High speed spindle with forced mechanical vibration assistance

Abstract

A spindle (1) for a machine tool is disclosed, comprising: - a housing (10), - a shaft (20) for driving a cutting tool, which shaft is rotatably mounted in the housing so as to be axially movable relative to the housing, - a single ball (200) axially inserted between a bearing ring (202) fixed relative to the housing and a bearing ring (201) movable with the shaft, one of these rolling rings defining an inclined bearing surface (231) which is not perpendicular to the axis of rotation of the shaft, so that the rotation of the ball produces an axial oscillation of the shaft.

Description

TECHNICAL FIELD

[0001] The present invention relates to a high-speed spindle with forced mechanical vibration assistance. BACKGROUND

[0002] The Applicant has developed various solutions for vibratory drilling in which the cutting tool, while it is rotating, is subjected to axial oscillations.

[0003] These oscillations can break up the chips and improve the drilling performance.

[0004] To generate the axial motion of the tool, many existing solutions are based on the use of rolling bearings, one or more raceways of which have a wavy surface.

[0005] Patents EP 2790860 B1 and EP 2501518 B1 describe examples of vibratory machining devices.

[0006] The rolling bearings are usually composed of balls which, during rotation, are kept in angular position with respect to each other by means of a rotating cage.

[0007] In the known solutions, the frequency of the axial oscillations depends on the rotational speed and on the number of undulations that the rolling bearings undergo while they are rotating.

[0008] The rotational speed of the tool depends on its cutting speed and on its diameter. Therefore, the more the diameter of the hole to be drilled is reduced, the more the rotational speed needs to be increased to maintain an equivalent cutting speed. However, the frequency of the axial oscillations cannot exceed a threshold value (of the order of 300 Hz) without generating excessive mechanical loads, especially considering the inertia of the moving parts. Therefore, the rotational speed of the known vibratory drilling spindles, which are based on the mechanical conversion of the rotational motion into axial vibratory motion, is usually limited to 10000 rpm.

[0009] In certain applications, it is necessary to produce a large number of small-diameter holes very quickly, for productivity reasons. Therefore, in traditional non-vibratory drilling, small-diameter drills are usually driven at rotational speeds much higher than 10000 rpm (for example of the order of 20000 rpm) to maintain their cutting speed. For certain materials, the length of the chips produced when cutting at these rotational speeds in traditional drilling is short and easily evacuable.

[0010] However, other materials produce longer chips during traditional drilling, which are not easily evacuable if not included in a chip evacuation cycle. Therefore, the choice of materials that can be machined in traditional drilling without reducing the productivity is still limited, which proves to be a disadvantage in certain applications.

[0011] Although there are pure mechanical vibration drilling solutions whose selection of the oscillation frequency is independent of the rotational speed of the shaft, these solutions are based on the use of electromechanical or piezoelectric elements, but these solutions are more expensive and complex than the existing pure mechanical solutions, and their implementation, if mechanically feasible, is still economically unfeasible in many applications, especially when it is desirable to minimize the changes made to the existing large number of machine tools during the implementation of the vibration drilling solution.

[0012] DE 102005002460 proposes a drilling tool comprising an oscillation unit incorporating a rolling bearing of the "thrust ball bearing" type having a single ball rolling between a first ring and a second ring. This rolling bearing is not designed to operate at high rotational speeds due to the centrifugal effect of the ball. A calibration spring generates a forward movement, keeping the rolling bearing in a compressed state.

[0013] US 3088342 describes an oscillating drilling tool having a rolling bearing of the "thrust ball bearing" type. The oscillation movement is achieved by means of a split ring which, given its arrangement and the step applied to the ball, generates an oscillation movement exhibiting a clear discontinuity. Therefore, this device cannot operate at high rotational speeds due to mechanical wear and the vibrations generated.

[0014] Therefore, to the best of the applicant's knowledge, there is still an unmet need to benefit from a compact spindle capable of rotating at high rotational speeds while subjecting the cutting tool to an axial oscillation at a frequency suitable for reducing the length of the formed chips. SUMMARY

[0015] The present invention aims to meet this need and achieves this aim by a spindle for a machine tool, having:

[0016] - a housing,

[0017] - a shaft for driving a cutting tool, rotatably mounted within the housing so as to be axially movable with respect to the housing,

[0018] - a single ball axially inserted between a rolling bearing ring fixed with respect to the housing and a rolling bearing ring movable with the shaft, one of these rings defining an inclined rolling bearing surface not perpendicular to the rotational axis of the shaft, so that the rotation of the ball generates an axial oscillation of the shaft.

[0019] The use of a single ball to generate the axial oscillating movement of the shaft makes it possible to maintain the frequency of the axial oscillation at a value compatible with the inertia of the parts to be moved, including rotational speeds greater than 10,000 rpm. Furthermore, the absence of a cage rotating with the ball reduces the heating of the rolling bearing at high rotational speeds. The invention makes it possible, if necessary, to manufacture a compact vibrating drilling mandrel that can replace a conventional mandrel without changing the machine tool.

[0020] Preferably, the balls are partially fitted in an annular groove formed in the shaft. This makes it possible to reduce the distance from the axis of its center of gravity, thereby reducing the imbalance associated with its rotation, as well as the bending moment exerted on the shaft by the balls.

[0021] Preferably, the fixed rolling bearing ring is the rolling bearing ring that defines the inclined rolling bearing surface. The inclined rolling bearing surface is advantageously planar, thereby making it possible to form it with a high degree of precision and a good surface state, which is advantageous for minimizing the friction between the balls and the rolling bearing ring.

[0022] This inclined rolling bearing surface is free of steps. The absence of steps limits the generation of vibrations and mechanical wear.

[0023] Advantageously, the axial cutting load is at least partially reacted on the rolling bearing ring that is fixed relative to the housing.

[0024] Preferably, the balls are made of ceramic, making it possible to optimize the strength / density ratio.

[0025] The balls are preferably located at the rear of the mandrel. This limits the effect of the bending moment on the guiding quality of the shaft at the tool.

[0026] The mandrel preferably has two sets of ball bearings located respectively at the front and at the rear of the mandrel. These rolling bearings are preferably angular contact and flange rolling bearings. The balls are preferably disposed behind the set of ball bearings at the rear.

[0027] The rolling bearings are preferably kept centered so as to be able to move axially by means of elastic strips having an oriented deformation and an annular overall shape. The elastic strips preferably have, on their outer circumference, fixed tabs that are fixed relative to the housing and tabs for retaining the rolling bearings between these fixed tabs, the flexibility of the part of the strip that extends between the fixed tabs and the tabs for retaining the rolling bearings allowing the rolling bearings to move axially during the axial oscillation of the shaft. The use of strips provides a clever solution to the problem of ensuring radial stiffness while allowing the axial movements necessary for the shaft to be able to oscillate axially. The strips have a high stiffness in the radial direction, but their small thickness allows them to bend to follow the axial movements of the rolling bearings. The strips can be superimposed to increase the radial stiffness while maintaining the axial flexibility.

[0028] Rolling bearings can be mounted on bearings rotating in translation relative to the strip, preferably by means of pins passing through the strip, the bearings having sectors forming a protrusion on their end edges against which the strip bears, the strip being in contact with the outer ring of the rolling bearings by its retaining tabs. These sectors make it possible to fix the retaining tabs of the strip relative to the bearings, while maintaining an axial clearance between the fixed zones, to allow the portions of the strip extending therebetween to bend, thus allowing the rolling bearings to move axially relative to the housing during axial oscillations of the shaft.

[0029] Plate springs for pressing the strip against the outer ring of the rolling bearings can be present. These plate springs can be omitted, as described below, in addition to being used as elastic members for exerting an axial preload on the shaft, if appropriate.

[0030] The mandrel has an elastic return member that returns axially rearward during rotation of the balls. This rearward axial preloading of the shaft is advantageously achieved by at least one plate spring. Thus, the mandrel can have at least one plate spring, or even a single plate spring, which exerts a return force rearward. This plate spring can be located at the front or at the rear of the mandrel. Placing the plate spring at the rear can avoid introducing a compression force along a considerable rotor length. The return force toward the rear of such an elastic member is advantageously maximum during non-zero cutting forces and is released when the cutting force is greater than 0.

[0031] The axial fixing of the strip relative to the housing can be achieved in various ways, but very preferably the strip is held at the fixed tabs with a series of spacers. Thus preferably the mandrel has a tubular main spacer fixed relative to the housing, and fixed positioning rings disposed on either side of the main spacer, between which the fixed tabs of the strip are clamped.

[0032] The mandrel preferably has bearing end rings on either side of the bearings, in which the aforementioned pins are fitted, one or more plate springs pressing against one end of these end rings, the other end resting against a surface fixed relative to the housing.

[0033] The housing is preferably closed at the rear by an end piece against which the rolling bearing ring of the inclined rolling bearing surface rests.

[0034] Preferably, the mandrel has a peripheral rolling bearing ring coaxial with the shaft for counteracting the centrifugal force of the balls. Counteracting centrifugal force is particularly advantageous for drilling at rotation speeds greater than 10,000 rpm.

[0035] The ratio d ball / d path is preferably between 1 / 4 and 1 / 2, where d ball represents the diameter of the balls, d path represents the diameter of the contact point of the balls with the inclined rolling bearing surface.

[0036] A further subject of the present application is a machining method, in particular a drilling method, in which the shaft of the spindle according to the present application is driven with a rotational speed of at least 10,000 rpm, for example between 15,000 rpm and 30,000 rpm, in particular approximately 15,000 to 20,000 rpm.

[0037] A further subject of the present application is a machining method, in particular a drilling method, in which the shaft of the spindle according to the present application is axially oscillated with a vibration frequency of between 0.4 and 0.6 oscillations per revolution, in particular approximately 0.5 oscillations per revolution.

[0038] During the rotation of the shaft, the spindle can be subjected to a forward movement in a conventional manner. BRIEF DESCRIPTION OF DRAWINGS

[0039] The application can be better understood by reading the following description of non-limiting exemplary embodiments thereof and by examining the drawings in which:

[0040] [ Figure 1 ] Figure 1 a perspective view of an example of a spindle according to the present application is shown schematically,

[0041] [ Figure 2 ] Figure 2 is a longitudinal section through a spindle, Figure 1

[0042] [ Figure 3 ] Figure 3 a rear portion of the spindle is shown in more detail,

[0043] [ Figure 4 ] Figure 4 a front portion of the spindle is shown in more detail,

[0044] [ Figure 5 ] Figure 5 a perspective view of a separate elastic strip is shown,

[0045] [ Figure 6 ] Figure 6 a perspective view of a separate bearing end ring is shown,

[0046] [ Figure 7 ] Figure 7 a perspective view of a separate bearing is shown,

[0047] [ Figure 8 ] Figure 8 a ring with an inclined rolling bearing surface is shown in axial section, and

[0048] [ Figure 9 ] Figure 9 an embodiment variant of a spindle is shown in longitudinal section. ​DETAILED DESCRIPTION

[0049] According to the spindle 1 of the application, in particular the spindle 1 shown in Figures 1 to 4 has a housing 10, which is preferably metallic, and has the overall shape of a cylinder rotating around a longitudinal axis X.

[0050] The housing 10 is mounted in a guide and thrust mechanism (not shown) of a machine tool known per se. A support 11 fixed to the housing allows the mechanism to axially move the spindle 1 the distance required to produce a hole.

[0051] The spindle 1 has a shaft 20 for carrying at the front a tool such as a drill bit (not shown) and for being coupled at the rear to a pulley 21 for driving it in rotation. The drill bit has a diameter for example less than or equal to 2.5 mm.

[0052] The rotational speed of the shaft 20 is for example between 10,000 and 20,000 revolutions per minute.

[0053] The application is not limited to a particular tool or to producing a hole. Performing a machining operation such as a milling operation, a counterboring operation, etc. proves to be particularly useful.

[0054] The shaft 20 is guided in rotation around the axis X relative to the housing 10 by a set of front rolling bearings 30 and a set of rear rolling bearings 40.

[0055] The set of front rolling bearings 30 has two angular contact rolling bearings 31 with a contact angle for example of 15°, each angular contact rolling bearing 31 having an inner ring 32 in contact with the shaft 20, balls 33, an outer ring 34 and a flange 35. The rolling bearings 31 abut each other and are mounted in a front bearing 50.

[0056] The set of rear rolling bearings 40 is implemented in a similar manner, with two angular contact rolling bearings 41 with a contact angle for example of 15°, each angular contact rolling bearing 41 having an inner ring 42 in contact with the shaft 20, balls 43, an outer ring 44 and a flange 45. The rolling bearings 41 abut each other and are assembled in a rear bearing 51.

[0057] The inner ring 42 of the last rolling bearing axially abuts the shoulder 23 of the shaft 20, as can be seen in particular in Figure 3 .

[0058] A tubular inner spacer 24 is mounted on the shaft 20 between the set of front rolling bearings 30 and the set of rear rolling bearings 40 and abuts at its ends the inner rings 32 and 42 of the respective rolling bearings.

[0059] A blocking ring 70 is fixed at the front to the shaft 20 and fixes the inner rings 32 of the rolling bearings 31, the inner spacer 24 and the inner rings 42 of the rolling bearings 41 and axially preloads them against the shaft.

[0060] In the example shown, the ring 70 is fixed to the shaft by means of three conical set screws 71, which make it possible to correct the out-of-roundness, if necessary.

[0061] The O-ring seal 72 is housed in a groove 73 in the shaft 20 and is pressed against the barrier ring 70.

[0062] The housing 10 is closed at the front by a front nut 90 screwed into it and at the rear by a rear closure 95, which can be held on the housing 10 in various ways, for example by means of a nut 96, as shown. Figure 2

[0063] The front nut 90 has a forwardly directed collar 190, which forms a bend 192 with a rearwardly directed collar 191 of the barrier ring 70.

[0064] The inner ring 195 is mounted at the rear on the shaft 20 and has a forwardly directed collar 196, which forms a bend 198 with a collar 197 of the closure 95.

[0065] The bends 192 and 198 form a non-contact sealing system at the front and at the rear of the mandrel 1, while providing a gap that allows rotational and translational movement without friction between the facing rotating and stationary parts.

[0066] The O-ring seal 199 is housed in a groove 27 of the shaft 20 and is pressed against a facing surface of the inner ring 195.

[0067] A series of spacers is arranged in the housing 10 in contact with the inner surface of the housing 10, fixed between the front nut 90 and the rear closure 95, i.e. from front to rear: a ring forming a front spacer 91, a ring forming a front bearing spacer 92, a ring forming a tubular main spacer 93, and a ring forming a rear bearing spacer 94.

[0068] Four stacks 100, 101, 102 and 103 of elastic strips 110 are respectively inserted axially between the spacers 91 and 92, between the spacers 92 and 93, between the spacers 93 and 94, and between the spacers 94 and 95.

[0069] In the example discussed, each stack 100, 101, 102 or 103 has at least two strips 110, for example five strips, one of which is shown separately in Figure 5 .

[0070] ​Each strip 110 has a generally annular overall shape and has fixing tabs 111 regularly distributed at its periphery, there being three of them in the example under discussion, which point radially outwards and which bear with their radially outer edges against the inner surface of the housing 10. The height of the fixing tabs 111 is slightly greater than the thickness of the bearing spacers 92 and 94.

[0071] The circular-arc portions 112 connecting the fixing tabs 111 carry, halfway along their length, other tabs 113 which point radially inwards. These tabs 113 each have a radial slot 114 which opens at one end onto the radially inner free edge of the tab 113 and at the opposite end into a circular hole 115 formed in the circular-arc portion 112.

[0072] The front bearing 50 is disposed between two bearing end rings 121 and 122. Pins 130 are fitted in drilled holes 140 and 141 corresponding to these end rings 121 and 122 and to the front bearing 50, in order to hold the rings 121 and 122 in a predetermined angular orientation relative to the front bearing 50.

[0073] These pins 130 pass through the holes 115 of the strips 110. The slots 114 make it easier to fit the pins 130. The stacks 100 and 101 are thus held in a predetermined position angularly relative to the bearing 50 and relative to the end rings 121 and 122.

[0074] As Figure 6 and Figure 7 It can be seen that the bearing 50 and the rings 121, 122 have, on their facing faces, a projecting sector 143 whose angular extent substantially corresponds to that of the tabs 113 and which encloses the tabs 113 between one another.

[0075] The rear bearing 51 is similarly disposed between bearing end rings 120 and 121, and pins 130 angularly fix the strips 110 disposed therebetween, as in the case of the front bearing 50.

[0076] The tabs 113 of the strips 110 are in axial contact with the outer rings 32 and 42 of the rolling bearings 31 and 41.

[0077] This assembly allows a certain freedom of movement of the set of rolling bearings 30 and 40 in the axial direction, while they are held centred thanks to the stiffness of the strips 110 in the radial direction, as will be described in detail below.

[0078] The main spacer 93 is formed at each of its ends with a shoulder 171 which is disposed rearward from an end portion 172 which surrounds the corresponding end ring 121 or 122.

[0079] A leaf spring 170 is mounted inside each end portion 172 and is inserted axially against the shoulder 171 and the end ring 121 or 122.

[0080] At the front, two stacked leaf springs 170 are mounted around the retaining ring 70 and axially inserted between the front nut 90 and the end ring 121, as shown. Figure 2 visible.

[0081] The closure 95 has a shoulder 176 and an end portion 177 in front of the shoulder 176, and the closure 95 extends around the adjacent end ring 122.

[0082] The leaf spring 170 is installed in the end portion 177 and axially inserted between the closure 95 and the adjacent end ring 122.

[0083] The leaf spring 170 clamps the elastic strip surrounding the front and rear rolling bearings via end rings 121 and 122 and via tabs 113 supported on the outer ring of the rolling bearings.

[0084] The presence of an additional leaf spring 170 at the front, between the nut 90 and the adjacent end ring 121, creates a permanent elastic load on the shaft 20 toward the rear, so as to press the balls 200 against the rings 201 and 202.

[0085] According to the present invention, the spindle 1 has a mechanism for generating axial oscillation of the shaft 20 when the shaft 20 rotates.

[0086] The mechanism has a single ball 200 that rolls between a rotating rolling bearing ring 201 mounted on and rotating with the shaft 20 and a fixed rolling bearing ring 202 carried by the closure 95.

[0087] A peripheral rolling bearing ring 203 is inserted into the closure portion 95, behind the shoulder portion 176, and extends around the path followed by the ball 200 as the ball 200 rotates. This peripheral rolling bearing ring 203 allows for reaction against centrifugal force during the rotation of the ball 200.

[0088] The rotating ring 201 rests against the shoulder 28 of the shaft 20, which is adjacent to the annular groove 29, the concavity of which is substantially consistent with the path followed by the ball 200.

[0089] The rolling bearing ring 202 has a planar rear surface 230 perpendicular to its axis and a planar, inclined front surface 231, as shown. Figure 8 As can be seen, the normal to the front surface forms an angle g with the axis of the rolling bearing ring 202, where g is a few degrees, for example, approximately 0.3° in the example discussed. The formula for g is: g = Arctan(amplitude / d) path ), where "amplitude" corresponds to the total peak / trough variation of the vibration oscillation, d path The diameter of the path at the contact point.

[0090] It can be seen that the rolling bearing surface 231 is free of steps.

[0091] Thus, during its rotation around the axis X, the ball 200 performs a periodic sinusoidal axial movement induced by the inclination of the front surface 231. The ball 200 is in contact only with the fixed rolling bearing ring 202, the rotating rolling bearing ring 201 and the peripheral rolling bearing ring 203 during its high speed rotation. As a single ball is used, the rolling of this ball induces a bending stress on the shaft, but this is still controlled and has an acceptable amplitude due to the relatively small distance between the ball 200 and the spindle axis 20.

[0092] The fact that the rolling bearing surface 231 is free of undulations and is a flat surface makes it possible to produce the rolling bearing surface 231 with a very good surface state very easily.

[0093] Preferably, the ball 200 is made of ceramic. Its diameter is preferably greater than or equal to 5 mm, so that the Hertz pressure at the contact point can be reduced. Its diameter is for example 6 mm.

[0094] In order to install the spindle 1, all the internal constituent elements can be placed on the shaft 20 and the assembly can be inserted through the front end of the housing 10, the closing portion 95 already in place, then the front screws 90 can be fixed.

[0095] The spindle 1 is operated as follows.

[0096] The shaft 20 is driven in rotation by the belt 21, for example by a belt.

[0097] The ball 200 rolls between the rolling bearing rings 201 and 202 and, in doing so, moves the shaft 20 forwards against the preload associated with the presence of the additional leaf spring 170 in the front part.

[0098] The movement of the shaft 20 is made possible by the presence of the strip 110, the arc-shaped portion 112 of which can bend thanks to the presence of the gap provided next to it by the sector 143. This bending allows the front bearing 50 and the rear bearing 51 to move axially to follow the oscillations generated by the movement of the ball 200.

[0099] An axial oscillation of the shaft 20 is thus obtained, the frequency of which is given by the rotational speed of the shaft 20 and by the Willis formula applied to a rolling bearing with three contact points.

[0100] The axial travel of the shaft 20 during the oscillatory movement is for example between 0.02 mm and 0.15 mm. The shaft of the spindle oscillates at a vibration frequency of 0.4 to 0.6 oscillations per revolution, for example approximately 0.5 oscillations.

[0101] The balls 200 are partially inscribed in a groove 29 in the shaft 20, the presence of which reduces the distance 200 from the axis X and thus reduces the unbalance phenomena associated with the use of a single ball 200. Furthermore, the distance travelled by the balls 200 and the wear resulting therefrom are reduced. Finally, the bending moments caused by the asymmetric load of a single ball are reduced.

[0102] Of course, the present application is not limited to the example just described.

[0103] For example, the housing 10 can be closed in a different way at the rear, as Figure 9 shown in the figure. In this figure, it is clear that the rear closure 95 is held in the housing by means of a resilient ring 300 mounted in a corresponding groove of the housing 10. The axial and radial space requirement of the housing is thereby reduced.

[0104] In addition to the leaf spring for providing axial preloading on the shaft, the leaf spring can also be dispensed with. The leaf spring for providing axial preloading on the shaft can be arranged at the rear, i.e. in a position in which the leaf spring 170 is located between the rear shoulder 171 and the ring 121 adjacent to the rolling bearing 41 located radially inside the bearing 51. Figure 2 In the figure, it is clear that the rear closure 95 is held in the housing by means of a resilient ring 300 mounted in a corresponding groove of the housing 10. The axial and radial space requirement of the housing is thereby reduced.

Claims

1. A high-speed spindle (1) for a machine tool, the spindle having: - Shell (10) - A shaft (20) for driving the cutting tool, the shaft being rotatably mounted within the housing so as to be axially movable relative to the housing. - A single ball (200) axially inserted between a rolling bearing ring (202) fixed relative to the housing and a rolling bearing ring (201) movable with the shaft, one of these rolling bearing rings defining an inclined rolling bearing surface (231) not perpendicular to the axis of rotation of the shaft, such that rotation of the ball produces axial oscillation of the shaft, the spindle being operable at a shaft speed greater than 10000 rpm. in, The ball bearings are partially fitted into an annular groove (29) with a radial opening formed in the shaft (20).

2. The mandrel as described in claim 1, wherein, The fixed rolling bearing ring (202) is the rolling bearing ring that defines the inclined rolling bearing surface (231).

3. The mandrel as described in claim 1, wherein, The inclined rolling bearing surface (231) is planar.

4. The mandrel as described in claim 1, wherein, The ball bearing (200) is made of ceramic.

5. The mandrel as claimed in claim 1, wherein, The ball bearing (200) is located at the rear of the spindle (1).

6. The mandrel as claimed in claim 1, wherein, The mandrel has two sets of rolling bearings (30, 40) located at the front and rear of the mandrel, respectively.

7. The mandrel as claimed in claim 1, wherein, The axial preload is ensured by at least one leaf spring (170) to the rearward axis.

8. The mandrel as claimed in claim 6, wherein, The rolling bearing is held by an annular integral strip (110) having fixed tabs (111) fixed relative to the housing on its outer circumference and tabs (113) for holding the rolling bearing between these fixed tabs. The flexibility of the portion of the strip extending between the fixed tabs (111) and the tabs (113) for holding the rolling bearing allows the rolling bearing to move axially during axial oscillation of the shaft.

9. The mandrel as claimed in claim 8, wherein, The rolling bearing is mounted on a bearing (50, 51) that prevents rotation relative to the strip by a pin (130) passing through the strip. The bearing has a sector (143) with a protrusion formed on its end edge. The strip abuts against the sector in the area of ​​the tab (113) for retaining the rolling bearing. The strip contacts the outer ring (34, 44) of the rolling bearing by the retaining tab (113).

10. The mandrel as claimed in claim 8, wherein, The mandrel has a leaf spring (170) for pressing the strip against the outer ring of the rolling bearing.

11. The mandrel as claimed in claim 8, wherein, The spindle has a tubular main spacer (93) fixed relative to the housing, and fixed positioning rings (92, 94) disposed on both sides of the main spacer (93), with the fixing tabs (111) of the strip (110) sandwiched between the main spacer (93) and the positioning rings (92, 94).

12. The mandrel as claimed in claim 8, wherein, The spindle has end rings (121, 122) on both sides of the bearings (50, 51), in which pins (130) are fitted. A leaf spring (170) presses against one end of these end rings and the other end abuts against the tab (113) for holding the strip.

13. The mandrel as claimed in claim 8, wherein, The rolling bearing is an angular contact rolling bearing.

14. The mandrel as claimed in claim 1, wherein, The spindle has a peripheral rolling bearing ring (203) coaxial with the shaft, which reacts to the centrifugal force of the balls (200).

15. The mandrel as claimed in claim 1, wherein, ratio d ball / d path Between ¼ and ½, where d ball d represents the diameter of the ball. path This indicates the diameter of the contact point between the ball and the surface of the inclined rolling bearing.

16. A processing method in which the shaft of the mandrel as claimed in claim 1 is driven at a rotational speed of at least 10,000 rpm.

17. A processing method, wherein the vibration frequency of the shaft of the mandrel as claimed in claim 1 is an axial oscillation between 0.4 and 0.6 times per revolution.

Images