Plate grinding / polishing device

Abstract

The invention relates to a plate grinding / polishing device (10) for surface grinding and / or polishing the sample surface on the lower side of, in particular, embedded and / or non-embedded samples by way of a rotating grinding / polishing plate (18), in particular for sample preparation for materialographic analysis, comprising: a grinding / polishing head (30) with a sample holder for inserting one or more samples, a lower housing (12) with a collecting trough (16) for collecting grinding and / or polishing suspension, a grinding / polishing plate (18) in the collecting trough (16), wherein different grinding pads, polishing pads and / or polishing cloths can be fastened releasably on the upper side (18a) of the grinding / polishing plate (18), in order to surface-grind and / or to polish the lower side of the samples which are pressed from above onto the grinding / polishing plate (18) by way of the respective grinding pad, polishing pad or polishing cloth, a first electric drive motor which is arranged in the grinding / polishing head (30) for the sample holder (34), a second electric drive motor which is arranged in the lower housing (12) for the grinding / polishing plate (18), a first drive spindle (66) for rotationally driving the sample holder (34), wherein the first electric drive motor comprises a first stator and a first rotor, wherein the first drive spindle (66) is connected coaxially to the first rotor, and the first electric drive motor forms, with the first drive spindle (66), a first coaxial direct drive for the sample holder (34), and / or a second drive spindle for rotationally driving the grinding / polishing plate (18), wherein the second electric drive motor comprises a second stator and a second rotor, wherein the second drive spindle is connected coaxially to the second rotor, and the second electric drive motor forms, with the second drive spindle, a second coaxial direct drive for the grinding / polishing plate (18).

Description

[0001] Disc grinder-polishing machine

[0002] Description

[0003] Field of the invention

[0004] The invention relates to a disc grinding / polishing device for surface grinding and / or polishing the sample surface on the underside of, in particular, embedded and / or non-embedded samples with a grinding / polishing disc in a collecting tray, in particular for sample preparation for materialographic analysis.

[0005] Background and general description of the invention

[0006] Disc grinders and polishers typically have two drives. One drive is located at the bottom and drives the grinding and polishing disc. The other drive is located at the top of the grinding and polishing head and drives the sample holder. The grinding and polishing disc typically operates at a speed between 50 and 1000 rpm. 1 and 500 mi 1The power is approximately 0.75 kW to 1.5 kW for a 300 mm grinding / polishing disc diameter or 2.2 kW for a 350 mm grinding / polishing disc diameter.

[0007] All in all, the well-known disc grinding and polishing machines have proven very successful in practice, but the inventors see further potential for improvement with regard to the circumstances explained below.

[0008] In known disc grinding and polishing machines, the drive is typically via single- or three-phase asynchronous electric motors, which, for example, have a nominal speed of approx. 1450 rpm 1 in a four-pole design. In order to provide the required speeds, especially in the lower speed range, without speed fluctuations, the speed is typically transmitted to the grinding / polishing plate via a belt drive with a relatively high reduction ratio, e.g., approximately 5:1.

[0009] Even lower speeds are required for the grinding / polishing head. These are typically around 20 mm 1 up to 200 mim 1 The grinding / polishing head is also typically driven by an asynchronous motor, similar to the grinding / polishing plate below. Therefore, the reduction ratios of the belt drive for the grinding / polishing head must be even more extreme than for the grinding / polishing plate, and are typically around 8:1 to 10:1 for the grinding / polishing head. However, this has the disadvantage that the drive pulley on the motor must be very small due to limited installation space. Furthermore, this results in the pulley's wrap angle being relatively small.

[0010] A further disadvantage of these high-speed asynchronous machines is that, especially in the lower speed range, a very high magnetizing current is required to achieve high torque, which is inefficient and causes a high level of heat generation.

[0011] Another disadvantage of belt drives is that the mass inertia of the drive increases quadratically with each gear ratio. A sudden blockage of the grinding / polishing plate or grinding / polishing head can cause the belt drive to slip, which can accelerate wear or even lead to failure.

[0012] Furthermore, due to the previously discussed unfavorable wrap angles and small drive pulley diameters, the belt must be dimensioned larger to transmit the required torque. This, in turn, causes significant deformation and thus flexing, which can accelerate belt wear.

[0013] In addition, the belt tension recommended by the manufacturer must be strictly adhered to, which should be ensured using a frequency measuring device, for example. If the belt is too tightly tensioned, this can lead to bearing damage on the drive motor. If the belt is not tensioned enough, it can slip, which in turn can lead to wear and complete failure. The belt on disc grinders and polishers should be retensioned regularly, which should typically be done by the customer. However, the customer usually does not have a measuring device available to check the belt tension, so in practice it often happens that the belt is tensioned too tightly. This can result in the bearings being overloaded and even in the possible failure of the drive motor due to bearing damage, which leads to expensive service at the customer's site.In practice, the belt drive of grinding and polishing machines is replaced periodically, which is not without its problems on-site. Firstly, the machine must be partially disassembled, and secondly, a measuring device for accurately determining the belt tension is often not available on-site, which can lead to the consequential damage described above.

[0014] The existing belt drives also have design disadvantages. First, a tensioning mechanism is required, which is typically achieved by transversely shifting the electric motor. The belt drives used for the electric motor and the adjustment range for the belt tension require a corresponding amount of space within the device.

[0015] A further disadvantage is that the belt tension, even if correctly adjusted, creates a permanent transverse force on the drive shafts of the grinding / polishing disc and the grinding / polishing head.

[0016] Furthermore, in the well-known disc grinding and polishing machines - either with individual pressure or with central pressure - the samples are pressed against the rotating grinding and polishing plate with a defined pressure force to ensure appropriate removal of material from the samples to be prepared. The strength of the pressure force varies depending on the preparation method and can typically be between 5 N and 100 N per sample with the individual pressure method and between 20 N and 750 N with the central pressure method. The force is typically generated pneumatically via a defined piston area. Due to their design, the seals, guides, etc. used for the pneumatic system exhibit friction that is not always constant. The friction can vary, for example, between static and sliding friction, due to temperature changes or contamination.

[0017] All of this can affect the precision of the grinding removal or, in general, the quality of the grinding and polishing results.

[0018] The invention therefore aims to provide a disc grinding / polishing device that guarantees high-quality grinding and polishing results. A further aspect of the problem is to provide a disc grinding / polishing device that provides reliable and high-quality pressure processes in the grinding / polishing head and ensures precise control of the grinding material removal.

[0019] A further aspect of the task is to provide a disc grinding / polishing device that avoids disadvantages of pneumatic feed for applying the grinding force and enables a compressed air supply in the grinding / polishing head for the individual pressure of the samples with high reproducibility and little impairment by temperature fluctuations.

[0020] A further aspect of the task is to provide a disc grinding / polishing device that optimally utilizes the available installation space, particularly in the grinding / polishing head, and, if necessary, enables reliable measurement of the contact pressure during grinding and / or polishing as well as precisely adjustable grinding removal.

[0021] Another aspect of the task is to provide a disc grinding and polishing machine that is reliable, low-wear and low-maintenance, and has low noise levels during operation.

[0022] The object of the invention is achieved by the subject matter of the independent claims. Advantageous developments of the invention are defined in the subclaims.

[0023] According to the invention, a disk grinding / polishing device is provided for surface grinding and / or polishing the sample surface on the underside of, in particular, embedded and / or non-embedded samples with a rotating grinding / polishing disk, in particular for sample preparation for materialographic analysis, e.g. for a subsequent hardness test or microstructure examination of the ground and polished underside of, in particular, embedded samples.

[0024] The disc grinding / polishing device comprises a grinding / polishing head with a sample holder for inserting one or more embedded or non-embedded samples. The sample holder can comprise, for example, a mounting disc with several, e.g., six, sample holders distributed symmetrically around the rotation axis, each for inserting an embedded or non-embedded sample.

[0025] Grinding and polishing of embedded samples is carried out in materialographic analysis, e.g., after sample pieces have been cut off using a cutting machine and the sample pieces have been subsequently embedded in embedding material in order to give the embedded samples a more or less standardized shape, e.g., in the form of cylinders with diameters between 25 mm and 50 mm. This is also referred to in the specialist world as metallographic embedding. The disc grinder / polishing machine is particularly suitable as a laboratory device for such embedded samples. However, the disc grinder / polishing machine can also work with non-embedded samples. For this purpose, the non-embedded samples can be placed directly in a special sample holder adapted to the samples.

[0026] The disc grinder / polishing machine also includes a base housing with a collecting tray for collecting the grinding and / or polishing slurry. During grinding, cooling is typically carried out with water, so that the suspension of grinding material and water can be collected in the collecting tray and drained off via a drain in the collecting tray. Polishing is performed using polishing slurries, such as diamond slurries, which are applied to the polishing disc or polishing cloth before and / or during the polishing process. The polishing slurry can also be collected in the collecting tray and drained off via the drain.

[0027] In the collecting tray, a horizontal grinding / polishing plate rotates around a vertical axis of rotation. Different grinding pads, e.g. sandpaper, sanding film, thin grinding wheels with different grain sizes and different abrasive particles, e.g. corundum or diamond, can be detachably attached to the top of the grinding / polishing plate in order to grind the samples one after the other with different grinding pads to an increasingly fine surface. Polishing pads and / or polishing cloths can then be detachably attached to the grinding / polishing plate in order to polish the same samples after grinding. The grinding and polishing pads or polishing cloths can be attached to the top of the grinding / polishing plate, e.g. magnetically, self-adhesive, with a vacuum and, if necessary, with additional adhesive layers. In this way, the underside of the samples pressed onto the grinding / polishing plate from above is ground flat and / or polished with the respective grinding pad, polishing pad or polishing cloth.Preferably, the same disc grinding and polishing machine can be used to first grind the embedded or unembedded materialographic samples (if necessary with different abrasive grits) and then immediately polish them (if necessary with polishing suspensions of different fineness), without having to remove the samples from the respective adapted sample holder. A cleaning station can also be provided if necessary.

[0028] The disc grinding / polishing device contains an upper first electric drive motor arranged in the grinding / polishing head for rotatingly driving the sample holder.

[0029] The disc grinding / polishing device further includes a lower second electric drive motor arranged in the lower housing for rotatingly driving the grinding / polishing disc.

[0030] The sample holder is driven by a first drive spindle, and the first electric drive motor has a first stator and a first rotor. The first drive spindle is connected coaxially, in particular by positive or frictional engagement, to the first rotor and extends, in particular, coaxially through the first rotor and the first stator, such that the first electric drive motor and the first drive spindle form a first coaxial direct drive for the sample holder. The sample holder is, in particular, coaxially and preferably detachably attached to a lower end of the first drive spindle.

[0031] Alternatively or additionally, the grinding / polishing plate is driven by a second drive spindle, and the second electric drive motor has a second stator and a second rotor. The second drive spindle is connected coaxially, in particular positively or frictionally, to the second rotor and extends in particular coaxially through the second rotor and the second stator, such that the second electric drive motor and the second drive spindle form a second coaxial direct drive for the grinding / polishing plate. The grinding / polishing plate is in particular coaxially attached, preferably detachably, to an upper end of the second drive spindle. The plate grinding / polishing device can therefore have its own coaxial direct drive, as defined above, either for the sample holder or for the grinding / polishing plate, or preferably for both.

[0032] The speed of the first electric drive motor is preferably in the range between 20 mim 1 and 200 mi 1 . The speed of the second electric drive motor is preferably in the range between 50 mim 1 and 600 mim 1 . The speeds can in particular be adjustable.

[0033] According to a preferred embodiment, the first and / or second electric drive motor is designed as a synchronous motor, in particular as a multi-pole or multi-pole torque motor. The electric drive motors are preferably designed as internal rotors.

[0034] Instead of conventional asynchronous motors with belt drives, torque motors are used as direct drives. The torque motors can be designed as sensorless synchronous motors with permanent magnets in the rotor (permanent magnet synchronous motor - PMSM). The respective stator can consist of several coils, which, when energized, generate magnetic fields that the associated rotor follows. The torque motors can run from standstill to the maximum speeds required here (approx. 200 rpm). 1 or 600 min 1) generate a very high torque and are used as direct drives, i.e. without a belt drive or gearbox. The respective rotor can be mounted directly coaxially onto the drive spindle of the grinding / polishing plate or the grinding / polishing head and therefore only transmits the drive torque. The connection between the respective rotor and the corresponding drive spindle can be made e.g. by form fit, e.g. with a key or by friction fit. Transverse forces which are exerted on the spindle by belts in conventional plate grinding / polishing devices are eliminated, which significantly reduces the bearing load and therefore wear. Furthermore, the drive is almost silent and completely maintenance-free, which means that on-site servicing at the customer's premises is no longer necessary. The drive units can be of compact construction, resulting in a slim design despite the high torque.The disc grinding / polishing device preferably has a vertical, motor-driven lifting mechanism by which the grinding / polishing head, including the first drive motor, is lowered onto the grinding / polishing disc for surface grinding and / or polishing the samples. This advantageously allows for high precision in the desired removal rate.

[0035] The lifting mechanism preferably has at least one, preferably at least two vertical guides, a recirculating spindle, e.g., a recirculating ball screw, and a recirculating spindle drive motor. The recirculating spindle drive motor preferably rotates the recirculating spindle and the spindle nut or recirculating guide (e.g., a recirculating ball guide of the recirculating ball screw) relative to one another to effect the vertical lifting movement of the grinding / polishing head along the vertical guides. This moves the grinding / polishing head up and down, allowing the samples to be precisely positioned in the sample holder during grinding and / or polishing.

[0036] The rotary spindle drive motor can be designed, for example, as a stepper motor with a rotary encoder.

[0037] According to a preferred embodiment, the grinding / polishing head is suspended from an L-shaped suspension having a vertical tower section and a horizontal bridge section. The vertical tower section can be attached to a device base in the lower housing and extend vertically upwards from the device base, in particular at the rear of the lower housing. The horizontal bridge section is in turn suspended from the vertical tower section and extends horizontally above the lower housing to the grinding / polishing head or to the area above the grinding / polishing plate. The grinding / polishing head is suspended from the front end of the bridge section opposite the tower section, so that the suspension, together with the grinding / polishing head, is essentially U-shaped.Preferably, the vertical lifting mechanism is arranged in the vertical tower section and raises and lowers the horizontal bridge section together with the grinding / polishing head and the first coaxial direct drive. Preferably, the first drive spindle is suspended in an axially elastic manner from rigid areas of the grinding / polishing head. The first drive spindle can be mounted above and below the first rotor, in particular by means of rolling bearings, preferably ball bearings. The lower bearing of the first drive spindle can be designed as a fixed bearing, in particular with at least one angular contact ball bearing or deep groove ball bearing, and can be preloaded via a wave spring to eliminate bearing play.

[0038] Furthermore, the upper bearing of the first drive spindle can be designed as a loose bearing, in particular with a cylindrical roller bearing, in order to accommodate an axial movement of the first drive spindle together with the first rotor relative to the first stator and the suspension of the grinding / polishing head.

[0039] The second drive spindle is also preferably mounted above and below the second rotor, in particular with angular contact ball bearings or deep groove ball bearings.

[0040] For surface grinding and / or polishing with central pressure, the specimens are clamped firmly in the specimen holder. By advancing the entire grinding / polishing head, including the first electric drive motor, a defined contact force FA is exerted on the specimen holder as central pressure via the first drive spindle.

[0041] In other words, the electromotive lifting mechanism for the grinding-Z-polishing head can be used to achieve central pressure via the sample holder, which enables precise control of the grinding removal.

[0042] Preferably, the contact pressure acting on the first drive spindle of the direct drive relative to the grinding / polishing head is measured using a force measuring device, particularly in the grinding / polishing head. Furthermore, the force measuring device can be used to determine a zero point of contact between the samples and the grinding / polishing plate when lowering the grinding / polishing head onto the grinding / polishing plate. The force measuring device measures the contact pressure FA, particularly between the first drive spindle and rigid areas of the suspension of the grinding / polishing head, particularly in response to the elastically springy axial movement of the first drive spindle relative to rigid areas of the suspension caused by the contact pressure. With central contact pressure, the force on the samples is therefore preferably not applied by pneumatic pistons, but rather by an electric motor, e.g., using a spindle drive.The force can be measured using the force measuring device, and this signal can be used to control the drive motor for the lifting mechanism in a closed loop. This motor, in turn, can apply the feed movement with precisely the correct load, e.g., via the ball screw. Likewise, the electric spindle drive of the lifting mechanism can output the exact travel length by calculating the motor position, e.g., using the rotary encoder. This also allows for precisely defined removal of the samples with a precisely defined feed force.

[0043] The grinding / polishing device preferably further comprises a zero-point determination device, which can detect the contact of the lower sample surface with the grinding / polishing plate or the grinding pad. This allows the precise zero point to be determined, i.e., the surface of the sample from which the material removal is measured. To determine the zero point, the impact of the sample on the grinding / polishing plate is detected when the grinding / polishing head is lowered. This advantageously allows the material removal of the sample during the grinding process to be precisely determined. This can be determined or adjusted to within hundredths to a few thousandths of a millimeter, which can be advantageous for penetrating specific layers of the sample.

[0044] Precise adjustment of the material removal rate is particularly possible with the electric motor-driven lifting mechanism, as this allows for a rigid feed drive that, unlike pneumatic force application, eliminates unknown frictional forces in the system and inaccuracies caused, for example, by the compressibility of the air. Thus, zero-point determination, in combination with the electric motor-driven lifting mechanism, exhibits a special synergistic effect.

[0045] To determine the zero point, i.e., to detect contact with the sample surface, the force measuring device can be used, as described above, since it emits a measurable signal even at the slightest contact of the sample with the SchleifZ polishing plate. The force measuring device can comprise one or more force sensors, e.g., strain gauges, which change their electrical resistance upon extension. The at least one force sensor or strain gauge can be mounted on a spring element of the force measuring device, e.g., a leaf spring element. The leaf spring elements can be arranged around the first drive spindle, preferably below the first drive motor.

[0046] The force measuring device can be ring-shaped and preferably extend coaxially around the first drive spindle of the first direct drive. The force measuring device can comprise a force distribution ring which extends coaxially around the first drive spindle. The counterforce FG acting upwards on the first drive spindle during the central pressure via the sample holder can be transferred to the force distribution ring, for example, via the lower bearing (e.g. two ball bearings) of the first drive spindle. The force distribution ring is, for example,with the in particular radial leaf spring elements, on which the at least one or more force sensors, in particular with strain gauges, can be applied, axially elastically spring-connected to the suspension of the grinding-polishing head in order to measure the pressure force FA with the strain gauges via the expansion of the strain gauges resulting from the central pressure due to the axial movement of the first drive spindle relative to the suspension.

[0047] Preferably, the motor shaft of the first electric drive motor, i.e. the first drive spindle, is suspended together with the first rotor in an axially elastic manner from the suspension of the grinding / polishing head. The axially elastic suspension of the motor shaft of the first electric drive motor or the first drive spindle on rigid components of the grinding / polishing head is preferably achieved by means of the force measuring device. The force measuring device is preferably generally annular and forms a force measuring flange which can be arranged in a ring around the motor shaft of the first electric drive motor or the first drive spindle. The motor shaft of the first electric drive motor or the first drive spindle extends coaxially through a central opening in the force measuring flange. The force measuring device or the force measuring flange are therefore preferably arranged coaxially to the first electric drive motor.Further preferably, the force measuring device and / or the force measuring flange are arranged simultaneously coaxially with the first rotor of the first electric drive motor and coaxially with the sample holder. The first motor shaft or the first drive spindle preferably extends coaxially through the force measuring device or the force measuring flange.

[0048] According to a preferred embodiment, the first rotor is axially displaceable and coaxially resiliently suspended relative to the first stator. The (central) pressure causes a coaxial displacement of the first rotor relative to the first stator against the spring force of the resilient suspension, and the force measuring device measures the force exerted on the resilient suspension by the coaxial displacement of the first rotor relative to the first stator.

[0049] In particular, the first drive spindle and the first rotor form the first motor shaft of the first drive motor. The first motor shaft with the first drive spindle and the first rotor is suspended, in particular, elastically spring-loaded from the grinding / polishing head. The force measuring device can measure the pressing force directly on the first motor shaft, in particular coaxially to the first drive spindle and coaxially to the first rotor or to the first motor shaft of the first drive motor. When the sample holder with the inserted samples is pressed against the grinding / polishing plate, in particular during central pressing, the first motor shaft is axially displaced relative to the first stator or relative to the rigid components of the grinding / polishing head in an elastically spring-loaded manner against the spring tension of the elastic suspension of the first motor shaft, and the force measuring device measures the force exerted by the first motor shaft on the elastically spring-loaded suspension of the first motor shaft.

[0050] The elastically springy suspension of the first motor shaft or the force measuring device is preferably arranged axially between the first drive motor and the lower bearing of the first drive spindle or the first motor shaft.

[0051] To obtain an unadulterated signal from the force measuring device, it is highly advantageous if no transverse forces, e.g., from a drive belt, are introduced into the force measuring device. This can be achieved particularly with the first coaxial direct drive, e.g., with the torque motor, which only introduces a drive torque into the shaft but does not influence the force measuring device. The axial direct drive therefore exhibits a special synergistic effect, especially in combination with the coaxial force measuring device.

[0052] The rotor and stator of the first direct-drive motor are therefore preferably axially displaceable relative to each other to accommodate the axial elastic movement of the first drive spindle when the samples are pressed against the grinding-polishing plate, particularly in the central pressure process. The rotary bearing of the first drive spindle can also accommodate the axial elastic movement when the samples are pressed against the grinding-polishing plate, e.g., by means of a cylindrical roller bearing.

[0053] Preferably, the user can enter a pressure force setpoint into a control device which controls the lifting mechanism, in particular the rotary spindle drive motor or

[0054] Stepper motor, and defines a closed control loop. Using the control loop, the control device then automatically regulates the pressure force exerted by the lifting mechanism on the sample holder on the grinding / polishing plate during the grinding and / or polishing process, in response to the pressure force measured by the force measuring device, to the set pressure force target value.

[0055] Preferably, the sample holder is designed as a multiple sample holder with several sample receptacles arranged symmetrically around the rotational axis of the first drive spindle. If necessary, in addition to the electric motor-driven feed during central pressure, the grinding / polishing head can have several individual pressure pistons that individually apply force to the samples, each of which is inserted into the corresponding sample receptacle.

[0056] The sample holder is designed, for example, to hold six samples arranged symmetrically around the axis of rotation of the first drive motor or the first drive spindle in order to grind and / or polish several samples simultaneously. For individual pressure, the samples are placed into the sample holders from above. With central pressure, the samples are additionally firmly clamped in the sample holders in order to exert the desired pressure for surface grinding and / or polishing centrally via the first drive spindle and the sample holder on all clamped samples. The individual pressure pistons can be actuated pneumatically. For this purpose, compressed air can be fed into the first drive spindle via a compressed air connection that is rotatable in particular relative to the first drive spindle. The compressed air connection is preferably arranged at the upper end of the first drive spindle or above the first electric drive motor.For example, an axial compressed air duct runs through the first drive spindle, which can direct the compressed air axially through the first rotor and the first stator to an air distributor below the first electric drive motor, which rotates with the first drive spindle. The air distributor can then distribute the compressed air radially through distribution channels to the individual pressure pistons to actuate them pneumatically. The air pressure can be adjusted using a pressure control valve to exert the required pressure on the grinding / polishing plate.

[0057] The invention also relates to a disc grinding / polishing device for surface grinding and / or polishing the sample surface on the underside of the samples, in particular of embedded and / or non-embedded samples, using a horizontally rotating grinding / polishing disc, in particular for sample preparation, e.g., as a sub-step of sample preparation for materialographic analysis, in particular with further features as described above. The disc grinding / polishing device according to this aspect comprises: a lower housing with a collecting tray for collecting grinding and / or polishing suspension, a horizontal grinding / polishing disc arranged in the collecting tray and rotating about a vertical axis of rotation, wherein various grinding pads, e.g., sandpaper, grinding foil, thin grinding discs of different grain sizes, e.g., corundum, diamond, etc., can be optionally mounted on the upper side of the grinding / polishing disc., polishing pads and / or polishing cloths are adhered to in order to grind and / or polish the underside of the samples pressed from above onto the grinding / polishing plate with the respective grinding pad, polishing pad or polishing cloth, wherein during operation grinding and / or polishing suspension can be collected in the collecting tray and discharged via a suspension outlet of the collecting tray, a grinding / polishing head with a sample holder for inserting one or more samples, a first drive spindle extending vertically in the grinding / polishing head, wherein the sample holder is coaxially connected to a lower end of the first drive spindle in order to drive the sample holder in a central rotational manner with the first drive spindle, a first electric drive motor arranged in the grinding / polishing head for driving the rotation of the first drive spindle, if necessary.with variable speed, wherein the first electric drive motor comprises a first stator and a first rotor, wherein the first drive spindle is connected coaxially, e.g. positively or frictionally, to the first rotor and extends coaxially in the first rotor and the first stator, such that the first electric drive motor with the first drive spindle forms a first coaxial direct drive for the sample holder.

[0058] Preferably, a second electric drive motor for the grinding / polishing plate is arranged in the lower housing if the grinding / polishing plate is to rotate simultaneously with the sample holder. The rotations can be co-rotating or counter-rotating.

[0059] Preferably, the second electric drive motor also forms a direct drive for the grinding / polishing plate. For this purpose, a second drive spindle is included that extends vertically from the lower housing through a bottom opening in the collecting tray into the collecting tray, and the grinding / polishing plate is connected at an upper end to the second drive spindle in order to drive the grinding / polishing plate in rotation with the second drive spindle. The second electric drive motor comprises a second stator and a second rotor, wherein the second drive spindle is connected coaxially, e.g. positively or frictionally, to the second rotor and extends coaxially in the second rotor and the second stator such that the second electric drive motor with the second drive spindle forms a second coaxial direct drive for the grinding / polishing plate.

[0060] Simple disc grinding / polishing machines without a grinding / polishing head and automatic pressure mechanism also exist, in which the sample is ground and polished manually. Even in these simple disc grinding / polishing machines, it is conceivable to use the described drive for the grinding / polishing plate. Therefore, the invention also relates to a disc grinding / polishing machine for surface grinding and / or polishing the sample surface on the underside of the samples, in particular of embedded or non-embedded samples, with a horizontally rotating grinding / polishing plate, in particular as a sub-step of sample preparation for materialographic analysis, in particular with further features as described above.The disc grinding and polishing device comprises: a lower housing with a collecting tray for collecting grinding and / or polishing suspension, a horizontal grinding and polishing plate which is arranged in the collecting tray and rotates about a vertical axis of rotation, wherein different grinding pads, e.g. sandpaper, sanding film, thin grinding wheels, different grain sizes, e.g. corundum, diamond etc., polishing pads and / or polishing cloths can be attached to the upper side of the grinding and polishing plate in order to work with the respective grinding pad, polishing pad orPolishing cloth to grind and / or polish the underside of the samples pressed from above onto the grinding / polishing plate, wherein during operation grinding and / or polishing suspension is collected in the collecting tray and discharged via a suspension outlet, a second drive spindle extending vertically from the lower housing into the collecting tray through a bottom opening in the collecting tray, wherein the grinding / polishing plate in the collecting tray is connected to an upper end of the second drive spindle in order to drive the grinding / polishing plate from below in rotation with the second drive spindle, a second electric drive motor arranged in the lower housing for driving the rotation of the second drive spindle, optionally at a variable speed, wherein the second electric drive motor comprises a second stator and a second rotor, wherein the second drive spindle is coaxial, e.g.is positively or frictionally connected to the second rotor and extends coaxially in the second rotor and the second stator, such that the second electric drive motor with the second drive spindle forms a second coaxial direct drive for the grinding / polishing plate.

[0061] In the following, the invention is explained in more detail using exemplary embodiments and with reference to the figures, wherein identical and similar elements are partly provided with the same reference numerals and the features of the various exemplary embodiments can be combined with one another.

[0062] Shown are: Fig. 1 a three-dimensional representation of a disc grinding-polishing device according to an embodiment of the invention with a cut-open grinding-polishing head, Fig. 2 a vertical cross section through the grinding-polishing head of the disc grinding-polishing device from Fig. 1,

[0063] Fig. 3 is a three-dimensional representation of a force measuring device according to an embodiment of the invention,

[0064] Fig. 4 a top view of the force measuring device from Fig. 3

[0065] Fig. 5 a section through the force measuring device along the line AA in Fig. 4

[0066] Fig. 6 is an exploded view of the grinding-polishing head and the suspension, Fig. 7 is a vertical cross-section through the lifting mechanism for the grinding-polishing head, Fig. 8 is a partially cut-away front view of the disc grinding-polishing device from

[0067] Fig. 1,

[0068] Fig. 9 a vertical cross-section through the grinding-polishing plate with collecting tray and drive of the plate grinding-polishing device from Fig. 1 ,

[0069] Fig. 10 an exploded view of the grinding-polishing plate with collecting tray and drive.

[0070] Detailed description of the invention

[0071] Referring to Fig. 1, the disc grinding / polishing device 10 has a base housing 12 with a display and / or input device 14, in this example in the form of a touch display, via which the user can enter desired operating parameters, such as the speed of the sample holder, the speed of the grinding / polishing disc, the contact pressure, the grinding removal rate, etc., into the control device (not shown). A collecting tray 16 for grinding and polishing suspension is embedded in the upper side 12a of the lower housing 12. The grinding / polishing disc 18 is arranged in the collecting tray 16 and rotates about a vertical axis of rotation 20 (Fig. 9). The user can optionally attach various grinding pads, polishing pads, or polishing cloths to the upper side 18a of the grinding / polishing disc 18. Grinding pads can be designed, for example, as silicon carbide or diamond grinding wheels, as sandpaper, or as sanding foils.

[0072] If necessary, a magnetic foil can also be used as an adhesive carrier. For polishing, polishing pads or polishing cloths can be adhered to the upper side 18a, which are used in combination with a polishing suspension, e.g., a diamond suspension. Water can be supplied to the grinding or polishing pads or polishing cloths via a tap 22, e.g., for wet grinding or rinsing. The grinding / polishing head 30 is suspended above the grinding / polishing plate 18 on a suspension 32. At the lower end of the grinding / polishing head 30, the central sample holder 34, in the present example as a six-fold sample holder, is fastened to the drive spindle 66 of the grinding / polishing head 30, wherein the sample holder 34 is driven in rotation about a rotation axis 21 (Fig. 2) of the grinding / polishing head 30. This sample holder 34 is designed, by way of example, for embedded samples.The materialographic samples (not shown) to be ground and polished, here in particular embedded, are inserted individually from above into sample holders 36 of the sample holder 34. For grinding and / or polishing with individual pressure, a pneumatically actuated individual pressure piston 38 is provided above each sample holder 36, with which the samples placed in the sample holder 34 can be individually subjected to individual pressure from above. For grinding and / or polishing with central pressure, the samples are clamped in the associated sample holder 36 and the entire sample holder 34 is subjected to axial force via the upper drive spindle 66 of the rotary drive in the grinding / polishing head 30 in order to press the samples against the grinding / polishing plate 18 with a defined pressure force FA or to advance the axial feed of the grinding / polishing head 30, in particular to achieve a defined material removal during the grinding process.

[0073] The suspension 32 for the grinding / polishing head 30 comprises a vertical tower section 42 with a lifting mechanism 44, by means of which a horizontal bridge section 46, at the front end of which the grinding / polishing head 30 is suspended, is raised and lowered. For grinding or polishing with central pressure, the bridge section 46 suspended from the lifting mechanism 44 is moved downward by means of the lifting mechanism 44 in order to effect the pressure force for the grinding or polishing process. The lifting mechanism 44 thus moves the entire grinding / polishing head 30 together with the suspension 32 in height. For this purpose, the lifting mechanism 44 in the exemplary embodiment has a stepper motor 48 with a rotary encoder, which effects the vertical stroke via the rotation of a ball screw 50. The suspension 32 or the bridge section 46 are guided by two vertical linear guides 52a, 52b, which absorb the bending moments.The lifting mechanism 44 is arranged in the rear vertical tower section 42, so that the tower section 42, the horizontal bridge section 46, and the grinding / polishing head 30, which may be housed in a head housing 47, form a U-shaped arm. Referring to Figs. 2-6, the upper stator 64 and the upper rotor 62 form an upper electric direct drive motor, in this example in the form of an upper synchronous or torque motor 60, for the sample holder 34. The rotational drive of the sample holder 34 is thus provided by the upper synchronous or torque motor 60 in the grinding / polishing head 30. The upper torque motor 60 is multi-pole and designed as an internal rotor, so that the upper rotor 62 rotates in the upper stator 64. The upper rotor 62 is hollow and coaxially accommodates the upper drive spindle 66, which is positively or frictionally connected to the upper rotor 62, in the present example positively by means of a key 68.Thus, the upper torque motor 60 with the upper drive spindle 66, which is coaxially connected to the upper rotor 62, forms an upper coaxial direct drive 61 for the sample holder 34, which is coaxially connected to the upper drive spindle 66 at the lower end.

[0074] The upper drive spindle 66 is mounted below and above the rotor 62, with the lower bearing 70 being designed as a fixed bearing and comprising angular contact ball bearings or standard deep groove ball bearings. In this case, the lower fixed bearing 70 consists of two deep groove ball bearings 70a, 70b. The lower bearing 70 is arranged in a bearing housing 71 and is preloaded by a wave spring 72. The preload serves to eliminate the bearing play. Both ball bearings 70a, 70b are spaced by an intermediate ring 74 and clamped internally by a clamping nut 76.

[0075] A force measuring device 80 is arranged on the upper drive spindle 66. In the present example, it is designed in the form of an annular force measuring flange 81 and extends around the upper drive spindle 66. The annular force measuring device 80 has an inner force distribution ring 82, which is subjected to a force by the upper drive spindle 66, in the present example via the lower bearing 70, when the counterforce FG of the pressure force FA acts axially on the upper drive spindle 66 via the sample holder 34 during central pressure. The force measuring device 80 comprises a leaf spring section 84, which radially connects the inner force distribution ring 82 to an outer force transfer ring 86. The leaf spring section 84 can, for example, comprise four radially extending leaf springs 85, which axially elastically connect the inner force distribution ring 82 to the outer concentric force transfer ring 86.The individual leaf springs 85 can, in particular, be evenly distributed around the upper drive spindle 66 of the upper coaxial direct drive 61. The outer force-absorbing ring 86 is supported, for example, on a rigid area of ​​the grinding / polishing head 30. A force sensor 87, e.g., a strain gauge 88, is attached to the leaf spring section 84—in the exemplary embodiment, on one of the leaf springs 85—which changes its ohmic resistance upon extension, so that the extension of the associated leaf spring 85 or leaf spring section 84 can be measured upon axial displacement of the upper drive spindle 66 relative to rigid components of the grinding / polishing head 30 or against the spring tension. Strain gauges can also be attached or glued to several, e.g., two or all (here four), leaf springs 85, which can further improve the accuracy of the force measurement.The measurement signals of the strain gauge(s) 88 can be amplified by a measuring amplifier 89 and transmitted to the control device of the disc grinder / polishing machine 10, in particular to regulate the contact force FA ZU. The measuring amplifier 89 can be attached directly to the force measuring device 80. For example, the measuring amplifier 89 is embedded in a recess 101 in the force measuring flange 81 and can be potted therein if necessary. In other words, the force measuring flange 81, or the inner force distribution ring 82, the leaf spring section 84, and the outer concentric force transfer ring 86 form an axially elastically springy suspension of the upper motor shaft of the upper synchronous or torque motor 60, formed by the upper drive spindle 66 and the upper rotor 62.

[0076] During central pressure, the grinding / polishing head 30 is moved axially downward via the lifting mechanism 44 until the samples clamped in the sample holder 34 touch the grinding / polishing plate 18. During further vertical advance with central pressure, the samples are pressed against the grinding / polishing plate 18 with a pressure force FA, whereby a corresponding counterforce FG acts axially or vertically upward on the upper drive spindle 66. This counterforce FG causes a deformation of the leaf springs 85 and thus an extension of the strain gauge 88, whereby the pressure force FA can be measured.

[0077] As an alternative to central pressure, the samples can also be pressed individually using the individual pressure pistons 38. The individual pressure pistons 38 are pneumatically actuated and moved downward against the upper side of the respective sample (not shown) against the pretension of the return springs 39. For pneumatic actuation of the individual pressure pistons 38, compressed air can be fed centrally into the upper drive spindle 66 via a compressed air connection 90. The compressed air connection 90 is rotatable relative to the upper drive spindle 66 and directs the compressed air downward through an axial compressed air channel 92, which extends as a central axial bore through the upper drive spindle 66. An intermediate piece 94 with a radial air distributor 96 is attached to the lower end of the upper drive spindle 66.The air distributor 96 directs the compressed air through an axial connecting channel 98 and respective radial distribution channels 102 to the individual pressure pistons 38 in order to actuate the individual pressure pistons 38 and press them against the inserted samples. The compressed air is thus guided through the compressed air connection 90 through the upper drive spindle 66 to the air distributor 96 and distributed via the radial air distribution channels 102 to the, for example, six, individual pressure pistons 38.

[0078] During operation, the upper drive spindle 66, which is firmly connected to the upper rotor 62, rotates with the air distributor 96 and the individual pressure pistons 38 as well as with the sample holder 34 fastened to the lower end of the upper drive spindle 66. The sample holder 34 can be fastened to the bottom of the upper drive spindle 66, for example, with a quick-release fastener 104.

[0079] During central pressure, the samples are firmly clamped in the sample holder 34, and the pressure force FA is applied to the sample holder 34 by advancing the entire grinding / polishing head 30 via the upper drive spindle 66. The pressure force FA is measured during the grinding and / or polishing process via the force measuring device 80. The measurement result of the force measuring device 80, in the present example in the form of the change in resistance of the strain gauge 88, is transmitted to the control device of the grinding / polishing device 10, wherein the control device actively controls the pressure force FA in a closed control loop in response to this measurement signal. In other words, the pressure force FA is measured via the force measuring device 80 or the force sensor 87 and, by feedback to the control device, is controlled in a closed control loop to a pressure force setpoint that can be entered via the input device 14.

[0080] The upper bearing 106 of the upper drive spindle 66 forms the floating bearing and, in this example, is designed as a cylindrical roller bearing. Its axial freedom of movement compensates for the axial deformation of the force measuring device 80 during central pressure. A sealing ring 108 seals the upper drive spindle 66 or the upper rotor 62 against a non-rotating cover plate 110.

[0081] Referring to Figs. 7 and 8, the tower section 42 is suspended, for example, from the rear of a device base 112, which forms the device base in the lower housing 12. Two vertical guide rods 53a, 53b are suspended from the device base 112 as part of the linear guides 52a, 52b. The bridge section 46, to whose front end the grinding / polishing head 30 is rigidly attached, has, at its end opposite the grinding / polishing head 30, guide sleeves 54a, 54b that slide vertically on the guide rods 52a, 52b. The vertical lifting drive of the lifting mechanism 44 is driven by the stepper motor 48. The vertical lifting drive can be designed as a spindle drive 49. More precisely, the stepper motor 48 drives the ball screw 50 via a coupling 116, which rotates in a spindle nut or in a ball screw guide 118 in order to effect the vertical movement of the suspension 32 and thus of the grinding-polishing head 30.In order to precisely control the vertical stroke movement of the grinding-polishing head 30, the stepper motor 48 can have a rotary encoder (not shown).

[0082] The tower section 42 can also be suspended from the device base 112 for horizontal movement. For this purpose, the tower section 42, in particular including the lifting mechanism 44, can be connected to the device base 112 for horizontal movement by horizontal linear guides 252a, 252b. In the present example, the tower section 42 is suspended from guide sleeves 254a, 254b, which slide horizontally on guide rods 253a, 253b. This allows the tower section 42, including the lifting mechanism 44, to perform a horizontal movement parallel to the grinding / polishing wheel 18. The drive of the horizontal displacement mechanism 244 can be effected via a spindle drive 249, e.g. with a ball screw 250 with an electric motor 248. The horizontal movement takes place, e.g., transversely to the horizontal bridge section 46. As a result, a horizontal pendulum movement of the samples can be generated when grinding the samples on the grinding-polishing plate 18, for example.This has the advantage that the grinding or polishing wheels wear evenly.

[0083] Generally defined, the disc grinding / polishing device 10 comprises a horizontal movement mechanism for the grinding / polishing head 30, by means of which the grinding / polishing head 30 including the first drive motor 60 and / or the force measuring device 80 as well as the lifting mechanism 44 can be moved transversely to the grinding / polishing plate 18.

[0084] Referring to Figs. 9 and 10, the lower stator 164 and the lower rotor 162 form a lower electric direct drive motor, in this example in the form of a lower synchronous or torque motor 160, for the grinding / polishing plate 18. The rotational drive of the grinding / polishing plate 18 is thus effected by means of the lower synchronous or torque motor 160. The lower torque motor 160 is designed as an internal rotor, so that the lower rotor 162 rotates in the lower stator 164. The lower rotor 162 is hollow and coaxially accommodates the lower drive spindle 166, which is positively or frictionally connected to the lower rotor 162, in the present example positively by means of a key 168. Thus, the lower torque motor 160, with the lower drive spindle 166, which is coaxially connected to the lower rotor 162, forms a lower coaxial direct drive 161 for the grinding / polishing plate 18, which is coaxially connected to the lower drive spindle 166 at the upper end.

[0085] The grinding / polishing plate 18 sits on top of the lower coaxial direct drive 161 to be driven by the lower drive spindle 166 in rotation about the lower rotation axis 20. The lower drive spindle 166 extends axially through a lower rotor 162. The lower rotor 162 and the lower drive spindle 166 are thus driven by the lower stator 164. Thus, the lower torque motor 160, together with the lower drive spindle 166, forms the lower coaxial direct drive 161 for the grinding / polishing plate 18, which is coaxially connected to the lower drive spindle 166.

[0086] The grinding / polishing plate 18 rotates to collect the grinding or polishing suspension in the collecting tray 16. The grinding / polishing plate 18 can be sealed against the collecting tray 16 by means of a sealing ring 169, e.g. with a lip seal, in order to keep grinding and polishing suspension away from the drive 161.

[0087] The lower drive spindle 166 is mounted axially above and below the lower torque motor 160 by means of a lower bearing 170 and an upper bearing 172. The bearings 170, 172 can be designed, for example, as deep groove or angular contact ball bearings. The grinding / polishing plate 18 is also seated on a plate holder 19, which is coaxially screwed from above to the lower drive spindle 166 and which allows for easy removal of the grinding / polishing plate 18. The grinding / polishing plate 18 can be held on the plate holder 19, for example, magnetically and with a positive fit.

[0088] An optional annular splash guard (not shown) can be attached to the upper edge of the collecting tray 16. The lower drive spindle 166 extends through a central bottom opening 176 in the collecting tray 16. The lower electric drive motor 160 can be flanged to the collecting tray 16 from below, coaxial with the bottom opening 176. The collecting tray 16 can be emptied via an outlet 178 and a drain 180.

[0089] It will be apparent to those skilled in the art that the embodiments described above are to be understood as examples, and that the invention is not limited to them, but can be varied in many ways without departing from the scope of the claims. Furthermore, it is clear that the features, regardless of whether they are disclosed in the description, the claims, the figures, or otherwise, also individually define essential components of the invention, even if they are described together with other features.

Claims

A disc grinding / polishing device (10) for flat grinding and / or polishing the sample surface on the underside of, in particular, embedded and / or non-embedded samples, using a rotating grinding / polishing disc (18), in particular for sample preparation for materialographic analysis, comprising: a grinding / polishing head (30) with a sample holder (34) for inserting one or more samples, a lower housing (12) with a collecting tray (16) for collecting grinding and / or polishing suspension, a grinding / polishing disc (18) in the collecting tray (16), wherein different grinding pads, polishing pads, and / or polishing cloths are detachably attachable to the upper side (18a) of the grinding / polishing disc (18) in order to flatten and / or polish the underside of the samples pressed onto the grinding / polishing disc (18) from above using the respective grinding pad, polishing pad, or polishing cloth,a first electric drive motor (60) arranged in the grinding / polishing head (30) for the sample holder (34), a second electric drive motor (160) arranged in the lower housing (12) for the grinding / polishing plate (18), a first drive spindle (66) for rotatingly driving the sample holder (34), wherein the first electric drive motor (60) comprises a first stator (64) and a first rotor (62), wherein the first drive spindle (66) is coaxially connected to the first rotor (62), and the first electric drive motor (60) forms a first coaxial direct drive (61) for the sample holder (34) with the first drive spindle (66), and / or a second drive spindle (166) for rotatingly driving the grinding / polishing plate (18), wherein the second electric drive motor (160) comprises a second stator (164) and a second rotor (162), wherein the second drive spindle (166) is coaxially connected to the second rotor (162),and the second electric drive motor (160) with the second drive spindle (166) forms a second coaxial direct drive (161) for the grinding / polishing plate (18).

2. Disc grinding and polishing device (10) according to claim 1, wherein the speed of the first electric drive motor (60) is in the range between 20 mim 1 and 200 mim 1 and / or the speed of the second electric drive motor (160) is in the range between 50 mim 1 and 600 mim 1 amounts.

3. Disc grinding and polishing device (10) according to one of the preceding claims, wherein the first and / or second electric drive motor (60, 160) is designed as a synchronous motor, in particular as a torque motor.

4. Disc grinding / polishing device (10) according to one of the preceding claims, wherein a vertical lifting mechanism (44) is included, by means of which the grinding / polishing head (30) is lowered onto the grinding / polishing plate (18) for surface grinding and / or polishing the samples.

5. Disc grinding / polishing device (10) according to claim 4, wherein the lifting mechanism (44) has at least one vertical guide (52a, 52b), a revolving spindle (50) and a revolving spindle drive motor (48), wherein the revolving spindle drive motor (48) rotates the revolving spindle (50) in a spindle nut or revolving guide (118) to effect a vertical lifting movement of the grinding / polishing head (30) along the at least one vertical guide (52a, 52b).

6. Disc grinding and polishing device (10) according to claim 5, wherein the rotary spindle drive motor (48) is designed as a stepper motor with a rotary encoder.

7. Disc grinding / polishing device (10) according to one of claims 4-6, wherein the grinding / polishing head (30) is suspended from a suspension (32) which has a vertical tower section (42) and a horizontal bridge section (46), wherein the vertical tower section (42) is attached to a device base (112) and extends vertically upwards from the device base (112), wherein the horizontal bridge section (46) is attached to the vertical tower section (42) and extends horizontally above the lower housing (12) to the grinding / polishing head (30), and wherein the grinding / polishing head (30) is suspended at an end of the bridge section (46) opposite the tower section (42), and / or wherein the lifting mechanism (44) is arranged in the vertical tower section (42) and raises and lowers the horizontal bridge section (46) together with the grinding / polishing head (30) and the first coaxial direct drive (61).

8. Disc grinding and polishing device (10) according to one of the preceding claims, wherein the first drive spindle (66) is mounted above and below the first rotor (62), and wherein the lower bearing (70) is designed as a fixed bearing, in particular with an angular contact ball bearing or deep groove ball bearing, and is preloaded in particular via a wave spring (72).

9. Disc grinding and polishing device (10) according to one of the preceding claims, wherein the first drive spindle (66) is mounted above and below the first rotor (62), and wherein the upper bearing (106) is designed as a loose bearing, in particular with a cylindrical roller bearing, in order to accommodate an axial movement of the first drive spindle (66) relative to the first stator (64), 10. Disc grinding and polishing device (10) according to one of the preceding claims, wherein the second drive spindle (166) is mounted above and below the first rotor (62), in particular with angular contact ball bearings or deep groove ball bearings.

11. Disc grinding / polishing device (10) according to one of the preceding claims, wherein the samples for surface grinding and / or polishing with central pressure can be firmly clamped in the sample holder (34) and by advancing the entire grinding / polishing head (30) including the first electric drive motor (60) via the first drive spindle (66) a defined pressure force (FA) is exerted as central pressure on the sample holder (34).

12. Disc grinding / polishing device (10) according to one of the preceding claims, wherein a device for zero point determination is included which detects the contact of the lower sample surface with the grinding / polishing plate (18).

13. Disc grinding / polishing device (10) according to one of the preceding claims, wherein the first drive spindle (66) and the first rotor (62) form a first motor shaft of the first drive motor (60) and the first motor shaft with the first drive spindle (66) and the first rotor (62) is suspended in an axially elastic manner on the grinding / polishing head (30).

14. Disc grinding / polishing device (10) according to claim 13, wherein the first motor shaft is axially displaced relative to the first stator (64) in an elastically resilient manner against the spring tension of the elastic suspension of the first motor shaft when the sample holder (34) is pressed against the grinding / polishing disc (18), and wherein a force measuring device (80) is included which measures the force exerted by the first motor shaft on the axially elastically resilient suspension of the first motor shaft.

15. Disc grinding / polishing device (10) according to one of the preceding claims, wherein a force measuring device (80) is included, which measures the pressure force (FA) acting on the first drive spindle (66) relative to the grinding / polishing head (30) and / or is arranged coaxially to the first electric drive motor (60) and / or coaxially to the first rotor (62).

16. Disc grinding / polishing device (10) according to one of the preceding claims, wherein the first rotor (62) is suspended axially displaceably and resiliently relative to the first stator (64), and wherein a pressure force against the grinding / polishing plate (18) causes a coaxial displacement of the first rotor (62) relative to the first stator (64), and wherein a force measuring device (80) is included which measures the force exerted on the resilient suspension by the coaxial displacement of the first rotor (62) relative to the first stator (66). Disc grinding and polishing device (10) according to one of claims 14-16, wherein the force measuring device (80) comprises at least one force sensor (87), in particular at least one strain gauge (88), which is arranged in particular radially outside the first drive spindle (66). Disc grinding / polishing device (10) according to one of claims 14-17, wherein the force measuring device (80) comprises a force distribution ring (82) which extends around the first drive spindle (66), wherein the counterforce (FG) acting upwards on the first drive spindle (66) which arises during the central pressure via the sample holder (34), in particular via the lower bearing (70) of the first drive spindle (66), is transferred to the force distribution ring (82), wherein the force distribution ring (82) is axially elastically coupled to the suspension (32) of the grinding / polishing head (30), and wherein the force measuring device (80) comprises at least one force sensor (87) by means of which the pressure force (FA) can be measured.Disc grinding / polishing device (10) according to one of claims 14-18, wherein a control device is included, into which a pressure force target value can be input, wherein the control device controls the lifting mechanism (44) and defines a closed control loop in which the pressure force (FA) exerted by the lifting mechanism (44) on the sample holder (34) on the grinding / polishing plate (18) is actively regulated to the set pressure force target value in response to the pressure force measured by the force measuring device (80).Disc grinding / polishing device (10) according to one of the preceding claims, wherein the sample holder (34) is designed as a multiple sample holder with a plurality of sample receptacles (36) which are arranged around the rotational axis (21) of the first drive spindle (66), wherein the grinding / polishing head (30) has individual pressure pistons (38) and the samples which are placed in the associated sample receptacle (36) are individually subjected to force by one of the individual pressure pistons (38). Disc grinding and polishing device (10) according to claim 20, wherein the individual pressure pistons (38) are pneumatically actuated, wherein the first drive spindle (66) has a compressed air connection (90) for introducing compressed air, wherein an axial compressed air channel (92) runs in the first drive spindle (66), which guides the compressed air axially through the first rotor (62) and the first stator (64) to an air distributor (96) below the first electric drive motor (60), and wherein the air distributor (96) distributes the compressed air radially to the individual pressure pistons (38) through distribution channels (102) in order to actuate them pneumatically.Disc grinding / polishing device (10) according to one of the preceding claims, comprising a horizontal movement mechanism (244) for the grinding / polishing head (30), by means of which the grinding / polishing head (30), including the first electric drive motor (60) and / or the force measuring device (80) and in particular a lifting mechanism (44) for the grinding / polishing head (30), can be moved transversely to the grinding / polishing plate (18) by motor.Disc grinding / polishing device (10) for surface grinding and / or polishing the sample surface on the underside of the sample with a rotating grinding / polishing plate (18), in particular for sample preparation, in particular according to one of the preceding claims, comprising: a lower housing (12) with a collecting tray (16) for collecting grinding and / or polishing suspension, a horizontal grinding / polishing plate (18) which is arranged in the collecting tray (16) and rotates about a vertical axis of rotation (20), wherein different grinding pads, polishing pads and / or polishing cloths can be detachably fastened on the upper side (18a) of the grinding / polishing plate (18) in order to be able to communicate with the respective grinding pad, polishing pad orPolishing cloth to grind and / or polish the underside of the samples pressed from above onto the grinding / polishing plate (18), a grinding / polishing head (30) with a sample holder (34) for inserting one or more samples, a first drive spindle (66) extending vertically in the grinding / polishing head (30), the sample holder (34) being connected to a lower end of the first. Drive spindle (66) is connected in order to drive the sample holder (34) in rotation with the first drive spindle (66), a first electric drive motor (60) arranged in the grinding-polishing head (30) for driving the rotation of the first drive spindle (66), wherein the first electric drive motor (60) comprises a first stator (64) and a first rotor (62), wherein the first drive spindle (66) extends coaxially in the first rotor (62), and the first electric drive motor (60) forms a first coaxial direct drive (61) for the sample holder (34) with the first drive spindle (66).

24. Disc grinding / polishing device (10) according to claim 23, further comprising a second electric drive motor (160) for the grinding / polishing disc (18) arranged in the lower housing (12).

25. Disc grinding / polishing device (10) according to claim 24, further comprising a second drive spindle (166) extending vertically from the lower housing (12) through a bottom opening (176) of the collecting tray (16) into the collecting tray (16), wherein the grinding / polishing plate (18) is connected to an upper end of the second drive spindle (166) in order to drive the grinding / polishing plate (18) in rotation with the second drive spindle (166), wherein the second electric drive motor (160) comprises a second stator (164) and a second rotor (162), wherein the second drive spindle (166) extends coaxially in the second rotor (162), and the second electric drive motor (160) forms a second coaxial direct drive (161) for the grinding / polishing plate (18) with the second drive spindle (166).

26. Disc grinding / polishing device (10) for surface grinding and / or polishing the sample surface on the underside of the samples with a rotating grinding / polishing plate (18), in particular for sample preparation, in particular according to one of the preceding claims, comprising: a lower housing (12) with a collecting tray (16) for collecting grinding and / or polishing suspension, a horizontal grinding / polishing plate (18) which is arranged in the collecting trough (16) and rotates about a vertical axis of rotation (20), wherein different grinding pads, polishing pads and / or polishing cloths can be detachably fastened on the upper side (18a) of the grinding / polishing plate (18) in order to be able to work with the respective grinding pad, polishing pad orPolishing cloth for flattening and / or polishing the underside of the samples pressed onto the grinding / polishing plate (18) from above, a second drive spindle (166) extending vertically from the lower housing (12) into the collecting tray (16), wherein the grinding / polishing plate (18) is connected to an upper end of the second drive spindle (166) in order to drive the grinding / polishing plate (18) in rotation with the second drive spindle (166), a second electric drive motor (160) arranged in the lower housing (12) for driving the rotation of the second drive spindle (166), wherein the second electric drive motor (160) comprises a second stator (164) and a second rotor (162), wherein the second drive spindle (166) extends coaxially in the second rotor (162), and the second electric drive motor (160) is connected to the second drive spindle (166) forms a second coaxial direct drive (161) for the grinding-polishing plate (18).The disc grinding / polishing device (10) according to claim 26, further comprising a grinding / polishing head (30) with a sample holder (34) for inserting one or more samples above the grinding / polishing plate (18), a first drive spindle (66) extending vertically in the grinding / polishing head (30), wherein the sample holder (34) is connected to a lower end of the first drive spindle (66) in order to drive the sample holder (34) in rotation with the first drive spindle (66), a first electric drive motor (60) arranged in the grinding / polishing head (30) for driving the rotation of the first drive spindle (66), wherein the first electric drive motor (60) comprises a first stator (64) and a first rotor (62), wherein the first drive spindle (66) is coaxially connected to the first rotor (62), and the first electric drive motor (60) is connected to the first drive spindle (66) forms a first coaxial direct drive (61) for the sample holder (34).

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