SE538061C2

SE538061C2 - Manufacture of structural elements in roller body bearings

Info

Publication number: SE538061C2
Application number: SE1450721A
Authority: SE
Inventors: Hans Lindén
Original assignee: Skf Ab
Priority date: 2014-06-12
Filing date: 2014-06-12
Publication date: 2016-02-23
Also published as: WO2015190980A1; SE1450721A1

Abstract

23ABSTRACT The present invention relates to a method for manufacturing structuralmembers of a rolling element bearing, comprising providing a workpiece,rotating the workpiece in relation to a first tool set, forming the workpiece in afirst forming process with the first tool set by providing a localized force withthe first tool set on the workpiece. Furthermore, the method comprisesforming a first and a second axial portion of the workpiece into a first and asecond structural member to form part of the rolling element bearing, whereinthe first and second structural members are arranged to be separated fromeach other to form cooperating structural members in the rolling elementbearing. The present invention also relates to an arrangement for manufacturing structural members of a rolling element bearing. For publication: Fig. 1

Description

FORIVIING OF STRUCTURAL ELE|\/IENTS OF ROLLING ELE|\/IENTBEARING Field of the lnvention The present invention relates to rolling element bearings and to themanufacturing of rolling element bearing. More specifically, the presentinvention relates to a manufacturing process for manufacturing structuralmembers of a rolling element bearing, and to a manufacturing arrangement for structural members of a rolling element bearing.

Background ArtRolling element bearings are used in a wide variety of applications with different operational conditions and load characteristics. The rolling elementbearing, also referred to as rolling bearing, is configured to carry a load byhaving rolling elements, such as balls or rollers, between an inner and anouter bearing ring. The rolling elements may be maintained in the rightposition between the inner and outer bearing rings by a cage. The inner ring,outer ring and cage are examples of structural members which are arrangedto cooperate with each other, and with the rolling elements, to form a rollingelement bearing. Generally, rolling element bearings have the advantage of agood tradeoff between cost, size, weight, carrying capacity, durability,accuracy, and friction.

During manufacturing of rolling element bearings, it is known to utilizeexpensive and complex manufacturing equipment for manufacturing each oneof the different structural members of the rolling element bearing separately inorder to provide favorable manufacturing in terms of cost per outputted unitand manufacturing accuracy. ln other words, a plurality of different machineryset ups are use, each being designed and adapted for manufacturing large 2quantities of a specific structural member at high speed, low costs per unit, and with high accuracy.

However, in order to provide all the structural members required forassembling a complete rolling element bearing, a plurality of differentmachinery set-ups and a large amount of different raw material formed into separate workpiece for the different structural members, are required.

Summarv of the lnvention ln view of the above-mentioned and other drawbacks of the prior art, ageneral object of the present invention is to provide improved and moreefficient manufacturing of structural members of a rolling element bearing,and a manufacturing arrangement for structural members of a rolling elementbeanng.

These and other objects are met by the subject matters provided in theindependent claims. Preferred embodiments of the invention are presented inthe dependent claims.

According to a first aspect thereof, the present invention relates to amethod for manufacturing structural members of a rolling element bearing,which method comprises providing a workpiece, rotating the workpiece inrelation to a first tool set, forming the workpiece in a first forming process withthe first tool set by providing a localized force with the first tool set on theworkpiece, which localized force causes material of the workpiece to form intoa rotation symmetric shape, wherein the forming is being performedaccording to predetermined design rules. Furthermore, the first formingprocess comprises forming a first axial portion of the workpiece into a firststructural member to form part of the rolling element bearing, and forming asecond axial portion of the workpiece into a second structural member to formpart of the rolling element bearing, wherein the first and second structuralmembers are arranged to be separated from each other to form cooperating structural members in the rolling element bearing.

The invention is based on the realization by the inventors that a singlemanufacturing process is used for manufacturing different structural membersfrom the same workpiece using the same manufacturing machine set-up. ln more detail, a single workpiece is advantageously used for formingdifferent structural members of a rolling elements bearing, which structuralmembers may be arranged to cooperate to form part in an assembled andoperational rolling element bearing. The manufacturing process further allowsfor reduced raw material waste, and low manufacturing costs. Also, logisticsaspects relating to setting up the manufacturing machinery into a completeand operational manufacturing set-up, and in terms of handling andtransportation of the raw material, is favorable, and may be arranged at lowercost, and with less energy and time. Furthermore, the manufacturing processis inherently flexible and with a single single manufacturing set-up operationalaccording to the present invention, structural member for a wide variety ofwith different rolling element bearings, e.g. with different forms and sizes, maybe manufactured. This provides more flexibility in the productionenvironments and reduces changeovers. For example, multiple operationscan be done in one manufacturing set-up, which reduces the need for e.g.multi-step grinding process that historically would involve two or threeseparate operations for a specific, separately manufactured, structuralmember of a rolling element bearing.

The invention is further advantageous in that the manufacturing ofstructural members for a rolling element bearing may be performed by asingle manufacturer from a single low-cost workpiece. Also, completemanufacturing capabilities utilizing the method according to the invention maybe set-up fast and at a low cost at different locations.

For example, the first forming process may comprise metal machiningtechniques, such as spinning, flow forming, necking-in and/or profilingtechniques. According to an exemplifying embodiment the first tool setcomprises one or more rollers for applying a localized force on the rotatingworkpiece. According to an exemplifying embodiment, the first forming 4process comprises cold rolling. For example, cold rolling may be performed with the metal below its recrystallization temperature, e.g. at roomtemperature, which increases the strength of the workpiece via strainhardening.

According to an exemplifying embodiment involving flow forming, theworkpiece, such as a disk or tube of metal, is formed over a mandrel by oneor more rollers using high pressure. The roller deforms the workpiece, forcingit against the mandrel, and may perform axially lengthening and radiallythinning of the workpiece.

According to an exemplifying embodiment of the method formanufacturing, the first forming process further comprises forming a thirdaxial portion of the workpiece into a third structural member to form part of therolling element bearing, and/or forming a fourth axial portion of the workpieceinto a fourth structural member to form part of the rolling element baring,wherein the third and/or fourth structural members are arranged to beseparated from each other and/or separated from the first and secondstructural members to form cooperating structural members in the rollingelement bearing. This allows for manufacturing of a plurality of structuralmembers of a rolling element bearing in a single manufacturing process froma single workpiece, with a single manufacturing machine set-up. For example,the first axial portion may be formed in the inner ring of the rolling bearing, thesecond and third axial portions may be formed into two separate cages, andthe fourth axial portion may be formed into the outer ring of the rollingbearing. Also, a fifth, or more, axial portions may be formed into structuralmembers of the bearing, such as a guide ring or spacer ring.

According to an exemplifying embodiment of the method formanufacturing, the manufactured structural members of the rolling elementbearing are at least two or more of the following: inner ring, first cage, secondcage, spacer ring, outer ring. 5According to an exemplifying embodiment of the method for manufacturing, the first forming process comprises forming the workpieceover a mandrel. For example, a mandrel may be described as a bar, e.g. ofmetal or other sufficiently hard and rigid material, that serves as a core around which the workpiece is shaped.

According to an exemplifying embodiment of the method formanufacturing, it further comprises a first treatment process in which the axialportions of the workpiece is machined in a turning process with a second toolset comprising one or more cutting tools. This advantageously allows formachining of all the axial portions in single method step, with reduced downtime. For example, inside and/or outside turning may be performed, i.e.removal of material from the radially outer surface or from the radially innersurface of the tubular workpiece. According to an exemplifying embodiment,the first turning process is a soft turning process being performed on theworkpiece before the workpiece has been subjected to a main hardening process.

According to a further exemplifying embodiment of the method formanufacturing, one of the axial portions of the workpiece is formed into acage. l\/loreover, the method further comprises a cage pocket cutting processinvolving cutting pockets for rolling elements in the axial portion of theworkpiece that is formed into a cage, the cutting being performed with apocket-cutting tool set. For example, according to an exemplifyingembodiment, the pocket cutting tool set comprises a tool, such as a punch,arranged to be forced through the workpiece to create a hole via shearing.The pockets may also be provided by using laser-cutting techniques with alaser-cutting device, or by using milling techniques with a milling cutter, or byusing waterjet cutting involving a high-pressure jet of water, or a mixture of water and an abrasive substance.

According to an exemplifying embodiment of the method for manufacturing, it further comprises hardening one or more of the axial 6portions of the workpiece. Thereby, different axial portions of the workpiece may be hardened in an efficient and continuous manufacturing process.Hardening may be arranged using various heating and/or quenchingtechniques. For example, the heating device for hardening the workpiece isarranged to heat the workpiece during the manufacturing process, withoutremoving the workpiece from its previous position, such as in a chuck in themachine set-up. According to an exemplifying embodiment, the axial portionof the workpiece is hardened using induction-hardening techniques, usinge.g. induction heating device. By using induction heating, the heating step ofthe hardening process is advantageously achieved by electromagneticinduction, where eddy currents are generated within the workpiece andresistance, leading to heating. For example, an electromagnet, such as oneore more coil, through which a high-frequency alternating current is passed, isused. Heat may also be generated by magnetic hysteresis losses in materialsthat have significant relative permeability. Advantageously, inductionhardening is used to selectively harden areas, such as specific axial portions,of the workpiece in an efficient manner with a coil arranged around, radiallyoutside and/or inside, the tubular-shaped workpiece, while reducing the effecton the properties of the part as a whole. According to an exemplifyingembodiment, the hardening process further comprises quenching of theworkpiece, such that the workpiece may undergo a martensitic transformationincreasing the hardness of selected portions of the workpiece.

According to an exemplifying embodiment of the method formanufacturing, it further comprises a second treatment process in which theaxial portions of the workpiece are machined with a third tool set. ln thesecond treatment process, the axial portions of the workpiece mayadvantageously be provided with accurate surface properties and structurefor operation in the rolling element bearing. The second treatment processmay for example involve machining processes such as turning, hard turningof hardened portions, grinding and/or polishing of e.g. contacting surface ofthe axial portions, which contacting surfaces are forming e.g. raceways of an 7inner or outer ring with high structural accuracy, or similar portions of the structural members.

According to an exemplifying embodiment, the second treatmentprocess comprises hard turning of the hardened workpiece. For example,hard turning allows for machining the axial portions of the workpiece in oneset up giving greater accuracies especially on features, such as concentricityand roundness. Furthermore, finish hard turning can advantageously removemore material per machining operation than e.g. grinding, allowing for fasterand more efficient manufacturing.

The second treatment process may be performed after a hardeningprocess of the workpiece, or hardening process of specific portions of the workpiece.

According to a further exemplifying embodiment of the method formanufacturing, the third tool set comprises one or more cutting tools forturning. For example, inside and/or outside hard turning may be performed,i.e. removal of hardened material from the radially outer surface or from the radially inner surface of the tubular-shaped workpiece.

According to an exemplifying embodiment of the method formanufacturing, it further comprises a workpiece splitting process forseparating the axial portions of the workpiece from each other to formseparate structural members of the rolling element bearing. Parting, or cutoffoperation of, the axial portions into separate structural member may forexample performed with a parting or cutting tool, wherein the workpiece is rotated in relation to the parting or cutting tool.

According to a further exemplifying embodiment of the method formanufacturing, the axial portions to be formed into the structural members ofthe rolling element bearing are consecutively arranged in a first axial directionof the workpiece. For example, the second axial portion is formed with aradially inner dimension, and the first axial portion is formed with a radiallyouter dimension, wherein the radially inner dimension of the second axial 8portion is larger than the radially outer dimension of the first axial portions.

This allows for that the finished structural members, when they have beenseparated into individual units, may be arranged to cooperate in a mannerwhere in the first structural portion, such as an inner ring, may be arrangedinside the bore of the second structural portion, which e.g. may be a cage, guide ring, or outer ring of the rolling elements bearing.

According to an exemplifying embodiment, the workpiece is handledand rotated by use of a dual spindle lathes/chuck arrangement allowing forefficient manufacturing and reduced downtime between different formingprocesses and between machining of different axial end portions of theworkpiece. For example, a dual spindle lathes with z-axis movement, i.e. theaxial direction of the workpiece, may be used. The workpiece may be securedby a first and a second clamping device, such as chucks, duringmanufacturing in a consecutive order, allowing for machining of the separateaxial ends of the workpiece. The first and second clamping devices may holdthe workpiece on the external surface, such as on the external surface of theouter ring, or on the internal surface, such as on the radially inner surface ofthe inner ring bore. The inner ring may also be secured by gripping theexternal surface, such as a gripping shoulder between or next to the racewayor raceways, if more than one, of the inner ring.

The workpiece may for example be form of metal. The starting shapeof the workpiece may e.g. be disc-shaped, puck-shaped, or a machinedblank. The workpiece may further have a rotational symmetry axis that isaligned with the rotational movement of the workpiece during forming operations.

According to a further aspect of the present invention, it relates to anarrangement for manufacturing structural members of a rolling elementbearing from a workpiece. The arrangement comprises a first tool set, aclamping device for supporting and rotating the workpiece in relation to thefirst tool set, wherein the first tool set is arranged to perform a first forming process comprising providing a localized force with the first tool set on the 9workpiece causing the material of the workpiece to form into a rotation symmetric shape. Furthermore, the first tool set is arranged to form a firstaxial portion of the workpiece into a first structural member to form part of thero||ing element bearing, and a second axial portion of the workpiece into asecond structural member to form part of the ro||ing element bearing, whereinthe first and second structural members are arranged to be separated fromeach other to form cooperating structural members in the ro||ing elementbearing. The arrangement is advantageous in similar manners as describedin relation to the first aspects the present invention, and embodiments thereof.

According to an exemplifying embodiment of the arrangement, the firsttool set is further arranged to form a third axial portion of the workpiece into athird structural member to form part of the ro||ing element bearing, and/or afourth axial portion of the workpiece into a fourth structural member to formpart of the ro||ing element baring, wherein the third and/or fourth structuralmembers are arranged to be separated from each other and/or separatedfrom the first and second structural members to form cooperating structuralmembers in the ro||ing element bearing.

According to an exemplifying embodiment of the arrangement, it furtherhas a second tool set comprising one or more cutting tools, wherein theclamping device is arranged to rotate the workpiece in relation to the secondtool set while the second tool set is arranged to perform a first treatmentprocess during which the axial portions of the workpiece is machined in aturning process by the one or more cutting tools.

According to an exemplifying embodiment of the arrangement, it furtherhas one or more pocket-cutting tool set for cutting pockets for ro||ing elementsin one or more axial portions of the workpiece which are formed into ro||ingelements bearing cages.

According to an exemplifying embodiment of the arrangement, it furtherhas one or more hardening device for hardening at least portions of one ormore of the axial portions of the workpiece.

According to an exemplifying embodiment of the arrangement, it furtherhas a third tool set comprising one or more cutting tools, wherein theclamping device is arranged to rotate the workpiece in relation to the third tool set while the third tool set is arranged to perform a second treatment process during which the axial portions of the workpiece is machined in a turningprocess by the one or more cutting tools.

According to an exemplifying embodiment of the arrangement, it furthercomprises a cut-off tool for performing a splitting process separating the axialportions of the workpiece from each other to form separate structuralmembers of the rolling element bearing.

The arrangement allows for continuous production of the workpieceinto separate structural members that are arranged to be assembled and tocooperate to form an operable rolling element bearing. The workpiece may forexample be manufactured continuously in motion during differentmanufacturing steps. Furthermore, simply by reconfiguring design of therotation symmetric shape into which the workpiece is formed and treated bythe arrangement during the manufacturing process, structural membershaving different dimension may be formed using the same workpiece andmachine set-up. This allows for manufacturing of rolling elements bearing ofdifferent size and purpose.

Generally, other objectives, features, and advantages of the presentinvention will appear from the following detailed disclosure, from the attacheddependent claims as well as from the drawings are equally possible within thescope of the invention.

Brief Description of Drawinds Embodiments of the invention will now be described, by way ofexample, with reference to the accompanying drawings, wherein: Figs. 1a-b are schematic views of an embodiment of the methodaccording to the present invention. 11Figs. 2a-c are schematic views of a first treatment process according to an embodiment of the present invention.

Fig. 3 is a schematic view of a cage pocket cutting process accordingto an embodiment of the present invention.

Fig. 4 is a schematic view of a hardening treatment process accordingto an embodiment of the present invention.

Fig. 5a is schematic view of a second treatment process according toan embodiment of the present invention.

Figs. 6a-b are schematic views of a workpiece sp|itting processaccording to an embodiment of the present invention.

Fig. 7 is a schematic view of a complete rolling element bearing havingstructural members form by the method according to the present invention.

Fig. 8 is a schematic view of a workflow and a machine arrangementaccording an embodiment of the method according to the present invention.

Fig. 9 is a schematic method flowchart according an embodiment of the present invention. lt should be understood that the drawings are not true to scale and, asis readily appreciated by a person skilled in the art, dimensions other thanthose illustrated in the drawings are equally possible within the scope of the invenﬁon.

Detailed Description of Embodiments of the lnvention ln the drawings, similar, or equal elements are referred to by equal reference numerals. ln Figs. 1a-b schematic views of an embodiment of the method 100according to the present invention are shown. A metal disc-shaped workpiece1 is arranged and secured to a mandrel 4 for being rotated in relation to a firsttool set 21 comprising a roller tool controlled and supported by a tool turret(not shown). The mandrel 4 comprises a forming shape over which the 12workpiece is formed such that axial portions 10, 11, 12, 13, and 14 with different properties are formed. ln more detail, the workpiece is formed in afirst forming process 101 by providing a localized force with the roller 21 onthe workpiece during rotation, which Iocalized force causes material of theworkpiece to form into a rotation symmetric shape, as illustrated in Fig. 1b.Spacer portions 15 (illustrated in Fig. 6a) are formed between the axialportions 10, 11, 12, 13, 14 of the workpiece 1, which spacer portions 15separate the different axial portion that are formed into structural members ofa rolling element bearing.

As shown in the embodiment in Fig. 1b, illustrated in a cut-out view,and with reference to Fig. 6b: the axial portion 10 is arranged to be formed into a structural member10' being an inner ring of a rolling element bearing, such as shown in Fig. 7, the axial portion 11 is arranged to be formed into the structural member11' being a guide ring of the rolling element bearing, the axial portion 12 is arranged to be formed into the structural member12” being a first cage of the rolling element bearing, the axial portion 13 is arranged to be formed into the structural member13” being a second cage of the rolling element bearing, and the axial portion 14 is arranged to be formed into the structural member14' being an outer ring of the rolling element bearing.

As further shown in Fig. 1b, the axial portions of the workpiece areformed in to shapes having structural features depending on their purpose.For example, the structural features on an axial portion being formed into aninner ring may be one or more outer raceways for rolling elements, such asraceway 10a and 10b formed on the radial outer surface of the axial portion10. ln a similar manner the axial portion 14 being form into the outer ring isprovided with structural features, such as inner raceways 14a. Also, the axialportions 12 and 13 being formed into cages may be provided with structuralfeatures, such as a curved cross sectional profile 13a for conforming with theavailable space between the outer and inner ring of a rolling elementsbeanng. 13During the first forming process, the structural features are partially finalized into semi-finished state, and may be further machined in preceding manufacturing and/or treatment processes. ln Figs. 2a-c, schematic views of a first treatment process 102according to an embodiment of the present invention are shown. ln the firsttreatment process 102, one or more the axial portions 10, 11, 12, 13, 14 ofthe workpiece 1 is machined in a turning process with a second tool set 22controlled and supported by a tool turret. The second tool set comprising oneor more cutting tools 22a, 22b for inside and outside turning of the axialportions 10-14 of workpiece 1. As shown, the workpiece is secured to aclamping device 50, such as a chuck, during the first treatment process. lnFig. 2a, the workpiece is secured by clamping device 50 at a first axial end ofthe workpiece, corresponding to axial portion 14, allowing for turning of theremaining axial portions 10, 11, 12 and 13 being accessible by the cuttingtools. ln Fig. 2b the workpiece is secured to the clamping device 50, by itsopposite axial end, such that axial portion 14 may be accessed and machinedby the tool set 22. ln Fig. 2c, a cut-out view of the workpiece 1 is shown,wherein cutting tool 22b is arranged to machine the internal, radially innersurface, of the axial portions 10, 11, 12, and 13 of the workpiece. ln Fig. 3, a schematic view of a cage pocket cutting process 103according to an embodiment of the present invention is shown. ln more detail,while the workpiece is remained in its previous position, being secured toclamping device 50, such as the chuck of a lath, axial portions 12 and 13 areprovided with pockets 12a and 13a for holding and guiding the rollingelements in the finished rolling bearing. The pockets 12a and 13a areprovided in a cage pocket cutting process 103 with a pocket-cutting tool set23 arranged to a tool turret 23c. As shown in the embodiment, the pocketcutting tool set 23 comprises a punch tool arranged to be forced through theworkpiece to create a hole via shearing. An internal support or counter holding device arranged inside the tubular body of the workpiece may be 14used to improve the cutting operation during the cage pocket cutting process 103. ln Fig. 4, a schematic view of a hardening treatment process 104according to an embodiment of the present invention is shown. The sameworkpiece is shown in two position during the manufacturing process, atwhich positions it is held at separate axial ends corresponding to the axialportions 14 and 10, by two separate cooperating c|amping devices 50a and50b which may e.g. form part in a dual spindle Iathes/chuck arrangement. Thec|amping devices are arranged to secure and rotate the workpiece during themanufacturing processes earlier to and following the hardening process. Asfurther shown, the hardening comprises heating selected portions of theworkpiece using coils 40a and 40b, arranged for passing a high-frequencyalternating current through for induction heating. First coil 40a has a smallerbore adapted to the radial dimension of the axil portion 10 being formed intothe inner ring. Second coil 40b has a larger bore adapted to the radialdimension of the axil portion 14 being formed into the outer ring. The first andsecond coils 40a and 40b are connected to a tool turret controlling theposition of the coils during the manufacturing. One or more tool set mayoperate on the workpiece simultaneously performing different forming andtreatment processes. Furthermore, hardening may also be performedsimultaneously as one or more tool set are operating on the workpieceperforming different forming and treatment processes. ln the hardeningprocess, an axial portion of the workpiece 1 to be heated is inserted into oneof the coils 40a or 40b. ln Fig. 5 a schematic view of a second treatment process 105according to an embodiment of the present invention, is shown. ln the secondtreatment process 105, the axial portions of the workpiece are machined witha third tool set 24 in order to form accurate and operable surfaces of thestructural members, such as raceways and contacting-surface with highaccuracy requirements. As shown, the second treatment process 105involves a hard turning machining processes using a first and second cutting tool 24a and 24b, being used for removing material from the external and internal surfaces of the workpiece. During the second treatment process 105,the workpiece may be secured and rotated by the first clamping device 50a.The second clamping device 50b (not shown) may be used for griping the axial portion 10 for hard turning the axial portion 14 of the workpiece. ln Figs. 6a-b, schematic views of a workpiece splitting process 106according to an embodiment of the present invention are shown. ln thesplitting process 106 the axial portions 10, 11, 12, 13, and 14 in Fig. 6a of theworkpiece are separated form each other to form separate structuralmembers 10”, 11”, 12”, 13”, and 14” in Fig. 6b of the rolling element bearing.As schematically shown, parting, i.e. the cutoff operation of, the axial portionsinto separate structural member is performed with a parting or cutting tool 60.For example, the workpiece may be gripped and rotated using the clampingdevice 50 in relation to the cutting tool in a turning operation. The cut-offoperation is e.g. performed by cutting away spacer portions 15 separating thedifferent axial portion of the workpiece. Thereby, separate structural members10”, 11”, 12”, 13”, and 14' arranged to cooperate to form part in a rollingelement bearing may be manufactured from a single workpiece in an advantageous manner. ln Fig. 7, a schematic cut-out view of a complete rolling elementbearing 70 having structural members formed by an embodiment of themethod according to the present invention is shown. ln more detail, theseparate structural members 10”, 11”, 12”, 13”, and 14” in Fig. 6b have beenassembled with additional structural members, such as rolling elements 16, into form a fully operational rolling element bearing 70. The illustrated rollingelement bearing 70 is a double row spherical roller bearing, comprising thecooperating structural members: inner ring 10", spacer ring 11", first cage 12” (not shown), second cage 13", and outer ring 14”. ln Fig. 8, a schematic view of a workflow including steps (a) (b) (c) (d)(e) according an embodiment of the present invention is shown. As illustrated, 16the Workflow starts with a disc-shaped workpiece 1 which is machined and processed in different steps (a) (b) (c) (d) (e) into structural members 10”, 11”,12”, 13”, and 14” of a rolling elements bearing. At step (a), described in moredetail in relation to Figs. 1a-b, the first forming process 101 is performed. Atstep (b), the workpiece is arranged in production position in clamping devices50a and 50b by moving the tubular body of the workpiece with mover device80. At step (c) and (d), described in more detail in relation to Figs. 2a-c, Fig.3, Fig. 4, and Fig. 5, the first treatment process 102, the cage pocket cuttingprocess 103, the hardening process 104, the second treatment process 105,are performed. During steps 8c-d the workpiece is moved from being held bythe first clamping device 50a to the second clamping device 50b. Theclamping devices are gripping the workpiece on opposite axial sides. The firstclamping device 50a is gripping the workpiece on a first axial side comprisingthe axial portion 14 being formed in the outer ring 14”, and the secondclamping device 50b is gripping the workpiece on a second axial sidecomprising the axial portion 10 being formed in the inner ring 10”, in order toallow for access for machining and hardening of each axial end 10 and 14 ofthe workpiece 1. At step (e), described in more detail in relation to Figs. 6a-b,splitting process 106 is performed.

Fig. 8 also schematically illustrates an arrangement 200 formanufacturing structural members 10” 11” 12” 13” and 14” of a rolling elementbearing from a workpiece 1. The arrangement 200 comprises a first tool setincluding rollers 21 and 21a arranged to roll form the workpiece 1 againstmandrel 4. For example, the workpiece may be supported and rotated by aclamping device. The arrangement further comprises a second tool set 22comprising one or more cutting tools, wherein the clamping devices 50a and50b are arranged to rotate the workpiece in relation to the second tool 22 forremoval of material from the workpiece in a turning operation. Furthermore, apocket cutting tool set 23 for cutting pockets for rolling elements in one ormore axial portions of the workpiece are include. The arrangement 200further includes a first and a second hardening device 40a and 40bcomprising induction heating coils for heating selected axial portions of the 17workpiece 1. As shown, the arrangement also has a third tool set 24 comprising one or more cutting tools, wherein the clamping devices 50a and50b are arranged to rotate the workpiece in relation to the third tool 24 forremoval of material from the workpiece in a hard turning operation. ln order toseparate the axial portions in order to form stand alone structural members10” 11' 12” 13' and 14” of a rolling element bearing, the arrangementcomprises a cut-off tool for performing a splitting process. A mover device 80is further included for moving the workpiece between different manufacturingprocesses and positions, such as between a roll forming position to a turningand/or hardening position. The tool sets 21, 22, 23, 24 and the mover device80 may be supported by one or more tool turrets, such as tool turret 23cshown in Fig. 3, controlled by a control unit arrangement 201 comprisinginstructions to perform the manufacturing process and schematic connectionsmeans 202 for controlling the position and operation of the tool sets 21, 22,23, 24, the hardening device 40a, 40b, the mandrel 4, the clamping devices50a and 50b, and the cutting tool set 60. ln Fig. 9, a schematic method flowchart 100 according an embodimentof the present invention is shown. As shown, the method comprises firstforming process 101 involving e.g. roll forming, first treatment process 102involing e.g. soft turning, pocket cutting process 103 involing e.g. punchingoperation, hardning process 104 involving e.g. induction hardening, secondtreatment process 105 involving e.g. hard turning, and a splitting process 106involing e.g. a turning operation with a cut-off tool. One or more of the steps102, 103, 104, 105 may be performed at least partly simultanesouly on the workpiece. lt should be noted that the invention has mainly been described abovewith reference to a few embodiments. However, as is readily appreciated by aperson skilled in the art, other embodiments than the ones disclosed aboveare equally possible within the scope of the invention, as defined by the appended patent claims. 18ln the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. Asingle apparatus or other unit may fulfill the functions of several items recitedin the claims. The mere fact that certain features or method steps are recitedin mutually different dependent claims does not indicate that a combination ofthese features or steps cannot be used to advantage. Also, different stepswhich are denoted with “first” or "second" do not indicate that these stepshave to be performed in this or in any particular order. For example, the cagepocket cutting process may be performed after hardening and/or secondtreatment processes of the raceway portions of the inner and/or outer rings.

Claims

19CLAIIVIS

1. Method (100) for manufacturing structural members (10”, 11”, 12113”, 14') of a rolling element bearing (70), comprising:providing a workpiece (1),rotating the workpiece in relation to a first tool set (21),forming the workpiece in a first forming process (101) with the first toolset by providing a localized force with the first tool set on the workpiece,which localized force causes material of the workpiece to form into a rotationsymmetric shape (3), wherein the forming is being performed according topredetermined design rules,characterized in that the first forming process comprisesforming a first axial portion (10) of the workpiece into a firststructural member (10”) to form part of the rolling element bearing, andforming a second axial portion (14) of the workpiece into asecond structural member (14”) to form part of the rolling elementbeanng,wherein the first and second structural members are arranged to beseparated from each other to form cooperating structural members in the rolling element bearing.

2. The method according to claim 1, wherein the first forming processfurther comprises forming a third axial portion (11) of the workpiece into a third structuralmember (11”) to form part of the rolling element bearing, and/or forming a fourth axial portion (12; 13) of the workpiece into a fourthstructural member (12”; 13”) to form part of the rolling element bearing, wherein the third and/or fourth structural members are arranged to beseparated from each other and/or separated from the first and secondstructural members to form cooperating structural members in the rolling element bearing.

3. The method according to any one of the preceding claims, wherein the manufactured structural members of the rolling element bearing are atleast two or more of the following: inner ring (10”), spacer ring (11”), first cage(12”), second cage (13”), and outer ring (14”).

4. The method according to any one of the preceding claims, whereinthe first forming process comprises forming the workpiece over a mandrel (4).

5. The method according to any one of the preceding claims, furthercomprising a first treatment process (102) in which the axial portions(10;1 1 ;12;13;14) of the workpiece is machined in a turning process with a second tool set (22) comprising one or more cutting tools (22a; 22b).

6. The method according to any one of the preceding claims, whereinone of the axial portions (12; 13) of the workpiece is formed into a cage(12';13”), the method further comprises a cage pocket cutting process (103)involving cutting pockets (12a, 13a) for rolling elements in the axial portion ofthe workpiece which is formed into a cage, the cutting being performed with a pocket cutting tool set (23).

7. The method according to any one of the preceding claims, further acomprising hardening (104) one or more of the axial portions (10;11;12;13;14) of the workpiece.

8. The method according to any one of the preceding claims, furthercomprising a second treatment process (105) in which the axial portions ofthe workpiece are machined with a third tool set (24).

9. The method according to any one of the preceding claims, furthercomprising a workpiece splitting process (106) for separating the axialportions (10;11;12;13;14) of the workpiece from each other to form separate structural members of the rolling element bearing.

10. 2110. The method according to any one of the preceding claims, wherein the axial portions (10;11;12;13;14) forming the structural members of therolling element bearing is consecutively arranged in a first axial direction ofthe workpiece.

11. The method according to claim 10, in which the second axialportion (14) is formed with a radially inner dimension (14r), and the first axialportion (10) is formed with a radially outer dimension (1 Or), wherein theradially inner dimension of the second axial portion is larger than the radiallyouter dimension of the first axial portions.

12. An arrangement for manufacturing structural members (10', 11”,12”, 13”, 14') of a rolling element bearing (70) from a workpiece (1), the arrangement comprising: a first tool set (21), a clamping device (50) for rotating the workpiece in relation to the firsttool set, wherein the first tool set is arranged to perform a first formingprocess comprising providing a localized force with the first tool set on theworkpiece causing the material of the workpiece to form into a rotationsymmetric shape (3), wherein the first tool set is arranged to form a first axial portion (10) ofthe workpiece into a first structural member (10”) to form part of the rollingelement bearing, and a second axial portion (14) of the workpiece into asecond structural member (14”) to form part of the rolling element bearing,wherein the first and second structural members are arranged to beseparated from each other to form cooperating structural members in the rolling element bearing.

13. The arrangement according to claim 12, further comprising asecond tool set (22) comprising one or more cutting tools (22a, 22b), wherein the clamping device is arranged to rotate the workpiece inrelation to the second tool set while the second tool set is arranged to performa first treatment process during which the axial portions (10;11;12;13;14) of 22the workpiece is machined in a turning process by the one or more cutting tools (22a, 22b).

14. The arrangement according to any one of claims 12-13, furthercomprising a one or more hardening device (40a; 40b) for hardening at leastportions of one or more of the axial portions (10;1 1 ;12;13;14) of the workpiece.

15. The arrangement according to any one of claims 12-14, further comprising a third tool set (24) comprising one or more cuttingtools (24a, 24b), wherein the clamping device is arranged to rotate the workpiece inrelation to the third tool set while the third tool set is arranged to perform asecond treatment process during which the axial portions (10;11;12;13;14) ofthe workpiece is machined in a turning process by the one or more cuttingtools (22a, 22b).