EP1745870A1 - Method of manufacturing base bodies of hollow axles - Google Patents

Abstract

The production process is for a hollow-shaft base body. The outer surface (4a, 4b) of a cylindrical blank is deformed to produce a preset diameter transition in the initial base body (2). The base body is then deformed on the outer surface and the inner surface (6) incrementally, using transverse conical rolls, to produce the finished base body (8).

Description

The present invention relates to a method for producing hollow shaft bodies, which comprises a first step, in which the outer surface of a cylindrical starting material is machined by forming to obtain at least a predetermined diameter transition in the longitudinal direction of a base body, and a further step, in which the base body for reshaping the outer and / or inner surface of the base body is formed incrementally to the hollow shaft main body comprises.

In the manufacture of, for example, automotive transmissions and the like, it is desirable to keep the overall weight of the transmission as low as possible. A weight saving can be achieved, for example, by designing the gear shaft as a hollow shaft. This reduces the overall weight of the transmission, and thus the overall weight of a motor vehicle in which the transmission is installed, which is desirable in terms of reducing fuel consumption.

The requirement to form a shaft as a hollow shaft, may also have gear technology reasons. For example, in a shaft-in-shaft or through drive, it is desirable to make this shaft partially or totally hollow. In particular, the trend of an increasing number of waves in a motor vehicle transmission leads to an increase in the overall weight of a transmission, so that in the context of resource conservation, such as material and fuel economy and environmental compatibility (emission reduction), measures must be taken to reduce the weight of the individual transmission shafts.

According to a method used in the prior art, the hollow shaft is manufactured by combining two known methods. In a first step of this process, a solid starting material is formed by swaging to a basic body. Alternatively, the main body can be formed by cross wedge rolling. Subsequent to this first step is then used to manufacture the Hollow shaft a bore or inner bore made in the longitudinal direction of the body machined. This hole is formed by means of a deep hole drilling as a through hole or blind hole. A deep hole drilling method indicates a machining in which the ratio between the bore diameter to be drilled and the length to be drilled is 1: 6 or greater.

The deep hole drilling requires special machines and tools (deep hole drills) and thus brings increased production costs. Further, with the methods described above it is not possible to have undercuts in the bore, i. along the inner surface of the hollow shaft produced. Finally, this method has the disadvantage that the requirement of conserving resources due to the machining is not met.

From the EP 0 052 077 B1 a method is known in which by extrusion two hollow body parts are produced. Subsequently, these body parts are joined together to form a hollow shaft body by a welding process. Due to the welding process, however, the material properties of such a hollow shaft body are adversely affected and the known method also has the disadvantage that measures must be taken to balance the hollow shaft body generated.

From the DE 197 05 279 A1 a method according to the preamble of claim 1 is known. In the generic method, first, the outer peripheral surface of the starting material is contoured by cold extrusion, and then a hole is formed in the solid material. Subsequent to the deep-hole drilling, in a further step the basic body is shaped by rotary swaging or cold extrusion. Since this known method has a machining step, a considerable portion of the material used is wasted. Furthermore, the extrusion results in a circumferentially anisotropic material flow, which is disadvantageous in waves. In addition, several forming stages are required for large cross-sectional changes and / or complicated workpieces. In order to realize the desired cross-sectional changes, further process steps such as compression and setting must be carried out. Frequently, moreover, must be between the individual forming stages a heat treatment be performed so that the material is reshapeable. Thus, it is not possible to produce basic body with large diameter changes on its outer peripheral surface economically by this known method. The use of several forming stages leads to an increased expenditure of time for the production of a hollow shaft main body and thus reduces the overall productivity of the process.

It is also known to contour hollow shafts by upsetting and / or internal high-pressure forming (IHU) in the axial and radial directions of the tube. By upsetting a material thickening is generated in any case on the outer peripheral surface in a predetermined range. In this known method, however, there is a risk that a circumferential, created radially from the inner circumference of the tube outwardly extending crease, which may be the basis of cracks in the material in the stress of the shaft, which lead to the failure of the shaft.

The hydroforming process is based in principle on the fact that a hollow part widened by hydrostatic internal pressure, simultaneously compressed in the axial and / or radial direction and finally expanded by an even higher pressure against the tool contours of a tool. However, this method is not preferable in view of the quality of the obtained hollow shaft main body. In particular, due to accumulation of material wrinkles on the hollow shaft body arise. In addition, the hydroforming process is not suitable in view of the necessary residual wall thickness of a gearbox hollow shaft.

The object of the invention is to overcome the disadvantages of the known methods. A further object of the invention is to provide a method with which hollow shafts with relatively large diameter jumps can be produced on the outside diameter in material accumulations typical of pinion shaft gearboxes.

The above objects are achieved by a method with the features of claim 1, which is characterized in that the starting material is formed by cross wedge rolling.

In a first step of the method according to the invention, the outer surface of a cylindrical starting material is processed by cross wedge rolling such that at least one predetermined diameter transition in the longitudinal direction of a base body is obtained.

In cross wedge rolling, the cylindrical stock is placed between two profiled rolls or flats to radially reshape the starting material, i. to achieve diameter changes or jumps at predetermined portions of the outer circumferential surface. An advantage of this method is that a good material economy is achieved because it hardly comes to material waste in this non-cutting production process. In addition, the cross wedge rolling has the advantage of low cycle times. If the starting material has a bore, a mandrel is introduced into the bore before the cross wedge rolling, whereby the desired material flow is conveyed on the outer circumferential surface during the forming and the preservation of the bore is ensured. But it can also be introduced simultaneously two mandrels at the respective end of the starting material. The mandrels can be arranged for this purpose movable and / or stationary. The mandrel is, for example, cylindrical with a smooth surface but may also have a certain surface geometry and / or diameter grading, which transfers during the cross wedge rolling on the inner peripheral surface of the starting material. Thus, by radial and tangential force application during the cross wedge rolling on the inner and / or outer peripheral surface, a desired surface contour is generated.

The intermediate product produced in the first step, ie the main body thus has, in particular on its outer circumferential surface, at least one predetermined desired diameter transition. The starting material is not limited to cylindrical starting materials having a circular cross section. Rather, starting materials with other cross-sectional shapes, such as rectangular cross-sections can be used. However, starting materials having a rotationally symmetrical cross section are to be preferred. However, the base body obtained after the first step preferably has a circular cross section with a contoured surface, ie is rotationally symmetrical. By the cross wedge rolling is the Body converted by tangential and radial force application. That is, during the forming process, the material flows predominantly radially inward, forming some protrusions, while at the same time effecting an axial extension of the starting material. By forming a plurality of circumferential recesses and / or elevations on the surface of the starting material, a base body is created in the first step, which may have a plurality of different outer diameters. In addition, the base body, if it is already hollow, be formed with varying wall thickness. The shaped recesses and / or elevations can be formed, for example, as almost cylindrical sections.

After the main body has been formed with the at least one predetermined diameter transition, the outer and / or inner surface of the main body is converted in a further step incrementally to a hollow shaft main body. Incremental forming as such is a known method and refers to a forming process in which the forming is not carried out in a single tool stroke, but the body is formed in several steps. The method according to the invention offers the possibility of representing the predominant outer and / or inner circumferential surfaces of the hollow shaft main body by contouring. The hollow shaft main body present after the further step preferably only has to be post-machined, where bearing seats of the hollow shaft are designed for rolling bearings and / or tooth flanks are formed on radial projections.

Due to the inventive combination of cross wedge rollers and incremental forming can be saved in the production of hollow shaft bodies due to the low cycle times during cross wedge rolling in addition to the material savings also considerable time. In addition, this combination creates greater flexibility in the molding of the hollow shaft base body, since in contrast to the generic state of the art no die is used for forming. Thus, a large reduction in cross-section can be performed without the need for further forming stages, as in the generic state of the art. Due to the rotationally symmetric machining is further obtained by the combination of the invention Both methods a uniform solidification, provided that the rotary kneading is carried out cold. Furthermore, the high imaging accuracy on the outer circumferential surface of the main body or hollow shaft body is advantageous.

According to a preferred embodiment, the starting material is formed during the first step by axial force introduction to form an axial bore. This bore may be a bore extending longitudinally of the stock or only a bore extending partially in the longitudinal direction of the stock. Furthermore, two bores can be generated by axial introduction of force at the respective end of the starting material. Preferably, the bore is formed by inserting at least one mandrel in the longitudinal direction of the starting material and forming the starting material radially outwardly. The mandrel may preferably be inserted into the stock material during cross wedge rolling such that the longitudinal axes of the stock material and the at least one dome coincide, the mandrel being held stationary as the stock material rotates between the rolls. Here, a tangential, radial and axial force introduction and a corresponding deformation takes place. Due to the combination of these forces acting gives an excellent contouring of the outer peripheral surface of the body. Since the starting material also transforms radially outward, the material flow is promoted against the profile of the rollers and achieved a dimensionally accurate adaptation of the surface of the starting material to the profile of the rollers. Preferably, the mandrel or spines are inserted axially at least to a region where a diameter transition is formed on the outer surface of the starting material. The insertion of the mandrel and the cross wedge rolling are preferably coordinated so that the mandrel enters the area towards the end of the cross wedge rolling. As a result, rectangular contours of the roller can be transferred to the base body with high accuracy in the first step.

Alternatively, according to a preferred embodiment, in a step preceding the first step, a bore extending in the longitudinal direction of the starting material may be formed in the starting material. This hole can, as described above, by axial force application, ie in particular during hot forming by Pressing a thorn are formed. In this case, for example, the starting material is introduced into the cross wedge rolling device and held there stationary and formed the bore by axial force application. Subsequently, the one or two axial bores having starting material is then cross wedge-rolled in the first step. However, the bore may alternatively be produced by other forming processes, such as extrusion or by machining prior to the first step.

According to a further alternative embodiment, an axial bore may be formed in the base body subsequent to the first step. For example, by machining.

Preferably, after the first step, the inner peripheral surface of the bore is reworked. Such post-processing is desirable for smoothing the inner peripheral surface and is performed by, for example, grinding, polishing, turning and / or the like. A contact surface (bore), which has been cleared of surface defects caused by deformation machining, for the at least one mandrel introduced during the incremental forming process contributes to increased quality of the hollow shaft main body.

According to a further preferred embodiment of the present invention, the main body is separated before the further step into a plurality of main body subunits and these main body subunits are each transformed in the further step to hollow shaft main bodies. This preferred development has the advantage that, by using a single starting material, ie a single blank, a plurality of hollow shaft main body can be produced, which leads to an increased productivity of this method. The separation of the main body subunits can be done by any method, however, in view of minimizing the material waste, a forming process for separating the main body into a plurality of main body subunits is preferred. Preferably, the main body is separated during the first step by a forming process. For example, by shear rollers or ridges, which are brought into effect at the end of the cross wedge rolling in the cross wedge rolling stand, the starting material into a plurality of main body subunits be separated.

Preferably, in the further step, the hollow shaft main body is formed incrementally by rotary swaging. By swaging, the inner and outer surfaces of the body are reshaped to obtain a hollow shaft body having desired inner surface and outer surface contouring. During swaging, a mandrel may be inserted at both ends of the body. According to a preferred embodiment, only one side of the body is incrementally formed in the further step by inserting a preferably stepped dome, while the other side is freely formed on its inner circumferential surface. The at least one mandrel can be arranged movable or stationary. If several mandrels are used, they can be arranged differently from each other, i. a mandrel can be arranged movable and the other stationary. These can also have on their peripheral surface diameter jumps and / or continuous diameter transitions. In the case of free forms, d. H. Incremental forming without a mandrel, an increased wall thickness can be achieved in this area.

Which method variant of rotary swaging is used depends on the desired geometry of the hollow shaft to be produced. Thus, the method variant Einstechrundkneten, in which the tools are also delivered radially, can be used when undercuts are desired on the inner or outer peripheral surface. If special requirements are placed on the inner surface of the hollow shaft body, swaging is performed using a dome. In this process variant, a mandrel is introduced into the bore during the forming process and thus, for example, a high dimensional accuracy and a good surface quality is achieved. Of course, other known process variants of rotary kneading, such as hot circular kneading in the further step of the method according to the invention can be used.

Preferably, the method produces a hollow-shaft main body which has a length-to-diameter ratio which is at least twice as long as the starting material. Thus, a relatively short non-slender starting material is formed into a long hollow shaft body. To determine the ratio is the lowest incrementally reshaped diameter decisive.

By combining the method steps according to the invention, i. by the combination of cross wedge rolling and incremental forming, preferably rotary swaging, relatively large, multiple outer diameter jumps can be realized. These multiple diameter jumps are realized, for example, by projections spaced apart from one another in the longitudinal direction on the outer circumferential surface with the same or different diameters. The multiple diameter jumps may also be stepped, i. be realized by adjacent, stepped up or down projections.

Figur 1

eine Längsschnittansicht eines schematischen ersten Ausführungsbeispiels mit der Darstellung des Grundkörpers in dem oberen Teil (V) und der Darstellung des Hohlwellen-Grundkörpers in dem unteren Teil (N);

Figur 2

eine Längsschnittansicht eines ersten Ausführungsbeispiels eines zur Herstellung eines Hohlwellen-Grundkörper geeigneten Grundkörpers;

Figur 3a-3d

jeweils Längsschnittansichten von Ausführungsbeispielen von Grundkörpern mit unterschiedlichen Bohrungen;

Figur 4a

eine Längsschnittansicht eines zweiten Ausführungsbeispiels eines nach dem ersten Schritt erhaltenen Grundkörpers;

Figur 4b

eine Längsschnittansicht eines Hohlwellen-Grundkörpers, erhalten durch inkrementelles Umformen des Grundkörpers gemäß Fig. 4a;

Figur 5a

eine Längsschnittansicht eines dritten Ausführungsbeispiels eines nach dem ersten Schritt erhaltenen Grundkörpers; und

Figur 5b

eine Längsschnittansicht eines Hohlwellen-Grundkörpers, erhalten durch inkrementelles Umformen des Grundkörpers gemäß Fig. 5a;

Further details, advantages and features of the present invention will become apparent from the following description of an embodiment in conjunction with the drawings. In this shows:

FIG. 1

a longitudinal sectional view of a schematic first embodiment with the representation of the main body in the upper part (V) and the representation of the hollow shaft main body in the lower part (N);

FIG. 2

a longitudinal sectional view of a first embodiment of a suitable for producing a hollow shaft main body body;

Figure 3a-3d

each longitudinal sectional views of embodiments of basic bodies with different holes;

FIG. 4a

a longitudinal sectional view of a second embodiment of a base body obtained after the first step;

FIG. 4b

a longitudinal sectional view of a hollow shaft base body, obtained by incremental forming of the base body of FIG. 4a;

FIG. 5a

a longitudinal sectional view of a third embodiment of a base body obtained after the first step; and

FIG. 5b

a longitudinal sectional view of a hollow shaft main body, obtained by incremental forming of the main body of FIG. 5a;

The essential method steps will be explained below with reference to the embodiment of Figure 1. First, a cylindrical starting material is converted in a first step by cross wedge rolling to a base body 2. The stock material is positioned between the two profiled rolls or jaws of a cross wedge rolling apparatus. The profiles present on these rollers, or jaws, are transferred to the starting material during the forming process. After forming by cross wedge rolling, the base body 2 thus obtained has a desired outer surface profile. That is, by the cross-sectional change by means of cross wedge rolling, the main body 2 has a contoured outer peripheral surface with predetermined diameter transitions. The base body 2 shown in FIG. 1 consists essentially of two cylindrical sections 4a, 4b, which form the ends of the main body 2. Between these two cylinder sections 4a, 4b, two elevations 3, 3 are formed, the flanks of which extend in the radial direction and between which an enlarged relative to the cylinder sections 4a, 4b in the radius, parallel to the base body 2 oriented base 5 is formed. However, this is only an embodiment and continuous transitions on the inner and / or outer peripheral surface of the component are also conceivable. In particular, can be formed with forming steps continuous diameter transitions and at the transition points radii, so that the strength disadvantageously affecting notches can be avoided.

Another exemplary outer surface contouring of the component obtained by cross wedge rolling is shown in FIG. According to this embodiment, two different elevations 3 ', 3 "are formed on the outer circumferential surface of the starting material, wherein the elevation 3' has a larger radius than the elevation 3". This embodiment has cylinder sections 4a, 4b with different diameters. Gears or seats for gears or bearings can be formed on the elevations 3 ', 3 "by means of reworking The number of elevations 3', 3" for forming such functional surfaces on the hollow shaft can be chosen as desired.

The embodiment shown in Figure 2 shows only a time recording of the starting material during the first step, since preferably also at least one extending in the longitudinal direction of the starting material bore is incorporated during the cross wedge rolling in the starting material. The starting material is reformed, for example, at temperatures known for hot working steel materials in the first step. In addition to the radial and tangential deformation, caused by the cross wedge rolling, an axial force application in the longitudinal direction of the starting material is exerted on the workpiece via a mandrel 9 or two mandrels 9a, 9b. In this way, a bore 10 with a constant diameter as shown in FIG. 3a can be generated. Alternatively, the inserted mandrel 9 may have on its peripheral surface diameter gradations and thus produce a bore 10 'as shown in FIG. 3b. The mandrel 9 can be guided either axially movable during cross wedge rolling or be arranged stationary. The exemplary embodiments according to FIGS. 3 a and 3 b show continuous bores 10, 10 'extending in the longitudinal direction of the starting material, but it is also possible to produce a blind hole 16, as shown in FIG. 3 c. The closed end is preferably severed before the further step. 3d shows a further exemplary embodiment, which has a main body with two bores 10 "which are not connected to one another. For this purpose, a mandrel is introduced into the starting material in each case at one end of the starting material.

The exemplary embodiments described above, ie the base bodies 2 according to FIGS. 3a to 3d, show the intermediate product obtained after the first method step. However, it is also possible to produce the bores 10, 10 ', 10 ", 16 after the cross wedge rolling by machining, for example, the embodiment shown in Fig. 2. A forming method, however, is preferable in view of the requirement of material saving. The production of a bore during cross wedge rolling by penetrating the at least one dome into the starting material, wherein the mandrel is introduced to a region corresponding to the contouring on the outer peripheral surface of the starting material, has the advantage that a material flow is effected radially outward This material flow contributes to a dimensionally accurate surface contouring, that is, because the material is in the range of the desired Elevations or projections is also pressed outwards against the profile of the rollers, the material adapts to the roll profiling very accurately.

After the first method step, the basic body 2 having the at least one bore 10, 10 ', 10 ", 16, after a possibly inserted mandrel or pins has been removed, is reworked, for example, the surface of the bore 10, 10', 10", 16 ground or over-turned to form a defined surface. This post-processing takes place at least at that portion of the bore 10, 10 ', 10 ", 16 at which a mandrel is applied by rotary swaging in a further step for incremental deformation of the base body.

During the rotary swaging, the outer and inner circumferential surfaces 4, 6 of the base 2 are deformed. The deformation of the inner peripheral surface 6 results from the deformation of the outer peripheral surface 4 of the base body 2 by the forming tools. That is, the rotary kneading takes place, with respect to the base body 2, from outside to inside and the material thus flows in the radial and axial directions. In order to limit a flow of material in the radial direction, a mandrel is introduced into the base body.

For example, in the embodiment shown in FIG. 1, a cylindrical mandrel is inserted into the bore 10 to provide a desired cylindrical geometry to the inner peripheral surface 6 of the body 2 during swaging. This one process variant of rotary kneading can be combined with the further process variant Einstechrundkneten, for example, to create undercuts. After the hollow base body 2 has been incrementally formed by rotary swaging in the further process step, it has the desired diameter transitions on the outer circumferential surface 12 of the hollow shaft main body 8, and an inner diameter impressed by the mandrel. That is, by machining the starting material according to this embodiment of the present invention, diameter jumps can be provided on the outer diameter. After the incremental processing of the central portion of the hollow shaft main body 8 remains substantially unchanged, with two extending in the radial direction elevations 3, 3 and the intermediate base 5, the wall thickness opposite the hollow body 2 was not changed. Thereafter, the inner peripheral surface 14 is machined to obtain cylinder portions 14 ', 14 ", 14"'. A longitudinal sectional view of this obtained after the rotary kneading and machining hollow shaft main body 8 is shown in the lower portion N of Fig. 1. As can be seen from the figure, rectangular contours or undercuts on the inner peripheral surface 14 of the hollow shaft main body 8 are possible in this first embodiment while maintaining high quality requirements.

The elevations 3 on the outer peripheral surface 12 of the hollow shaft 8 can be machined for molding, for example, gears, bearing seats, splines and rolling teeth. If desired, a heat treatment, hardening treatment and the like may follow to meet the requirements imposed on a transmission shaft.

The second exemplary embodiment shown in FIGS. 4a and 4b is produced by first of all forming the basic body 2 'shown in FIG. 4a by means of cross-wedge rolling. This has a single survey 3 '. On the right side of the elevation 3 'in FIG. 4a, the base body 2' has a short cylinder section 4b 'with a smaller outside diameter than the cylinder section 4a' located on the left side of the elevation 3 '. For this basic body 2 ', the hollow shaft main body 8' shown in FIG. 4b is formed by kneading the left cylindrical section 4b '. Here, a mandrel 18 is used, which has four discrete cylinder sections 20a-20d, which merge into one another continuously via three cone sections 22a-22c. In the process, the right-hand part of the basic body 2 'remains unprocessed during rotary swaging and the incremental deformation takes place only in the length segment marked R, whereby the rotary swaging rollers move from right to left in the axial direction and in this case the predominant length of the cylinder section 4a' is more than double extend axial length. The obtained after the rotary kneading inner and outer peripheral surface of the hollow shaft main body 8 'is shown in Fig. 4b in a solid line. Within the solid lines are dot-dashed lines, which represent the finished contour of the finished hollow shaft. Thereafter, the hollow shaft main body 8 'machined on its outer peripheral surface as on its inner peripheral surface spanhebend. In addition, the ends of the hollow shaft main body 8 'are tapped.

A further embodiment is shown in FIGS. 5a and 5b in the same way as explained with reference to FIGS. 4a and 4b. The basic body 2 "shown in FIG. 5 a is first of all, after introduction of a dome 18", formed incrementally on the side lying to the right of the elevation 3. Thereafter, the mandrel 18 "is removed, after which the side of the intermediate product lying to the left of the elevation 3 is incrementally reshaped, whereby no mandrel is inserted, and the inner contour of the left part is thus freely formed during the forming lying region of the body 2 "is not transformed incrementally. The hollow shaft base body, which is thus incrementally shaped under half-warm to warm conditions, is then machined to obtain the dot-dashed outline shown in FIG. 5b. This indicates the finished part.

4b and 5b it can be seen that the hollow shaft main bodies 8 ', 8 "according to these exemplary embodiments were processed by the rotary swaging near-to-net-shape.in particular, the respective dot-dashed lines illustrate that only a minimal span-lifting Machining is required to obtain each of the desired final contour of the embodiments of Figures 4 or 5. Referring to Figure 4b, for example, an excess length at the respective ends of the hollow shaft main body 8 'is separated, and the outer peripheral surface minimally machined to the survey with the largest diameter to get a right-angled transition.

LIST OF REFERENCE NUMBERS

2, 2 '

body

3, 3 ', 3 "

survey

4a, 4b

cylinder section

5

reason

6

Inner surface

8,8 ', 8 "

Hollow-body

9, 9a, 9b

Mandrel (cross wedge rolling)

10, 10 ', 10 "

drilling

12

outer peripheral surface

14

inner peripheral surface

14 ', 14 ", 14"'

cylinder section

16

blind

18

Thorn (swaging)

20a-d

Cylinder sections of the mandrel

22a-c

Cone sections of the spine

V

Longitudinal view before the next step

N

Longitudinal view after the next step

R

Incrementally reshaped area

Claims (13)

Method for producing hollow-shaft basic bodies (8), comprising: a first step, in which the outer surface (4) of a cylindrical starting material is machined by forming to obtain at least a predetermined diameter transition in the longitudinal direction of a base body (2), and a further step in which the base body (2) for reshaping the outer and / or inner surface (4, 6) of the base body (2) is formed incrementally to the hollow shaft base body (8), characterized in that the starting material is transformed by cross wedge rolling. A method according to claim 1, characterized in that the starting material during the first step by axial force introduction to form an axial bore (10) is formed. A method according to claim 2, characterized in that by introducing at least one mandrel (9) in the longitudinal direction of the starting material, the bore (10) is formed and the starting material is radially outwardly formed. A method according to claim 3, characterized in that the mandrel (9) is inserted in the axial direction at least to a region in which a diameter transition is formed on the outer surface of the starting material. A method according to claim 1, characterized in that in a preceding step in the first step in the starting material extending in the longitudinal direction of the starting material bore (10) is formed. A method according to claim 5, characterized in that the bore (10) is formed in the preceding step by forming under axial force application. A method according to claim 1, characterized in that following the first step in the base body (2) an axial bore is formed. Method according to one of claims 2 to 6, characterized in that after the first step, the inner peripheral surface of the bore (10) is post-processed. Method according to one of the preceding claims, characterized in that the main body (2) is separated before the further step into a plurality of main body subunits and that these main body subunits are each transformed in the further step to hollow shaft main bodies (8). A method according to claim 9, characterized in that the base body (2) is separated during the first step by a forming process. Method according to one of the preceding claims, characterized in that in the further step, the base body (2) is incrementally formed by rotary swaging. Method according to one of the preceding claims, characterized in that one side of the main body (2) in the further step after insertion of a mandrel (18) is transformed incrementally. Method according to one of the preceding claims, characterized in that by the method, a hollow shaft main body (8) is generated, which has a length at least twice as large to diameter ratio as the starting material.

Images