprofil aufweisenden Kernrolle und Gegenrollen solange fortgesetzt, bis das Strangpreßprofil zum Fertigdurchmesser gebogen und die Enden fluchtend zusammenstoßen.
• e) Nach Festspannen auf einer mit dem Fertigprofil versehenen Kernform durch mehrere mit Fertigprofil versehene backen findet das Schweissen des Querstosses statt.

The solution to the problem is that the following process steps are selected:

• a) The extruded profile provided with addition is clamped at its front end and pre-embossed or rounded on a core shape which has the finished profile and is too small in diameter compared to the finished diameter of the wheel rim.
• b) After the clamping piece has been cut to length, the pre-bent extruded profile is bent or rounded to approximately 360 degrees on a core mold which has the finished profile and is too large in diameter compared to the finished diameter of the wheel rim.
• c) Subsequently, on a roll bending machine with a core molding roll having the finished profile and counter rolls, after fixing the rear end of the circularly bent extruded profile, it is rolled or bent to the finished diameter.
• d) After the end piece has been cut to length, the rolling or bending process is continued with a core roll having the finished profile and counter rolls until the extruded profile is bent to the finished diameter and the ends collide in alignment.
• e) After clamping on a core shape provided with the finished profile by several with finished profile baking takes place the welding of the cross joint.

These procedural steps are treading a completely new path. It is inevitable that the profile will be deformed during cold working, and stresses will also arise from the cold working. According to the invention, however, the devices are selected so that an extruded profile with an excess length, i.e. used with addition, as the rim would require, and these deforming and stress-absorbing pieces are selected by the appropriate choice of process steps and devices so that they are at the beginning and end of the extruded profile and then after the corresponding process steps can be cut to length. Thus, in the first two process steps, a core shape is used around which the extruded profile is bent, while the following step then rolls, i.e. a device is used which is suitable for rolling operations.

The welding of the transverse joint is also carried out in such a way that tensions are avoided by tightening them in a specific sequence, as specified in the claims, and if necessary using a core shape with its dimensions.

Subsequent to the welding process, a calibration process takes place, the various possibilities being specified in the claims here.

The workflow is then such that the clamping of the core stretching device first straight rim profile with excess length, the rim profile is already the finished profile.

Pre-bending or rounding on a smaller core shape then takes place. This small undersize is necessary to compensate for a spring deflection that occurs after this pre-bending. After the suspension, the true radius of the rim is reached, i.e. the smaller core shape takes this springing into account.

The clamping piece is then cut to length, by means of which bending was possible; this chuck is unusable because it is badly deformed.

Bending or rounding then takes place on the same device, up to approximately 360 degrees on a core shape that is too large in relation to the finished diameter. The entire processing of the actual dimension must go through this first preforming step.

After the extruded profile has been prepared in this way, it is then further processed on a core roll bending device.

This core roll bending device has a very small core roll inside and two roll outside, which have the finished profile. About an extended end piece, which was already at the addition of the straight extrusion profile, then this already bent extrusion profile, which acts as a lever, is brought to the actual radius dimension via this end bending part. When this radius dimension is reached, this extended end piece is cut to length, since it is also unusable again because of its severe deformation. Now the bending or rounding to 360 degrees takes place again with a very small core forming roll and two forming rolls. It is now almost the shape-retaining state of the rim in an almost stress-free state.

The rim is then completed by the subsequent welding process of the cross joint. Uniform. There has been a certain thinning of the profile, and in order to take this thinning into account, the core shape on which the rim is clamped during the welding process has a small oversize dimension. The clamping process on this core shape takes place in a certain chronological order, since otherwise tension fields can build up on the circumference of the rim or even compressions, which are noticeable after the welding shape is opened due to out-of-roundness. The most appropriate sequence for this tensioning process is specified in the claims. Different welding processes can be used, e.g. Inert gas welding with tungsten innert gas (TIG) or gas pressure welding, which takes place under heat and pressure, also electron beam welding or inert gas welding metal innert gas (MIG), as well as cold press welding.

It is also essential that the weld seam shells have an exact, unchanged dimension compared to the profile cross-section when the subsequent calibration process takes place. Depending on the way in which the welding process takes place, it would also be conceivable to be able to do without the calibration process. If minor out-of-roundness is caused by residual stress fields from the weld joint, slight excess being leveled cleanly so that there are no visible transitions, these can be minor Dimensional deviations of the profile width at both ends, caused by the positive locking, are brought to exact dimensions during the rolling process. In these calibration procedures, the core roll has a slight oversize compared to the nominal size (caused by thinning the profile). This calibration is carried out with one or more outer mold rolls, e.g. two outer mold rolls, in which the various possibilities are described in the claims, namely core stands, outer rolls run, core runs, outer rolls stand (a particularly expedient design) or core runs and outer rolls run. The rim is clamped onto the core shape and brought to the final shape and size with several revolutions.

Alternatively, it is also possible that the inner roller rotates, the outer shape and rim run between the inner shape and roller and standing, smooth outer rollers. The rim is placed in the outer shape (clamped) and calibrated with inner form rollers, one or more.

The final shape and size is achieved.

An embodiment of the invention is shown in the drawing; go at it. from the drawing and the description further features of the invention.

• 1 shows a front view of the core stretch bending device,
• Fig. 2 is the top view of Fig. 1,
• 3 shows the process during the pre-bending, corresponding to FIG. 2,
• 4 shows a further phase of this pre-bending,
• 5 shows a further method step on the core stretch bending device,
• 6 shows another phase of the work flow,
• 7 is a front view of a core roll bending apparatus in a front view;
• Fig. 8 is the top view of Fig. 7,
• 9 shows another working phase in the bending process on the core roll bending device,
• 10 shows a further phase of the work process,
• 11 shows a calibration device,
• Fig. 12 shows schematically the chronological order when clamping before the welding process.

In the figures, the same numbers indicate the same parts. The letters from a - s show the different work processes in chronological order. The extruded profile 1 is shown in the figures. This extruded profile has the finished profile of the rim. The core stretching device has a core shape 2, this core shape 2 is also moved by the clamping jaw 5 in the direction of the arrow 18 by drivers 19, which are located on the turntable 20 of this core stretching device. This arrangement is important because the jaws must be moved in the direction of arrow 19 and then in the direction of arrow 21 when loosening, and by this entrainment the profile is protected, it is not exposed to great frictional forces, since it is only stressed at the clamping point by the power transmission. is deformed. Of course, the clamping jaw 5 and the core shape 2 have the finished profile. The straight extruded profile 1 is guided into the device in the direction of arrow 23, there being guide profiles 3 and counter profiles 4 which, pressed against one another, prevent the finished profile of the extruded profile 1 from being deformed when it is deformed in the core stretching device. The profile pieces for the guide profile, counter profile and the clamping jaws are made of an elastic material in order to reduce all deformations to a minimum.

It can then be seen from FIG. 3 that after loosening the clamping jaws 5 the clamping piece 6 is removed, since it had to take up the deformation work during the pre-bending or rounding.

The further operations, which are then shown in FIG. 3 or FIG. 4, show that the bending is now carried out up to approximately 360 degrees, it is essential that before inserting the curved profile in the direction of arrow 24 into the counter profile 4 Edges must be chamfered so that this counter profile is not damaged.

By moving in the direction of arrows 25 and 26, guide and counter profiles 3 and 4 are moved towards or away from one another in order to initiate or end the bending process.

The bending piece 6.1, which was subsequently present on the clamping piece 6, is now also removed; since it again had to take up the additional deformation work than after bending up to 360 degrees was rounded and now there is too large a diameter.

It then continues to work on the core roll bending device, which shows FIGS. 7 and 8.

This core roll bending device is then rounded by means of the forming rolls 8 and the core bending roll 9 until the finished diameter is reached. Now the end piece 6.1 can then be cut to length, which in turn had to take up substantial deformation work, as shown in FIG. 8, because this piece, as it were, acting as a lever, allows the rounding process.

The turntable 11 also has guide disks 12 which are arranged above and below the extruded profile 1 in order to avoid springing open. These plates are not shown in detail in FIGS. 7 and 8.

FIGS. 9 and 10 show the core roll bending process at a different point in time, namely, as shown in FIG. 10, when the weld joint has already formed because the finished dimension has been reached. In the exemplary embodiment, two form rollers 8 are present; by moving in the direction of arrow 27 in one direction or the other, the contact pressure can be increased or decreased in accordance with the desired diameter.

The finished dimension is then reached in FIG. 10.

Subsequently, as much as is rounded on a mandrel with oversize, as shown in FIG. 11, or embossed by the shaping rollers that - as shown in FIG. 12 - the welding process can take place. Here it is essential that the rim to be welded is only opposite the weld seam 13 by pressing jaws 15 on the mandrel 28 the two clamping points 16 are closed, and finally the two clamping points 17. It can be seen that the clamping points 15, 16 lie on the side of the rim opposite the transverse joint, while the clamping points 17 are adjacent. The clamping points 17 are closer to the center line than the clamping points 16.

It is of course possible to produce a rim instead of one piece from several pieces, which would result in more weld seams.

It is always essential that the inventive idea is realized in the present method, namely to connect a bending roll device to a bending stretching device, whereby of course these two stations can also be interchanged if the workpiece or the profile requires this. It is only essential that the deformation work in the case of deformations in this extruded profile only have an effect on the end pieces by directing the process steps, these can be easily removed, and it is much cheaper to have waste on extruded profiles than cumbersome process steps, such as stress relief annealing Having to put up with heat treatments and cumbersome rework.

With regard to FIGS. 2 and 3, it is pointed out that a one-sided pre-bending is also sufficient, so that a two-sided pre-bending does not have to be carried out — as described above in FIGS. 2 and 3.

Claims (12)

1. Process for the production of round bodies, for example wheel rims for motor vehicles, the rim being made in particular from an aluminum alloy as an elongated extruded profile with a final cross-sectional shape, rounded to the wheel shape and connected in the transverse joint by a weld, characterized by the following process steps: a) the extruded profile provided with addition is clamped at its front end and pre-bent or rounded on a core shape which has the finished profile and is too small in diameter compared to the finished diameter of the wheel rim, b) after the clamping piece has been cut to length, the pre-bent extruded profile is bent or rounded to approximately 360 degrees on a core shape which has the finished profile and is too large in relation to the finished diameter of the wheel rim, c) then, on a roll bending machine with a core form roller having the finished profile and counter rollers, after fixing the rear end of the circularly bent extruded profile, the latter is rolled or bent to the finished diameter, d) after the end piece has been cut to length, the rolling or bending process is continued with a core roll having the finished profile and counter rolls until the extruded profile is bent to the finished diameter and the ends collide in alignment, a) after clamping on a core shape provided with the finished profile by means of several outer jaws provided with finished profile, the transverse joint is welded. 2. The method according to claim 1,
characterized in that the clamping of the extruded profile before the welding process takes place at a first point only with respect to the cross joint, then two clamping points are closed at the same distance from the side opposite the cross joint and finally two clamping points are closed at the same distance adjacent to the cross joint. 3. The method according to claim 2,
characterized in that the core shape used for welding has an excess corresponding to the degree of thinning of the profile. 4. The method according to claims 2 and 3, characterized in that the weld seam shells have an exact, unchanged dimension compared to the profile cross section. 5. The method according to claims 1 to 4, characterized in that a calibration process is carried out by a profiled core form roller with a slight oversize compared to the finished profile such that one or more profiled outer form rollers press the welded rim against the core form roller. 6. The method according to claim 1 and 5,
characterized in that the The core roll is standing and the outer rolls are rotating. 7. The method according to claim 1 and 5,
characterized in that the core forming roller rotates and the outer rollers rotate in a standing position. 8. The method according to claim 1 and 5,
characterized in that the core roll and the outer rollers rotate. 9. The method according to claims 1 and 5 to 8, characterized in that the rim is clamped onto the rotating, profiled core form roller and is pressed against the stationary outer mold rollers during the rolling process in one or more revolutions to the final shape dimension. 10. The method according to claim 1 and 5 to 8, characterized in that the core rolls move around the circumference. 11. The method according to claim 1 and 5,
characterized in that the rim is clamped into a profiled outer shape and is brought to the final shape dimension in one or more revolutions with profiled inner shaping rollers. 12. The method according to claims 1 and 5 and 11, characterized in that a profiled inner roller rotates the profiled outer shape with the rim, the outer shape and rim running between the inner shaping roller and standing, smooth outer rollers.

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