Method for Grinding an Indexable Insert and Grinding Wheel for Carrying Out the Grinding Method
The invention relates to a method for grinding an indexable insert, wherein its narrow sides are moved along the circularly contoured circumferential surface of a rotating grinding surface and are ground thereby, having the following movements for the grinding process that are coordinated to one another using CNC control"
a) the indexable insert is caused to rotate about a rotational axis that runs perpendicular to its plane;
b) a grinding spindle that bears and drives the grinding wheel and the rotational axis of the indexable insert are displaced relative to one another in two displacement axes that run perpendicular to one another, the displacement axes being located in parallel planes or the same plane,
c) the grinding spindle and the indexable insert are pivoted relative to one another about a pivot axis that is perpendicular to the planes in which the displacement axes and the rotational axis of the indexable insert are located,
in accordance with the preambles to claims 1 through 3
Such a grinding method is known from DE 42 40 053 Al. In this known method, the narrow sides of the indexable insert are ground with a narrow grinding wheel that has a cylindrical circumferential contour. The grinding wheel is driven by a grinding spindle that can be displaced in two honzontal planes that are perpendicular to one another The indexable insert is disposed in a clamping device that can be pivoted about a vertical axis The clamping device has two clamping plungers that clamp the indexable insert on its wide sides and cause it to rotate A desired clearance angle can be ground on the narrow sides of the indexable inserts in that the
clamping device is pivoted about the vertical pivot axis During the grinding process, the following four movements are continuously coordinated with one another using CNC control the rotational movement of the indexable insert about its driven rotational axis (C axis), the movement of the grinding spmdle towards the first displacement axis (Z axis) and the second displacement axis (X axis), and the pivot movement of the clamping device about the vertical pivot axis (B axis) In this manner it is possible to grind flat narrow sides on the indexable insert that have the desired clearance angle
Past conventional grinding processes, in which the narrow sides of the indexable insert are ground with pot-shaped grinding wheels, are intended to be improved using the known method in accordance with DE 42 40 053 Al However, there were difficulties in accomplishing the grinding process with four movement axes controlled in an interpolating manner using CNC Therefore in the known method in accordance with DE 42 40 053 Al it is also expressly required that during grinding of the narrow sides the cylmdncally contoured narrow grinding wheel is moved back and forth, oscillating, in the axial direction overlapping the controlled direction, which is intended to continuously correct the contact of the individual grinding grains on the grinding wheel Nevertheless, in practice it has been demonstrated that the grinding results did not lead to the anticipated improvement The results of the grinding, that is the quality of the ground narrow sides, demonstrated that the grinding wheel wear was too high and that there was unsatisfactory precision
Presumably therefore, even after the publication of the suggestion according to DE 42 40 053 Al, additional suggestions for impioving grinding with pot-shaped inserts were provided , such as e g DE 43 01 214 Al Although the grinding result may have been improved, the pot-shaped grinding wheels provided to this end were particularly complicated, specifically they were constructed in multiple parts Since frequently bevels must also be ground when grinding indexable inserts, at least two cylindncal abrasive layers that were m different planes were necessary The narrow sides of the indexable insert were ground with the one abrasive layer that was placed lower, while the required bevels were to be ground with the second abrasive layer disposed in a different axial plane Grinding with pot-shaped grinding wheels also involved
difficulties in terms of mutual accessibility of the surfaces to be ground on the indexable insert Therefore the improved method was also not economically satisfactory when gnnding indexable inserts with pot-shaped grinding wheels
Known in a simple device for finish grinding worn indexable inserts in accordance with DE 295 14 702 Ul is finish grinding the indexable inserts using a grinding wheel that has the sectional profile of a double cone The device is for gnnding indexable inserts whose wide sides have a rhombic contour The indexable inserts are fastened to a tool earner Grinding wheel and tool carrier can be moved relative to one another in two horizontal directions and vertically By raising and lowenng the gnnding wheels, a hollow gnnd can be formed on the indexable insert or a clearance angle can be formed The reason the contour of the grinding wheel is in the shape of a double cone is so that different narrow sides of the indexable insert are ground successively on the one or other tapered surface of the gnnding wheel. For this, the clamped indexable insert must merely be pivoted on the tool earner, there being at least one linear contact This type of gnnding is not comparable to a grinding method that is to be performed economically dunng mass production of indexable inserts
The underlying object of the invention is therefore to create a gnnding method of the type initially cited in the foregoing, with which method indexable inserts can be mass produced economically and in which indexable inserts the narrow sides are high quality, even when using sintered materials that are difficult to cut, and the desired dimensional, shape, and positional tolerances are maintained.
A first solution for this object succeeds with the all of the features of claim 1 In it, a grinding wheel is used that has a forward-tapering leading area and a cyhndncal trailing area attached thereto The gnnding method is conducted such that the leading area, which forms a lead angle relative to the contour of the indexable insert, performs longitudinal grinding using the pnnciple of peel gnnding and thus is the first to pass over the narrow side of the indexable insert The leading area accomplishes rough grinding, for instance rough cutting The majonty of the
gnnding allowance is removed by the leading area. Because the leading area, at the site of its largest diameter, transitions to the cyhndncal trailing area, there is a direct transition from rough gnnding to finish gnnding on the surface of the narrow sides The two processes can thus occur simultaneously.
It has been demonstrated that in the inventive procedure very good gnnding results are obtained in conjunction with significantly improved service life for the grinding wheels, 1 e the wear on the grinding wheels is significantly reduced This can be attributed to the fact that during peel gnnding cooling conditions are substantially improved with a grinding wheel that tapers forward in the longitudinal direction of the grinding process so that the grinding wheel is protected and a minimum amount of heat is introduced into the workpiece in the gnnding zone The connected trailing area is clearly shorter than the leading area, it can be e g only one-third of the gnnding wheel thickness When gnnding by means of the trailing area, there is linear contact between the gnnding wheel and the narrow side of the indexable insert because the gnnding wheel is disposed perpendicular to the narrow side of the indexable insert However, at this point only relatively little matenal is removed and the contact length is short Thus here as well the heat stress on the grinding wheel and the workpiece is limited The clearly reduced thermal stress on the gnnding wheel has proved to be cntical when gnnding hard sintered matenals that are difficult to cut It was possible to clearly increase the service life of the grinding wheel in this manner In addition, blanking dies made of ceramic matenals can be machined using the gnnding method
A second solution to the underlying object of the invention results from all of the features in claim 2 The applicant has determined that slightly pivoting the gnnding wheel with respect to the indexable insert can lead to results that are as good as the onentation perpendicular to the contour of the narrow side when grinding in accordance with the first solution. When proceeding in accordance with claim 2, the gnnding wheel forms a lead angle in the leading area and forms a clearance angle in the trailing area in terms of the narrow side of the indexable insert that is to be ground This also occurs when the trailing area of the grinding wheel is cylmdncally contoured, as in the procedure in accordance with claim 1 In this case, the gnnding wheel only
grinds with the tapering leading area up to the greatest grinding wheel diameter As can be seen, lead angle and clearance angle lead to a further improvement m cooling The method in accordance with claim 2 can also occur using peel gnnding With particularly hard sintered materials the rough grinding and finish grinding may be performed with two different gnnding wheels
However, if the trailing area is also embodied tapering starting from the largest diameter of the gnnding wheel, a larger lead angle and a larger clearance angle result without the gnnding wheel having to be tilted or pivoted particularly sharply with respect to the indexable insert
A third solution for the object underlying the invention is provided in claim 3 Applicant has determined that the trailing area may even be completely omitted and that the procedure corresponding to claim 2 may also be performed with a gnnding wheel that has in its circumferential area a tapenng contour, for instance a conical contour, and is guided with the small diameter in front over the narrow sides of the indexable insert The advantage of this solution is also particularly based on the improved cooling that results on the surface of the gnndmg wheel and the indexable insert.
Various designs are possible for the three aforesaid procedures and they are provided m the subordinate claims
When the leading area m claims 1 and 2 is characterized as being forward-tapenng, this indicates that the grinding wheel moves with respect to an indexable insert that is axially stationary. Fundamentally, however, only a relative movement between indexable insert and gnnding wheel is necessary in the advancing direction of the longitudinal grinding so that the term "forward" is only a guideline for the nature of the grinding wheel
Since indexable inserts having a clearance angle have a larger and a smaller wide side, there is the question of the direction in which the gnnding wheel should be moved relative to the indexable insert Fundamentally, both directions of movement are possible, that is, a movement
by the insert from the small wide side to the larger wide side and vice versa However, it has been found that with hard sintered matenals and higher grinding power, in accordance with a first design of the inventive method it is better to guide the grinding wheels from the larger wide side of the indexable inserts via its narrow sides to the smaller wide side The reason for this is that when grinding from the larger wide side the endangered cutting edge does not chip as easily in the area having the large sectional dimension as when this cutting edge is reached by the gnndmg wheel from the narrow side Grinding pressure and thermal load are thus lower when grinding this cutting edge.
In accordance with another design of the method, peel grinding can also occur in the procedure in accordance with claim 2 or 3
In accordance with another advantageous design, it is provided that the tapenng of the leading area and/or of the trailing area (claims 1 and 2) or even the entire tapenng contour of the rotating gnndmg wheel (claim 3) is shaped as an envelope of a cone The circumferential lines of the leading area, trailing area, or gnnding wheel that can be seen in the longitudinal section are thus straight lines In terms of production engineering, this is a particularly favorable embodiment when dressing the grinding wheel However, it must be noted this is by no means mandatory for technical grinding reasons The tapering may thus also be embodied curved, e g as a spherical surface or hollow fillet, this being largely a function of the particular method being used for hard matenals to be ground
In many cases, in particular in the procedure in accordance with claim 1, it is enough to undertake the entire graduation of the grinding, that is from rough cutting to finish gnnding, using the leading area and trailing area of the grinding wheel With the conical gnnding wheel in accordance with claim 3 finish machining can also be accomplished in one pass using longitudinal and peel gnnding. However, in the case of particularly hard sintered matenals and particularly high grinding stress, it can also be necessary to divide the gnnding process between two gnnding wheels This is the subject matter of another advantageous design of the inventive method, successive grinding processes having different gnnding wheel specifications but the
same fundamental structure being used for rough cutting and finish cutting The grinding machines necessary for this, for instance having pivotable grinding headstocks that bear two grinding spindles, belong to the prior art
Despite the leading area and trailing area (claims 1 and 2), the grinding wheels necessary for performing the inventive method have a relatively simple structure Since the fundamentally disk-like basic shape of the grinding wheel is retained, mutual accessibility of the indexable insert having the circularly contoured circumferential surface, but also having the lateral surfaces of the grinding wheel, does not present any difficulties. In accordance with another advantageous design of the inventive method it is therefore possible with nothing further to gnnd the bevels of the indexable insert, which are located between the narrow sides and the wide sides, in the same clamping using the lateral surfaces of the rotating grinding wheel Thus, in one and the same clamping, the narrow sides of the indexable insert and the bevels that are arranged between the individual flat narrow sides or between the narrow sides and the wide sides of the indexable insert can be ground with one and the same grinding wheel
Finally, there is a particularly simple and thus advantageous option for performing the inventive method when the indexable inserts do not have to have a clearance angle. The narrow sides of the indexable inserts then run perpendicular to their wide sides, and the relative pivotabihty of grinding wheel and indexable insert about a special pivot axis can be omitted
The invention also relates to a special grinding wheel for performing the grinding method in accordance with claim 1 or 2 and according to claims 4 through 6 and 8 through 10, which refer thereto, the inventive grinding wheel is provided in claim 11 Corresponding to the different grinding processes that are to be performed using the leading area and the trailing area of the grinding wheel, the cutting material disposed on the circularly contoured circumferential surface of the grinding wheel always comprises diamond grains having a ceramic or metallic bond; however, the specifications for the grinding wheel differ in the leading area and in the trailing area In the leading area, the cutting material and its bond can apply in particular to the
requirements for rough cutting and in the trailing area they can apply to finish cutting, that is e g they can be finer
One refinement of the inventive grinding wheel is comprised in that, for grinding the bevels, provided on the lateral surfaces of the grinding wheel as well is an abrasive layer that can then have grinding wheel specifications that differ from those in the circularly contoured circumferential surface of the grinding wheel
As has already been noted for the design of the method, in accordance with another design the inventive grinding wheel can have the tapermg of the leading area and/or of the trailing area in the shape of an envelope of a cone without a determination being necessary for technical grinding reasons
The invention shall now be explained in greater detail using exemplary embodiments depicted in drawings. The figures depict the following
Figure 1 depicts a view from above onto the essential parts of a grinding machine with
which the inventive method is performed,
Figure 2A is a side view and a partial sectional view of an indexable insert to be ground,
Figure 2B provides a detail from the partial sectional view in accordance with Figure 2A,
Figure 3 depicts a longitudinal section and an end view in the area of the workpiece
receiving unit for the workpiece headstock for the grinding machine in accordance with Figure 1,
Figure 4 depicts the principles for the applicable influencing variables when grinding the
narrow sides of an indexable insert,
Figure 5 depicts the gnndmg contact at the beginning of longitudinal grinding;
Figure 6 depicts a phase of the gnnding process that has progressed further,
Figure 7 depicts a gnnding phase at the end of the finish grinding,
Figure 8 illustrates a gnnding method that has been modified relative to Figures 4 through
7, the rotating gnndmg wheel being slightly pivoted relative to the indexable insert,
Figure 9 is a depiction similar to Figure 8, the rotating grinding wheel having a modified
contour, however;
Figure 10 clarifies how, with the inventive grinding method, even bevels can be ground on the indexable insert using the same gnnding wheel and the same clamping,
Figure 11 corresponds to Figure 10, the bevel being ground on the opposing side of the
indexable insert,
Figure 12 explains another vanant of the inventive method, the gnndmg wheel having a continuous tapenng contour in its circumferential area
Figure 1 provides a schematic depiction of a view from above of a gnnding machine that corresponds to a normal universal circular and non-circular gnnding machine Only the essential parts are depicted A gnnding table 2 on a machine bed 1 can be moved in the direction of a first displacement axis 3 The displacement axis 3 is identified as the Z axis, as is normal for gnnding machines The gnnding table 2 bears a workpiece headstock 4 having a receiving unit 5 and a centenng insert 6 The tailstock 7, having a centering receiving unit 8 and a thrust bolt 9, is ananged at a distance from the workpiece headstock 4 Workpiece headstock 4 and tailstock 7 can normally be moved towards one another, but also can normally be moved jointly The
indexable insert 10 to be ground can be affixed to, centered, and securely clamped on the centering insert 6 using the thrust bolt 9 of the tailstock 7
The indexable insert 10 can be rotationally dnven using the workpiece headstock 4. Thus, during grinding the indexable insert 10 rotates about the dnven rotational axis 11 The latter is generally called the C axis in grinding machines Arranged at a distance from the gnnding table 2 is a gnnding headstock 12 that can be pivoted about a pivot axis 13 that runs perpendicular to the plane of the drawing The pivot axis 13 is normally called the B axis The gnnding headstock 12 can be moved relative to the gnndmg table 2 in the direction of the second displacement axis 15 by means of a slide 14 The second displacement axis 15 is normally called the X axis in grinding machines
The gnnding headstock 12 bears a first grinding spindle 16 having a first gnnding wheel 18 and a second gnnding spindle 17 having a second grinding wheel 20 Each of the two grinding wheels 18, 20 has a circularly contoured circumferential surface 18a The associated rotational axes of the first and second grinding spindles 16, 17 and gnnding wheels 18, 20 are labeled 19 and 21
A dressing spindle 22 having a dressing wheel 23 also belongs to the grinding machine and the two grinding wheels 18 and 20 can be positioned against it for dressing
The ability of the grinding headstock 12 to pivot about the pivot axis 13 permits the first gnnding wheel 18 and the second grinding wheel 20 to be pivoted selectively into gnndmg contact with the indexable insert 10 and also ensures that the required pivot movement of the grinding wheel dunng grinding is possible. In this case the pivot movement of the gnnding headstock 12 about the pivot axis 13 is included in the CNC control for the entire gnnding machine
Thus, in the gnnding machine for performing the inventive gnnding method, four possible CNC-controlled movements are mutually coordinated with one another
Rotation of the indexable insert 10 about the driven axis 11 (C axis),
Displacement of the indexable insert 10 via the grinding table 2 in the direction of
the first displacement axis 3 (Z axis),
Displacement of the grinding headstock 12 relative to the grinding table 2 in the
direction of the second displacement axis 15 (X axis),
Pivoting of the grinding headstock 12 about the pivot axis 13 (B axis)
The first and second displacement axes 3,15 and the driven rotational axis 10 are located in parallel planes, they can even all be m the same plane The pivot axis 13 is perpendicular to these planes or this plane
What the CNC-controlled coordination of the four movement options attains, like a non-circular grinding machine, is that the narrow sides of the indexable insert 10 obtain the desired contour In general flat surfaces having bevels in the transitions from the narrow sides to the two wide sides are sought
The indexable insert 10 to be ground is depicted in detail in Figures 2A and 2B At the beginning of the grinding process its wide sides 10a, b are already finish-machined Indexable inserts generally comprise sintered hard metal or ceramic materials, the wide sides 10a, 10 can be can be produced with satisfactory accuracy and fineness just by sintering If higher accuracy is required, the wide sides are ground in a preceding work step By means of a fastening bore 26 the indexable inserts can for instance be exchanged and rotated in workpiece retaining elements In general they have a clearance angle 27 so that their narrow sides 24 run at an incline to the wide sides Therefore the one wide side 10a is larger than the other wide side 10b The narrow sides 24 transition into one another via bevels 25. Bevels 28 can also be worked m in the transition between the narrow sides 24 and the wide sides 10a, 10b, see Figure 2B. In this case, a bevel angle 29 occurs in the edge area. Recesses 30 can be located in the wide sides 10a, 10b of the indexable inserts, or the wide sides 10a, 10b can be formed by the recesses 30 The clearance angle 27 can be omitted in certain applications so that the narrow sides 24 run perpendicular to the wide sides 10a, b. The individual angles depend on the purpose for which the indexable
insert 10 will be used, especially the cutting task and the matenal to be machined that is to be cut with the indexable insert 10
Figure 3 provides an enlarged depiction of the details of the workpiece headstock. The aforesaid receiving unit 5 is fastened to the receiving part 31 for the workpiece headstock 4 using screws 32 The receiving unit 5 includes the clamping insert 6, which is provided with graduated bores in its longitudinal direction Longitudinally movable therein is a centering bolt 37 that is pre-stressed towards the tailstock 7 by a compression spring 34 The inner end of the compression spring 34 is supported against a pressure plate 35. The pressure plate 35 simultaneously retains the centering bolt 37 with a nut 36. Rotating about the dnven rotational axis 11 causes the clamping insert 6 to rotate The indexable insert 10 is placed on the centering bolt 37 and is also supported on the shoulder of the clamping insert 6 Since the workpiece headstock 4 and tailstock 7 can be positioned relative to one another, the indexable insert 10 is clamped securely between the clamping insert 6 and the thrust bolt 9 of the tailstock 7 and caused to rotate in a non-positive fit The structure depicted also enables rapid exchange, suitable for mass production, of the indexable inserts to be ground Parts handling for loading into and unloading from the device is preferably completely automatic
Figure 4 provides a schematic depiction of the grinding process and its fundamental determining variables The indexable insert 10, which is provided with a grinding allowance 38, is dnven to rotate about the driven rotational axis 11 The extended surface of one narrow side 24 forms the geometnc determining line 39 for the grinding process for this narrow side
The gnnding wheel 18 rotates about its rotational axis 19, the actual grinding body being clamped as usual between two clamping flanges 40. The rotating circumferential surface 18a of the gnnding wheel 18 is circularly contoured, i e , there is a circular contour m each radial plane of the grinding wheel However, in its active grinding area the grinding wheel 18 constitutes a leading area 41 and a trailing area 42 The leading area 41 is embodied tapenng in the axial direction The gnnding wheel 18 decreases from a greatest diameter 43 to a smaller diameter for its front lateral surface The front lateral surface is defined by the advancing direction 44 in
which the relative movement of the grinding wheel 18 takes place relative to the indexable insert 10 along the geometric determination lines 39. The indexable insert 10 can be moved and the grinding wheel can be stationary in the axial direction or vice versa
In Figure 4, the contour of the leading area 41 is depicted as a conical contour. The surface line of the leading area 41 that can be seen is thus a straight line However, this is by no means mandatory; the surface line can also be curved, e g convex or shaped as a concave fillet, depending on the technological requirements of the cutting process However, these shapes can also be freely determined depending on the shape of the workpiece and the grinding task Figure 4 also depicts that the mutual movement between the grinding wheel 18 and the indexable insert 10 in the advancing direction 44 begins with the larger wide side 10a and ends with the smaller wide side 1 Ob This is the generally preferred grinding direction because it reduces the risk that the circumferential edge of the indexable insert 10, which is disposed between the wide side 10a and the narrow side 24, will chip during grinding. However, it is also fundamentally possible to work with a different grinding direction so that the mutual movement begins with the smaller wide side 1 Ob
Connected to the leading area 41 is a trailing area 42 that in this instance is cylindncally contoured so that the diameter of the trailing area is also the largest diameter of the leading area The two areas transition into one another in the area of the largest diameter 43
The grinding method is controlled in that, for rough grinding, peel grinding occurs in the leading area 41 and finish grinding occurs in the trailing area 42 As is known, with peel grinding the grinding wheel 48 is positioned such that the entire grinding allowance 38 is removed in a single longitudinal pass Thus, while the peel grinding occurs using a tapering contour of the leading area, during finish grinding there is linear contact between the trailing area 42 and the narrow side 24 of the indexable insert 10
The grinding process occurs based on longitudinal grinding, the grinding wheel 18 being guided relative to the indexable insert 10, as is also illustrated in detail in Figures 1 through 7 Figures 5
through 7 depict the enlarged detail U from Figure 4, but m more advanced phases of the gnnding process
The rough grinding and finish grinding can be performed as rough cutting and finish cutting However, in certain applications, that is with sintered materials that are particularly difficult to cut, it can be useful to divide rough cutting and finish cutting between two different grinding wheels as the gnnding machine m accordance with Figure 1 makes possible in a known manner. In this case, the two grinding wheels 18 and 20 have the same fundamental structure but different gnnding wheel specifications
Even if the machining process is fundamentally based on longitudinal grinding, it must always be taken into consideration that the four different movements being continuously coordinated with one another with CNC control must be changed so that the desired result occurs
Figures 4 through 7 together depict the progress of the longitudinal gnnding with great clanty In accordance with Figure 4, the gnnding wheel 18 is first positioned against the indexable insert 10 and contacts the gnnding allowance 38 precisely with the leading area at the location of the larger wide side 10a In the phase in Figure 5, a majonty of the gnnding allowance has already been removed by the leading area 41 and the trailing area 42 is just about to be used. In accordance with Figure 6, there is complete linear contact between the trailing area 42 and the rough-ground nanow side 24 Although the rough gnnding has not yet concluded, the finish gnnding now begins with the entire axial extension of the trailing area 42 In Figure 7 the finish gnnding with the trailing area 42 has just ended and the grinding process has thus concluded It should be noted that the bevels 25 between the individual narrow sides 24 are also ground dunng the course of the gnnding process descnbed herein.
Figure 8 illustrates a gnnding process that has been modified compared to the grinding process depicted in Figures 4 through 7
The reference numbers for the depicted parts of the grinding machine and the indexable insert remain the same However, a new series of reference numbers has been added for the rotating grinding wheel 48, because although the latter itself has not been changed, it has been moved to a different pivot position relative to the indexable insert 10 While in accordance with Figure 4 the grinding wheel 18 is positioned perpendicular to the surface line of the narrow sides 24, in the depiction in accordance with Figure 8 the grinding wheel 48 is pivoted forward about the tilt angle 47. This can easily be adjusted and maintained by means of the pivot axis 13 The grinding wheel 48 again has a forward-tapering leading area 49 and a cylindrical trailing area 50 Because of this, the circularly contoured circumferential surface 48a forms a lead angle 45 in the leading area 49 with respect to the resultant narrow side 24 of the indexable insert 10 and a clearance angle 46 in the trailing area 50. The clamping flanges for the rotating grinding wheel 48 are again labeled 40, their rotational axis 51, and their largest diameter 52.
The grinding wheel 48 is guided relative to the indexable insert 10m the advancing direction 44 corresponding to longitudinal grinding on the narrow side 24 of the indexable insert 10 Peel grinding is preferred.
In the trailing area 50, it is no longer linear contact with the narrow side 24 of the indexable insert 10, but rather there is only point contact through the largest diameter 52 However, it has been demonstrated that even in this manner the desired contours can be reliably machined on the narrow sides 24 of the indexable insert 10. All of the machining can be done using peel grinding. If the grinding allowance 38 to be machined is greater, the contour can be ground in multiple steps; I e , the grinding allowance is removed incrementally The clearance angle 46 in the trailing area 50 leads to improved cooling because the linear contact between the indexable insert 10 and the trailing area 50 is eliminated
The subject-matter of Figure 9 is a variant of the method sequence illustrated in Figure 8 In this case, the contour of the trailing area 50 is not cylindrical, but rather tapers in opposition to the advancing direction 44 for longitudinal grinding, that is, it tapers toward the end of the grinding wheel 48 The contour of the tapering can preferably be conical, although other contours are also
conceivable with nothing further A larger lead angle 53 can be obtained in the leading area and a greater clearance angle 44 can be obtained in the trailing area 50 using the modified shape of the gnnding wheel in accordance with Figure 9 without the grinding wheel 48 having to be tilted more sharply relative to the lateral surface 24 of the indexable insert 10 Comparing the cutting angles 47 in Figures 8 and 9 illustrates this well Longitudinal grinding can be performed with nothing further in the method in accordance with Figure 9, as well
Finally, Figures 10 and 11 depict how bevels 28 that are located in transition area between the wide sides 10a, b and the narrow sides 24 can be ground with the same gnnding wheels 18 that grind the nanow sides 24 To this end, the wide sides 55, 56 of the grinding wheel 18 are also provided with an abrasive layer and are positioned laterally at an angle against the transition area between the wide sides 10a, b and the nanow sides 24 of the indexable insert 10
Thus, for performing the aforesaid gnnding method in accordance with the invention, gnnding wheels are required that have two different areas axially, specifically a leading area 41, 49 and a trailing area 42, 50. While the leading area 41, 49 is embodied tapenng towards the first lateral surface 55 of the gnnding wheel 18, 48, the trailing area 42, 50 can be embodied cyhndncal or also tapenng toward the second lateral side 56 Since indexable inserts 10 comprise sintered hard metal or ceramic matenals, the cutting matenal is formed by diamond grains with a ceramic or metal bond As a rule, the grinding wheel specifications in the leading area 41, 49 will be different from those m the trailing area 42, 50, because as a rule the leading area 41, 49 works like a type of rough grinding, that is, must remove larger quantities of matenal then the trailing area 42, 50 and works more coarsely. The trailing area 42, 50 can be finer and softer in terms of its gnnding specifications because the required surface characteristics must be attained primarily by the trailing area
The abrasive layers on the lateral surfaces 55, 56 of the gnnding wheels 18, 48 are also formed from ceramically or metallically bonded diamond grains and, conesponding to their purpose, which is to gnnd the bevels 28 on the indexable insert 10, themselves have different gnnding wheel specifications than the leading area 41 or the trailing area 42, 50
In fact, it has been found that advantageous results can be obtained when the method is performed with a grinding wheel that does not have any trailing area The grinding wheel then practically comprises only the leading area, that is, it has in its circumferential area a tapering contour, which in the simplest instance is a conical contour, and is guided, with its smallest diameter in front, across the narrow sides of the indexable inserts Figure 12 depicts this case
Figure 12 again depicts the indexable insert 10 with its wide sides 1 Oa, b and its narrow sides 24 Here, as well, the reference numbers are the same, as are those for the workpiece receiving unit for the grinding machine and as are the four essential movement axes C, B, X, and Z What is different from the previous depictions is that in this case the circularly contoured circumferential surface 58 of the grinding wheel 57 has a constant and continuously tapering contour, in the depicted exemplary embodiment it is that of the envelope of a cone with straight surface lines The conical form is not mandatory, however. Indexable insert 10 and grinding wheel 57 are again tilted or pivoted towards one another about the tilt angle 60 and are guided relative to one another as for longitudinal grinding The circumferential edge 61 formed on the larger lateral surface 63 of the grinding wheel 57 is in grinding contact with the indexable insert 10, and the smaller lateral surface 62 of the grinding wheel is onented forward in the advancing direction 64 of the longitudinal grinding As can be seen, a lead angle 59 is again formed between the circumferential surface 58 of the grinding wheel 57 and the narrow side 24 of the indexable insert 10
List of reference numbers
1 Machine bed
2 Grinding table
3 First displacement axis (Z axis)
4 Workpiece headstock
5 Receiving unit
6 Clamping insert
7 Tailstock
8 Centering receiving unit
9 Thrust bolt
10 Indexable insert
10a, b Wide side
11 Driven rotational axis (C axis)
12 Grinding headstock
13 Pivot axis (B axis)
14 Slide
15 Second displacement axis (X axis)
16 First grinding spindle
17 Second grinding spindle
18 First grinding wheel
18a Circularly contoured circumferential surface
19 First rotational axis
20 Second grinding wheel
21 Second rotational axis
22 Dressing spindle
23 Dressing wheel
24 Narrow side
25 Bevel (on narrow side)

26 Fastening bore
27 Clearance angle
28 Bevel (on wide side)
29 Bevel angle
30 Recess
31 Receiving part
32 Screw

34 Compression spring
35 Pressure plate
36 Nut
37 Centering bolt
38 Grinding allowance
39 Geometric determination line
40 Clamping flange
41 Leading area
42 Trailing area
43 Largest diameter
44 Advancing direction for longitudinal grinding
45 Lead angle for leading area
46 Clearance angle for trailing area
47 Tilt angle
48 Grinding wheel
48a Circularly contoured circumferential surface
49 Leading area
50 Trailing area
51 Rotational axis
52 Largest diameter
53 Lead angle for leading area
54 Clearance angle for trailing area
55 First lateral surface
56 Second lateral surface
57 Grinding wheel
58 Circularly contoured circumferential surface
59 Lead angle
60 Tilt angle
61 Large circumferential edge
62 Small lateral surface
63 Large lateral surface
64 Advancing direction for longitudinal grinding

Patent claims
1. Method for grinding an indexable insert (10), wherein its narrow sides (24) are moved
along the circularly contoured circumferential surface (18a) of a rotating grinding wheel (18) and are ground thereby, having the following movements for the grinding process that are coordinated to one another using CNC control:
a) the indexable insert (10) is caused to rotate about a rotational axis (11) that runs perpendicular to its plane;
b) a grinding spindle (16) that bears and drives said grinding wheel (18) and said rotational axis (11) of said indexable insert (10) are displaced relative to one another in two displacement axes (3, 15) that run perpendicular to one another, said displacement axes (3, 15) and said rotational axis (11) being located in parallel planes or the same plane;
c) said grinding spindle (16) and said indexable insert (10) are pivoted relative to one another about a pivot axis (13) that is perpendicular to the planes in which said displacement axes (3, 15) and said rotational axis (11) of said indexable insert (10) are located;
characterized in that
d) the grinding process is based on longitudinal grinding, said circularly contoured circumferential surface (18a) of said rotating grinding wheel (18) being guided relative to said narrow sides (24) of said indexable insert (10) beginning at the one wide side (10a) to the other wide side (10b) of said indexable insert (10);
e) during the longitudinal grinding a forward-tapering leading area (41) that is located on said grinding wheel (18) is used that acts on said narrow sides (24) of said indexable insert (10) by peel grinding in the context of rough grinding;
f) the trailing area (42) of said grinding wheel (18), which is connected to said leading area (41) and is disposed therebehind during longitudinal grinding, is cylindrically shaped and acts on said narrow sides (24) of said indexable insert (10) through linear contact in the sense of finish grinding.
2. Method for grinding an indexable insert (10), wherein its narrow sides (24) are moved
along the circularly contoured circumferential surface (48a) of a rotating grinding wheel (48) and are ground thereby, having the following movements for the grinding process that are coordinated to one another using CNC control:
a) the indexable insert (10) is caused to rotate about a rotational axis (11) that runs perpendicular to its plane;
b) a grinding spindle (16) that bears and drives said grinding wheel (48) and said rotational axis (11) of said indexable insert (10) are displaced relative to one another in two displacement axes (3, 15) that run perpendicular to one another, said displacement axes (3, 15) and said rotational axis (11) being located in parallel planes or the same plane;
c) said grinding spindle (16) and said indexable insert (10) are pivoted relative to one another about a pivot axis (13) that is perpendicular to the planes in which said displacement axes (3, 15) and said rotational axis (11) of said indexable insert (10) are located;
characterized in that
d) the grinding process is based on longitudinal grinding, said circularly contoured circumferential surface (48a) of said rotating grinding wheel (48) being guided relative to said narrow sides (24) of said indexable insert (10) beginning at the one wide side (10a) to the other wide side (10b) of said indexable insert (10);
e) during the longitudinal grinding a forward-tapering leading area (49) that is located on said grinding wheel (48) is used that acts on said narrow sides (24) of said indexable insert (10) by peel grinding in the context of rough grinding;
f) the trailing area (50) of said grinding wheel (48), which is connected to the largest diameter (52) of said leading area (49) and is disposed therebehind during longitudinal grinding, starting from said diameter (52) is cylindrically embodied or is embodied tapering towards the end;
g) said rotating grinding wheel (48) is guided in a pivot position relative to said narrow sides (24) of said indexable insert (10) such that said leading area (49) forms a lead angle (45, 53) and said trailing area (50) forms a clearance angle (46, 54) relative to said
narrow sides (24) and a point grinding contact occurs between said largest diameter (52) of said grinding wheel (48) and said narrow sides (24) of said indexable insert (10).
3. Method for grinding an indexable insert (10), wherein its narrow sides (24) are moved
along the circularly contoured circumferential surface (58) of a rotating grinding wheel (57) and are ground thereby, having the following movements for the grinding process that are coordinated to one another using CNC control:
a) the indexable insert (10) is caused to rotate about a rotational axis (11) that runs perpendicular to its plane;
b) a grinding spindle that bears and drives said grinding wheel (57) and said rotational axis (11) of said indexable insert (10) are displaced relative to one another in two displacement axes (3, 15) that run perpendicular to one another, said displacement axes (3, 15) and said rotational axis (11) being located in parallel planes or the same plane;
c) said grinding spindle and said indexable insert (10) are pivoted relative to one another about a pivot axis that is perpendicular to the planes in which said displacement axes (3, 15) and said rotational axis (11) of said indexable insert are located;
characterized in that
d) the grinding process is based on longitudinal grinding, said circularly contoured circumferential surface (58) of said rotating grinding wheel (57) being guided relative to said narrow sides (24) of said indexable insert (10) beginning at the one wide side (10a) to the other wide side (10b) of said indexable insert (10);
e) said rotating grinding wheel (57) has a tapering contour in its circumferential area and is guided with the smaller diameter over said narrow sides (24) of said indexable insert
(10);
f) said rotating grinding wheel (57) is guided in a pivot position relative to said narrow
sides (24) of said indexable insert (10) such that its circumferential surface (58) forms a
lead angle (59) relative to said narrow sides (24) and a point grinding contact occurs
between said largest diameter of said grinding wheel (57) and said narrow sides (24) of
said indexable insert (10).
4. Method in accordance with any of claims 1 through 3, characterized in that the relative movement between said rotating grinding wheel (18, 48) and said indexable insert (10) during longitudinal grinding begins at said larger wide side (10a) of said indexable insert (10) and ends at said smaller wide side (10b).
5. Method in accordance with claim 2 or 3, characterized in that the longitudinal grinding is performed using peel grinding.
6. Method in accordance with claim 1 or 2, characterized in that the tapering of said leading area (41, 49) and/or of said trailing area (50) is shaped like the envelope of a cone.
7. Method in accordance with claim 3, characterized in that the tapering contour of said rotating grinding wheel is shaped like the envelope of a cone.
8. Method in accordance with any of claims 1 through 7, characterized in that for rough cutting and finish cutting, successive grinding processes are provided with grinding wheels (18, 20) having different grinding wheel specifications but the same basic structure.
9. Method in accordance with any of claims 1 through 8, characterized in that bevels (28) of said indexable insert (10) that are located between said narrow sides (24) and said wide sides (10a, b) are ground in the same clamping with the lateral surfaces (55, 56) of said rotating grinding wheel (18).

10. Method in accordance with any of claims 1 through 3 or 5 through 9, characterized in that when grinding indexable inserts without an undercut the relative pivotability of rotating grinding wheel and indexable insert about a particular pivot axis is omitted.
11. Grinding wheel for performing the grinding method in accordance with claim 1 or 2 and in accordance with claims 4 through 6 and 8 through 10, which refer thereto, having a
circularly contoured circumferential surface (18a, 48a), characterized by the following features:
a) at least in its circumferential area in the axial direction said grinding wheel (18, 48) has two different areas;
b) starting from the greatest diameter of said circularly contoured circumferential surface (18a, 48a), the first area, which is the leading area (41, 49) during longitudinal grinding, is embodied tapering towards a first lateral surface (55);
c) the second area, which connects to the greatest diameter of the first area and which is the trailing area (42, 50) during longitudinal grinding, is embodied cylindrical or tapering towards the second lateral surface (56);
d) the cutting material comprises diamond grains, having a ceramic or metallic bond, the grinding wheel specifications in said leading area (41, 49) differing from those for said trailing area (42, 50).

12. Grinding wheel in accordance with claim 11, characterized in that at least one of its lateral surfaces (55, 56) is also provided with an abrasive layer, the cutting material of which comprises ceramically or metallically bonded diamond grains and the grinding wheel specifications of which differ from those in said circularly contoured circumferential surface (18a, 48a) of said grinding wheel (18, 48).
13. Grinding wheel in accordance with claim 11 or 12, characterized in that the tapering of said leading area (41, 59) and/or of said trailing area (42, 50) is shaped like the envelope of a cone.