EP3663043B1 - Grinding tool - Google Patents

Description

The present invention relates to a grinding tool for processing a workpiece, in particular laminated safety glass, comprising a carrier device with a central coupling area for coupling the grinding tool to a rotary drive of a grinding machine and a grinding layer which is arranged on the circumference of the carrier device and which has grinding segments that are in a Grinding direction are spaced from each other.

The invention further relates to a grinding machine comprising at least one rotary drive and at least one such grinding tool, wherein the at least one grinding tool is coupled or can be coupled to the rotary drive of the grinding machine via the central coupling area of the carrier device.

A grinding tool of the type specified is, for example, from WO 99/54089 A1 known. This grinding tool has a carrier disk and a grinding layer arranged on the circumference. This grinding layer in turn has a large number of recesses distributed over the circumference. These recesses are essentially V-shaped or U-shaped in a plan view.

Furthermore, from the EP 1 518 647 A2 , which forms the basis for the preamble of claim 1, a grinding tool is known which has a first group of grinding segments and a second group of grinding segments, which are formed by triangular shapes standing on the head and / or by grinding segments in parallelogram shape between triangular grinding segments.

The material that is removed when processing laminated safety glass with such grinding tools, however, forms a serpentine abrasive abrasion, as shown in FIG Figure 1 the present application is shown.

This results in a disadvantage that the material removed in the form of a serpentine abrasive material hinders the grinding process, so that the machining process has to be interrupted and the abrasive material removed.

The object of the invention is to avoid at least the disadvantage described above and to provide a grinding tool and an improved grinding machine which are improved compared to the prior art.

These objects are achieved by the features of independent claims 1 and 12.

Advantageous embodiments of the invention are defined in the dependent claims.

An essential idea with regard to the grinding tool according to the invention is that at least one first group of at least two grinding segments following one another in the grinding direction is provided, the grinding segments of this first group having a first orientation relative to the carrier device, and that at least, preferably precisely, one Another group of at least two grinding segments following one another in the grinding direction is provided, the grinding segments of the at least one further group having a second orientation deviating from the first orientation relative to the carrier device, and wherein the first and the at least one further group successively in the grinding direction on the Carrier device are arranged. This measure ensures that the material removed during a grinding process tears, so that no serpentine grinding abrasion occurs, which would hinder the grinding process.

According to one exemplary embodiment, it can be provided that the grinding segments of the groups provided each extend essentially over the same angular range of the carrier device. Preferably, exactly one further group of at least two grinding segments following one another in the grinding direction is provided, the grinding segments of the first group and of precisely one further group each essentially being the same Extend over an angular range of approx. 180 ° of the carrier device. If, on the other hand, three further groups of at least two grinding segments following one another in the grinding direction are provided, the grinding segments of the first group and the three additional groups each extend essentially over an angular range of approximately 90 ° of the carrier device.

In the case of a grinding machine comprising at least one rotary drive and at least one grinding tool, wherein the at least one grinding tool is coupled or can be coupled to the rotary drive of the grinding machine via the central coupling area of the carrier device, it can be provided that the grinding machine comprises at least, preferably precisely, two grinding tools, and wherein at least one of the at least two grinding tools is designed according to the invention, wherein the at least two grinding tools are adjacent to one another, preferably screwed to one another, or, preferably by means of at least one spacer, spaced from one another via the respective central coupling area of the carrier device with the rotary drive of the grinding machine.

Fig. 1

einen schlangenförmigen Schleifabrieb, welcher bei Verwendung eines Schleifwerkzeugs gemäß dem Stand der Technik auftritt,

Fig. 2a, 2b

jeweils eine perspektivische Ansicht eines Drehantriebes einer Schleifmaschine mit zwei damit gekoppelten Schleifwerkzeugen in zwei verschiedenen Ausführungsformen,

Fig. 3

einen Drehantrieb einer Schleifmaschine mit zwei damit gekoppelten und aneinander anliegenden Schleifwerkzeugen in einer Ansicht von vorne,

Fig. 4

einen Drehantrieb einer Schleifmaschine mit zwei damit gekoppelten und voneinander beabstandeten Schleifwerkzeugen in einer Ansicht von vorne,

Fig. 5

eine Detaildarstellung einer Umfangsfläche eines Schleifwerkzeugs,

Fig. 6

eine weitere Detaildarstellung der Umfangsfläche eines Schleifwerkzeugs gemäß einer weiteren Ausführungsform,

Fig. 7a-7h

weitere Detaildarstellungen eines Teilbereichs der Umfangsfläche eines Schleifwerkzeugs gemäß alternativen Ausführungsformen,

Fig. 8

ein Schleifwerkzeug in einer Schnittdarstellung, und

Fig. 9a-9c

jeweils weitere Schnittdarstellungen eines Schleifwerkzeugs mit unterschiedlich ausgebildeten Schleifsegmenten.

Further details and advantages of the invention are explained in more detail below on the basis of the description of the figures with reference to the drawings. Show in it:

Fig. 1

a serpentine abrasive abrasion, which occurs when using a grinding tool according to the prior art,

Figures 2a, 2b

each a perspective view of a rotary drive of a grinding machine with two grinding tools coupled therewith in two different embodiments,

Fig. 3

a rotary drive of a grinding machine with two grinding tools coupled to it and resting against one another in a view from the front,

Fig. 4

a rotary drive of a grinding machine with two grinding tools coupled to it and spaced apart from one another in a view from the front,

Fig. 5

a detailed representation of a peripheral surface of a grinding tool,

Fig. 6

a further detailed representation of the peripheral surface of a grinding tool according to a further embodiment,

Figures 7a-7h

further detailed representations of a partial area of the circumferential surface of a grinding tool according to alternative embodiments,

Fig. 8

a grinding tool in a sectional view, and

Figures 9a-9c

further sectional views of a grinding tool with differently designed grinding segments.

Regarding the in Figure 1 The serpentine abrasive material 18 shown, reference is made to the description of the prior art in the introduction to the description.

Figure 2a shows a perspective view of a grinding machine 16 (not shown in more detail) with a rotary drive 3, two grinding tools 1 a, 1 b being coupled to the rotary drive 3. The grinding machine 16 can have an electric drive for the rotary drive 3. For the sake of clarity, however, the grinding machine 16 has not been shown in more detail. The grinding tools 1a, 1b each include a carrier device 2 with a central coupling area 6 for coupling the respective grinding tool 1a, 1b to the rotary drive 3 of the grinding machine 16. The grinding tools 1a, 1b also have an abrasive coating 4, which is arranged on the circumference of the carrier device 2 is. The grinding layer 4 of the grinding tool 1a furthermore has the grinding segments 5a, 5b, which are spaced apart in the grinding direction SR, and the grinding layer 4 of the grinding tool 1b has the grinding segments 5c, 5d, which are also spaced apart in the grinding direction SR. It should be noted that the Grinding tools 1a, 1b can be used in both grinding directions SR. The individual grinding segments 5a, 5b, 5c, 5d of the respective grinding tool 1a, 1b are connected to one another via an abrasive-free layer or an abrasive layer. It can be provided that at least some of the grinding segments 5a, 5b, 5c, 5d of the groups provided are designed in one piece. In addition, an intermediate covering 13 is provided here, the grinding segments 5a, 5b, 5c, 5d of the groups provided being formed, preferably in one piece, with the intermediate covering 13. However, such an intermediate covering 13 is not absolutely necessary. The carrier device 2 also has a circumferential surface 12, the grinding segments 5a, 5b, 5c, 5d of the groups provided projecting from the circumferential surface 12 in the radial direction RR.

It can be seen that the grinding tools 1a, 1b each have at least one first group of at least two grinding segments 5a, 5c following one another in the grinding direction SR, the grinding segments 5a, 5c of this first group having a first orientation 7a, 7c relative to the respective carrier device 2, and that at least, preferably precisely, one further group of at least two consecutive sanding segments 5b, 5d in the sanding direction SR is provided, the sanding segments 5b, 5d of the at least one further group having a second orientation deviating from the first orientation 7a, 7c 7b, 7d relative to the carrier device 2, and wherein the first and the at least one further group are arranged one after the other in the grinding direction SR on the carrier device 2. Furthermore, empty spaces 9 can be seen which are formed between the individual grinding segments 5a, 5b, 5c, 5d, each within a group. It can therefore be provided that the grinding segments 5a, 5b, 5c, 5d of the intended groups are spaced apart from one another by empty spaces 9, preferably with the grinding segments 5a, 5b, 5c, 5d within one of the intended groups being separated from one another by identically designed empty spaces 9 . It can be provided, for example, that the empty spaces 9 to The spacing of the grinding segments 5a, 5c of the first group from one another is mirror-symmetrical to the empty spaces 9 for spacing the grinding segments 5b, 5d of the at least one further group from one another (see also in this regard Figure 5 or Figure 6 ).

In the exemplary embodiment shown, the empty spaces 9 can be designed as grooves which, in a top view, can be designed essentially in the form of a parallelogram (see again in this regard Figure 5 or Figure 6 ). In addition, the provided groups of at least two grinding segments 5a, 5b, 5c, 5d following one another in the grinding direction SR can be connected to one another via at least one additional grinding segment 10 (grinding tool 1b) and / or at least one additional empty space 11 (grinding tool 1a).

Figure 2b shows a perspective view of the grinding machine 16 (not shown in more detail) with a rotary drive 3, two grinding tools 1 a, 1 b again being coupled to the rotary drive 3. In contrast to the Figure 2a In this case, no intermediate covering 13 is provided and the grinding segments 5a, 5b, 5c, 5d of the respective grinding tool 1a, 1b are arranged directly, but without contact with one another, on the corresponding carrier device 2. At this point, reference is made to a preferred embodiment of the grinding machine 16. A first grinding tool 1 a is designed in such a way that the grinding segments 5 a, 5 b are soldered directly onto the carrier device 2. The second grinding tool 1b, on the other hand, differs in that the grinding segments 5c, 5d are connected to one another via an abrasive-free layer or an abrasive layer. The resulting abrasive coating 4 is connected either via an intermediate coating 13 or directly to the corresponding carrier device 2 by sintering. In a grinding machine 16 with at least two grinding tools 1a, 1b it can be provided that recesses 9 between the individual grinding segments 5a, 5b, 5c, 5d in only at least one of the Grinding tools 1a, 1b are formed. Such recesses 9 are not absolutely necessary in grinding tools 1a, 1b with grinding segments 5a, 5b, 5c, 5d, which each have a V-shaped recess 15. In this regard, reference is made to the description of the figures in FIG Figure 9b referenced.

Figure 3 shows a grinding machine 16 in a view from the front (not shown in more detail) with the rotary drive 3 and two grinding tools 1a, 1b coupled to the rotary drive 3. The grinding tools 1a, 1b rest against one another and can be fastened to one another by means of screws, for example. Alternatively, the grinding tools 1a, 1b can also be attached to one another via flanges. It can be seen here that at least one water supply 17 can be provided for cooling the intended grinding tools 1a, 1b and / or for transporting away grinding debris 18 that arises when machining a workpiece 19, for example laminated safety glass. It can also be seen that the empty spaces 9 are arranged essentially at an angle to the axial direction AR. The axial direction AR runs essentially in the direction of the axis of rotation DA of the grinding tools 1a, 1b. In addition, the grinding tools 1a, 1b each have two end faces 14a, 14b aligned essentially normal to the axis of rotation DA of the respective grinding tool 1a, 1b (see FIG Figure 4 ), wherein the grinding segments 5c, 5d of the groups provided have a recess 15 formed essentially centrally between the two end faces 14a, 14b and essentially parallel to the two end faces 14a, 14b, for example for the formation of two chamfers on the workpiece 19 to be machined . In addition, the surfaces 23a, 23b, 23c, 23d of the respective grinding segments 5a, 5b, 5c, 5d involved in the grinding process can be seen. It can be provided that the sums of the surfaces 23a, 23b, 23c, 23d of the grinding segments 5a, 5b, 5c, 5d of the at least two grinding tools 1a, 1b involved in the grinding process are of different sizes. The sum of the surfaces 23a, 23b of the grinding segments 5a, 5b of the first grinding tool 1a involved in the grinding process is preferably smaller than the sum of the surfaces 23c involved in the grinding process, 23d of the grinding segments 5c, 5d of the second grinding tool 1b. This is advantageous because the first grinding tool 1a serves to remove a large amount of material in accordance with the requirements. The second grinding tool 1b, on the other hand, serves to finalize the workpiece 19. Therefore, the grinding segments 5c, 5d of this second grinding tool 1b can each have a recess 15 for shaping the workpiece 19.

Figure 4 shows a front view of the grinding machine 16 with the rotary drive 3 and two grinding tools 1a, 1b coupled to the rotary drive 3, the two grinding tools 1a, 1b being spaced from one another. In this regard, a spacer can also be arranged between the two grinding tools 1a, 1b. It can be seen here that the carrier device 2 has a width B in the axial direction AR and the empty spaces 9 extend essentially over the entire width B. Alternatively, the empty spaces 9 can also only extend over part of the width B. Furthermore, it can be provided that a first grinding tool 1a of the at least two grinding tools 1a, 1b has more grinding segments 5a, 5b, 5c, 5d than a second grinding tool 1b of the at least two grinding tools 1a, 1b.

Figure 5 shows the circumferential surface 12 of the carrier device 2 of the grinding tool 1a with the grinding layer 4, which has the grinding segments 5a, 5b. The angular ranges 8a, 8b can be seen here. It can therefore be provided that the grinding segments 5a, 5b of the groups provided each extend essentially over the same angular region 8a, 8b of the carrier device 2. In the present case, exactly one further group of at least two grinding segments 5b following one another in the grinding direction SR is provided, the grinding segments 5a of the first group and precisely one further group 5b each essentially extending over an angular range 8a, 8b of approx. 180 ° Support device 2 extend.

Figure 6 shows analogous to Figure 5 the circumferential surface 12 of the carrier device 2 of the grinding tool 1b with the grinding layer 4, which has the grinding segments 5c, 5d. Here, too, exactly one further group of at least two grinding segments 5d following one another in the grinding direction SR is provided, the grinding segments 5c of the first group and precisely one further group 5d each essentially extending over an angular range 8a, 8b of approx. 180 ° of the carrier device 2 extend.

Figures 7a to 7h show different embodiments of grinding segments 5a, 5b of an abrasive coating 4 of a grinding tool 1a. It can be provided that the grinding segments 5a of the first group are aligned essentially mirror-symmetrically or point-symmetrically to the grinding segments 5b of the at least one further group. Furthermore, it can be provided that the grinding segments 5a, 5b are designed essentially identically within one of the groups provided, preferably wherein the grinding segments 5a, 5b of the groups provided are designed essentially mirror-symmetrically. As in the Figures 7g and 7h shown, the individual grinding segments 5a, 5b can also be formed in several parts.

Figure 8 shows a sectional view of the grinding tool 1a. The channels 20 can be seen here, which are formed in the grinding tool 1a. It can therefore be provided that the grinding tool 1a has at least one channel 20 running at least in sections in the radial direction RR for the conduction of a cooling fluid, preferably wherein the at least one channel 20 has at least one first opening 21 arranged in the central coupling area 6 and a second opening 21 in the area of the Has grinding segments 5a, 5b arranged opening 22. The grinding tools 1a, 1b can therefore be supplied with a cooling fluid, for example water, both externally (water supply 17) and internally (channels 20). At this point, it is pointed out that the channels 20 are also separated by an intermediate covering 13 that may be provided and one that may be provided Abrasive-free layer or an abrasive layer, wherein the abrasive-free layer or the abrasive layer can connect the individual abrasive segments 5a, 5b to one another, extends through. As a result, a cooling fluid can be conducted through the carrier device 2 in the direction of the grinding segments 5a, 5b, as a result of which cooling of the grinding tool 1a and / or removal of abrasive material 18 is possible.

Figures 9a to 9c each show a grinding segment 5c arranged on the carrier device 2 according to different embodiments in a sectional illustration. The recess 15 can be seen in each case, which is trapezoidal in cross-section ( Figure 9a ), V-shaped ( Figure 9b ) or arched ( Figure 9c ) can be formed. The depressions 15 of the grinding segments 5a, 5b, 5c, 5d are determined as a function of the desired edge profile of the workpiece 19 to be machined, whereby, of course, such depressions 15 are not absolutely necessary. In the case of V-shaped recesses 15 in the grinding segments 5a, 5b, 5c, 5d, however, no recesses 9 are absolutely necessary between the individual grinding segments 5a, 5b, 5c, 5d, since only the Edge areas of the glass panes are processed. There is therefore no formation of serpentine abrasive material 18, which is why recesses 9 between the individual grinding segments 5a, 5b, 5c, 5d with V-shaped depressions 15 are not absolutely necessary. It can also be seen that the channels 20 can also extend through the individual grinding segments 5c.

Finally, the different configurations of the abrasive coating 4 and its arrangement on the carrier device 2 are described again. The individual grinding segments 5a, 5b, 5c, 5d can therefore each be connected directly to the carrier device 2 and can be designed without contact with one another. Alternatively, the individual grinding segments 5a, 5b, 5c, 5d can also be connected to one another via an abrasive-free layer or an abrasive layer, the grinding segments 5a, 5b, 5c, 5d are connected to the carrier device 2 via this layer. For the embodiments mentioned, it is also possible for an intermediate covering 13 to be arranged between the grinding segments 5a, 5b, 5c, 5d and the carrier device 2 or between the abrasive-free layer or the abrasive layer and the carrier device 2. Furthermore, it is possible for the grinding segments 5a, 5b, 5c, 5d to be formed by recesses in the grinding layer 4, so that embodiments similar to FIG US 2012/0178345 A1 are included. The grinding segments 5a, 5b, 5c, 5d can, however, also be arranged in depressions in the carrier device 2. With regard to the grinding machine 16, it should be noted that, depending on the application, the desired edge profile and the required quality, several, preferably four, grinding tools 1a, 1b can be provided, the provided grinding tools 1a, 1b being used one after the other to machine the workpiece 19.

List of reference symbols:

1a Grinding tool 18th Abrasion 1b Grinding tool 19th workpiece 2 Carrier device 20th channel 3 Rotary drive 21 First opening of a canal 4th Abrasive coating 22nd Second opening of a canal 5a Grinding segment 23a Surface of a grinding segment 5a 5b Grinding segment 5c Grinding segment 23b Surface of a grinding segment 5b 5d Grinding segment 6th Coupling area 23c Surface of a grinding segment 5c 7a First alignment 7b Second alignment 23d Surface of a grinding segment 5d 7c First alignment 7d Second alignment 8a Angular range 8b Angular range AR Axial direction 9 White space B. width 10 Additional grinding segment THERE Axis of rotation 11 Extra white space RR Radial direction 12th Circumferential surface SR Grinding direction 13th Intermediate layer 14a Face 14b Face 15th deepening 16 Grinding machine 17th Water supply

Claims (15)

1. Grinding tool (1a, 1b) for processing a workpiece (19), in particular laminated safety glass, comprising a carrier device (2) having a central coupling region (6) for coupling the grinding tool (1a, 1b) to a rotary drive (3) of a grinding machine (16) and a grinding layer (4), which is arranged circumferentially on the carrier device (2) and which comprises grinding segments (5a, 5b, 5c, 5d) which are spaced apart from one another in a grinding direction (SR), having a first and second group of grinding segments, characterized in that at least the first group of at least two grinding segments (5a, 5c) following one another in the grinding direction (SR) is provided, the grinding segments (5a, 5c) of this first group having a first orientation (7a, 7c) relative to the carrier device (2), and in that at least, preferably exactly, one further group of at least two grinding segments (5b, 5d) following one another in the grinding direction (SR) is provided, the grinding segments (5b, 5d) of the at least one further group having a second orientation (7b, 7d) relative to the carrier device (2) which differs from the first orientation (7a, 7c), and the first and the at least one further group being arranged successively in the grinding direction (SR) on the carrier device (2).
2. Grinding tool (1a, 1b) according to claim 1, wherein the grinding segments (5a, 5b, 5c, 5d) of the provided groups each extend substantially over a same angular range (8a, 8b) of the carrier device (2), preferably wherein exactly one further group of at least two grinding segments (5b, 5d) following one another in the grinding direction (SR) is provided, wherein the grinding segments (5a, 5b, 5c, 5d) of the first group and of the exactly one further group each extend substantially over an angular range (8a, 8b) of approximately 180° of the carrier device (2).
3. Grinding tool (1a, 1b) according to claim 1 or 2, wherein the grinding segments (5a, 5b, 5c, 5d) of the provided groups are spaced apart from one another by empty spaces (9), preferably wherein the grinding segments (5a, 5b, 5c, 5d) within one of the provided groups are spaced apart from one another by identically formed empty spaces (9), particularly preferably wherein the empty spaces (9) for spacing the grinding segments (5a, 5c) of the first group from one another are formed mirror-symmetrically to the empty spaces (9) for spacing the grinding segments (5b, 5d) of the at least one further group from one another.
4. Grinding tool (1a, 1b) according to the preceding claim, wherein the empty spaces (9) are formed as grooves, preferably wherein the empty spaces (9) are formed substantially in the shape of a parallelogram in a plan view, and/or wherein the empty spaces (9) are arranged substantially obliquely to the axial direction (AR).
5. Grinding tool (1a, 1b) according to any one of claims 1 to 4, wherein the carrier device (2) has a width (B) in the axial direction (AR) and the empty spaces (9) extend substantially over the entire width (B).
6. Grinding tool (1a, 1b) according to any one of claims 1 to 5, wherein the provided groups of respectively at least two grinding segments (5a, 5b, 5c, 5d) following one another in the grinding direction (SR) are connected to one another via at least one additional grinding segment (10) and/or at least one additional empty space (11).
7. Grinding tool (1a, 1b) according to any one of claims 1 to 6, wherein the grinding segments (5a, 5c) of the first group are aligned substantially mirror-symmetrically or point-symmetrically to the grinding segments (5b, 5d) of the at least one further group, and/or the grinding segments (5a, 5b, 5c, 5d) within one of the provided groups are formed substantially identically, preferably wherein the grinding segments (5a, 5b, 5c, 5d) of the provided groups are formed substantially mirror-symmetrically.
8. Grinding tool (1a, 1b) according to any one of claims 1 to 7, wherein the carrier device (2) has a circumferential surface (12) and the grinding segments (5a, 5b, 5c, 5d) of the provided groups project in a radial direction (RR) from the circumferential surface (12).
9. Grinding tool (1a, 1b) according to any one of claims 1 to 8, wherein at least some of the grinding segments (5a, 5b, 5c, 5d) of the provided groups are formed integrally in themselves, and/or wherein an intermediate coating (13) is provided and the grinding segments (5a, 5b, 5c, 5d) of the provided groups are formed, preferably integrally, with the intermediate coating (13).
10. Grinding tool (1a, 1b) according to any one of claims 1 to 9, wherein the grinding tool (1a, 1b) has two end faces (14a, 14b) aligned substantially normal to the axis of rotation (DA) of the grinding tool (1a, 1b), wherein the grinding segments (5a, 5b, 5c, 5d) of the provided groups have a recess (15) formed substantially centrally between the two end faces (14a, 14b) and substantially parallel to the two end faces (14a, 14b), for example for forming two chamfers on the workpiece (19) to be processed, preferably wherein the recess (15) is trapezoidal, V-shaped or arc-shaped in cross-section.
11. Grinding tool (1a, 1b) according to any one of claims 1 to 10, wherein the grinding tool (1a, 1b) comprises at least one duct (20) extending at least in sections in the radial direction (RR) for conducting a cooling fluid, preferably wherein the at least one duct (20) has at least a first opening (21) arranged in the central coupling region (6) and a second opening (22) arranged in the region of the grinding segments (5a, 5b, 5c, 5d).
12. Grinding machine (16) comprising at least one rotary drive (3) and at least one grinding tool (1a, 1b) according to any one of the preceding claims, wherein the at least one grinding tool (1a, 1b) is coupled or can be coupled to the rotary drive (3) of the grinding machine (16) via the central coupling region (6) of the carrier device (2).
13. Grinding machine (16) according to claim 12, wherein the grinding machine (16) comprises at least, preferably exactly, two grinding tools (1a, 1b), and wherein at least one of the at least two grinding tools (1a, 1b) is formed according to any one of claims 1 to 11, wherein the at least two grinding tools (1a, 1b) are coupled or can be coupled to the rotary drive (3) of the grinding machine (16) in an abutting manner, preferably screwed to one another, or, preferably by means of at least one spacer, spaced apart from one another via the respective central coupling region (6) of the carrier device (2).
14. Grinding machine (16) according to claim 12 or 13, wherein at least one water supply (17) is provided for cooling the provided grinding tools (1a, 1b) and/or for removing grinding abrasion (18) which is produced during the processing of, for example, a laminated safety glass.
15. Grinding machine (16) according to claim 13 or 14, wherein a first grinding tool (1a) of the at least two grinding tools (1a, 1b) has more grinding segments (5a, 5b, 5c, 5d) than a second grinding tool (1b) of the at least two grinding tools (1a, 1b), and/or wherein the sums of the surfaces (23a, 23b, 23c, 23d) of the grinding segments (5a, 5b, 5c, 5d) of the at least two grinding tools (1a, 1b) involved in the grinding process are of different sizes.

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