Grinding disc unit for a lateral surface grinding machine

Abstract

The invention relates to a grinding disc unit (400) for use in a lateral surface grinding machine, comprising a main part (410) which defines a disc rotational axis (402) and which is installed or can be installed on a tool spindle such that the disc rotational axis (402) runs coaxially to the spindle axis, wherein a circumferential region (412) of the main part (410) has a plurality of installation regions (420) which are offset to one another in the circumferential direction of the main part and which comprise securing devices for securing a respective exchangeable tool segment (500) to the main part (410). A tool segment (500) has a cutting means support (510), which comprises installation structures for securing the cutting means support in one of the installation regions, and a cutting fitting (520) on a cutting fitting side, said cutting fitting forming an abrasive functional surface of the tool segment. The abrasive functional surfaces of the cutting fittings are arranged on a lateral surface of the grinding disc unit, said lateral surface being oriented perpendicularly to the disc rotational axis, within an annular functional region (430) at a radial distance to the disc rotational axis (402). An installation region (420) has a receiving device (440) with stop surfaces for receiving a tool segment (500) in a defined position and a quick-clamping device (470) which can be switched between an open configuration and a clamping configuration, wherein in the open configuration, a tool segment (500) can be inserted into the receiving device (440) or can be removed from the receiving device, and in the clamping configuration, the tool segment is pressed against the stop surfaces and can be fixed on the main part (410) in a specified position.

Description

[0001] Grinding wheel unit for a side face grinding machine

[0002] FIELD OF APPLICATION AND STATE OF THE ART

[0003] The invention relates to a grinding wheel unit for use in a side face grinding machine as well as to a side face grinding machine equipped with at least one such grinding wheel unit and to a method for producing a grinding wheel unit.

[0004] The face grinding machine can, in particular, be a double face grinding machine. Double face grinding machines can be used, for example, for the simultaneous grinding of essentially plane-parallel, circular workpiece surfaces on a disc-shaped workpiece section. One possible application is the grinding of surfaces of a circular brake section of a brake disc, especially a coated brake disc.

[0005] Upcoming tightening of regulations on fine particle emissions from motor vehicles suggests that future brake discs for motor vehicles will have to be designed to release fewer fine particles during braking. One approach to this is to coat the brake discs, or rather their surface sections intended as friction surfaces, with a thin functional layer made of a more wear-resistant material. In a coated brake disc, the surfaces of the annular braking section each bear a functional layer that is rotationally symmetrical with respect to the rotation axis, the free surface of which is designed as the friction surface of the brake disc.

[0006] The manufacturing process for a coated brake disc comprises one or more coating operations for coating the surfaces of the braking section of the brake disc with a functional layer intended to reduce wear due to the relatively high mechanical hardness of individual carbides. Alternatively or additionally, a corrosion-inhibiting effect may also be present. Such functional layers often consist essentially of metal and can have a single layer or multiple layers with different properties. Such coatings can be applied, for example, by flame spraying or laser cladding. Typical layer thicknesses can range between 50 μm and 350 μm. The coatings are usually applied on both sides. The documents EP 2 746 613 A2 and WO 2019 / 021161 A1 disclose examples of coated brake discs.

[0007] The carbides of the functional coatings are generally relatively hard mechanically, and the coatings have a relatively rough surface after coating. A subsequent grinding process is intended to create a sufficiently flat surface on the coating that is optimized for braking function. For example, the specifications for friction surfaces of a brake disc can be such that a mean roughness Ra determined according to DIN EN ISO 4288 should be in the range of 1 μm to 3 μm - 3.2 μm, and a flatness deviation of no more than 20 μm (cf. WO 2021 / 224308 A).

[0008] Double-side face grinding machines are often used for grinding brake discs.

[0009] Document DE 10 2021 132 468 B3 contains a detailed description of particulate matter problems caused by braking and specific problems during the grinding of brake discs with a coating that is difficult to machine. It describes a device for grinding the flat sides of a coated brake disc for a motor vehicle. The device comprises at least two grinding wheels, of which a first grinding wheel is provided for pre-grinding the flat side by a large allowance, and a second grinding wheel is provided for finish-grinding the flat side by a small allowance. The two grinding wheels are designed as cup wheels that are axially displaceable relative to one another and nested inside one another.

[0010] The document DE 20 2023 100 514 U1 describes, among other things, a double-sided surface grinding machine suitable for grinding brake discs on both sides, which

[0011] Position data determination systems which, on the one hand, determine the axial position of the workpiece surface and, on the other hand, the axial position of the abrasive side surface of a grinding wheel facing the workpiece surface in relation to the same reference coordinate system. A control unit of the grinding machine can, in at least one phase of the grinding operation, control at least one grinding parameter depending on the workpiece position data and / or the tool position data. This provides a user with a tool for optimising "his" grinding process. The grinding wheels are designed as cup wheels segmented in the circumferential direction with individually replaceable and individually adjustable strip-shaped grinding segments. The document EP 4 147 821 A1 discloses, among other things,A device constructed in the manner of a double-side surface grinding machine for machining a hard-coated workpiece surface of a rotationally symmetrical workpiece, comprising a workpiece drive device for generating a rotational movement about a workpiece rotation axis, at least one grinding wheel drive device for generating a rotational movement about a grinding wheel rotation axis, at least one feed device for bringing the grinding wheel into contact with the workpiece surface, and at least one adjustment device for adjusting the grinding wheel rotation axis and the workpiece rotation axis relative to one another so that the grinding wheel rotation axis and the workpiece rotation axis are not parallel. The grinding wheels of the exemplary embodiment are shown as segmented cup wheels.

[0012] TASK AND SOLUTION

[0013] The invention is based on the object of providing a grinding wheel unit designed in the manner of a segmented cup wheel for use in a face grinding machine, the use of which can increase the productivity of the grinding process, particularly in the grinding of difficult-to-machine workpiece surfaces, without compromising the machining quality. Furthermore, a face grinding machine and a method for manufacturing a grinding wheel unit are to be provided.

[0014] To achieve this object, the invention provides a grinding wheel unit having the features of claim 1. Furthermore, a side face grinding machine equipped with at least one such grinding wheel unit and a method for producing a grinding wheel unit are provided. Advantageous further developments are specified in the dependent claims. The wording of all claims is incorporated into the description by reference.

[0015] According to one aspect of the invention, a grinding wheel unit for use in a side face grinding machine is provided. The side face grinding machine has at least one tool spindle which can be driven in rotation about a spindle axis by means of a spindle drive. The term “grinding wheel unit” refers to a grinding wheel composed of multiple components or individual parts. The grinding wheel unit has a base body which defines a wheel rotation axis. The base body can be manufactured from a single piece or composed of multiple parts and preferably has a mass distribution which is essentially rotationally symmetrical to the wheel rotation axis. The grinding wheel unit is mounted on the tool spindle or can be mounted there in such a way that the wheel rotation axis runs coaxially to the spindle axis when the base body is mounted on the tool spindle.

[0016] The base body has, in its circumferential area, a plurality of mounting areas arranged offset from one another in the circumferential direction of the base body, each having devices for attaching an interchangeable tool segment to the base body. The circumferential area is an area that extends from a radially outer circumferential surface of the base body over a certain radial width inwards. The radial width of the circumferential area can, for example, be in the range from 2% to 20%, in particular in the range from 2% to 10%, of the radius of the base body. A tool segment extends only over a fraction of the circumference of the grinding wheel unit, which can have many tool segments around its circumference. The number of these can, for example, be in the range from 10 to 20, but may also be higher or lower.

[0017] A tool segment comprises a cutting means carrier with mounting structures for fastening the cutting means carrier or the cutting means carrier in a mounting area and a cutting coating on a cutting coating side, which forms an abrasive active surface of the tool segment. In a fully configured state of the grinding wheel unit, the abrasive active surfaces of the cutting coatings of the tool segments are essentially arranged in a common side surface of the grinding wheel unit oriented perpendicular to the wheel rotation axis within an annular active area of ​​the grinding wheel unit with a radial distance from the wheel rotation axis. The annular active area can be relatively narrow in relation to the radius or radius of the base body. The annular active area can, for example, have a width measured in the radial direction that is in the range of 5% to 20% of the radius or radius of the base body.Such a grinding wheel unit can also be described as a circumferentially segmented cup grinding wheel with interchangeable tool segments.

[0018] This configuration offers the advantage that, for example, in the case of advanced wear of the cutting pads, the entire grinding wheel unit does not have to be removed from the tool spindle and replaced with a fresh one. Instead, the base body can remain mounted on the tool spindle, and only the tool segments are replaced. This concept is particularly advantageous for double-side face grinding machines, as replacing complete grinding wheel units is generally difficult and time-consuming due to the limited space available.

[0019] The inventors recognized that, despite these conceptual advantages, with conventional segmented cup wheels with interchangeable tool units, it is relatively complicated and time-consuming, even for experienced machine operators, to replace tool segments with worn cutting surfaces on a grinding wheel unit, replace them with tool segments with fresh cutting surfaces, and then restore the grinding wheel to a ready-to-use state. The time required for tool changes is not usable for productive operation, which is why productivity suffers when significant time is required for tool changes.

[0020] The claimed invention provides a remedy here and leads to significantly shorter idle times for tool changes and to an increase in productivity by shortening tool change times.

[0021] According to one formulation, this is achieved in that each of the assembly areas has a receiving device provided for receiving a tool segment with position-determining stop surfaces for the position-defined receiving of a tool segment on the base body and a quick-action clamping device which can be switched between an open configuration and a clamping configuration, wherein in the open configuration a tool segment can be inserted into the receiving device or removed from the receiving device and in the clamping configuration the tool segment can be pressed against the stop surfaces and can be fixed in a predetermined position on the base body.

[0022] This concept essentially does not require any adjustment options that would allow the position of an installed tool segment in relation to the base body to be adjusted or set using suitable adjustment devices, e.g., adjustment screws. Instead, the position of the newly installed tool segment on the base body can be fixed in several different directions by the design and arrangement of the stop surfaces of the holder on the base body and the corresponding counter surfaces on the cutting tool carrier, in particular with regard to the axial position (position in the direction parallel to the grinding wheel rotation axis, with regard to the radial position (with regard to the grinding wheel rotation axis), and with regard to a tangential position or a position in the circumferential direction of the grinding wheel unit). However, adjustment options can be provided if required. This can, for example,be useful for readjusting a tool segment after a tool breakage. One adjustment option can be created, for example, by forming the axial stop surface on an axially displaceable component which normally rests on an axial stop surface of a recess in the base body, is located between the base body and the cutting means carrier and can be axially displaced slightly, for example by means of suitable adjusting screws, if necessary in order to axially raise the tool segment. It is also possible to form an inclined wedge surface on the underside of the cutting means carrier and / or as an axial stop surface of a recess in the base body, which interacts with a flat wedge element which can be adjusted, for example in the radial direction, which is arranged between the cutting means carrier and the base body and which, in the event of a radial displacement, causes an axial displacement of the cutting means carrier relative to the base body.

[0023] The quick-clamping device can be operated very quickly and easily, either manually or automatically (for example, using a robot or an electric screwdriver with monitoring), as only one or more appropriately designed actuating elements need to be activated to switch between the open and clamped configurations. Changing tool segments can thus be easily performed manually or semi-automatically by an operator. Changing a tool segment can also be performed quickly and easily using a simply constructed robot.

[0024] Especially when machining difficult-to-machine workpiece surfaces, such as coated brake discs, which are associated with high tool wear, the reduction in tool change times made possible by the invention contributes significantly to increased productivity. Furthermore, no adjustment work is required to adjust the position and alignment of a tool segment when changing tool segments, thus systematically avoiding potential errors due to misalignment. This can contribute to increasing productivity while maintaining at least the same quality of the grinding result, and possibly even improving the quality of the grinding result.

[0025] Preferably, the clamping device is configured such that it can be switched between the open configuration and the clamped configuration by actuating a single actuating element. This is particularly convenient and facilitates rapid tool changes, as, for example, an operator can use one hand to actuate the actuating element and the other hand to handle the tool segments being removed and installed. A single operator is therefore sufficient. Changing a tool segment can also be performed quickly and easily using a robot with a simple gripper and / or an actuating tool.

[0026] According to a further development, a receiving device has a recess in the base body, wherein the recess is open outwards in the radial direction (relative to the wheel rotation axis) and has at least one radial stop surface in the opposite direction (i.e. radially inwards), and is open towards the lateral surface in the axial direction, i.e. parallel to the grinding wheel rotation axis, and has at least one axial stop surface in the opposite direction. As a result, the axial position and the radial position of the tool segment in relation to the base body are fixed by stops, so that no adjustment is possible in this respect. As long as the stop surfaces are clean, there is no possibility of attaching a tool segment incorrectly, i.e. not in the correct position, to the base body. This promotes rapid tool changes.If necessary, insertion chamfers can be provided on the tool segment and / or on the recess to prevent jamming during installation.

[0027] Preferably, in the area of ​​a radial stop surface and / or in the area of ​​an axial stop surface on the surfaces bounding the recess, two or more circumferentially offset webs with recessed sections in between are provided. The upper sides of the webs serving as stop surfaces are manufactured with high precision. In some embodiments, the flatness of the contact surfaces is tolerated to within a few hundredths of a mm, e.g., 0.02 mm. A length dimension relative to the contact surface can be manufactured with tolerances of the same order of magnitude.

[0028] In preferred embodiments, the quick-action clamping device is designed in the manner of a dovetail clamping device. The dovetail contour is preferably oriented such that the tool segment can be inserted and removed from the dovetail clamping device in the axial direction of the grinding wheel unit, i.e., in a direction parallel to the wheel rotation axis. Due to the interlocking structures on the tool segment or its cutting medium carrier on the one hand and the dovetail clamping device on the other, the latter secures the inserted tool segment in the circumferential direction with a bidirectional positive fit in the closed configuration. The tool segment is secured against the machining forces on the axial stop surface of the base body, additionally by means of a frictional connection caused by the clamping forces.Closing the dovetail clamping device also fixes the tool segment bidirectionally in the radial direction, namely on the one hand on the radially inner stop surfaces and on the other hand on a flank of the dovetail clamping device.

[0029] The dovetail clamping device is preferably designed such that the receiving structures have a fixed dovetail flank and an adjustable dovetail flank lying opposite in the circumferential direction, and the dovetail flanks define a dovetail groove which has a radially inner groove bottom surface and narrows radially outwards.

[0030] If only one of the flanks of the dovetail clamping device is movable, the position of the tool segment can be specified with particularly high precision by resting it on the opposite flank.

[0031] According to a further development, the quick-release clamping device has a wedge-shaped clamping element that can be moved radially via an actuating screw. The actuating element is preferably oriented radially and is therefore easily accessible in the radial direction, which is particularly advantageous in confined installation spaces.

[0032] Preferably, one of the wedge surfaces of the clamping element forms the movable flank of the associated dovetail clamping device, so that the wedge-shaped clamping element contacts directly with the cutting means carrier of the tool segment.

[0033] Particularly preferred are embodiments in which the wedge-shaped clamping element can be moved both radially inwards and radially outwards, i.e. bidirectionally, via an actuating screw oriented in the radial direction. The actuating screw can have a section with a right-hand thread and a section with a left-hand thread, so that clockwise rotation of the actuating screw forces movement of the wedge-shaped clamping element in a radial direction (e.g., inwards) and counterclockwise rotation forces an active movement in the opposite direction (e.g., radially outwards). This enables a quick tool segment change even when the surfaces contacting one another in the region of the clamping device are firmly seated and, for example, the wedge element is clamped and cannot be easily moved out of its position.

[0034] The inventors have identified further possibilities for optimizing processes and grinding results when using segmented cup wheels. According to one proposal, a tool segment has a segmented cutting coating on the cutting coating side of the cutting means carrier, which comprises at least two cutting material bodies arranged at a mutual distance from one another. This measure can be provided for one or more tool segments, preferably for all tool segments of the grinding wheel unit. This aspect is also referred to in this application as "double segmentation," and corresponding grinding wheel units as "doubly segmented cup wheels." It has been shown that by segmenting the cutting coating of a tool unit, further degrees of freedom can be achieved for optimizing the grinding process and the grinding result.

[0035] A segmented cutting layer can comprise only exactly two cutting material bodies. Preferably, the segmented cutting layer comprises three, four, five, six, or more cutting material bodies. The number and design of the individual cutting material bodies can be adapted to the machining task within wide limits.

[0036] In preferred embodiments, the cutting material bodies each have a narrow effective surface which is delimited by two longitudinal edges running parallel or almost parallel to one another in the longitudinal direction of the cutting material body and transverse edges running transversely to the longitudinal edges, wherein a length of the effective surface measured parallel to at least one of the longitudinal edges between the transverse edges is several times greater than a width of the effective surface measured perpendicular to it. The length can, for example, be at least three times as large as the width; it is often advantageous if the aspect ratio between length and width is in the range of 3 to 6. Such narrow effective surfaces can, for example, be realized on strip-shaped or plate-shaped cutting material bodies. This enables relatively high surface pressures and correspondingly high machining performances to be achieved.At the same time, liquid machining aids, such as cooling lubricants or similar, can be introduced through the gaps between the cutting tool bodies. This facilitates efficient cooling and also allows for the efficient removal of grinding residues.

[0037] Cutting material bodies can be arranged on the cutting surface side of the cutting tool carrier so that, when the tool segment is mounted, they are aligned in the tangential direction of the grinding wheel unit, i.e., essentially perpendicular to the radial direction. For example, two, three, or more cutting material bodies can be arranged in a row at a distance from one another on one cutting surface side. It is also possible to arrange two or more rows of cutting material bodies with relatively narrow effective surfaces, offset from one another in the radial direction and running in the tangential direction.Among other things, variants of tool segments with segmented cutting coating have proven successful in the machining of coated grinding wheels. These comprise two or more cutting material bodies arranged at a distance from one another, which, when the tool segment is mounted, are oriented obliquely to the radial direction and obliquely to the circumferential direction in such a way that the effective surfaces within the annular effective area of ​​the grinding wheel unit are aligned neither tangentially nor radially, but obliquely to these two directions.

[0038] The invention also relates to a surface grinding machine comprising at least one grinding wheel unit of the type presented for the first time in this application.

[0039] The invention also relates to a method for producing a grinding wheel unit of the type first presented in this application. The method provides—in short—for dressing the cutting surfaces of all tool segments for a grinding wheel unit in a package operation, simultaneously by surface grinding, before the tool segments are then separated and attached to their respective mounting areas. Before the dressing operation, a tool segment group is formed that contains all the tool segments to be attached to the base body of the grinding wheel unit. These tool segments are held as a package in a fixed spatial relationship to one another such that the cutting surface sides of the cutting medium carriers lie in a common plane.The cutting surfaces of the tool segments are then simultaneously dressed together by surface grinding in such a way that, after dressing is completed, the abrasive active surfaces of all cutting surfaces in the tool segment group lie in a common plane. This ensures that the active surfaces are more or less in the same plane (the side surface of the grinding wheel unit) immediately after the tool segments are installed on the base body, so that no dressing operation is necessary after the base body is equipped with fresh tool segments. A short conditioning process may be necessary to expose cutting grains by resetting the bond, ensuring that the cutting edges are efficient from the start. This means that productive work can resume shortly after the tool segments are installed.

[0040] BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Further advantages and aspects of the invention emerge from the claims and from the description of exemplary embodiments of the invention, which are explained below with reference to the figures. Fig. 1 shows a schematic side view of an exemplary embodiment of a double-side surface grinding machine which is designed for grinding coated brake discs and which has two segmented cup wheels according to a

[0042] embodiment;

[0043] Fig. 2 shows an oblique perspective view of an embodiment of a

[0044] grinding wheel unit;

[0045] Fig. 3 shows an enlarged detail of the grinding wheel unit with an empty holder and quick-clamping system;

[0046] Fig. 4 shows an assembly of the dovetail clamping device with a wedge-shaped clamping element;

[0047] Fig. 5 shows a tool segment with inclined cutting edges forming a segmented cutting surface;

[0048] Fig. 6 shows a variant of a tool segment with a projection on the cutting surface side of the cutting means carrier;

[0049] Fig. 7 shows another variant of a tool segment with segmented cutting surface.

[0050] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0051] Fig. 1 shows a schematic side view of an embodiment of a grinding machine 100 designed for grinding essentially plane-parallel, circular workpiece surfaces 01, 02 on a disc-shaped workpiece section of workpieces WS1, WS2 in the form of brake discs WS1, WS2. In the example, the grinding machine is configured for grinding surfaces on both sides of a circular brake section BA of coated brake discs.

[0052] Each brake disc has a base body, made of gray cast iron, for example, with a central hub section NA, which serves to attach the brake disc to a vehicle axle, and a circular brake section BA that encloses the hub section. The mass distribution of the base body is generally rotationally symmetrical to the brake disc's axis of rotation. The brake section has two axially opposite, parallel surfaces (upper workpiece surface 01 and lower workpiece surface 02).

[0053] In an upstream phase of the manufacturing process, these were provided with a coating or functional layer that is rotationally symmetrical with respect to the rotation axis, the exposed surface of which will ultimately serve as the friction surface of the brake disc. The coating can, for example, contain a stainless steel alloy with tungsten, titanium, and / or silicon carbide and be very hard. In the example case, both sides were coated using a special variant of laser deposition welding, namely a variant of extreme high-speed laser deposition welding, also known as the "EH LA process." The coating can also be applied by other methods, e.g., high-velocity oxygen spraying (HVOF) or cold gas spraying.

[0054] The grinding machine 100 is configured as a numerically controlled rotary transfer machine with two work stations, namely a loading station 110 for loading and unloading and a grinding station 120. All functions are implemented via control commands from a control unit 190 of the operating control system, which can be arranged locally (on or next to the machine) or remotely, e.g., in another room, and in the example case can be operated via a connected display and control unit 195 with a graphical user interface.

[0055] For transporting the brake discs between the work stations 110, 120, an internal machine transport system with a rotary table or turntable 150 is used, which is mounted on or in the machine base 102 so that it can rotate about a vertical turntable axis 152 and can be rotated indefinitely about the turntable axis by means of a rotation drive 105.

[0056] The loading station 110 is located on the left side in Fig. 1. There, a first brake disc (here WS1) is held on a workpiece spindle 154 in a horizontal orientation, i.e. with a vertically aligned axis of rotation (“turntable arrangement”). Loading can be carried out, for example, by means of a robot or other handling device or manually. The fastening can be carried out, for example, by clamping it to a workpiece holding device or workpiece holder 155 of the workpiece spindle in such a way that the brake disc is clamped or mounted in a rotationally fixed manner and the rotation axis of the brake disc is coaxial with the rotation axis 156. A rotationally fixed connection to the workpiece spindle can also be achieved by holding it down or securing it from above. In the example, vertically movable hold-down devices 158 are provided.A brake disc loaded in this way is then transported by rotating the rotary table 180° clockwise to a working position 125 in the area of ​​the grinding station 120. There, the work steps of the grinding operation (one or more) take place fully automatically. In the loading station 110, a previously completely ground brake disc can be removed at the same time and a new, not yet ground one can be clamped in. After grinding is completed, the brake disc, which has been completely ground on both sides, is transported by a 180° rotation to the loading station 110, from where it can be unloaded, for example, by means of a robot or other handling device, or manually. A new brake disc to be ground can be clamped onto the then freed workpiece spindle, so that, with the exception of the changeover times, both workpiece spindles are occupied with brake discs and are each in different phases of handling.

[0057] The grinding machine machines the workpiece surfaces using the double-side face grinding process. At the grinding station 120, the grinding machine 100 has a grinding unit 121 with two tool spindles (upper tool spindle 132-1 and lower tool spindle 132-2), ideally arranged coaxially to one another on a frame part, each carrying a grinding wheel (upper grinding wheel 130-2 and lower grinding wheel 130-2). The grinding wheels have facing abrasive side surfaces 135-1 and 135-2, respectively, and are arranged such that these grinding surfaces axially define a grinding chamber 133. Each of the grinding wheels can be rotated about the associated rotational axis 136-1 or 136-2 independently of the other grinding wheel by means of an associated spindle drive or rotational drive (upper rotational drive 134-1 or lower rotational drive 134-2) and can be moved by means of its own feed drive (upper feed drive 131-1 orlower feed drive 131-2) can be fed or advanced parallel to the assigned rotation axis with a predeterminable feed speed profile.

[0058] The grinding machine 100 comprises a first position measuring system 200 equipped with pneumatic distance sensors S1-1 and S2-1 for determining workpiece position data representing the axial position of a workpiece surface O1, O2 at at least one surface location with respect to a machine-fixed reference coordinate system RKS, as well as a second position measuring system 300 equipped with pneumatic distance sensors S1-2 and S2-2 for determining tool position data representing the axial position of an abrasive side surface 135-1, 135-2 facing the workpiece surface O1, O2 with respect to the same reference coordinate system RKS. The control unit 190 can control at least one grinding parameter in at least one phase of the grinding operation depending on the workpiece position data and / or the tool position data. The sensors can be calibrated as needed via integrated reference elements RE1, RE2-1, and RE2-2.Details of these components and their function are described, for example, in DE 2020 23 100 514 U1, to whose disclosure reference is made in this regard.

[0059] The grinding wheels 130-1, 130-2 are designed as circumferentially segmented cup wheels with individually replaceable tool segments according to an embodiment of a grinding wheel unit described in this application.

[0060] Figure 2 shows an oblique perspective view of an embodiment of a grinding wheel unit 400, which can be used in the grinding machine described above as the upper grinding wheel 130-1 and / or the lower grinding wheel 130-2. In the example, both grinding wheels are constructed identically.

[0061] The grinding wheel unit 400 has a base body 410, which essentially has the shape of a flat, round disc, which has a greater thickness in the outer peripheral section 412 than in the inner region enclosed thereby. The peripheral section or peripheral region is a region that extends inward from a radially outer peripheral surface 413 of the base body over a certain radial width. The radial width of the peripheral region can, for example, be less than 10% of the radius of the base body.

[0062] The mass distribution of the base body is rotationally symmetrical to the wheel rotation axis 402, which, when the grinding wheel unit is mounted, runs coaxially with the spindle axis of the corresponding tool spindle. A central through-hole and additional holes in the interior area of ​​the base body are among the devices 411 with which the base body can be attached to the tool spindle with coaxial axes.

[0063] In the example, the base body has eighteen mounting areas 420 in its circumferential section 412, each occupying a circumferential angular range of 20° and having fastening devices for attaching a respective replaceable tool segment 500 to the base body. The tool segments 500 are constructed identically to one another. Figure 5 shows an enlarged view of a tool segment 500 of the type shown in Figure 2.

[0064] The tool segment 500 has a plate-shaped cutting tool carrier 510, which can be machined from solid material, for example, by material removal, or manufactured using an additive manufacturing process. In the example, the cutting tool carrier is made of a steel material. In a segment coordinate system SKS, the length of the cutting tool carrier measured in the longitudinal direction L is several times greater than the width measured perpendicular to it in the width direction B; a ratio can, for example, be between 3:1 and 6:1 and is approximately 5:1 in the example. The height measured in the height direction H is greater than the width and smaller than the length and corresponds approximately to three to five times the width.

[0065] The cutting tool carrier 510 has a flat underside 512, an outer side 513 perpendicular thereto, an inner side 514 opposite thereto in the width direction, and a cutting-coating side 515 opposite the underside, on which the cutting tool carrier carries a cutting coating (general reference numeral 520). The upper side of the cutting coating opposite the underside forms the abrasive active surface 525 of the tool segment 500.

[0066] The abrasive active surfaces of the individual tool segments lie more or less precisely in a common plane, which forms the side surface of the grinding wheel unit oriented perpendicular to the wheel rotation axis 402. Within this side surface, all abrasive active surfaces of the cutting surfaces lie within an annular active area 430, the width of which, measured in the radial direction R, is only a fraction of the radial extent of the grinding wheel unit between the wheel rotation axis 402 and the outer edge, for example, only 5% to 20% of this radial extent. During workpiece machining, the grinding wheel unit only comes into material-removing contact with the workpiece surface to be ground with the grinding surfaces of the active area 430. In this respect, this corresponds to the function of a conventional cup grinding wheel.

[0067] The annular effective area 430 is relatively narrow compared to the radius or radius of the base body 410. In this embodiment, the annular effective area has a width measured in the radial direction that lies in the range of 2% to 10% of the radius or radius of the base body.

[0068] In Fig. 2, it is also clearly visible that the annular effective region 430 protrudes radially outward beyond the circumferential surface 413 of the base body 410. The annular effective region 430 thus extends outward beyond the circumferential surface of the base body. In other words, the annular effective region 430 has an outer radius that is larger than the radius or radius of the base body, resulting in a radial projection 414. The projection 414 can, for example, be 1% or more, 2% or more, or 5% or more of the radius of the base body. When the tool segments 500 are mounted in their respective associated mounting regions 420 on the circumference of the base body 410, the longitudinal direction L of the tool segments is oriented tangentially to the disk rotation axis 402, the width direction is approximately in the radial direction to the disk rotation axis, and the height direction is parallel thereto.The direction parallel to the disk rotation axis is also referred to here as the axial direction.

[0069] One of the distinguishing features of the 400 grinding wheel unit is that the individual tool segments can be mounted on the base body in the correct installation position very quickly and removed just as quickly to be replaced with tool segments with fresh cutting surfaces when needed. This allows for quick tool changes without having to remove the base body from the tool spindle. After the tool change, the tool segments are then seated in a precisely specified position on the base body, so that either subsequent joint dressing of the cutting surfaces is not necessary or any dressing required can be completed in a short time. The special design and configuration of the base body in the respective assembly areas contributes to this.

[0070] The design of a mounting area 420 can be seen particularly well in Fig. 3, which shows, among other things, a side view of an mounting area without the tool segment to be mounted later therein. Located in the mounting area is a receiving device 440, which is essentially designed as a recess in the material of the peripheral section 412 of the base body 410, wherein its side surfaces, which are at an angle to one another, have a special structure and serve as stop surfaces for the position-defined reception of a tool segment 500. The recess in the base body is open outwards in the radial direction R of the base body and forms a radial stop surface 442 towards the disk rotation axis 402 for the facing side surface 514 of the cutting means carrier.The recess is open in the axial direction towards the side surface of the grinding wheel unit, but does not extend to the other side of the base body, but forms an axial stop surface 444 at a certain distance from the top side of the base body, which is in contact with the underside 512 of the cutting means carrier when the tool segment is installed.

[0071] The radial and axial stop surfaces are not designed as simple flat surfaces, but are stepped off several times, so that on each of the stop surfaces two webs are formed which are located at a distance from one another, the free surfaces OB of which are each coplanar and have been machined with a high mechanical precision, e.g. with a flatness in the range of 0.02 mm. As can be clearly seen in Fig. 3 on the tool segment used, the cutting medium carrier can be used in such a way that the underside 512 of the cutting medium carrier rests on the respectively facing flat surfaces OB of the webs of the axial stop surface, with free space still remaining in the area between the webs and to the sides of the webs. The situation is corresponding on the inward-facing radial support surface, where two parallel webs with coplanar upper sides are also formed, which serve as stop surfaces for the side surface of the cutting medium carrier.

[0072] These stop surfaces make it possible to precisely specify the position of an inserted tool segment in both the axial and radial directions, eliminating the need for subsequent adjustments in these directions. Accordingly, no complicated adjustment devices are required or provided.

[0073] The exact position definition in the circumferential direction is also obtained by contact with a stop surface, which is explained below in connection with the description of the quick-action clamping device.

[0074] For the position-defined fastening of a tool segment to the base body, each of the mounting areas is equipped with a quick-action clamping device 470, which is designed in the manner of a dovetail clamping device. The quick-action clamping device acts essentially in the circumferential direction or tangential direction of the grinding wheel unit in such a way that the effective width of the holding device for the holder can be adjusted in the circumferential direction so that a larger width can be set for inserting and replacing a tool segment 500, which allows removal and insertion in the axial direction (open configuration). The dovetail clamping device can also be converted into a closed clamping configuration by simple actuation, in which an inserted tool segment can be clamped with force components acting in the circumferential direction and thus fixed to the base body.

[0075] For this purpose, the recess of the receiving device 440 has a circumferentially acting stop surface 446, which is perpendicular to the axial stop surface and at an angle other than 90° to the radial stop surface. The inclined surface (stop surface 446) formed on the material of the base body serves as the fixed flank of the dovetail contour of the dovetail clamping device. The inclination is such that the inclined flank can be gripped behind in the radial direction. On the opposite side in the circumferential direction is the movable part of the dovetail clamping device. This comprises a wedge-shaped clamping element 460 (see Fig.4), which, when assembled, widens from radially inward to outward, is supported with a circumferentially directed side on a support surface of the base body lying in a radial plane, and has a flat inclined surface 447 on the circumferentially opposite side, which serves as an adjustable flank of the dovetail clamping device. The fixed flank 446 and the circumferentially opposite adjustable flank, together with the radial support surface, form a dovetail groove that widens from radially outward to radially inward toward the radial contact surface 442.

[0076] The cutting medium carriers 510 of the tool segments 500 to be inserted each have a corresponding bevel in the area of ​​the end faces oriented obliquely to the tangential direction, so that the cutting medium carriers of the tool segments are not exactly cuboidal in shape, but rather have a trapezoidal shape in section along the LB plane, such that they are wider on the inside than on the radial outside. If such a tool segment is inserted into the receiving device from above (or below) in the axial direction with the clamping device open, a positive locking effect is already established even with the clamping device open, such that falling out of the tool segment in the radial direction is no longer possible.

[0077] The quick-action clamping device 470, designed as a dovetail clamping device, can be conveniently switched between the open configuration (for inserting or removing a tool segment) and the clamping configuration (for securing an inserted tool segment) by actuating a single actuating element. It is just as easy to release the dovetail clamping device again in order to remove a tool segment. This functionality is explained, among other things, in connection with Fig. 4. This shows a clamping assembly 472, which is part of the dovetail clamping device and comprises the wedge-shaped clamping element 460, an actuating screw 462, and a counter-bearing element 464 that is cylindrical over a large part of its circumference.The counter bearing element 464 is inserted into a cylindrical blind hole 465 at the edge of the mounting area in the base body and has a threaded hole perpendicular to the flattened side into which an end threaded section of the actuating screw 462 can be screwed.

[0078] The wedge-shaped clamping element 460 has a radially continuous bore with an internal threaded portion into which an external threaded portion engages when the actuating screw 462 is inserted. One of the threaded portions is a left-hand thread, the other is a right-hand thread. This means that when the actuating screw 462 is turned in one direction (for example, clockwise), the wedge-shaped clamping element is advanced toward the counter-bearing element. When the actuating screw is turned in the opposite direction, the radial distance between the counter-bearing element and the clamping wedge is forcibly increased, so that the clamping device can be released with the appropriate torque even if it has become jammed, for example, if it has been engaged with the tool segment for a long time.

[0079] A tool change, or more precisely a change of the tool segments on the base body of the grinding wheel unit, is very easy using the following procedure. Let's start with a fully assembled grinding wheel unit whose grinding surfaces are worn out after extended operation and therefore need to be replaced. To do this, the grinding wheel rotation is stopped and the tool segments are gradually removed. To release a tool segment from its corresponding holder, an operator or a robot simply has to turn the actuating screw 462 of the wedge-shaped clamping element in the opening direction, which forcibly moves the clamping wedge outwards and opens the dovetail clamping device. The tool segment can then be removed and replaced with a fresh one.By turning the actuating screw in the opposite direction, the tool can be firmly reattached to the holding fixture and pressed against the axial, radial, and circumferential stop surfaces. Such a tool change can be performed quickly for all tool segments, significantly reducing tool change times compared to conventional solutions.

[0080] The grinding wheel unit and its tool segments are characterized by further special features which, independent of the special features enabling rapid tool segment changes, can also be provided in other generic grinding wheel units.

[0081] A special feature is that the tool segments 500 of the exemplary embodiment each have a segmented cutting coating on the cutting coating side 515 of the cutting means carrier 510. A segmented cutting coating in this sense has at least two cutting material bodies arranged at a mutual distance from one another. In the example, the tool segment 500 has five identical cutting material bodies 522, each with relatively narrow, rectangular active surfaces 525. Each of the cutting material bodies contains irregularly shaped cutting grains of different shapes and sizes, which are bonded within a bond system. By selecting the type of cutting coating formed in this way, a grinding tool can be precisely adapted to the desired machining task. Cutting grains can be, for example, diamond grains or grains made of cubic boron nitride (CBN).Cutting grains can also be made of corundum and / or other types of ceramic materials, such as SiC. The bond can be made of a ceramic material or synthetic resin, for example. Metallic bond systems, such as electroplated bonds or sintered bonds, are also possible, as are brazed bonds.

[0082] In the example shown in Fig. 5, the abrasive cutting material bodies 522 are each mounted on a metallic base 524 and, together with the base, form a cutting bar 530. A cutting material body can be attached to the base, for example, by sintering, soldering, gluing, or by means of another adhesive layer. It is also possible for a cutting bar to consist entirely of a cutting material body, meaning no stabilizing base is present.

[0083] The cutting tool carrier 510 has a total of five receiving grooves 516 on its cutting surface side with a rectangular cross-section and a width dimensioned such that a cutting bar 530 can be inserted into a receiving groove with minimal lateral play and secured there, for example by gluing. The receiving grooves are arranged at equal distances from one another, with the distance measured in the width direction approximately corresponding to the width of the receiving grooves. In the example case, a cutting bar 530 is inserted into each of the receiving grooves 516; in other embodiments, one or more receiving grooves remain free, so that, for example, only three cutting bars arranged at greater distances from one another can be accommodated. A cutting tool carrier can also have more or fewer receiving grooves; advantageously, there should be at least three.

[0084] A special feature here is that the receiving grooves or the cutting bars accommodated therein are oriented at an angle to the longitudinal direction L of the cutting means carrier and also at an angle to the width direction B of the cutting means carrier. The acute angle SW between the width direction L of the cutting means carrier and the longitudinal direction LS of the cutting bars 530 is in the example case in the range of 20° to 40°, in particular approximately 30°. This means that the longitudinal directions LS of the cutting bars, when the tool segment is mounted on the base body, are oriented at an angle to the radial direction R of the grinding wheel unit so that they are inclined by approximately 20° to 40° relative to the radial direction. This inclined cutting means arrangement has proven in numerous tests to be advantageous for several reasons compared to other orientations with cutting bars, which are also possible. For example, Fig.7 shows an embodiment of a tool segment with a segmented cutting surface, consisting of three cutting bars 530 arranged in a row, which are oriented in the longitudinal direction of the cutting means carrier or, in the assembled state, in the tangential direction of the grinding wheel unit. In other variants, only two cutting bars arranged in a row are provided, e.g., with dimensions of 6x10x30 mm (WxHxL).

[0085] Tests have shown that, compared to conventional non-segmented grinding wheels, segmented grinding wheels offer improvements in cooling and flushing with coolant, as well as wear reduction. The rectangular shape allows for optimized production.

[0086] In addition to these advantages of segmented cutting surfaces, the inclined cutting means arrangement, which is shown as an example in Fig. 5, offers further advantages. Among other things, the cooling lubricant flushing is further improved. This is attributed, among other things, to the fact that the inclined cutting bars 530 of the grinding wheel unit act similarly to inclined turbine blades when they rotate, so that the rotation of the grinding wheel forces the cooling lubricant to flow through the inclined spaces between the cutting bars, both to better cool the cutting bars and to quickly remove abrasion. This allows for a further reduction in wear.

[0087] It has also been shown that the angled position can ensure a better distribution of machining forces on the workpiece. While the effective area achieved in the radial direction is relatively narrow for cutting bars that are arranged essentially in the tangential direction of the cutting disc unit, the effective area of ​​an inclined cutting bar of the same width is significantly broadened due to the angled position, which leads to a better distribution of the load. This results in a wider cutting area in the radial direction, over which the force is applied over a larger zone.

[0088] In addition, the total effective engagement surface for cutting bars of a given width is substantially larger in the case of multiple inclined cutting bars than in the case of tangential cutting bars of the same width. The inclined position of cutting bars also offers the possibility, in principle, of accommodating a relatively large number of particularly effective cutting bar leading edges in the tangential direction. "Leading edge" refers to the longitudinal edge of a cutting bar 530 that leads in the direction of rotation of the grinding wheel unit and is the first to engage the workpiece to be machined. Thus, a tool segment of the type shown in Fig. 5 has five leading cutting body edges, each extending over a relatively large width in the radial direction (width direction).

[0089] In previous tests, machining scenarios with down-cut and up-cut grinding, as well as with different diameters of grinding wheel units and different cutting edge angles, were investigated. Under the investigated boundary conditions, inclinations in the range of approximately 30° ± 5° (as in the example in Fig. 5) proved to be particularly favorable. Deviations from this can also be favorable under other machining conditions, but it appears that acute angles SW with respect to the radial direction of a grinding wheel unit should generally not exceed 45°.

[0090] In the examples shown in Figures 5 and 6, all cutting material bodies are positioned at an angle to the radial and tangential directions of the grinding wheel unit, using the inclination angle. However, this is not mandatory. In an embodiment not shown, inclined cutting edges alternate with cutting edges oriented in the tangential direction, which are arranged near the outer circumference of the grinding wheel unit. Thus, such a grinding wheel unit has a larger total effective area in the immediate vicinity of the radial edge than in the more inward region of the effective area of ​​the segmented cup wheel defined by the cutting pads. Such a variant can be advantageous if the machining situation allows only a small overrun of the grinding wheel unit over the area to be ground.

[0091] There are also machining tasks in which the surface to be ground is difficult for the grinding wheel unit to access. For example, there are brake discs whose hub section widens starting from the level of the braking sections to be ground, so that the diameter of the hub section is smaller at the level of the braking sections than at an axial distance from it. The area of ​​the braking section below the projection thus formed cannot be reached with conventional grinding wheel units, since the circumference of the grinding wheel unit would collide with the upper projection of the hub section when approaching the hub section, so that an inner zone of the braking section is not reached by the cutting elements. According to the inventors' proposals, such problems can be solved with tool segments of the type shown in Fig. 6.The tool segment 600 has a cutting tool carrier 610, which has a greater width in the section on the cutting surface side than in the opposite end section near the underside. In other words, the cutting tool carrier has a projection 612 toward the cutting surface side, so that the width BWW of the effective surface of the inclined cutting bars 630 (effective in the radial direction of the grinding wheel unit) is significantly greater here than the width BS of the cutting tool carrier on its underside.

[0092] If such tool segments are attached to the base body of the grinding wheel unit, the latter has an outer effective area on the abrasive side surface that extends further outward in the radial direction, so that the outer radius of the effective area is larger than the outer radius of the base body. In other words, the effective area formed by the angled cutting edges can extend beyond the imaginary axial extension of the cylindrical outer contour of the base body. This also allows the radially inner zone of the braking section to be reached for grinding without the grinding wheel unit colliding with the hub section of the brake disc.

Claims

Patent claims 1. Grinding wheel unit (400) for use in a side face grinding machine (100), which has at least one tool spindle (132-1, 132-2) which can be driven in rotation about a spindle axis (136-1, 136-2) by means of a spindle drive (134-1, 134-2), comprising: a base body (410) which defines a wheel rotation axis (402) and is or can be mounted on the tool spindle (136-1, 136-2) in such a way that the wheel rotation axis (402) runs coaxially to the spindle axis; wherein the base body (410) has, in a radially outer circumferential region (412), a plurality of mounting regions (420) arranged offset from one another in the circumferential direction of the base body, with fastening devices for fastening a respective replaceable tool segment (500, 600) to the base body (410);wherein a tool segment (500, 600) has a cutting means carrier (510) with mounting structures for fastening the cutting means carrier in one of the mounting areas and a cutting lining (520) on a cutting lining side (515), which forms an abrasive active surface of the tool segment, wherein the abrasive active surfaces of the cutting linings are arranged in a side surface (135-1, 135-2) of the grinding wheel unit oriented perpendicular to the wheel rotation axis within a radially outer annular active area (430) at a radial distance from the wheel rotation axis (402), so that the grinding wheel unit is designed in the manner of a cup wheel segmented in the circumferential direction, characterized in that a mounting area (420) has a receiving device (440) with stop surfaces (442, 444) for receiving a tool segment (500, 600) in a position-defined manner and a; Quick-action clamping device (470) which can be switched between an open configuration and a clamping configuration, wherein in the open configuration a tool segment (500, 600) can be inserted into the receiving device (440) or removed from the receiving device and in the clamping configuration the tool segment can be pressed against the stop surfaces and fixed in a predetermined position on the base body (410).

2. Grinding wheel unit according to claim 1, characterized in that the quick-clamping device (470) can be switched between the open configuration and the clamping configuration by actuating a single actuating element (462).

3. Grinding wheel unit according to claim 1 or 2, characterized in that a receiving device (440) comprises a recess in the base body (410), wherein the Recess is open outwards in the radial direction (R) and has at least one radial stop surface (442) in the opposite direction and is open towards the side surface in the axial direction and has at least one axial stop surface (444) in the opposite direction, wherein preferably in the region of a radial stop surface (442) and / or in the region of an axial stop surface (444) on the surfaces delimiting the recess, two or more webs offset from one another in the circumferential direction with intermediate recessed sections are provided, wherein the upper sides (OB) of the webs serving as stop surfaces are manufactured with high precision.

4. Grinding wheel unit according to one of the preceding claims, characterized by at least one of the following features: a number of tool segments (500, 600) is in the range from 10 to 20; the annular effective region (430) has a width measured in the radial direction (R) that is 2% to 20% of the radial extent of the grinding wheel unit between the wheel rotation axis (402) and an outer edge of the grinding wheel unit; the annular effective region (430) has a width measured in the radial direction (R) that is 2% to 20% of the radius of the base body; the grinding wheel unit has an outer effective region on the abrasive side surface, which extends outwards in the radial direction such that the outer radius of the effective region is larger than the outer radius of the base body.

5. Grinding wheel unit according to one of the preceding claims, characterized in that the quick-action clamping device (470) is designed in the manner of a dovetail clamping device, wherein preferably a dovetail contour is oriented such that insertion and removal of the tool segment (500, 600) from the dovetail clamping device can be carried out in a direction parallel to the wheel rotation axis (402).

6. Grinding wheel unit according to claim 5, characterized in that the dovetail clamping device (470) has a fixed dovetail flank and a circumferentially opposite adjustable dovetail flank and the dovetail flanks delimit a dovetail groove which has a radially inner groove bottom surface and narrows radially outward.

7. Grinding wheel unit according to one of the preceding claims, characterized in that the quick-clamping device (470) has a wedge-shaped clamping element (460) which is arranged over a, preferably radially oriented, Actuating screw (462) is movable in the radial direction (R), wherein preferably at least one of the following features is realized: i) a wedge surface of the wedge-shaped clamping element forms a movable flank of an associated dovetail clamping device (470) ii) the wedge-shaped clamping element is movable both radially inwards and radially outwards by means of the actuating screw (462), iii) the actuating screw (462) has a section with a right-hand thread and a section with a left-hand thread.

8. Grinding wheel unit according to one of the preceding claims, characterized in that a tool segment (500, 600) on the cutting coating side (515) of the cutting means carrier (510, 610) has a segmented cutting coating (520) which comprises at least two cutting material bodies (522) arranged at a mutual distance from one another, wherein the cutting coating preferably has three, four, five, six or more cutting material bodies.

9. Grinding wheel unit according to one of the preceding claims, characterized in that the cutting material bodies each have a narrow, in particular rectangular, active surface (525) which is delimited by two longitudinal edges running parallel or almost parallel to one another in the longitudinal direction of the cutting material body and transverse edges running transversely to the longitudinal edges, wherein a length LW of the active surface measured parallel to the longitudinal edges between the transverse edges is several times greater than a width BW of the active surface measured perpendicular to the longitudinal edges, wherein preferably an aspect ratio between the length LW and the width BW is at least 3:1 and / or is in the range from 3:1 to 6:

1.

10. Grinding wheel unit according to one of the preceding claims, characterized in that a tool segment (500, 600) has at least one cutting material body (525) which, in the assembled state of the tool segment, is oriented obliquely to the radial direction (R) and obliquely to the tangential direction (T) of the grinding wheel unit (400) in such a way that the longitudinal direction of the active surface within the annular active region (430) of the grinding wheel unit is aligned neither tangentially nor radially, but obliquely to these two directions, wherein preferably a tool segment (500, 600) has two or more cutting material bodies (525) arranged at a mutual distance from one another, which are oriented obliquely to the radial direction and obliquely to the tangential direction of the grinding wheel unit in the assembled state of the tool segment.

11. Grinding wheel unit according to claim 10, characterized in that a longitudinal direction (LS) of an obliquely oriented cutting material body (522) encloses an acute angle (SW) of a maximum of 45° with a radial direction (R) of the grinding wheel unit, wherein the angle is preferably in the range from 15° to 40°, in particular approximately 30°.

12. Grinding wheel unit according to one of the preceding claims, characterized in that the base body has a circumferential surface which lies within a minimum enveloping circle coaxial with the wheel rotation axis and in that the cutting means carriers of the tool segments have a projection on the cutting coating side such that when the tool segment is mounted, the cutting coating projects in the radial direction by an overrun width beyond the minimum enveloping circle, wherein preferably an annular effective surface of the grinding wheel unit defined by the effective surfaces of the cutting coatings has an outer radius which is larger than the radius of the base body.

13. Side face grinding machine (100) for grinding a substantially flat workpiece surface on a workpiece section (WA) of a workpiece (WS1, WS2), in particular a double-side face grinding machine for grinding workpiece surfaces of a circular ring-shaped brake section of a brake disc, comprising a grinding unit (121) with at least one tool spindle (132-1, 132-2) which carries a grinding wheel (130-1, 130-2) with an abrasive side surface (135-1, 135-2), wherein the grinding wheel is rotatable about the associated rotational axis (136-1, 136-2) by means of an associated rotational drive (134-1, 134-2) and can be fed parallel to the associated rotational axis by means of an infeed drive (131-1, 131-2), at least one workpiece spindle (154) with a workpiece holder (155) for rotationally fixed Holding the workpiece (WS1, WS2),wherein the workpiece holder is rotatable by means of a rotary drive (157) about a rotational axis (156) extending parallel or obliquely to the rotational axis of the grinding wheel and is arranged in a working position at least during a phase of a grinding operation such that the workpiece section (WA) of the received workpiece comes into contact with the abrasive side surface, characterized in that the grinding wheel is designed as a grinding wheel unit (400) according to one of the preceding claims.

14. A method for producing a grinding wheel unit according to any one of claims 1 to 12, comprising the following steps: Forming a tool segment group from all tool segments to be attached to the base body in such a way that the tool segments are held in a fixed spatial relationship to one another and the cutting surface sides lie in a common plane; Joint dressing of all cutting surfaces of the tool segments of the tool segment group by surface grinding in such a way that the abrasive active surfaces of all cutting elements lie in a common plane; Installing the tool segments in the assigned holders on the base body.

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