GRINDING MACHINE AND METHOD FOR GRINDING WORKPIECES THAT HAVE AXIAL BORES AND PLANAR EXTERNAL SURFACES TO BE MACHINED ON BOTH SIDES

Abstract

A grinding machine for machining workpieces includes a workpiece headstock and two grinding headstocks. A first grinding headstock has two grinding spindles each with one grinding wheel for grinding first and second planar and non-planar external surfaces. A second grinding headstock has a grinding spindle having a grinding wheel for grinding a central bore in the workpiece, and a clamping device to clamp the workpiece. First, the bore and the first planar and any non-planar external surface are ground on one side of the workpiece. Then, the workpiece is clamped in the bore. The second planar external surface can then be ground in the same grinding machine with one of the grinding wheels of the first headstock. The clamping device attached to the second grinding headstock is such that the central axis of the clamping device is exactly aligned with the central axis of the workpiece headstock.

Claims

1.-22. (canceled)

23. Grinding machine for the complete machining of workpieces with a central bore, planar and/or non-planar external surfaces, which has a first grinding headstock with an external grinding wheel for the machining of the external surfaces, a workpiece headstock for the clamping of the workpiece and a second grinding headstock with an internal grinding wheel for the machining of the internal surface of the bore, whereby the workpiece can be clamped in a first clamping position in a clamping chuck of the workpiece headstock for the machining of at least a first one of the planar external surfaces pointing in the direction of the second grinding headstock and of the bore on a central axis, characterized in that, the second grinding headstock supports a clamping device, which is movable in relation to its central axis in such a way that it can be inserted into the already ground bore of the workpiece, and the workpiece can be clamped at a place by the clamping device in a second clamping position, in which the central axis of the clamping device in the second clamping position with the central axis of the clamping chuck aligns in the first clamping position, and both clamping positions exist at least temporarily simultaneously, whereby, by means of the external grinding wheel, in the second clamping position after the first clamping position has been released, at least a second one of the planar external surfaces pointing in the direction of the workpiece headstock can be ground.

24. Grinding machine in accordance with claim 23, characterized in that, the clamping device is movable axially and is, in particular, controlled by CNC.

25. Grinding machine in accordance with claim 23, characterized in that, the clamping device is a mandrel, which is driven in a rotary manner.

26. Grinding machine in accordance with claim 25, characterized in that, the mandrel has a hydro-expansion element.

27. Grinding machine in accordance with claim 23, characterized in that, the first grinding headstock has two grinding spindle units with corresponding grinding wheels for the machining of the first and of the second planar external surfaces, whereby the grinding spindle units move into the X1 and Z1 axial direction and from the grinding headstock around a B-axis in a CNC-controlled manner.

28. Grinding machine in accordance with claim 27, characterized in that, the first grinding headstock has a truing spindle with a diamond truing disk for the truing of the internal grinding wheel.

29. Grinding machine in accordance with claim 23 characterized in that, the grinding spindle unit positioned on the second grinding headstock can be moved in the X2 and Z2 axial direction in a CNC-controlled manner.

30. Grinding machine in accordance with claim 23, characterized in that, the workpiece headstock has two workpiece spindles, each with one clamping chuck, which are positioned opposite one another and can be swiveled, by means of a rotating unit, out of a first position, in which at least the first planar external surface and the bore of the workpiece to be ground can be ground, into a second position, in which the finish-ground workpiece is in a loading position.

31. Grinding machine in accordance with claim 23, characterized in that, the first and the second grinding headstock are each positioned on a cross-slide unit.

32. Grinding machine in accordance with claim 23, characterized in that, the internal and the external grinding wheel can be brought into grinding engagement in a controlled manner in such a way that at least the first planar external surface and the bore are at least temporarily simultaneously ground.

33. Process for the complete grinding of workpieces with a central bore and planar and non-planar external surfaces on a grinding machine with the features in accordance with claim 23, in which a workpiece clamped in a tool headstock is, first of all, essentially finish-ground on its first external surfaces by means of an external grinding wheel and is finished in the bore, at least temporarily by means of an internal grinding wheel; and a clamping device positioned on a grinding headstock supporting the internal grinding wheel is subsequently inserted into the bore; and the workpiece is likewise clamped at least temporarily simultaneously as the clamping by the workpiece headstock in such a way that the central axes of the clamping chuck of the workpiece headstock and the clamping device on the second grinding headstock align with one another; after which the clamping is released by the workpiece headstock, and thereafter the second external surfaces positioned essentially opposite the first external surfaces are ground.

34. Process in accordance with claim 33, in which the clamping device is controlled hydraulically from its release position into its clamping position and vice versa.

35. Process in accordance with claim 33, in which the clamping device is controlled mechanically, electrically or electromagnetically out of its release position and into its clamping position and vice versa.

36. Process in accordance with claim 33, in which the workpiece headstock swivels a loaded workpiece into a grinding position.

37. Process in accordance with claim 33, in which the first planar and non-planar external surfaces are ground essentially simultaneously by means of a profiled grinding wheel.

38. Process in accordance with claim 33, in which the second planar external surfaces are ground in a straight infeed plunge grinding process.

39. Process in accordance with claim 33, in which the second planar external surfaces and additional non-planar external surfaces are ground essentially simultaneously in the angular infeed plunge grinding process by means of the grinding wheel.

40. Process in accordance with claim 33, in which cooling lubricant for the internal grinding wheel is fed through the interior of the workpiece headstock.

41. Process in accordance with claim 33, in which the cooling lubricant is distributed in the bore on the internal grinding wheel through the conical design of the end of the internal grinding wheel.

42. Process in accordance with claim 33, in which the internal grinding wheel rough-grinds the bore with the first grinding area and finish-grinds it with the second grinding area.

43. Process in accordance with claim 42, in which the internal grinding wheel rough-grinds the bore with the first grinding area by means of infeed plunge grinding.

44. Process in accordance with claim 42, in which the internal grinding wheel with the first grinding area rough-grinds the bore by means of peel grinding.

Description

[0036] Additional advantages, characteristics, and possibilities of use of the present invention will now be illustrated in further detail by means of the diagrams. The diagrams depict the following:

[0037] FIG. 1: A top view of the grinding machine in accordance with the invention in basic representation;

[0038] FIG. 2: A partial sectional view of the cutting plane A-A for the workpiece headstock from FIG. 1;

[0039] FIG. 3: In basic representation, the simultaneous engagement of a profiled grinding wheel of the first grinding headstock and of the internal grinding wheel of the second grinding headstock;

[0040] FIG. 4: A position of the second grinding headstock, in which the clamping device is aligned in relation to the central axis of the clamping device of the workpiece headstock and is shortly before the insertion of the workpiece into the bore;

[0041] FIG. 5: A subsequent position of the second grinding headstock at the position in accordance with FIG. 4 upon insertion into the bore of the workpiece and the clamping device in the clamping position;

[0042] FIG. 6: The workpiece clamped into the bore by means of the clamping device which, in the straight plunge grinding process, undergoes a grinding of the opposing planar side;

[0043] FIG. 7: An enlarged depiction of the grinding of the opposing planar side by means of a straight plunge grinding wheel;

[0044] FIG. 8: A grinding of the opposing planar side by means of an angular infeed grinding process or angular plunge grinding wheel, respectively;

[0045] FIG. 9: An internal grinding of the bore of the workpiece by means of an internal grinding wheel with a rough-grinding and a finish-grinding area with simultaneous feeding of cooling lubricant through the workpiece headstock to the grinding position; and

[0046] FIG. 10: An internal grinding of the bore with an internal grinding wheel with a rough-grinding and a finish-grinding area upon rough-grinding in the peel grinding process and finish-grinding in the plunge grinding process.

[0047] FIG. 1 depicts, in basic representation, a top view of the grinding machine in accordance with the invention, which also carries out the process in accordance with the invention. A first grinding headstock 2, a second grinding headstock 17, and a workpiece headstock 9, which are present in a defined relation to one another, are positioned on a machine base 1. The first grinding headstock 2 supports a first grinding spindle 3, on which a grinding wheel 3.1 is positioned. An additional grinding spindle 4, which accommodates an additional grinding wheel 4.1, is attached to the first grinding headstock 2. The grinding wheel 4.1 is profiled and serves for the grinding of the first planar external surfaces 14.1, as well as the non-planar external surfaces 14.4 of a workpiece 14, which is clamped in a clamping device 12 of a first workpiece spindle 10 which, being controlled by CNC, sets the axis C1 of the workpiece 14 in rotation. The profiled grinding wheel 4.1 is brought into grinding engagement on the workpiece 14 controlled by CNC by means of the axes X1 and Z1 of the first grinding spindle unit 2.

[0048] The first grinding headstock 2 has, in addition, a B-axis proceeding perpendicularly in the drawing plane, so that, by means of a swiveling movement around the B-axis of the grinding headstock 2, the profiled grinding wheel 4.1 or the grinding wheel 3.1 can optionally be brought into engagement with the workpiece. The grinding wheel 3.1 is provided for the grinding of the second planar external surface 14.2 on the workpiece. In the representation depicted in FIG. 1, the second planar external surface 14.2 is clamped within the clamping device 12 of the workpiece spindle 10, and thus cannot be ground while this is clamped.

[0049] The profiled grinding wheel 4.1 is configured in such a way and can be brought into grinding engagement on the external contour to be ground, that the internal grinding wheel 19.1, which is positioned on the second grinding headstock 17 with the grinding spindle 19, can simultaneously be brought into the bore 14.3 of the workpiece 14, at least temporarily, so that the bore 14.3 of the workpiece can be completely finish-ground, without cycle time being lost as a result. In contrast to that, the grinding operations are carried out in succession on the external surfaces and on the internal surface in grinding machines or processes in accordance with the state of the art.

[0050] The second grinding headstock 17 is configured as a combination unit, while an additional clamping device 20 is mounted on the grinding headstock, which clamping device, can, on the one hand, be moved by means of the CNC axes X2 and Z2 with the grinding headstock 17 within the X2-Z2 plane, and whereby, in addition, the clamping device 20 can undergo an axial displacement 21 along a central axis 20.1.

[0051] After the planar 14.1 and the non-planar external surfaces 14.2, as well as the internal surface of the bore 14.3, are completely finish-ground, the grinding headstock 17 aligns, in relation to its central axis into the X2 direction process, to the extent that the central axis 20.1 of the clamping device 20 aligns with the central axis 10.1 of the workpiece spindle 10 of the workpiece headstock 9. In this position of the headstock 17, the clamping device 20 is inserted into the bore 14.3 and accommodates the workpiece in the form of a clamping. The workpiece is thereby clamped over a defined, relatively short time, both in the clamping device 12 of the workpiece headstock 9, and by means of the clamping by the clamping device 20. After the clamping of the workpiece 14 has been carried out by means of the clamping device 20, the clamping device 12 is detached from the workpiece headstock 9 and the second grinding headstock 17 is moved. As a result, the second planar external surface 14.4 is released, so that, by means of the first grinding headstock 2, the grinding wheel 3.1 can enter into the grinding position. The grinding wheel 3.1 is configured as a planar grinding wheel, so that the second planar external surface 14.2 is produced by way of straight plunge grinding. It is thus possible to finish-grind a workpiece, particularly in the form of a gearwheel for transmissions, in one and the same grinding machine in relation to the front, as well as the rear external side surfaces and the internal surfaces of the bore. Thereby, it can be ensured that the individual ground portions on the workpiece are finish-ground with slight dimensional, positional, and form tolerances to one another.

[0052] The workpiece headstock 9 is configured in such a way that two spindles, which are positioned opposite one another in a 180° placement, are present on the workpiece headstock 9. In the diagram, on the right side, the workpiece headstock 10 is provided with its central axis 10.1 and the clamping device 12 attached to it. On the left side of FIG. 1, the second workpiece spindle 11 is provided with its central axis 11.1 and the clamping device 13. While the workpiece spindle, with its clamping device 12, has clamped a just ground or even a completely finish-ground workpiece 14, a workpiece 15 still not ground is already clamped with the second workpiece spindle 11, i.e., with its clamping device 13. The workpiece 15 can be driven by the second workpiece spindle 11 by means of a CNC-controlled axis C2. The workpiece headstock 9 is now swivelably positioned in such a way that, first of all, the workpiece 15 newly accommodated in the loading position can be brought into a grinding position. This takes place in a very short time because of the double arrangement of the workpiece spindle on the workpiece headstock 9. It is achieved thereby that the auxiliary process times in the grinding machine are minimized.

[0053] A truing spindle 16 with a truing disk 16.1, by means of which the grinding wheels 3.1 and 4.1 of the first grinding headstock can be trued, is additionally attached to the workpiece headstock 9. The first grinding headstock 2 has an additional truing spindle 5 with a diamond truing disk 6, by means of which the internal grinding wheel 19.1, which is also termed a grinding mandrel, can be trued.

[0054] Next to the machine base 1 of the grinding machine, the feeding of the raw parts to the grinding machine and the removal of the finished parts from the mandrel 20 and from the grinding machine take place fully automatically with a handling system, not depicted, through the feed belt/discharge belt 22 which is positioned, in FIG. 1, left side, next to the machine base 1 of the grinding machine. In order to feed the workpieces to the grinding machine or to unload them from the machine after they have been finish-ground, special handling devices are provided, which are not described separately here, since they are not of separate significance for the present invention. Through the arrangement of two workpiece spindles 10, 11 on the workpiece headstock 9, it is possible to carry out the loading with new raw workpieces 15 provided for the grinding in the auxiliary process time. The swiveling of the raw workpieces from the loading position requires, with the present workpiece headstock 9, for example, less than 2 seconds. The loading into the clamping chuck 13 can, in regard to the time necessary for it, be carried out in all cases, to the extent that this is not critical, in a shorter time than the grinding time requires for the complete grinding of the workpiece 14. In any event, the loading into a clamping chuck with the clamping and the corresponding handling movements usually take place within a time of approx. 8 seconds. Since this takes place in the auxiliary process time, i.e., in a time in which the workpiece 14 is machined, the entire cycle time for a workpiece can be further reduced, which has a favorable effect on the production costs of the workpieces.

[0055] FIG. 2 depicts, in a partial section along the plane A-A in accordance with FIG. 1, how the arrangement of the two workpiece spindles 10, 11 on the workpiece headstock 9 is designed. Both workpiece spindles 10, 11 can be swiveled, by means of a rotating unit 23, from a grinding position which, in FIG. 2, corresponds to the placement of the workpiece 14, into a loading position which, in FIG. 2, corresponds the workpiece 15. Thus, the two workpiece spindles 10, 11 can alternately be moved into the machining position. The machine base 1 is marked schematically in this partial sectional view A-A of the workpiece headstock. As a result of the fact that the workpiece spindle 10, i.e., in FIG. 2, the lower workpiece spindle for the grinding of the external and internal contours of the workpieces 14, is positioned closer to the machine base during the grinding engagement, the thermal change of the grinding machine is eliminated to the greatest extent possible and the rigidity of the entire assembly is, because of the improved leverage effect, likewise greater.

[0056] As a result, a greater precision can be achieved during the grinding process, in relation to the attainable maximum dimensional and shape precisions on the finish-ground workpiece. As already mentioned in connection with the description of FIG. 1, during the grinding operation on the workpiece 14, a loading onto the workpiece spindle 11 or of the clamping device 13 is carried out with a new raw workpiece 15. That means that the loading takes place during the grinding process. The loading movements are programmed in such a way that the loading cycle, for example, does not coincide with the point in time of obtaining the final dimension on the workpiece 14. Through this special programming, an additional optimization of the attainable quality of the workpiece 14 in the grinding machine is possible. The loading and unloading of the workpiece is, therefore, carried out in so-called auxiliary process time. In order to carry out the actual grinding process on the workpiece 14, only a swiveling process of the workpiece 15 into the position of the workpiece 14 in accordance with FIG. 2, which takes only a small amount of time, needs to be carried out. The workpiece 15 becomes, so to speak, a workpiece 14, if the grinding operation is taken up on the workpiece or if this has completely ended. As a result, the actual time for the unloading or the cycle time does not count, but only the swiveling time out of the loading position into the grinding position.

[0057] An enlarged partial view of the area of the grinding machine in accordance with FIG. 1 is depicted in FIG. 3, which depicts the workpiece headstock 10 with the workpiece 14 clamped, in which the grinding wheel 4.1 is in engagement therewith and the internal grinding wheel 19.1 for the grinding of the internal surface of the bore 14.3 is likewise engaged with the second grinding headstock 19. During the machining, the workpiece 14 is—as depicted in this figure—firmly clamped in the clamping chuck 12. For the precise alignment and for the determination of the longitudinal position in the clamping chuck, the workpiece 14 is in contact with a stop ring 24 in the clamping chuck. Now, with such a plane of reference, the workpiece 14, which is firmly clamped in the clamping chuck 12 by means of the workpiece spindle 10 and rotationally driven controlled by CNC in relation to its external contour, in the form of the first planar external surfaces 14.1 and non-planar external surfaces 14.4, is ground by means of the profiled external grinding wheel 4.1 on the grinding spindle 4. The bore 14.3 of the workpiece 14 is ground, simultaneously with the internal grinding wheel 19.1, which is driven in a rotary manner by the grinding spindle 19 attached to the second grinding headstock 17. These two machining steps can be carried out at least partially or completely simultaneously. The latter is obviously only applicable if the machining times for both machining processes are approximately equally long. The time-parallel machining of the external surfaces 14.1 and 14.4, as well as of the bore 14.3, leads to reduced machining times or cycle times, and thus to reduced workpiece expenses. Since both the drives for the external grinding wheel 4.1, and those for the internal grinding wheel 19.1, are controlled by CNC, both machining processes can, if this should be advantageous for a specific workpiece, also be carried out partially or completely, in staggered succession. This could, indeed, increase the cycle time, but, for considerations of grinding technology, can definitely be advantageous for specific workpieces.

[0058] In FIG. 3, the feeding direction of the internal grinding wheel 19.1 or of the grinding pin, during the grinding, is indicated in the direction of arrow 30. In principle, however, it may also be advantageous to carry out the feeding direction in the reverse direction. This depends greatly on the structural configuration of the grinding machine. By this measure, rigidity values and temperature drifts out of the grinding machine can be positively exploited, so that the grinding results are further optimized in regard to precision.

[0059] A clamping device 20 is also attached, preferably in the form of a mandrel, which is depicted in the area of the headstock 17 depicted in the partial section, to the same casing as that on which the grinding spindle 19 is attached to the second grinding headstock 17. The mandrel is driven in an automatic, axially displaceable (21) and rotary manner. Because of the possibility that the second grinding headstock 17 is also configured along its X2 and Z2 axis in a movable manner, the mandrel 20 can align its central axis 20.1 with an aligning orientation to the central axis 10.1 of the workpiece spindle 10 and, in this position, carry out, in relation to the support position of the workpiece in the space, a clamping that is identical to the clamping by the workpiece spindle 10 with the clamping chuck 12. In this way, a high precision of the machining of the workpiece is possible since, for each of the two clampings, the same position of the workpiece in relation to the central axis is reduced in the clamped condition.

[0060] The grinding with both the internal grinding wheel 19.1 and the external grinding wheel 4.1, mostly takes place with CBN coating, whereby ceramically bound CBN coating is preferably used. Other abrasives, such as corundum or other bonds of the CBN coatings, for example, are obviously also possible, whereby the respective optimal grinding coatings are each selected in accordance with the machining task.

[0061] In the mandrel 20 depicted in FIG. 3 and, specifically, on its left-hand side, a clamping element 25, which is automatically opened or closed, i.e., is clamped by the grinding program, is shown in the end area and is provided for the actual clamping of the workpiece 14 in the bore 14.3. In this case, a hydro-expansion clamping element is depicted. Such a hydro-expansion clamping element is expanded through being acted upon with a hydraulic fluid for the activation of the clamping. For release, the pressure of the hydraulic fluid is reduced correspondingly. Other clamping elements, such as collet chucks or even an internal clamping chuck, i.e., a mechanical chuck, are obviously also possible.

[0062] In FIG. 4, the final machining of the planar and non-planar external surfaces 14.1, 14.4 has taken place, and the internal surfaces of the bore 14.3 of the workpiece 14 have been finished and the grinding headstock 17 has been moved, through its CNC-controlled axes, in such a way that the internal grinding wheel 19.1 is positioned in parallel to the central axis 10.1 of the workpiece spindle in such a way that the mandrel 20 is located immediately in front of the bore 14.3 of the workpiece 14 in order to finally be able to be brought into its corresponding axial displacement 21 for the purpose of the clamping in this bore 14.3. The geometry of the workpiece spindle 10, as well as the grinding spindle 19 for the internal grinding wheel 19.1, is thereby selected in such a way that there are no obstructing contours between the workpiece headstock and the grinding spindle 19 or the internal grinding wheel 19.1.

[0063] In order to achieve an improved distribution of the cooling lubricant, even in the internal grinding wheel 19.1 or the grinding pin, upon a feeding of the cooling lubricant through the workpiece spindle 10, it is advantageous to provide the grinding pin with a conical extension 19.2.

[0064] FIG. 5 now depicts, in relation to FIG. 4, the moment at which the mandrel 20 is, after its axial displacement 21, moved into the bore 14.3 and holds the workpiece 14 there in a clamped manner. The clamping is thus carried out in such a way that the central axis of the mandrel 20.1 aligns precisely with the central axis 10.1 of the workpiece spindle 10. At this moment, the workpiece is clamped, both with the clamping chuck 12 of the workpiece spindle 10, as well as with the mandrel 20 of the grinding headstock 17, and thus clamped twice, so to speak. Only if the complete clamping of the workpiece 14 is carried out by means of the mandrel 20 in the bore 14.3 the clamping chuck 12 of the workpiece 14 can be detached and the grinding headstock 17 moved along its CNC-controlled axis and, specifically so, to the right in FIG. 5.

[0065] The clamping and the handing over of the workpiece 14 from the clamping chuck 12 to the mandrel 20 can take place upon a stationary or a rotating workpiece spindle 10. Upon a clamping with rotating workpiece spindle 10, the mandrel 20 must then also rotate with the same rotational speed and the same rotational direction. Thereby, the reclamping time can be optimized.

[0066] If the grinding headstock 17 has been moved with the workpiece 14 (see FIG. 6), then the second planar external surface 14.2 can be ground with the external grinding wheel 3.1, which is held on the corresponding grinding spindle 3 and is driven thereby, since the workpiece 14 is now clamped completely and reliably and precisely with the mandrel 20 in the inner bore of the workpiece by means of the hydro-expansion clamping element 25.

[0067] If the workpiece has been clamped with the mandrel 20 and the mandrel has set the workpiece into rotation, which is indicated by the circular arrow on the right-hand side, then the second planar external surface 14.2 is also ground by a likewise-driven external grinding wheel 3.1. The internal grinding wheel 19.1 is, with its grinding spindle 19 in this position, moved to the side, so to speak, and brought out of engagement.

[0068] The mandrel is configured in such way that its concentricity error is, in general, only a few μm. As a result, in accordance with this process and with this grinding machine, highly precise workpieces can be produced in a single grinding machine on both sides and on one and the same grinding machine, in the sense of a complete machining of the workpieces.

[0069] Depending on the configuration of the workpiece 14, it is, naturally, also possible for non-planar external surfaces to be ground on the opposing planar side 14.2. In such a case, for example, a profiled grinding wheel can be used instead of the straight plunge grinding wheel 3.1 and, namely, of the type of external grinding wheel 4.1 depicted in FIG. 3.

[0070] The machining situation in accordance with FIG. 6 is depicted in FIG. 7, in enlarged representation, whereby the second planar external surface 14.2 is additionally stepped. With the planar grinding wheel 3.1, both parts of the planar external surface 14.2 can obviously be reliably ground.

[0071] The position for the grinding of the second planar external surface 14.2 is depicted in FIG. 8 by analogy to FIG. 6, but by means of an external grinding wheel 3.1, which is used in the angular plunge grinding process. This external grinding wheel 3.1 is then positioned, during the corresponding arrangement with its grinding spindle 3, on the first grinding headstock 2 (not depicted here). With such an arrangement, additional non-planar external surfaces can also be ground on the opposing planar side, i.e., cylindrical or conical sections on the workpiece on its second side, if applicable, for which either the external grinding wheel 3.1 depicted or a profiled grinding wheel in accordance with its embodiment given in FIG. 3, but under another angular placement or adjustment, can be used. Whether the opposing planar side by way of a straight plunge grinding or an angular plunge grinding is machined depends on the grinding task required and, naturally, also on the geometry of the workpiece 14. The grinding machine in accordance with the invention can, in this regard, be correspondingly adjusted on an individual basis on the workpiece and the grinding task adjusted, without the basic design depicted in FIG. 1 having to be differently configured.

[0072] An additional preferred embodiment of the grinding machine is depicted in FIG. 9, upon the grinding of the bore 14.3 of the workpiece 14 by means of the internal grinding wheel 19.1. For the sake of clarity, the external grinding wheel 4.1 (see FIG. 3) has been omitted here. The internal grinding wheel 19.1 is configured as a grinding mandrel and has two grinding areas 19.1.1 and 19.1.2 with different grinding coatings. The first, advancing grinding coating 19.1.1 serves for the rough-grinding of the internal surfaces of the bore 14.3, and the second, trailing grinding coating 19.1.2 serves for the finish-grinding of the bore. Since the diameter of the second grinding coating 19.1.2 is greater than that of the first grinding coating 19.1.1, after the ending of the rough-grinding by means of the first grinding coating 19.1.1 the grinding headstock 17 with the grinding spindle 19, is obliquely adjusted to the central axis corresponding to the X2 axis, and this second grinding area 19.1.2 is inserted into the bore for the finish-grinding. The first grinding area 19.1.1 then projects into the open space within the workpiece spindle 10. As a general rule, the rough-grinding wheel should be the one which is furthest away from the bearing of the spindle. Such two-stage internal grinding wheels 19.1 are used, above all, if the bore 14.3 of the workpiece 14, for example, has increased grinding allowances or if the grinding allowances vary strongly from the pre-machining. This rough-grinding can also be advantageous, depending on which material is to be machined.

[0073] A grinding coating 19.1.2 with ceramically bound CBN is also used here for the finish-grinding, so that correspondingly good surface qualities and a high precision are achieved. For the rough-grinding, grinding can likewise be carried out with ceramically bound CBN; however, a grinding coating 19.1.1 with galvanically coated CBN coating can likewise be used. Grinding wheels with galvanically coated CBN generally have a greater stock removal capacity, and they are, as a result, particularly well suited for rough-grinding processes. Upon such a two-stage internal grinding wheel 19.1, the optimization of the grinding processes and the achievable precision are possible with the same technical machine design.

[0074] During the grinding, it is necessary for cooling lubricant 26 to be supplied to the grinding wheel 19.1 which is engaged. In accordance with this embodiment, the cooling lubricant 26 is fed through the interior of the workpiece spindle 10 and moved forward to the actual grinding engagement. In order to obtain an improved distribution of the cooling lubricant 26, the forward part, i.e., the rough-grinding area 19.1.1 of the internal grinding wheel 19.1, can have a conical attachment for the improved distribution of the cooling lubricant 26. Such a conical attachment does not have to be present, however. The advantage of such a conical attachment 27 on the forward end of the internal grinding wheel 19.1 consists of a lower turbulence of the cooling lubricant 26 upon the feeding to the grinding position, whereby the supply of the grinding zone with cooling lubricant, and thereby the grinding conditions, are improved. As a result, this has a positive effect on the precision of the grinding result and the surface properties of the finish-ground workpiece.

[0075] FIG. 10 shows an additional preferred embodiment, analogous to that depicted in FIG. 9, in which the internal grinding wheel 19.1 is likewise provided in two stages, with a first, advancing grinding area 19.1.1 and a second, trailing grinding area 19.1.2. The first, advancing grinding area 19.1.1 has a greater diameter than the second, trailing grinding area 19.1.2. The first grinding area 19.1.1 is constructed clearly narrower than the one of the second grinding area 19.1.2, since, with the rough-grinding area 19.1.1 by way of the peel grinding, a relatively large allowance is ground away, whereby CBN is advantageously used as a grinding coating. If the rough-grinding is ended, then the internal grinding wheel 19.1 is moved so far into the bore, with its second grinding area 19.1, that the bore can be finish-ground by way of the internal cylindrical grinding, particularly also the plunge grinding. Thereby, the first grinding area 19.1.1 is moved so far into the open space within the workpiece spindle 10 that the second grinding area 19.1.2 can be moved, through the X2 axis of the grinding spindle 19, to the internal surface of the bore 14.3 to be ground.

[0076] The forward grinding area 19.1.1 of the internal grinding wheel 19.1 likewise has a conical attachment 27, which serves for the more uniform distribution of the cooling lubricant 26 to the corresponding grinding engagement point.

[0077] The arrows indicated in the clamping chuck 12 on the clamping jaws are intended to show that the clamping chuck holds the workpiece 14 in the clamped condition, as long as surfaces to be ground are machined.

[0078] In this implementation of the rough-grinding, the grinding time on the workpiece can be optimized by the rough-grinding with the first grinding area 19.1.1 with the infeed direction of the internal grinding wheel 19.1 in the direction of the clamping chuck 12 on the clamped workpiece 14, in such a way that the “running-in movement” of the grinding pin 19.1 is already used for the rough-grinding. This makes it possible for complete final grinding to be carried out with a very low grinding allowance with the second grinding area 19.1.2 of the internal grinding wheel 19.1. In this way, the entire grinding time for the bore 14.3 can be completely optimized.

[0079] By combining a grinding headstock for the internal grinding and a clamping device into a single construction unit, the advantages of the grinding spindle, which in any event requires a high stability, can be used for both parts of the combined unit for clamping devices requiring a high precision.

LIST OF REFERENCE NUMBERS

[0080] 1 Machine base

[0081] 2 First grinding headstock

[0082] 3 Grinding spindle unit

[0083] 3.1 External grinding wheel

[0084] 4 Grinding spindle unit

[0085] 4.1 External grinding wheel

[0086] 5 Truing spindle for grinding mandrel (bore grinding)

[0087] 6 Diamond truing disk

[0088] 7 X1-/Z1 CNC axes

[0089] 8 B-axis

[0090] 9 Workpiece headstock

[0091] 10 Workpiece spindle

[0092] 10.1 Central axis

[0093] 11 Workpiece spindle

[0094] 11.1 Central axis

[0095] 12 Clamping chuck

[0096] 13 Clamping chuck

[0097] 14 Workpiece

[0098] 14.1 First planar external surface

[0099] 14.2 Second planar external surface

[0100] 14.3 Bore

[0101] 14.4 Non-planar external surface

[0102] 15 Workpiece

[0103] 16 Truing spindle for grinding wheels (external grinding)

[0104] 16.1 Truing disk

[0105] 17 Second grinding headstock

[0106] 18 X2-/Z2 CNC axes

[0107] 19 Grinding spindle unit

[0108] 19.1 Internal grinding wheel/grinding pin

[0109] 19.1.1 First grinding area

[0110] 19.1.2 Second grinding area

[0111] 19.2 Conical extension

[0112] 20 Mandrel

[0113] 20.1 Central axis

[0114] 21 Axial displacement

[0115] 22 Feed belt/discharge belt

[0116] 23 Rotating unit

[0117] 24 Stop ring

[0118] 25 Clamping element

[0119] 26 Cooling lubricant

[0120] 27 Front conical attachment of the internal grinding wheel

[0121] 30 Infeed direction