EP1526946B1 - Method and system for grinding a rotationally symmetric machine part comprising a longitudinal borehole - Google Patents

Abstract

Disclosed is a machine part (5) with a conical effective surface, which is machined by means of a device comprising a machine bed (1), a longitudinally movable grinding bench (7), and a workpiece spindle head (2) that clamps the machine part (5) by means of clamping jaws (4) via a chuck (3). The conical effective surface of the machine part (5) is ground by means of a first grinding disk (14) in a vertical grinding mode by longitudinally moving the grinding bench (7) in the direction of the longitudinal axis (6). The associated grinding spindle head (10) is provided with a first grinding spindle (12) for the first grinding disk (14) and a second grinding spindle (13) for a second grinding disk (16) that is fixed to a grinding arbor (15). The grinding spindle head (10) is fixed to a grinding spindle carriage (9) so as to be pivotable around a vertical shaft (11), said grinding spindle carriage (9) being movable in the direction of the x-axis via a displacement motor (8). B indicates the swiveling direction of the grinding spindle head (10) while X and Z represent the common axes referred to in CNC technology. The first grinding disk (14) can be driven out of the area of the machine part while the second grinding disk (16) can be made to act upon the machine part (5) in order to internally grind a longitudinal borehole.

Description

The invention relates to a method for grinding a rotationally symmetrical machine component provided with a longitudinal bore, whose one end-side end surface is designed as an effective surface in the form of a particularly flat truncated cone shell with a contour which is rectilinear or curved in cross-section, according to the preamble of claim 1.

The machine components to be ground with this method are present, for example, in transmissions with continuously variable transmission, as required in motor vehicles. Here, two machine components face each other with facing active surfaces. The active surfaces thus form an annular space with an approximately wedge-shaped cross section, in which a tension member such as a chain or a belt, depending on the distance of the active surfaces of each other back and forth between different radii. Since such a transmission must work very accurately and transmit large torques, high demands are placed on the dimensional accuracy and the surface quality of the machine components. This also applies to the associated grinding operations, especially when grinding the active surface.

The method mentioned in the introduction is carried out according to the state of the art known from operational practice in individual operations, that is to say in a plurality of fixtures. Here, the active surface is ground by means of corundum grinding wheels in Schräginstechverfahren. For internal cylindrical grinding of the longitudinal bore located on the machine component, the machine component must then be clamped in another machine, where the inner cylindrical grinding of the bore wall can take place with a correspondingly small grinding wheel.

The known method has various disadvantages. First of all, grinding wheels of conical or highly stepped diameter are required, which are difficult to manufacture and finish. In such grinding wheels with peripheral areas of very different diameters and the peripheral speeds of the grinding areas are different. This means that the decisive cutting speed at the grinding point must be different and therefore can not be optimal everywhere. As a result, this leads to areas of different roughness, which has an adverse effect on the effective area. Finally, there are also problems with the cooling by means of the usual emulsions and grinding oils. When Schrägeinstechschleifen namely arises at the grinding point a narrowing wedge, the cooling lubricant can not be optimally supplied. The result is thus an uneven cooling of the grinding point. It is due to all these difficulties that the previously mentioned known method has hitherto been carried out with corundum grinding wheels, which have a significantly lower service life and must be dressed more frequently than the now widespread CBN wheels.

The DD 143 700 deals with a device for grinding tungsten plates, which are used, inter alia, as rotating electrodes in x-ray tubes. This Wolframteller has the graphic representation of the contour of a truncated cone, in which the inclination of the surface line relative to the base is about 30 °. In this known device, the Wolframteller is clamped in a workpiece holder, which is pivotable relative to the device frame about a vertical axis. Opposite the workpiece holder is a longitudinal support, which is displaceable in a horizontal plane. On the longitudinal support a cross slide is arranged, which carries a grinding spindle for driving a small cylindrical grinding wheel, which serves for the internal grinding of a bore in the tungsten plate. Separately from this cross slide, the longitudinal support also carries a rigid electric grinding spindle for driving a tapered grinding wheel. With the tapered grinding wheel, a face and the cone-shaped area of the tungsten plate are to be ground. To do this, the tapered grinding wheel and the tungsten plate must be brought into the correct position by pivoting the workpiece holder and moving the longitudinal support and by manually operated feed controls. Something else than an oblique grinding in the area of the cone shroud is the DD 143 700 not to be taken. The partly manually operated known device is cumbersome and with manual skill to use.

From the EP 1 022 091 A2 a machine tool for grinding workpieces is known, in which there are two cylindrical grinding wheels of different sizes on a revolver, which in turn is arranged on a sliding carriage. By pivoting the turret by 180 °, the two grinding wheels can be selectively brought to bear against different areas of a rotationally symmetrical workpiece. The workpiece is arranged in a workpiece holder, which in turn is displaceable on a carriage in the longitudinal direction of the workpiece. For grinding, the workpiece is set in rotation. In this known machine tool also the workpiece holder can be adjusted at an angle of +/- 30 ° obliquely to the direction of displacement of the workpiece holder. In the EP 1 022 091 A2 It is not explained how the grinding is to occur when tilting the workpiece holder. However, since the pivoting of the grinding wheel-carrying turret is expressly specified in steps of 90 °, it is reasonable to conclude that longitudinal grinding with a grinding wheel is also intended for this known machine tool if conical outer contours with a considerable angle of inclination of the cone are to be ground ,

JP 2000-271827 describes the grinding of machine components whose one end face is formed as an active surface 24 in the form of a flat truncated cone with a straight contour in cross section and clearly show how the skilled person has proceeded so far when grinding such workpieces. In this case, the active surface of the machine component is ground by a grinding wheel with a conical contour is guided radially along the effective surface. The movement takes place in two mutually perpendicular components. For this purpose, the grinding spindle 53, 54 is arranged on a cross slide. Thus, there is a circumferential longitudinal grinding in a direction A with delivery in a direction perpendicular thereto B. Since nothing is said about a pivoting of the grinding spindle, the entire assembly including the conically contoured first grinding wheel is set to specific angular conditions on the machine component to be ground.

The invention is based on the object to provide a method of the initially mentioned type, with which the processing time is shortened and yet a better grinding result is achieved.

For the claimed in claim 7 system applies mutatis mutandis, the same task.

The solution of this problem consists in accordance with the process steps listed in the characterizing part of claim 1 in that at the one hand held on its outer circumference machine component first the active surface is ground in the perpendicular grinding process by a first cylindrical grinding wheel delivered with its rotating peripheral surface perpendicular to the effective surface is moved by the machine component in the direction of its rotational and longitudinal axis relative to the first grinding wheel, wherein the axial extent of the first grinding wheel covers the radial oblique stretch of the active surface, and then in the same clamping the inner wall of the longitudinal bore is ground by a second grinding wheel of smaller diameter by pivoting a wheel spindle, which carries at least the first and the second grinding wheel, introduced into the longitudinal bore of the machine component and delivered radially against the inner wall becomes.

In the method according to the invention, the machine component to be ground thus remains in a single set-up in which all grinding operations are carried out. This is made possible by first placing a first cylindrical grinding wheel perpendicular to the active surface and then inserting a second cylindrical grinding wheel of smaller diameter into the longitudinal bore of the machine component and hitting it radially against the inner wall. The possibilities of bringing two different grinding wheels on different working surfaces of one and the same workpiece into effect are generally known to the person skilled in the art.

A special feature of the inventive solution is that the first grinding wheel with its rotating peripheral surface is made perpendicular to the inclined running effective surface, the axial extent or the width of the first grinding wheel covers the radial oblique extension of the effective surface.

Thus, the active surface is ground with the cylindrical peripheral surface of the grinding wheel in a perpendicular grinding process, wherein the delivery is effected by a mutual relative displacement.

The advantage is a constant cutting speed over the entire width of the grinding wheel. This ensures an increased surface quality and surface structure. In addition, optimized dressing parameters are obtained when dressing the grinding wheel, because during dressing the same parameters, namely an identical dressing speed as during grinding as well as the same speed ratios and feed values are achieved. Because the cutting speed of the grinding wheel remains the same over the effective area, the achievable surface roughness is constant. Due to the same cutting speed of the grinding wheel over the complete conical surface, optimum values for the machining volume per unit of time can be achieved.

With Schrägeinstechschleifen, however, this is not the case. Assuming the outer diameter of the conical effective surface of a value of for example 190 mm and a subsequent to the effective surface mean diameter (in the region of the longitudinal bore) of about 40 mm, the workpiece speed changes by the rotation of the workpiece during grinding by a factor 4.75. The height of the conical surface is thus about 75 mm.

With an assumed diameter of the corundum grinding wheel of 750 mm, the cutting speed at the outside diameter of the conical surface is then about 80% of the cutting speed of the grinding wheel at the small diameter of the conical surface. This is in contrast to the machining volume, since this is the largest at the large diameter on the conical surface. As a result, the cutting speed ratio to the cutting volume, which must be removed via the conical surface, is substantially improved by the grinding wheel set perpendicular to the conical surface.

It also results in significantly improved conditions when cooling the grinding zone, because when grinding the active surface practically the same conditions as in perpendicular grinding, so that a constant narrow cooling zone is present, the cooling lubricant can be well supplied and he leaves quickly.

Overall, such advantages that the grinding method of the invention can be best performed with ceramic bonded CBN grinding wheels. Overall, a significantly reduced number of cycles on modern processing machines is achieved at the same time significantly improved grinding result.

In principle, it would indeed be possible for the first grinding wheel to be set in a strictly radial direction against the effective surface of the machine component to be ground by moving the first grinding spindle transversely to its longitudinal extent and in an oblique direction towards the machine component. The machine component would have to be arranged in this case at a constant position of the associated machine bed. The device required for carrying out the method, however, becomes simpler if, according to the method according to the invention, the feed takes place by the machine component being displaced in the direction of its rotational and longitudinal axis relative to the first grinding wheel. Of this movement is attributable to the grinding point on the active surface only an obliquely directed component, but deviates only by a small amount from the direction of the longitudinal axis, so that there is almost a vertical grinding in the usual sense. This results in a smaller force component in the radial direction of the active surface, so that it is possible to work with optimized feeds when grinding the tread. This also reduces the grinding time, and nevertheless results in improved accuracy in the grinding state of the effective surface.

The subsequent internal grinding of the longitudinal bore can be made by longitudinal grinding. In this case, the method of peel grinding in question, in which immediately ground to the final diameter. But it is also possible that the inner wall of the longitudinal bore is ground by Einstechschleifen.

The last method is particularly in question if, according to a further advantageous variant of the method of the inner wall of the longitudinal bore individual axial sections are ground.

In a further embodiment of the method according to the invention, at least three grinding wheels are provided, which are brought into their operative position by pivoting of three grinding spindles carrying the grinding wheels. By the method thus expanded further grinding operations can be carried out, or it can, for example, the internal cylindrical grinding also take place in the usual stages of roughing and finish grinding.

Finally, the order is not mandatory, after which first the active surface of the machine component and then the inner walls of the longitudinal bore are ground. The reverse order is also possible. The grinding expert will determine the order of operations depending on the design of the machine component, because in this case the amount of heating during grinding and the type of clamping is important.

• mit einer Spanneinrichtung zum einseitigen Einspannen des Maschinenbauteils an seinem Außenumfang und zu seinem Drehantrieb,
• mit einem Schleifspindelschlitten, der in einer quer zu der Rotations- und Längsachse des Maschinenbauteils verlaufenden Richtung verfahrbar ist,
• mit einer Einrichtung zur Längsverschiebung des Maschinenbauteils in Richtung seiner Rotations- und Längsachse,
• mit einem Schleifspindelstock, der über eine senkrecht zu der Verschiebungsebene des Schleifspindelschlittens verlaufende Schwenkachse an diesem befestigt ist und mindestens zwei jeweils für sich in Wirkstellung schwenkbare Schleifspindeln trägt,
• mit einer an der ersten Schleifspindel angeordneten und durch diese angetriebenen ersten zylindrischen Schleifscheibe, die zum Senkrechtschleifen der an dem Maschinenbauteil befindlichen Wirkfläche bestimmt ist sowie eine axiale Erstreckung aufweist, die größer ist als die radiale Schrägerstreckung der Wirkfläche,
• und mit einer an der zweiten Schleifspindel angeordneten und durch diese - angetriebenen zweiten zylindrischen Schleifscheibe, die einen kleineren Durchmesser als die erste Schleifscheibe aufweist und zum Innenrundschleifen der Längsbohrung des Maschinenbauteils bestimmt ist,
• wobei je nach Schwenkstellung des Schleifspindelstockes entweder die erste Schleifscheibe mit ihrer rotierenden Umfangsfläche an der zu schleifenden Wirkfläche des Maschinenbauteils anliegt und durch Längsverschiebung des Maschinenbauteils (5) ein Senkrecht-Schleifen der Wirkfläche (24) bewirkt oder die Achse der zweiten Schleifscheibe im Abstand parallel zur Rotations- und Längsachse des Maschinenbauteils verläuft.

According to claim 7, the invention also relates to a system consisting of a grinding device and a rotationally symmetrical machine component of the already mentioned in connection with the method known manner, wherein the machine component is ground in the grinding device. The system is provided

• with a clamping device for unilaterally clamping the machine component on its outer circumference and to its rotary drive,
• with a grinding spindle slide, which is movable in a direction transverse to the rotational and longitudinal axis of the machine component,
• with a device for longitudinal displacement of the machine component in the direction of its rotational and longitudinal axis,
• with a grinding headstock, which is fastened to it via a pivot axis extending perpendicular to the displacement plane of the grinding spindle slide and carries at least two grinding spindles which can be pivoted in each case in operative position,
• with a first cylindrical grinding disk arranged on the first grinding spindle and driven thereby, which is intended for the vertical grinding of the active surface located on the machine component and has an axial extension which is greater than the radial oblique extension of the effective surface,
• and with a second grinding wheel arranged on and driven by the second grinding spindle, which has a smaller cylindrical grinding wheel Diameter as the first grinding wheel and is intended for internal cylindrical grinding of the longitudinal bore of the machine component,
• depending on the pivot position of the wheelhead either the first grinding wheel rests with its rotating peripheral surface on the active surface to be ground of the machine component and by longitudinal displacement of the machine component (5) perpendicular grinding of the active surface (24) causes or the axis of the second grinding wheel at a distance parallel to Rotation and longitudinal axis of the machine component runs.

If the procedure described in the introduction is followed when operating this system, first the grinding spindle slide is moved in the correct manner to the clamped machine component and the grinding headstock is rotated such that the first grinding spindle with the cylindrical peripheral surface of the first grinding wheel attached to it touches the working surface of the grinding wheel Machine component is employed. The first grinding spindle must in this case occupy an angular position relative to the rotational and longitudinal axis of the machine component, which is less than 90 °. Then, the active surface can be ground by the first grinding wheel in the vertical grinding process, that is, with its known advantages. Subsequently, the grinding spindle slide is moved transversely to the rotational and longitudinal axis of the machine component slightly outward and rotated on the grinding spindle slide grinding headstock about its pivot axis until the axis of rotation of the second grinding spindle with the associated second grinding wheel is approximately in the rotational and longitudinal axis of the machine component. The second grinding wheel is then moved into the longitudinal bore of the machine component and delivered radially, so that the internal cylindrical grinding of the longitudinal bore is made. In this way, all necessary grinding operations on the machine component are done in a single setup. A prerequisite, however, in any case, a first grinding wheel, the axial extent or width is greater than the oblique extension of the active surface, because only by the vertical grinding process of the active surface can be done with all its advantages.

A structurally advantageous development of the system according to the invention is that in the arrangement of two grinding spindles on the wheelhead whose axes are parallel to each other and the two grinding wheels on the same side of the grinding headstock are mounted. In this way, there is a change between the two machining operations with only small displacement and pivoting paths of the grinding headstock.

If further grinding operations are to be carried out or one of the individual operations is to take place in several stages, then it may be advantageous if, according to a further embodiment, three grinding spindles are mounted on the grinding headstock at an angular distance of 120 °, each with one grinding wheel. In this case, one of the three grinding spindles is then optionally brought into the operative position.

Advantageously, the clamping device is a chuck with centrally adjustable clamping jaws, which is also driven for rotation. Such chucks have proven to be reliable and are known.

According to a further embodiment, it is advantageous if the clamping device is located on a grinding table, which is movable relative to the grinding spindle slide in the rotational and longitudinal axis of the machine component. The feed movement during grinding of the active surface is then carried out by the grinding table is moved with the machine component relative to the first grinding wheel in the longitudinal direction of the machine component.

• Figur 1 ist eine Ansicht die zu dem erfindungsgemäßen System gehörende Vorrichtung in einer ersten Bearbeitungsphase.
• Figur 2 stellt eine der Figur 1 entsprechende Ansicht in der darauffolgenden Bearbeitungsphase dar.
• Figur 3 hat eine Schnittdarstellung des zu schleifenden Maschinenbauteils zum Gegenstand.
• Figur 4 erläutert die Durchführung des erfindungsgemäßen Verfahrens in der ersten Bearbeitungsphase.
• Figur 5 ist die der Figur 4 entsprechende Darstellung der zweiten Bearbeitungsphase.

The invention will be explained in more detail in an embodiment with reference to figures. The figures show the following:

• FIG. 1 is a view of belonging to the system according to the invention device in a first processing phase.
• FIG. 2 represents one of the FIG. 1 corresponding view in the subsequent processing phase.
• FIG. 3 has a sectional view of the machine component to be ground on the subject.
• FIG. 4 explains the implementation of the method according to the invention in the first processing phase.
• FIG. 5 is that the FIG. 4 corresponding representation of the second processing phase.

FIG. 1 first explains schematically the system according to the invention, with which the inventive method can be performed. Here, a device for grinding the machine component in the view from above is shown. On a machine bed 1 is a workpiece headstock 2. This is provided with a chuck 3, which is driven for rotation and at which there are four jaws 4, which are centrally controlled. 5 designates the machine component to be ground, which will be explained in more detail below.

The workpiece headstock 2 has a longitudinal axis 6, which at the same time means the axis of rotation of the chuck 3. When the machine component 5 is clamped in the chuck, the workpiece headstock and the machine component 5 have a common common rotational and longitudinal axis.

In the illustrated embodiment, the workpiece headstock 2 is attached to a grinding table 7. Together with the workpiece headstock 2, the grinding table 7 is moved in the direction of the longitudinal axis 6, which is at the same time the usual Z-axis in the sense of a CNC control.

On the machine bed 1 is still a grinding spindle slide 9, which can be moved by means of a Verstellmotors 8 in a direction transverse to the longitudinal axis 6 of the workpiece spindle stock 2. On the grinding spindle slide 9 a grinding headstock 10 is arranged pivotable about a pivot axis 11. The pivoting direction is indicated by the rotary arrow B. The pivot axis is perpendicular to the grinding spindle slide 9 and will thus normally run vertically.

On the wheelhead are a first grinding spindle 12 and a second grinding spindle 13. The rotation and drive axes of the two grinding spindles are parallel. On the grinding spindle 12, a first grinding wheel 14 is attached. The grinding spindle 13 is equipped with a second grinding wheel 16 which is mounted on a grinding mandrel 15. As the FIG. 1 clearly shows, the first grinding wheel 14 and the second grinding wheel 16 are both arranged on the same side of the grinding headstock 10.

In FIG. 1 is the first processing phase of the grinding process shown, in which the first grinding wheel 14 abuts with its peripheral surface on the effective surface to be ground of the machine component 5.

FIG. 2 on the other hand, in otherwise the same view represents the second processing phase in which the axis of the second grinding wheel 16 extends at a distance parallel to the longitudinal axis 6 of the workpiece spindle stock 2.

To move from the position according to FIG. 1 in the position according to FIG. 2 To get to first, the grinding spindle slide 9 in the direction of the X-axis, ie transverse to the direction of the longitudinal axis 6, something to be driven outwards. Then, the grinding headstock 10 can be pivoted on the grinding spindle slide 9 by an angle of slightly more than 90 °, after which the second grinding spindle 13 with the second grinding wheel 16 from FIG. 2 apparent position. The pivoting movement is also in FIG. 2 again indicated by the rotary arrow B.

FIG. 3 shows the machine component to be ground 5 in an enlarged sectional view. The machine component is rotationally symmetrical to the rotation and longitudinal axis 17. It consists of a hub part 18 and a conical flange 19 and is penetrated over its entire length by the longitudinal bore 20.

The longitudinal bore can be stepped, so that does not have to be ground on the entire length. In general, it is sufficient if the longitudinal bore on the axial sections 21, 22 and 23 is ground. The conical flange 19 is formed at its large end face and end face in the manner of a flat truncated cone with a straight contour in cross section.

The illustrated machine component serves as a conical disk in a continuously variable transmission; in the assembled state slides on the active surface 24, a chain, a belt or the like. In this case, two active surfaces 24 face each other; by changing the mutual distance, the radius on which the chain or belt slides can be changed, resulting in different gear ratios. Thus, it becomes clear how important the accurate and careful grinding of the active surface 24 for the function of the finished continuously variable transmission.

This in FIG. 3 shown machine component has a cylindrical clamping surface 25 and flat stop surface 26, which serve for clamping in the already mentioned chuck 3. The clamping jaws 4 enclose the cylindrical clamping surface 25, while the axial stop is ensured by the stop surface 26 on the clamping jaws 4. The machine component 5 is thus tensioned on one side outside, so that the entire end face extending in FIG. 3 located on the right side, and especially the active surface 24 are free for editing. In addition, a small grinding wheel can be inserted into the longitudinal bore 20 for the purpose of internal grinding.

In FIG. 4 is the first processing phase shown, in which the active surface 24 of the machine component 5 is ground by vertical grinding.

Here, first of all - as already mentioned - the machine component 5 is clamped between the clamping jaws 4 of the chuck 3. The workpiece spindle is then driven for rotation, usually by a variable speed electric motor. Thus, the machine component 5 rotates about its rotational and longitudinal axis 17, which is now identical to the longitudinal axis 6 of the workpiece spindle stock 2.

The first grinding spindle 12 with the first grinding wheel 14 has already been based on FIG. 1 described position. By now the machine table 7 with the workpiece headstock 2 in the direction of the Z-axis in FIG. 4 The axial extension 28 of the second grinding wheel 14 is slightly larger than the radial oblique extension of the machine component 5. Thus, the entire active surface 24 by the first grinding wheel 14 sanded in the vertical grinding process with the advantages described above.

The first grinding wheel 14 is a ceramic-bonded CBN wheel, which ensures long service life.

FIG. 5 illustrates the second processing phase, which is in accordance with the view FIG. 2 equivalent. In the illustration according to FIG. 5 is the second grinding wheel 16 already in the The axis of rotation of the second grinding wheel 16 is located at a distance parallel to the common longitudinal axis 6 of the workpiece spindle stock 2 and the machine component 5. In this phase, an internal cylindrical grinding at the sections 21, 22 and 23 the longitudinal bore 20 made, this cylindrical grinding can be done as longitudinal grinding, peeling grinding or plunge grinding.

References list

1

machine bed

2

Workhead

3

chuck

4

jaws

5

machine part

6

longitudinal axis

7

grinding table

8th

adjusting

9

Grinding spindle slide

10

Wheelhead

11

swivel axis

12

first grinding spindle

13

second grinding spindle

14

first grinding wheel

15

grinding arbor

16

second grinding wheel

17

Rotation and longitudinal axis

18

hub part

19

cone flange

20

longitudinal bore

21

axial section

22

axial section

23

axial section

24

effective area

25

clamping surface

26

stop surface

27

contact line

28

axial extent

Claims (11)

1. Method for grinding a rotationally symmetrical machine component (5) which is provided with a longitudinal bore (20) and one frontal end face of which is designed as an active face (24) in the form of a flat frustoconical surface area with a contour of rectilinear cross section, characterized in that, on the machine component (5) held on one side on its outer circumference, that active face (24) is first ground by the vertical grinding method, in that a first cylindrical grinding wheel (14) is advanced with its rotating circumferential face vertically against the active face (24), in that the machine component (5) is displaced in the direction of its axis of rotation and longitudinal axis (17) with respect to the first grinding wheel (14), the axial extent (28) of the first grinding wheel (14) covering the oblique radial extent of the active face (24), and in that, in the same chucking fixture, the inner wall of the longitudinal bore (20) is then ground, in that a second grinding wheel (16) of smaller diameter is introduced into the longitudinal bore (20) of the machine component (5) and advanced radially against the inner wall as a result of the pivoting of a grinding-spindle headstock (10) which carries at least the first (14) and the second (16) grinding wheel.
2. Method according to Claim 1, characterized in that the inner wall of the longitudinal bore (20) is ground by longitudinal grinding.
3. Method according to Claim 2, characterized in that the inner wall of the longitudinal bore (20) is ground by rough grinding.
4. Method according to Claim 1, characterized in that the inner wall of the longitudinal bore (20) is ground by plunge-cut grinding.
5. Method according to one of the preceding claims, characterized in that individual axial portions (21, 22, 23) of the inner wall of the longitudinal bore (20) are ground.
6. Method according to one of the preceding claims, characterized in that at least three grinding wheels are brought into their active position as a result of the pivoting of three grinding spindles carrying the grinding wheels.
7. System, consisting of a grinding device and of a rotationally symmetrical machine component (5) which is provided with a longitudinal bore (20) and one frontal end face of which is designed as an active face (24) in the form of a flat frustoconical surface area with a contour of rectilinear cross section, the machine component being ground in the grinding device,

   - with a chucking arrangement for chucking the machine component (5) on one side along its outer circumference and for its rotary drive,

   - with a grinding-spindle slide (9) which is movable in a direction running transversely with respect to the axis of rotation and longitudinal axis (17) of the machine component (5),

   - with an arrangement for the longitudinal displacement of the machine component (5) in the direction of its axis of rotation and longitudinal axis (17),

   - with a grinding-spindle headstock (10) which is fastened to the grinding-spindle slide (9) via a pivot axis (11) running vertically with respect to the plane of displacement of the said grinding-spindle slide (9) and which carries at least two grinding spindles (12, 13) each pivotable independently into the active position,

   - with a first cylindrical grinding wheel (14) which is arranged on the first grinding spindle (12) and is driven by this and which is intended for the vertical grinding of the active face (24) located on the machine component (5) and has an axial extent (28) which is greater than the oblique radial extent of the active face (24),

   - and with a second cylindrical grinding wheel (16) which is arranged on the second grinding spindle (13) and is driven by this and which has a smaller diameter than the first grinding wheel (14) and is intended for the internal cylindrical grinding of the longitudinal bore (20) of the machine component (5),

   - and, depending on the pivoting position of the grinding-spindle headstock (10), either the first grinding wheel (14) bearing with its rotating circumferential face against the active face (24), to be ground, of the machine component (5) and causing vertical grinding of the active face (24) as a result of the longitudinal displacement of the machine component (5), or the axis of the second grinding wheel (16) running parallel to and at a distance from the axis of rotation and longitudinal axis (6) of the machine component (5).
8. System according to Claim 7, characterized in that, when two grinding spindles (12, 13) are arranged on the grinding-spindle headstock (10), their axes run parallel to one another and the two grinding wheels (14, 16) are mounted on the same side of the grinding-spindle headstock (10).
9. System according to Claim 8, characterized in that three grinding spindles are mounted on the grinding-spindle headstock, each with a grinding wheel, at an angular interval of 120 degrees in each case.
10. System according to one of Claims 7 to 9, characterized in that the chucking arrangement is a clamping chuck (3) having centrally adjustable clamping jaws (4).
11. System according to one of Claims 7 to 10, characterized in that the chucking arrangement is located on a grinding table (7) which is movable with respect to the grinding-spindle slide (9) along the axis of rotation and longitudinal axis (17) of the machine component (5).

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