PROCESSING MACHINE AND METHOD AS WELL AS MANUFACTURING PLANT FOR THE PRODUCTION OF COATED BRAKE DISCS

Description

[0001] The invention relates to a processing machine for use in the production of a coated brake disc, a method for producing a coated brake disc and a production plant for producing a coated brake disc.

[0002] A brake disc is the part of a disc brake that is non-rotatably connected to the wheel, upon which the brake pads attached to a brake caliper act to decelerate rotational movement. A brake disc is usually point-symmetrical or rotationally symmetrical to an axle center through which the axis of rotation of the brake disc passes. A brake disc has the actual braking surface or friction surface and an inner hub section with the offset axle attachment or hub. The braking surface forms a circular ring on the brake disc.

[0003] Conventional brake discs for the mass market are usually made of gray cast iron. Gray cast iron brake discs are now reaching their limits in terms of corrosion and wear behavior, among other things. While there are also brake discs made of ceramic materials, these are expensive and currently only available for high-end vehicles.

[0004] 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 the surface sections intended as friction surfaces, with a thin functional layer of more wear-resistant material. The friction surfaces of brake discs typically extend in a circular ring around a central hub area around the rotational axis of the brake disc. Accordingly, the coated sections are designed to be rotationally symmetrical to the rotational axis.

[0005] In the production of coated brake discs, the manufacturing process includes at least one coating operation for coating the metallic base body of a brake disc with at least one functional layer, which generally consists essentially of metal and can, for example, have a wear-reducing and / or corrosion-inhibiting function. A functional layer can have one or more layers with different properties. This is usually followed by further processing operations, particularly grinding operations, to prepare the surface of the functional layer so that it can serve as the friction surface of the brake disc.

[0006] WO 2021 / 122951 A1, for example, discloses a device for coating brake discs, in particular by means of laser deposition welding. The device comprises a base with a housing forming a work space, a workpiece carrier in the work space, wherein the workpiece carrier is designed to receive a base body of a brake disc, a coating head designed to produce a coating on the base body, a handling device that generates relative movements between the workpiece carrier and the coating head, and a multi-stage extraction device for extracting excess material from the work space. Among other things, the coating of brake discs using laser deposition welding, in particular using high-performance laser deposition welding processes, such as the EHLA process, is described. The system is intended to be suitable for large-scale production.

[0007] The abbreviation "EHLA" stands for "Extreme High-Speed ​​Laser Material Deposition." This is a variant of laser cladding in which the deposition powder is melted not on the surface of the object to be coated (brake disc), but before the material reaches the surface. This allows relatively thin layers to be created at relatively high speeds. This process was developed at the Fraunhofer Institute for Laser Technology ILT and RWTH Aachen University.

[0008] DE 10 2011 100 456 A1 discloses a corresponding laser cladding process designed for applying wear-resistant and / or corrosion-resistant coatings to a base body with high deposition rates. The process utilizes powdered material that is supplied to a component and melted by thermal energy generated and applied by a laser at a distance from the surface to be coated, bonding it to the component.

[0009] Document EP 3 789 511 A1 discloses a coating device for metallically coating workpieces, in particular brake discs. The coating device has a housing enclosing a work space and a holding device for holding at least one workpiece in the work space. At least two application devices are arranged in the work space, which are designed for the simultaneous application and melting of metal powder. In one embodiment, a brake disc is arranged with a horizontal axis of rotation and coated simultaneously on both sides. This is intended to enable efficient production.

[0010] DE 10 2020 007 581 A1 discloses a device for coating brake discs comprising at least one swivel table with driven workpiece supports for receiving the brake disc to be coated, at least one inductive heating device for preheating and / or heating the brake disc, at least one processing optics, at least one powder application nozzle, wherein at least one sensor system for measuring the layer thickness is provided, wherein the processing optics, the powder application nozzle and the sensor system for measuring the layer thickness can be driven simultaneously. TASK AND SOLUTION

[0011] Against this background, the object of the invention is to provide a processing machine for use in the production of a coated brake disc, a method for producing a coated brake disc and a production plant for producing a coated brake disc, which enable the production of coated brake discs at moderate unit costs on an industrial scale.

[0012] To achieve this object, the invention provides a processing machine usable in the production of a coated brake disc, having the features of claim 1. Furthermore, a method for producing a coated brake disc, having the features of claim 10, and a production system, having the features of claim 14, are provided, which comprises at least one processing machine. Preferred developments are specified in the dependent claims. The wording of all claims is incorporated into the content of the description by reference.

[0013] A coated brake disc has a base body that has a rotationally symmetric mass distribution with respect to a rotational axis of the brake disc and comprises a central hub section and a circular ring-shaped braking section surrounding the hub section. The braking section has two axially opposite surfaces, each bearing a coating that is rotationally symmetric with respect to the rotational axis, the free surface of which is designed as the friction surface of the brake disc. The desired macrostructure and microstructure of the free surface of the coating can be created, for example, by grinding the initially possibly rough, possibly grooved and / or wavy surface of the coating. The brake disc (uncoated or coated) is also referred to briefly as the "workpiece" in this application.

[0014] To carry out method steps of the method, a processing machine is provided which has a transport system comprising a movable spindle support unit which supports at least one workpiece spindle. A workpiece spindle is a functional unit or an assembly comprising several components with different functions. The workpiece spindle is mounted so as to be rotatable about a spindle rotation axis relative to the spindle support unit. It has a workpiece holding device which is designed such that a workpiece held on the workpiece holding device in the form of a brake disc or a base body of the brake disc is rotated about the spindle rotation axis when the workpiece spindle rotates.

[0015] In preparation for machining, the workpiece is secured to the workpiece holding fixture, e.g., by clamping. For brake discs, the fastening is carried out so that the brake disc's rotational axis is positioned as coaxially as possible with the spindle's rotational axis. The workpiece is preferably secured during a phase in which the workpiece spindle is not rotating around the spindle's rotational axis, but is stationary.

[0016] The spindle carrier unit of the transport system is then moved to transport the workpiece, which is held on the workpiece spindle, to a machining position at a machining station. The location where the workpiece is loaded onto the workpiece spindle is thus located away from the location where machining is performed. The internal transfer within the machine is performed by the transport system.

[0017] A processing machine for carrying out the method accordingly has several, i.e., two or more, work stations arranged along a transport path and accessible by the workpiece spindle, which work stations comprise a loading station and at least one machining station with at least one machining unit for machining at least one side of the workpiece. In the loading station, the workpiece is secured to the workpiece holding device of the workpiece spindle, which is then moved to the machining station together with the workpiece held thereon.

[0018] When the workpiece is in the machining position of the machining station, a machining operation is performed in which a section of at least one side of the workpiece that is rotationally symmetrical to the spindle rotation axis and / or the workpiece's rotation axis is machined. The workpiece is rotated about the spindle rotation axis by rotating the workpiece spindle at a working speed. The machining unit then machines the rotating workpiece.

[0019] The term "working speed" can describe a specific speed that should remain constant within tolerances during the machining process. However, the term "working speed" also encompasses a more or less extensive speed range, ranging from a minimum to a maximum speed. The working speed can change within this range during machining, possibly according to a temporal speed profile specified by the control system. For example, the working speed can vary such that the relative speed between a locally acting machining tool and the surface remains constant in all radial positions.

[0020] Depending on the machining technology used, in many embodiments the rotating workpiece and the machining unit are moved relative to one another during workpiece rotation in order to achieve surface machining. This relative movement can be generated, for example, by moving a machining unit while the workpiece spindle with the workpiece mounted thereon is not moved to a different position during machining. However, it is also possible for the machining unit to remain stationary during machining while the workpiece spindle moves with the rotating workpiece carried by it. A combination with a moving machining unit and a workpiece spindle moved transversely to the spindle rotation axis is also possible.If a machining technique is used that acts simultaneously over the entire radial extent of the area to be machined, a relative movement in addition to the workpiece rotation can also be omitted.

[0021] In some embodiments, the processing comprises the creation of a rotationally symmetric functional coating or a functional layer on at least one surface of the brake section. The method and the processing machine are then configured to create a rotationally symmetric functional layer on at least one surface of a workpiece. A "rotationally symmetric functional layer" is a more or less thin layer of material with a specific technical function, which is applied to the surface to be coated in such a way that the coating material is distributed essentially rotationally symmetrically to an axis of symmetry of the rotationally symmetric functional layer. In brake discs, the functional layer is applied in a circular region around the axis of rotation of the brake disc in order to provide the friction surface for the brake pads.In a fully coated brake disc, the functional coating often has several layers with different functions, such as an adhesion layer and a wear layer applied on top. However, single-layer functional coatings are also possible.

[0022] Another form of processing is grinding a functional layer applied to the brake section to smooth its initially overly rough surface and reduce any existing waviness and / or thickness variations. The processing machine can thus also be configured as a grinding machine. Processing can also involve preparing a surface for subsequent processing, e.g., by roughening it with a laser or mechanically, or by other means. Processing can also include cleaning with or without cleaning agents.

[0023] A workstation can also be designed as a measuring station, which generally does not change the workpiece and therefore does not represent any processing.

[0024] In a machining station, the workpiece is rotated around the spindle's rotation axis at a working speed by rotating the workpiece spindle. A machining unit then processes the rotating workpiece.

[0025] According to one aspect of the claimed invention, the workpiece spindle is set into rotation at an increasing speed after the workpiece is secured to the workpiece holding device and before reaching the machining position, and the workpiece held on the workpiece spindle is thereby moved into the machining position already rotating at an entry speed. This means that after the workpiece is secured to the workpiece spindle, the spindle is already accelerated and thus rotated at an increasing speed before the workpiece spindle arrives at the machining station due to the movement of the spindle support unit. The drive system and the control unit can be configured accordingly and are configured accordingly in an operating mode.

[0026] The acceleration of the rotary movement can begin immediately after the workpiece is secured to the workpiece holding device, i.e. before the spindle carrier unit is set in motion to leave the loading station and transport the workpiece spindle to the machining station.

[0027] With this process control, the workpiece is already rotating at an entry speed when it reaches the machining position in the machining station. This entry speed can essentially correspond to the desired operating speed for the machining process, so that machining can begin without delay as soon as the workpiece is in the machining position. However, the entry speed can also deviate from the operating speed, e.g., be lower than the operating speed, requiring an additional, short acceleration phase.

[0028] In any case, this approach allows the unproductive downtime required to accelerate the workpiece spindle from standstill to operating speed to be partially or completely shifted to a phase before the start of the machining operation. Accordingly, the dwell time of the workpiece or the workpiece spindle supporting the workpiece in the machining station is essentially reduced to the time required for machining the rotating workpiece, possibly plus a very short period of time to change the speed from the entry speed to the operating speed.

[0029] Compared to other procedures in which the workpiece is first positioned in the machining station and only there gradually brought up to working speed, processes with pre-acceleration can significantly reduce the dwell time of a workpiece in a machining station because at least part of the acceleration phase for generating the working speed already takes place in advance outside the machining station.

[0030] By accelerating the workpiece rotation between loading and the start of the machining operation in the machining station, a significant time saving can be achieved, which is particularly advantageous for processes with high machining outputs or correspondingly short dwell times in the machining station. A further advantage is that more time is available for the workpiece spindle to accelerate from standstill to operating speed. This allows even workpieces with higher masses to be gradually brought up to speed without overloading the drives, and / or allows smaller and / or weaker and / or more economical spindle drives to be used.

[0031] This acceleration of the rotary movement before reaching the machining station can be provided regardless of the spindle drive arrangement. It can be advantageously used, for example, in machining centers with "traveling" spindle drives. The acceleration can also be provided in machining centers with at least one frame-mounted spindle drive according to a further development of the invention described below.

[0032] The advantages of this approach are particularly evident in machining processes that require the workpiece to rotate at relatively high speeds during machining. Typical speeds can be in the range of more than approximately 100 rpm, preferably in the range from 150 rpm to 600 rpm, for example in the range from 200 rpm to 500 rpm. This means that laser deposition welding or other additive processes can be completed within short machining times. For other machining processes, lower speeds in the range of one or fewer workpiece revolutions per minute may be more advantageous, such as in grinding.

[0033] As mentioned, the processing machine can be configured, for example, as a coating machine used in a coating process.

[0034] Using the coating process and the coating machine, it is possible to provide workpieces with a rotationally symmetrical functional layer on one side only.

[0035] Some embodiments, however, are designed for double-sided coating, wherein in a first coating operation a first rotationally symmetric functional layer is applied to a surface region of a first side and in a second coating operation a second rotationally symmetric functional layer is applied to a surface region of a second side.

[0036] In some process variants, the first and second coating operations are performed in overlapping time periods, i.e., in phases or completely simultaneously. For simultaneous coating of two opposite sides, it may be advantageous to position the workpiece with a horizontal rotation axis in the coating station and to coat the opposite sides, which are essentially located in vertical planes, simultaneously.

[0037] In other embodiments, however, the first and second coating operations are performed sequentially. In particular, the workpiece may be secured to the workpiece holding device in a first orientation for the first coating operation, released from the workpiece holding device after the first coating operation, turned from the first orientation to a second orientation in a turning operation, and reattached to the workpiece holding device in the second orientation. The second side can then be coated.

[0038] Although such turning operations are also possible in embodiments with horizontally oriented spindle rotation axes, turning is preferably used in combination with an arrangement of the workpiece in which the spindle rotation axis of the workpiece spindle is oriented vertically, so that the surfaces to be coated lie substantially in a horizontal plane.

[0039] In the case of simultaneous coating on two opposite sides of the workpiece, it may be sufficient for the coating machine to have a single workstation designed as a coating station. Even in process variants in which the workpiece is turned between a first and a second coating operation, a single coating station may be sufficient, provided that the possibility exists to turn the workpiece after the first coating operation and then perform the second coating operation. The coating station can have an integrated turning unit for this purpose.

[0040] According to a further development, the coating machine is designed such that it has at least two, in particular exactly two, work stations arranged separately from one another, which are designed as coating stations.

[0041] A coating machine designed for this purpose according to a further development comprises several workstations arranged along the transport path of the transport system, which have, in this order, a loading station, a first coating station with at least one coating unit for coating a first side of the workpiece, a turning station for turning a workpiece held on a workpiece spindle, and at least one second coating station for coating a second side of the workpiece. The process steps "coating the first side," "turning," and "coating the second side" are thus spatially separated and approached sequentially by internal machine transfer or transport.

[0042] To produce rotationally symmetrical functional layers on two surface sections of a workpiece located on opposite sides of the workpiece, the following steps can be carried out, for example: arranging the workpiece in a first orientation on the workpiece holding device of a workpiece spindle in a loading operation; transporting the workpiece held on the workpiece spindle to a first coating station; producing a first rotationally symmetrical functional layer on a first side of the workpiece in the first coating operation, wherein the workpiece is rotated about a rotation axis by rotating the workpiece spindle by means of a spindle drive and coating material is applied from a coating unit to the surface of the first side to be coated; transporting the workpiece held on the workpiece spindle to a turning station;Turning the workpiece from the first orientation to a second orientation in a turning operation; transporting the turned workpiece held on the workpiece spindle to a second coating station; creating a second rotationally symmetrical functional layer on the second side of the workpiece in the second coating station, wherein the workpiece is rotated about a rotation axis by means of a second drive by rotating the workpiece spindle, and coating material is applied from a coating unit to the surface of the second side to be coated; transporting the workpiece held on the workpiece spindle to an unloading station; removing the workpiece from the workpiece spindle in an unloading operation.

[0043] A separate unloading station can be provided from the loading station. This is useful, for example, if the transport system is designed for linear transport, i.e., transport along a straight transport path. In preferred embodiments, however, an internal machine transport system with a closed transport path is provided, so that the loading station also functions as an unloading station. This allows the machine to be loaded with uncoated workpieces and the removal of coated workpieces at the same transfer point. This enables the realization of highly efficient coating machines with compact dimensions and correspondingly small space requirements or footprints. Furthermore, linking several such coating machines with an external conveyor system makes this particularly easy.

[0044] In some embodiments, the transport system comprises a rotary table or turntable that rotates around a table axis as a spindle support unit. The table axis can be oriented vertically or horizontally, and possibly also at an angle to the horizontal and vertical.

[0045] In a closed transfer or closed transport route, the loading station also functions as an unloading station, i.e., it is used for loading and unloading. However, this is not mandatory. For example, a linear transport route is also possible, where the loading station and unloading station are located at different ends of the transport route.

[0046] The coating process and the coating machine can be implemented using different coating technologies. According to one development, a coating unit is designed as a laser deposition welding unit and configured to radiate a metal powder toward the surface to be coated and simultaneously guide a laser beam that is focused in a focal area such that the metal powder is melted in the focal area and deposited on the workpiece surface to form the functional layer.

[0047] It is particularly preferred if the coating unit is configured for the so-called EHLA process. The abbreviation EHLA stands for "Extreme High-Speed ​​Laser Material Deposition" (sometimes also for "Extreme High-Speed ​​Laser Material Deposition") and allows for particularly high deposition rates, so that the desired coating surfaces can be coated within short coating times. In the EHLA process, the interaction of the metal powder with the focused laser beam occurs predominantly or exclusively within a focal area located some distance in front of the surface to be coated (see, for example, DE 10 2011 100 456 A1). Other laser deposition welding processes can also be used, especially those in which the impinging metal powder is first melted on the workpiece surface.

[0048] As an alternative to laser cladding, the following coating processes can be used: flame spraying, in particular high-velocity flame spraying (HVOF, high-velocity oxygen fuel), i.e. a thermal coating process for surface treatment, a cold spray process or similar.

[0049] In some embodiments, a contribution to trouble-free operation with the lowest possible risk to the environment is made by providing each coating station with a separate protective housing that encloses a work area of ​​the coating station. Particularly when a laser deposition welding unit or another laser-based coating unit is provided as the coating unit, this can increase the safety of the environment against misdirected laser radiation. Furthermore, powder removal, e.g., by extraction, can be used more effectively. Furthermore, the risk of powder being carried over to another processing position and / or another process is reduced.

[0050] Each protective housing preferably accommodates only the effective area of ​​a single processing unit, especially a laser coating unit. This allows for high safety requirements to be met and allows for compact designs. Furthermore, powder carryover is avoided in laser coating units.

[0051] According to a further development, a special feature of the method and the processing machine lies in the manner in which the (at least one) workpiece spindle is driven. According to one formulation, a torque for rotating the workpiece spindle is transmitted to the workpiece spindle with the aid of a torque transmission device from a stationary spindle drive that is not movable with the spindle support unit. The drive system of the processing machine thus has at least one stationary spindle drive, for example, mounted fixedly to the frame (i.e., on the machine frame), and a torque transmission device for transmitting torque from the spindle drive to at least one associated workpiece spindle.

[0052] This concept eliminates the need for so-called "traveling" spindle drives. A "traveling" spindle drive is a spindle drive that is attached to the spindle support unit and can move with it. With a traveling spindle drive, the transmission of torque from the spindle drive to the workpiece spindle can be solved relatively easily. For example, an output shaft of the spindle drive can be mounted coaxially with the workpiece spindle. However, this design advantage in torque transmission is offset by significant disadvantages regarding the design freedom in the machine layout and the dynamics of the movements. The spindle support unit must then bear not only the weight of at least one workpiece spindle and any workpiece attached to it, but also the weight of the associated spindle drive.In addition, the power and signal supply to the spindle drive must be designed in such a way that they are maintained even when the spindle support unit is moving. According to the inventors' findings, eliminating the need for a moving spindle drive offers significant advantages. While the design of the torque transmission device or drive train may require some structural effort, the advantages of a lower weight load on the spindle support unit and the associated increased dynamics, as well as the advantages of a simpler supply of (usually electrical) power and signals to the spindle drive, far outweigh these disadvantages.

[0053] The technological advantages are particularly evident when a spindle support unit supports multiple workpiece spindles, for example, two, three, four, or more. If these are also coupled with non-traveling spindle drives, the weight of the spindle support unit with workpiece spindles remains moderate, the system's dynamics remain high, and the control and power supply can be implemented simply and reliably.

[0054] According to a further development, the spindle carrier unit carries a plurality of workpiece spindles, in particular three or four workpiece spindles, wherein an associated spindle drive mounted on the frame is provided for each of the workpiece spindles.

[0055] It is possible to design the structure so that a detachable drive connection is provided between the spindle drive and the workpiece spindle. For example, a frame-mounted spindle drive can be provided at each workstation of a multi-station machining center, which is temporarily coupled to the workpiece spindle located at that workstation.

[0056] In preferred embodiments, however, each workpiece spindle is permanently connected to an associated (stationary) spindle drive. This eliminates potential sources of interference when connecting and disconnecting the spindle drive and the workpiece spindle. Furthermore, a permanent connection between the workpiece spindle and the associated spindle drive allows the workpiece spindle to be driven even when the spindle carrier unit is moving to transfer the workpiece spindle.

[0057] According to a further development, at least one spindle drive drives several workpiece spindles simultaneously, e.g., exactly two. From a design perspective, the number of spindle drives may be smaller than the number of workpiece spindles, e.g., only half as many. This can reduce the design effort and cost of the drive system.

[0058] In preferred embodiments, the spindle support unit has a rotary table that is rotatable about a rotary table rotation axis by means of a rotary table drive. The term "rotary table" in the context of this application refers to the component that can be rotated relative to the machine frame, which usually has a flat design and is therefore also referred to as a rotary table plate. The rotatable component can be circular, but this is not mandatory. A rotary table can also be cross-shaped, for example. In some embodiments, the rotary table rotation axis is aligned vertically, so that the rotary table lies in a horizontal plane. However, the rotary table rotation axis can also be aligned obliquely or perpendicular to the vertical direction, in particular in the horizontal direction.The workpiece spindles can be arranged on the circumference of the rotary table so that they can be transported along a circular or circular-arc-shaped transport path between the workstations of a multi-station machining center. Two workpiece spindles can form a pair and be driven by a common spindle drive. For example, workpiece spindles can be distributed so that there are pairs of diametrically opposed workpiece spindles. According to a further development, a common spindle drive is provided for each of the two workpiece spindles in a pair of diametrically opposed workpiece spindles. In such embodiments, the number of spindle drives is only half the number of workpiece spindles. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Further advantages and aspects of the invention emerge from the claims and from the description of embodiments of the invention, which are explained below with reference to the figures. Fig. 1 shows an oblique perspective view of an embodiment of a processing machine configured as a coating machine for coating brake discs; Fig. 2 shows a split sectional view of an embodiment of a rotary table coating machine to explain an example of a drive concept; Fig. 3 shows an example of a production plant with several coating machines and a downstream grinding machine; Figs. 4 to 6 schematically show alternative drive concepts according to other embodiments. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0060] In the following, various aspects of processes for the production of coated brake discs and some of the processing machines and systems that can be used are explained using examples.

[0061] Fig. 1 shows an oblique perspective view of an embodiment of a processing machine 100 designed as a rotary transfer machine, which is configured as a coating machine for coating workpieces in the form of brake discs BS1 to BS4. Fig. 2 shows a split sectional view of the coating machine with components of the drive system. In Fig. 2 the cutting planes to the left and right of a central rotary table axis 152 are offset by 90° from each other, ie the illustration shows two cutting planes rotated by 90° to each other.

[0062] Each of the brake discs 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 rotational axis RB of the brake disc. The brake section has two axially opposite, parallel surfaces. These are each to be coated with a coating or functional layer that is rotationally symmetrical with respect to the rotational axis, the free surface of which ultimately serves as the friction surface of the brake disc.

[0063] In the example case, the circular brake surfaces are to be coated on both sides using a special variant of laser cladding, namely a variant of extreme high-speed laser cladding, which is also known as the "EHLA process".

[0064] The coating machine 100 is configured as a numerically controlled rotary transfer machine with a total of four workstations. All functions are implemented via control commands from a control unit 190, which can be located locally (on or next to the machine) or remotely, e.g., in another room. Fig. 1 Located at the front is a loading and unloading station 110, also referred to here as the first station ST1. There, a brake disc (here BS1) is mounted in a horizontal orientation, i.e., with a vertically aligned rotation axis ("turntable arrangement"), on a workpiece spindle, which will be described later. Fastening can be achieved, for example, by clamping it to a workpiece holding device on 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 spindle rotation axis. A rotationally fixed connection to the workpiece spindle can also be achieved by holding it down or securing it from above.

[0065] A brake disc loaded in this way is then transported by rotating the rotary table 90° clockwise to a processing position in a first laser coating station 120-1, also referred to as the second station ST2. In this station, the upper first side of the braking section of the brake disc is coated. A further indexing of 90° moves the brake disc coated on one side to a turning station 130 (third station ST3), in which the brake disc coated on one side is gripped by a manipulator, removed from the workpiece holding device, and rotated 180° about an axis perpendicular to the rotation axis so that the previously lower, still uncoated second side is on top. In this orientation, the brake disc is placed back on the workpiece spindle and clamped.

[0066] A further cycle of 90° then brings the brake disc to a second laser coating station 120-2 (fourth station ST4), in which the previously uncoated second side of the brake disc is coated.

[0067] The brake disc, coated on both sides, is then rotated 90° to the first station ST1, i.e. to the loading and unloading station 110, from where it can be unloaded, for example, by means of a robot or other handling device or manually.

[0068] A brake disc to be newly coated can be clamped onto the workpiece spindle that is then freed up, so that, with the exception of the changeover times, all four workpiece spindles are occupied with brake discs and are each in different phases of processing or coating.

[0069] Each of the two laser processing stations 120-1, 120-2 contains a single laser processing unit 122. The term "laser processing unit" refers to an application device that radiates a powdered starting material, typically a metal powder, toward the surface to be coated and simultaneously guides a laser beam. This beam is focused in the EHLA process so that the metal powder is melted before reaching the workpiece surface and then deposited onto the workpiece surface in its molten state to form the functional layer. The metal powder is stored in separate storage containers and fed to the laser processing units by powder conveyors 127.

[0070] The laser processing units each have drives for horizontal or axial movement. With the horizontal movement, the laser processing unit can be moved radially relative to the workpiece's rotation axis to apply spiral laser deposition welding tracks to the surface to be coated. The axial movement is used for positioning and adjusting the exact distance to the surface.

[0071] It is possible for the coating unit designed as a laser processing unit to be oriented with respect to the surface to be coated such that the melting laser beam is oriented substantially in the normal direction to the surface. In the exemplary embodiment, however, the coating unit designed as a laser deposition welding unit has a main axis running parallel to the beam exit direction of the laser beam, which is inclined at an angle of more than 5°, e.g. up to approximately 10°, to the spindle rotation axis and / or to the surface normal of the surface to be coated. This makes it easy to avoid disruptions to the coating process caused by laser radiation reflected from the surface to be coated. This enables continuous operation of the coating unit with substantially uniform application properties without significant traces of smoke.

[0072] The turning station 130 (third station ST3) has a gripper 132 that can grip the brake disc at its periphery, as well as a drive for turning the workpiece by rotating the gripper around a horizontal axis of rotation. A vertical translational machine axis is provided for the gripper for lifting and placing.

[0073] To transport the brake discs between the workstations, an internal machine transport system is used, comprising a rotary table or turntable 150, which is mounted on or in the machine base 160 for rotation about a vertical rotary table axis 152 and is infinitely rotatable about the vertical rotary table axis by means of a rotary table drive 155. The plate-shaped rotary table is mounted for rotation on a base plate 162 fixed to the frame by means of crossed roller bearings. As shown in Fig. 2 As can be clearly seen, the rotary table drive 155 is mounted laterally next to the rotary table on the base plate 162 and drives the rotary table via a toothed belt 156, which runs over the toothed circumference of the rotary table and a corresponding drive gear on the output shaft of the rotary table drive.

[0074] To carry out the coating process, the brake discs must be rotated around their rotational axis. At the same time, the laser coating is applied in a more or less spiral pattern from the inside to the outside, or vice versa, by moving the laser processing units radially to the rotational axis of the brake discs. The rotational speed is continuously varied so that the local deposition speed remains essentially constant throughout the entire section of the brake section to be coated.

[0075] The brake discs must be set into relatively fast rotation for the coating process. Typical operating speeds for the coating process can be in the range of several hundred revolutions per minute, for example, between 200 rpm and 600 rpm. This is achieved as follows.

[0076] The rotary table 150 or the rotary table plate, which serves as the spindle support unit 150, carries four workpiece spindles 170-1 etc., each circumferentially offset by 90°, at four positions P1 to P4, each circumferentially offset by 90°. Two workpiece spindles 170-1 and 170-2, located at 90° angles to each other, at positions P1 and P2 are in Fig. 2 visible in longitudinal section.

[0077] Each of the workpiece spindles is mounted in a bearing sleeve 171 fixedly mounted on the top of the rotary table 150, allowing unlimited rotation about a vertical spindle rotation axis 172 relative to the bearing sleeve or rotary table 150. Each freely rotatable workpiece spindle has a clamping head 173 at its upper end, which serves as an adjustable workpiece holding device 173 for securing the brake disc BS. The clamping head is actuated from below by means of a pneumatic actuator 180. A flat contact surface of the brake disc rests on the flat top of the clamping head.

[0078] The actuators 180 for operating the clamping head and the workpiece holding device 173 are not attached to the rotary table 150, but are mounted on a console of the machine frame 160, each in the area of ​​the loading station and the turning station. The clamping head 173 is actuated via a pressure rod 174 that protrudes from the lower end of the workpiece spindle. The clamping head is preloaded in the clamping configuration, so that in the absence of pressure, the clamping head clamps the workpiece. Pressure from below on the pressure rod releases the workpiece.

[0079] Instead of a clamping head that is operated from the side of the workpiece spindle, a hold-down device can also be provided.

[0080] The circular sector-shaped areas of the workpiece spindles or the brake discs mounted thereon are mechanically separated from each other on the top side of the rotary table 150. For this purpose, an arrangement of vertical protective plates 157 is provided on the top side of the rotary table, each of which demarcates a 90° sector around a workpiece spindle from the other sectors.

[0081] Each of the laser processing stations 170-1, 170-2 has its own cover or housing 125-1, 125-2, which largely encloses the associated workspace, i.e., the area of ​​interaction between the laser processing unit and the brake disc. The laser processing unit protrudes from above through an upper opening in this housing into the workspace enclosed by the housing.

[0082] There is no overall cover covering the two laser processing stations, the turning station, and the loading and unloading station. This allows for easy access to the loading and unloading station during loading and unloading. In the area of ​​the turning station 130, protective devices can be provided to protect an operator from unintentional access to the turning area.

[0083] The drive system 200 for rotating the workpiece spindles or the brake discs mounted thereon has some special features which are described below, especially with reference to the Fig. 2 be explained in more detail.

[0084] As mentioned, the workpiece spindles 170-1, etc., are supported by the rotary table 150, which serves as the spindle support unit 150. The drives for generating the rotary motion of the workpiece spindles, i.e., the spindle drives, are not attached to the rotary table, but rather are fixed or fixed to a component of the machine frame 160 in the area below the base plate 162. The rotary table 150 therefore has no moving spindle drives for the tool spindles. This saves considerable weight.

[0085] Furthermore, although a spindle drive is provided for each workpiece spindle, the construction is designed in such a way that only two spindle drives (first spindle drive 220-1, second spindle drive 220-2) are required for the four workpiece spindles.

[0086] The torque for rotating a workpiece spindle is transmitted from the associated frame-mounted spindle drive to the workpiece spindle by means of a torque transmission device (general reference numeral 230).

[0087] The 200 drive system features two independent drive trains for the four workpiece spindles, with two diametrically opposed workpiece spindles each driven by a common spindle drive. The spindle drive is permanently coupled to the two associated workpiece spindles, allowing torque to be transmitted not only when a workpiece spindle is in one of the work positions, but also during rotation of the rotary table for switching between work stations. Torque is thus transmitted independently of the work stations. This makes it possible to drive a workpiece spindle even while the rotary table is rotating.

[0088] The spindle drives are installed in a fixed location, allowing for easy power supply to the drives. Both drive trains run coaxially to each other and coaxially to the rotary table axis. For this purpose, nested hollow shafts are integrated into the drive trains, which feature drive and output elements staggered in height.

[0089] Based on the Fig. 2 A possible implementation is explained which is used in the embodiment of Fig. 1 can be realized. For better comprehension, the following meanings of the terms are highlighted again. The exemplary embodiment of the coating machine has four work stations ST1 to ST4, namely the loading and unloading station (first station ST1), the two laser processing stations (second station ST2 and fourth station ST4), and the turning station (third station ST3). These stations are spatially fixed or stationary relative to the machine frame 160.

[0090] The rotating plate 150 of the rotary table, which serves as the spindle support unit, supports four workpiece spindles at four positions P1 to P4, each circumferentially offset by 90° from each other. The "positions" of the workpiece spindles rotate with the rotary table. Each rotary table position P1 to P4 is successively transferred to each of the work stations ST1 to ST4 as the rotary table rotates. Positions P1 and P3, as well as positions P2 and P4, are diametrically opposite each other on the rotary table axis.

[0091] The vertical section in the left part of Fig. 2 passes through the loading and unloading station or the turning station, which are diametrically opposite each other. Where the brake disc BS is mounted on the top of a workpiece spindle (right part of Fig. 2 ), for example, there is a laser processing station.

[0092] The workpiece spindles at position P1 and position P3 (in Fig. 2 The two spindles (not shown) of the rotary table are located diametrically opposite each other to the rotary table axis. They are driven by a common first spindle drive 220-1, which is fixedly mounted on a component of the machine frame 160 with its output shaft vertically aligned. The first spindle drive 220-1 is continuously drive-connected to the two associated workpiece spindles via a torque transmission device 230-1 consisting of several components.

[0093] The torque transmission device 230-1 comprises a gear 222 mounted on the output shaft of the first spindle drive, which meshes with a lower gear ring of a first hollow shaft 224-1, which is rotatably mounted coaxially to the rotary table axis 152 and has an upper gear ring at an axial distance above the lower gear ring. This upper gear ring meshes with a lower gear ring of a transmission element 226 mounted with a vertical axis of rotation, which has an upper gear ring that serves as one of two deflection elements for a toothed belt 228, the other deflection element of which, equipped with teeth, is attached to the workpiece spindle 170-3.

[0094] Diametrically opposite, an analog torque transmission to the third workpiece spindle is provided. This ensures that the first spindle drive 220-1 is permanently connected to each of the two diametrically opposite workpiece spindles at positions P1 and P3.

[0095] For the two other, diametrically opposed workpiece spindles at positions P2 and P4, there is a second spindle drive 220-2, which is mounted on the machine and drives a gear that engages a lower gear ring of a second hollow shaft 224-2, which is also rotatably mounted coaxially to the rotary table axis 152. The second hollow shaft also has an output-side gear ring, axially offset from the drive-side gear ring, which Fig. 2 can be seen above the output-side gear ring for the first drive train. The rotation is then transmitted to the associated workpiece spindles via a transmission element with two gear rings and a toothed belt that also runs around the workpiece spindles.

[0096] The two drive trains for the respective pairs of workpiece spindles are arranged in the area of ​​the interconnected hollow shafts 224-1, 224-4, coaxial with each other and coaxial with the rotary table axis 152. The lower gear rings of the hollow shafts serve as the drive element, and the upper gear rings serve as the output element of the respective hollow shaft.

[0097] The two hollow shafts sit on an inner bearing sleeve 225, which is mounted on the rotary table 150, centered on the rotary table axis 152. The bearing sleeve has an internal through-channel that can be used as a supply channel for cables connecting any components on the rotary table (optional).

[0098] The coating machine 100 can be operated as follows. During a coating process, a brake disc coated on both sides has just been removed from the loading and unloading station 110 manually, semi-automatically, or automatically using a handling system. To do this, the pressure rod 174 of the clamping head was pneumatically actuated from below using the actuator 180, releasing the brake disc. A new, still uncoated brake disc or its base body is clamped onto the now free clamping head. By releasing the clamping head, it switches to a clamping configuration that is stored without energy and thus securely grips the workpiece even in the event of any malfunctions. When the workpiece is placed on top and clamped, the workpiece spindle 170-1 does not rotate.

[0099] The uncoated brake disc is then to be transported to the first laser processing station 120-1 (first station ST1) by further indexing the rotary table by 90° clockwise. To enable the laser coating process to begin there immediately after the workpiece arrives, without the need for further acceleration, the workpiece spindle at position P1 is set into rotation at increasing speed immediately after the workpiece is placed and clamped using the first spindle drive 220-1, thus accelerating it. The increase in speed also continues as the rotary table rotates for transport to the first laser processing station 120-1, so that the workpiece already enters the laser processing station 120-1 at a considerable input speed, so that further acceleration to the required working speed is not necessary or can be achieved within a very short time.Thus, the coating process in the laser processing station can begin essentially immediately after the already rapidly rotating workpiece has reached the processing position within the laser processing station.

[0100] While the coating process is running, a new, fully coated workpiece can be removed at the loading and unloading station and a new, uncoated workpiece can be inserted and secured.

[0101] After the laser-based coating process is complete, the rotary table is indexed. Before, during, or immediately after the start of the rotation, the spindle drive is decelerated, so that the rotation of the brake disc, which is coated on one side, is slowed down. This causes it to reach the turning station 130, rotating more or less slowly or already at a standstill. There, the brake disc is grasped at its outer circumference using a gripper, released from the workpiece holding device by lowering the workpiece spindle and / or raising the workpiece gripper, rotated 180°, and then repositioned on the workpiece spindle. To remove, rotate, and reposition the clamping head, the pressure is released from below by pressing on the pressure rod. Once the brake disc is repositioned, the pressure is released and the clamping head clamps the workpiece automatically.

[0102] Immediately after the turning operation is completed, and possibly even before the next cycle begins, the spindle drive is restarted so that the single-sided coated brake disc is accelerated to essentially its operating speed on its way to the second laser processing station (station ST3), where it arrives already rotating rapidly. The laser coating operation can begin immediately after the workpiece spindle arrives at the correct working position. Once this operation is complete, the first spindle drive brakes the workpiece spindle again before and during the process of moving to the loading and unloading station, allowing the workpiece to be unloaded immediately upon arrival.

[0103] Further operations can be carried out during a machining cycle. Among other things, one embodiment provides for the workpiece to be cleaned after completion of the first coating operation and before the start of the turning operation and / or after the second coating operation and before removal. This allows loose residues of coating material and / or powder residues to be removed, preventing such contaminants from being carried over to subsequent operations. Cleaning can be carried out, for example, by suction and / or by blowing off the contamination. Alternatively or additionally, the workpiece can be excited with ultrasound for cleaning or to assist cleaning in order to detach loosely bound contaminants from the workpiece. Such cleaning operations can potentially significantly improve the final quality of the coated brake disc.

[0104] Such a coating machine can therefore initially take uncoated brake disc base bodies and apply a functional coating to both sides. This requires very short cycle times, particularly because acceleration processes to the operating speed can be initiated and, if necessary, completed before the brake disc arrives at the respective laser processing station. This minimizes waiting times within the laser processing station. This means that, even with continuous powder feed in the laser processing stations, very little time and material is wasted between individual coating operations. This enables highly productive production of double-sided coated brake discs at low overall costs, especially for operating resources.

[0105] Based on Fig. 3 An embodiment of a production system 400 for producing coated brake discs is explained. Integrated into the production system are two coating machines 100A and 100B of the type described, as well as a grinding machine 460, which can also be configured as a processing machine of the type described here (without traveling spindle drives). The functional coating for the brake discs should have two layers: an adhesive layer applied directly to the metallic base body and a wear layer applied thereon, which is significantly harder than the gray cast iron material of the base body.

[0106] The production plant 400 includes Fig. 3 On the left, a pre-test station 410, where the delivered brake disc base bodies are tested for suitability for coating. In this example, type recognition also takes place in the pre-test station. Certain characteristic features of the delivered base bodies (e.g., outer diameter, type and size of contact surfaces, and / or distance between the rotation axis and friction surface) are measured to identify the brake disc type. Depending on the detected type, the programming of the processing machines can then be automatically selected. This means that the production facility is, in principle, capable of handling small series down to batch sizes of one.

[0107] The standardized, usable base bodies are then conveyed to a coating system 420 via a linear conveyor line. This system comprises, in a substantially circular arrangement, an input measuring station 422, a first coating machine 100A for generating the adhesion layer on both sides, a downstream control unit 424 for monitoring the coating properties of the adhesion layer, a downstream second coating unit 100B for generating the wear layer on both sides of the brake disc, and a downstream control station 426 for monitoring the quality of the wear layer. The transfer to these individual units and the finished or inspected brake discs from these units is achieved via a central robot unit 440, whose working area extends to the loading and unloading stations of the two coating machines as well as the corresponding stations of the control stations.

[0108] After the two individual layers of the functional coating have been applied, the finished coated brake discs have heated up; typical temperatures can be in the range of up to 200 °C or higher. Furthermore, the exposed surface of the wear layer is usually still relatively rough or grooved, as it is formed by the exposed backs of laser deposition weld beads. Furthermore, the layer thicknesses on the two sides may differ and / or the total thickness may still be too large. A grinding station 460 is provided in the production facility to eliminate these defects.

[0109] To ensure that the subsequent grinding operation results in finished coated brake discs that meet tolerances, a cooling line 470 is installed between the coating stations and the grinding station. This cooling line allows the brake discs, still warm after laser coating, to cool to approximately room temperature. The cooling line also serves as a buffer to compensate for possible differences in operating speeds between the coating system and the grinding machine.

[0110] Similar to the coating machine, the grinding machine can have a movable spindle support unit with two or more workpiece spindles, whose associated spindle drives do not move with the spindle support unit but are mounted fixed to the frame. Depending on the type of grinding process (single-sided grinding or synchronous grinding on both sides), a turning station may or may not be provided. In the example, both surfaces are ground simultaneously using a variant of double-side surface grinding, so a turning station is unnecessary.

[0111] If necessary, multi-stage grinding processes can be implemented, e.g., a two-stage grinding process with pre-grinding and fine grinding. These operations can be integrated into a single processing machine if necessary. It is also possible to provide two separate processing machines for pre-grinding and subsequent fine grinding.

[0112] After the grinding operation(s) are completed, the brake discs are conveyed to a washing station 480, from which they exit toward a final measuring station 490. The entire production line is controlled by a central control unit 405. This allows the cycle times of the individual processing stations to be coordinated to ensure a continuous production process with high unit output.

[0113] It goes without saying that Fig. 3 This is just one example of a possible variant for the design of a production facility. Other configurations are possible. For example, the components could be arranged differently depending on the space available, e.g., in a U-shaped, I-shaped, or O-shaped configuration. Processing machines and other stations can be arranged along the sides of a main conveyor line and served by cross conveyors.

[0114] There are also numerous alternative possibilities for the design and function of the processing machine within the scope of the invention disclosed here. Fig. 4 , 5 and 6 show various alternatives by way of example. For reasons of comparability, the same reference numerals are used for identical or corresponding features and components as in the first embodiment. The associated transport system in each case has a spindle support unit in the form of a rotary table 150 with a vertical rotary table axis 152.

[0115] In Fig. 4 the cutting planes to the left and right of the central rotary table axis 152 are offset by 90° from each other, ie the illustration shows two cutting planes rotated by 90° to each other.

[0116] In the first alternative embodiment in Fig. 4 An internally hollow support 156 is mounted centrally on the machine frame 160 for rotation about the vertical rotary table axis 152. This supports the plate of the rotary table 150, i.e., the spindle support unit, and is driven by the rotary table drive 155, which engages the lower end of the element 155 via gears. Arranged within the hollow support 155 is the first spindle drive 220-1, whose output is coaxial with the rotary table axis and coupled to a gear located at the level of the rotary table plate.

[0117] On the left, a workpiece spindle 170-1 is shown, which carries a gear ring that is coupled to the central gear via a larger intermediate gear ring, transmitting torque. The actual rotary table has the same arrangement, diametrically opposite each other, so that two diametrically opposed workpiece spindles are jointly driven by the first spindle drive 220-1 and are constantly connected to it.

[0118] The workpiece spindles (right part of the figure), which are circumferentially offset by 90°, are driven by the second spindle drive 220-2. Its output gear meshes with the lower gear of a hollow shaft 224-2, which is arranged concentrically to the rotary table axis 152 and has an upper gear ring at an axial distance from the lower gear ring, which meshes with a gear ring attached to the lower end of the workpiece spindle unit 170-2. When the spindle motor is rotated, the hollow shaft rotates around the rotary table axis, thereby driving the rotation of the coupled workpiece spindles.

[0119] In this solution, a hollow shaft 224-2 coaxial to the rotary table is provided only on one drive train (from the second spindle drive).

[0120] In Fig. 5 A second alternative design option for the drive system is shown. The rotary table drive 155 is arranged centrally to the rotary table rotation axis; for example, it can be a central torque motor. The rotary table plate is mounted on a support shaft that is rotatably mounted on the machine frame 160. The left-hand part of the figure shows the first spindle drive 220-1, which is coupled to the workpiece spindles at positions P1 and P3. At the upper end of the output shaft is a drive gear that meshes with a lower ring gear of a first hollow shaft 224-1, which is rotatably mounted with inwardly directed toothing on the underside of the rotary table 150 about the rotary table's rotation axis. The hollow shaft has an axially offset upper ring gear, the inwardly directed toothing of which meshes with a gear at the lower end of the workpiece spindle 170-1 to be driven.

[0121] The right-hand part of the figure shows the drive train, which originates from the second spindle motor 220-2 and drives the spindles at positions P2 and P4. Here, the torque transmission device comprises a second hollow shaft 224-2, which is rotatably mounted on a bearing element attached to the underside of the rotary table coaxially to the rotary table axis 152. The outwardly directed upper gearing of the second hollow shaft meshes with a gear at the lower end of the associated workpiece spindle 170-2. This solution thus utilizes two hollow shafts 224-1, 224-2, each rotatable coaxially to the rotary table axis 152, each with gearing at different axial levels.

[0122] In Fig. 6A third alternative is shown schematically, with the partial figures to the left and right of the rotary table axis representing sectional planes offset by 90°. The rotary table output is mounted within the central area of ​​the machine frame 160, for example, in the area of ​​the rotary table axis. The first spindle motor 220-1, shown on the left, for positions P1 and P3 of the tool spindles, uses its output gear to drive a first hollow shaft 224-1, which is mounted on the machine frame with outward-facing teeth coaxially rotatable about the rotary table axis. The upper gear ring of the hollow shaft meshes with the drive gear of the workpiece spindle 170-2 at position P1.

[0123] In the second drive train shown on the right, from the second spindle drive 220-2 to the workpiece spindles at positions P2 and P4, the torque transmission device comprises a second hollow shaft 224-2, which is rotatably mounted relative to the first hollow shaft 224-1 and relative to the machine frame 160 coaxially to the rotary table axis. This hollow shaft absorbs the rotary motion of the output gear of the second spindle drive and transmits it via its upper gear ring to the input-side drive gear of the workpiece spindle.

[0124] A skilled person can use these variants or variations depending on the ambient conditions and the drive requirements to drive workpiece spindles mounted on a rotating spindle support unit (here, a rotary table) with spindle drives mounted on the frame. While the torque transmission in these examples is primarily via gears, other drive elements, such as belts or the like, can also be used at certain points in the drive train.

Claims

1. Processing machine (100) for use in the manufacture of a coated brake disc (BS) having a main body having a rotationally symmetrical mass distribution with respect to a rotational axis (RA) of the brake disc and comprising a central hub portion (NA) and an annular brake portion (BA) surrounding the hub portion, wherein the brake portion has two axially opposite surfaces, each bearing a rotationally symmetrical functional layer with respect to the rotational axis, the free surface of which is formed as the friction surface of the brake disc, wherein the processing machine comprises: a machine base (160); a transport system having a spindle carrier unit (150) which is movable relative to the machine base and which carries at least one workpiece spindle (170) which is rotatably mounted relative to the spindle carrier unit (150) about a spindle rotation axis (172) and has a workpiece holding device (173) which is designed in such a way that a main body received on the workpiece holding device (173) can be rotated substantially around the rotation axis (RA) coaxial with respect to the spindle rotation axis (172) when the workpiece spindle (170) is rotated; a plurality of workstations (ST1 to ST4) arranged along a transport path and accessible by the workpiece spindle (170), comprising a loading station (110, ST1) and at least one processing station (120-1, 120-2) with at least one processing unit (125) for processing at least one side of the brake portion; a drive system (200) with at least one spindle drive (220) for generating rotary movements of the workpiece spindle (170) around the spindle rotation axis in response to control signals from a control unit (190), characterized in that the drive system (200) and the control unit (190) are configured in such a way that, after fastening a brake disc to the workpiece holding device in the loading station (110) before the processing station is reached, a workpiece spindle (170) can be set in rotation with increasing speed by means of an assigned spindle drive in such a way that the workpiece received on the workpiece spindle can be moved rotationally into the processing position at an entry speed.

2. Processing machine according to Claim 1, characterized in that the drive system (200) and the control unit (190) are configured in such a way that an acceleration of a rotational movement of the workpiece spindle begins immediately after fastening of the workpiece to the workpiece holding device, before the spindle carrier unit is set in motion to transport the workpiece spindle to the processing station.

3. Processing machine according to Claim 1 or 2, characterized in that the drive system (200) and the control unit (190) are configured in such a way that the workpiece spindle is accelerated up to a working speed of more than 100 rpm provided for a processing operation in the processing station, in particular up to a working speed in the range from 150 rpm to 600 rpm, wherein the entry speed corresponds substantially to the working speed desired for the processing operation, with the result that the processing operation can begin without delay as soon as the workpiece is situated in the processing position, or wherein the entry speed is lower than the working speed, with the result that a further, short acceleration phase is required.

4. Processing machine according to Claim 1, 2 or 3, characterized in that that the drive system (200) has at least one spindle drive (220), mounted fixedly on the frame, and a torque transmission device (230) for transferring torques from the spindle drive to at least one associated workpiece spindle (170), wherein the spindle carrier unit (150) preferably carries a plurality of workpiece spindles, in particular three or four workpiece spindles (170-1 to 170-4), and an assigned spindle rotary drive (220-1, 220-2), mounted fixedly on the frame, is provided for each of the workpiece spindles.

5. Processing machine according to one of the preceding claims, characterized in that the drive system is configured in such a way that each workpiece spindle (170) is drive-connected to an associated spindle drive (220) permanently, in particular also during a movement of the spindle carrier unit (150).

6. Processing machine according to one of the preceding claims, characterized in that the transport system has, as a spindle carrier unit (150), a rotary table (150) which can be rotated by means of a rotary table drive (155) about a, preferably vertical, rotary table axis (152), and in that a plurality of workpiece spindles (170) are arranged on the rotary table in such a way that they can be transported on a circular or arcuate transport path between workstations (ST1 to ST4) of the processing machine, wherein workpiece spindles (170) are preferably distributed on the rotary table (150) in such a way that there are pairs of workpiece spindles, wherein a common spindle drive (220-1; 220-2) is provided in each case for two workpiece spindles (170-1, 170-3; 170-2, 170-4) of a pair, wherein the workpiece spindles of a pair preferably lie opposite each other diametrically with respect to the rotary table axis (152), and / or wherein a hollow shaft (224) rotatable coaxially with the rotary table axis (152) is integrated into at least one torque transmission device between a spindle drive (220) and a plurality of workpiece spindles (170) drive-coupled thereto, which has a drive element and an output element in an axially staggered manner, wherein two drive trains with nested hollow shafts (224-1, 224-2) with height-staggered drive elements and output elements are preferably integrated.

7. Processing machine according to one of the preceding claims, characterized in that the processing machine is configured as a coating machine (100), wherein at least one processing station is configured as a coating station with at least one coating unit, wherein the coating machine (100) preferably has at least two, in particular exactly two, separately arranged workstations which are designed as coating stations.

8. Processing machine according to Claim 7, characterized in that the coating machine (100) is designed for two-sided coating of a brake disc, preferably in such a way that a first coating operation for coating a first side and a second coating operation for coating a second side of the brake portion lying axially opposite the first side can be carried out successively in time, and / or characterized in that the coating machine (100) has a plurality of workstations (ST1 to ST4) arranged along the transport path of the transport system, which in this order comprise a loading station (110), a first coating station (120-1) with at least one coating unit for coating a first side of a brake disc, a turning station (130) for turning a brake disc received on a workpiece spindle, and at least one second coating station (120-2) for coating a second side of the brake disc and an unloading station, wherein the loading station preferably also acts as an unloading station.

9. Processing machine according to Claim 7 or 8, characterized in that a coating unit is designed as a laser deposit welding device which, during operation, emits a metal powder in the direction of the surface to be coated and at the same time guides a laser beam which is preferably focused in such a way that the metal powder is melted before reaching the workpiece surface and is deposited on the workpiece surface in the melted state in order to form the functional layer, and / or in that a coating unit can be moved in a manner which is drive-controlled vertically and horizontally, and / or a surface on the upwardly directed side of the workpiece can be coated in each coating operation.

10. Method for producing a coated brake disc (BS) comprising a main body having a rotationally symmetrical mass distribution with respect to a rotational axis (RA) of the brake disc and comprising a central hub portion (NA) and an annular brake portion (BA) surrounding the hub portion, wherein the brake portion (BA) has two axially opposite surfaces, each bearing a rotationally symmetrical functional layer with respect to the rotational axis, the free surface of which is formed as the friction surface of the brake disc, wherein the method comprises the following steps: providing a transport system with a movable spindle carrier unit (150) which carries at least one workpiece spindle (170) which is rotatably mounted relative to the spindle carrier unit about a spindle rotation axis (172) and has a workpiece holding device (173) which is designed in such a way that a main body of a brake disc which is received on the workpiece holding device is rotated substantially around the rotation axis (RA) of the main body when the workpiece spindle is rotated; fastening the main body to the workpiece holding device (170) ; moving the spindle carrier unit (150) of the transport system for transporting the main body received on the workpiece spindle into a processing position of a processing station (120); processing the brake portion (BA) on at least one of the sides, wherein the workpiece is rotated by rotation of the workpiece spindle (170) at a working speed around the spindle rotation axis, characterized in that, after fastening the workpiece to the workpiece holding device (173) before the processing position is reached, the workpiece spindle (170) is set in rotation with increasing speed and the workpiece received on the workpiece spindle is moved rotationally into the coating position at an entry speed.

11. Method according to Claim 10, characterized in that the acceleration of the rotational movement begins immediately after fastening the workpiece to the workpiece holding device, before the spindle carrier unit is set in motion in order to transport the workpiece spindle to the processing station.

12. Method according to Claim 10 or 11, characterized in that the workpiece spindle is accelerated up to a working speed of more than 100 rpm provided for a processing operation in the processing station, in particular to a working speed in the range from 150 rpm to 600 rpm, wherein the entry speed corresponds substantially to the working speed desired for the processing operation, with the result that the processing operation can begin without delay as soon as the workpiece is situated in the processing position, or wherein the entry speed is lower than the working speed, with the result that a further, short acceleration phase is required.

13. Method according to one of Claims 10 to 12, characterized in that the processing comprises the production of a rotationally symmetrical functional coating with respect to the rotational axis on at least one side of the brake portion in a coating operation, wherein the main body is rotated by rotation of the workpiece spindle at a working speed around the spindle rotation axis and coating material is applied by a coating unit to the surface to be coated, wherein the workpiece preferably has a first side and a second side lying opposite in an axial direction, and, in a first coating operation, a first rotationally symmetrical functional layer is applied to a surface region of the first side and, in a second coating operation, a second rotationally symmetrical functional layer is applied to a surface region of the second side, wherein the first and the second coating operations are preferably carried out sequentially, and / or wherein the workpiece is attached in a first orientation to the workpiece receiving device for the first coating operation, is released from the workpiece receiver after the first coating operation, is turned from the first orientation into a second orientation in a reversing operation, and is attached to the workpiece receiving device in the second orientation.

14. Production facility for the production of coated brake discs (BS) comprising a main body having a rotationally symmetrical mass distribution with respect to a rotational axis (RA) of the brake disc and comprising a central hub portion (NA) and an annular brake portion (BA) surrounding the hub portion, wherein the brake portion has two axially opposite surfaces which each bear a rotationally symmetrical functional layer with respect to the rotational axis, the free surface of which is formed as the friction surface of the brake disc, characterized in that the production facility comprises at least one processing machine (100A, 100B) according to one of Claims 1 to 9.

15. Production facility according to Claim 14, characterized by at least one of the following features: (i) the production facility comprises one or more of the processing machines configured as a coating machine (100A, 100B) for two-sided coating of a brake disc, wherein a coating machine preferably has at least one laser deposit welding unit which is configured to emit a metal powder in the direction of the surface to be coated and at the same time to guide a laser beam which is focused in a focus area in such a way that the metal powder is melted in the focus area and is deposited on the workpiece surface to form the functional layer; (ii) the production facility has at least one grinding machine (460) downstream of the last coating machine, which is preferably designed as a processing machine according to one of Claims 1 to 9, wherein a cooling section (470) for cooling coated brake discs is preferably arranged between the coating machine and the grinding machine.