DE102022125705A1 - Disc grinder/polishing machine - Google Patents

Abstract

The invention relates to a disk grinding/polishing device (10) 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 (18), in particular for sample preparation for materialographic analysis, comprising: 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 disk (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) forms with the second drive spindle (166) a second coaxial direct drive (161) for the grinding/polishing plate (18).

Description

Field of the invention

The invention relates to a disk 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 disk in a collecting tray, in particular for sample preparation for materialographic analysis.

Background and general description of the invention

Disc grinders/polishing machines typically have two drives. One drive is located at the bottom and drives the grinding/polishing disc. The other drive is located at the top of the grinding/polishing head and drives the sample holder. The grinding/polishing disc is typically driven at a speed between 50 min ^-1 and 500 min ^-1 . The power is around 0.75 kW to 1.5 kW for 300 mm grinding/polishing disc diameter or 2.2 kW for 350 mm grinding/polishing disc diameter.

All in all, the known disc grinding/polishing devices have proven to be very effective in practice, but the inventors see further potential for improvement with regard to the circumstances explained below.

In known disc grinding/polishing devices, the drive is typically provided by single- or three-phase asynchronous electric motors, which, for example, have a nominal speed of approx. 1450 min ^-1 in the four-pole version. In order to provide the required speeds, especially in the lower speed range, in a stable manner without speed fluctuations, the speed is typically transmitted to the grinding/polishing disc via a belt drive with a relatively large reduction ratio, e.g. approx. 5:1.

Even lower speeds are required for the grinding/polishing head. These are typically around 20 min ^-1 to 200 min ^-1 . The grinding/polishing head is also typically driven by an asynchronous machine, 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 has to be very small because the installation space is limited. This also means that the wrap angle of the pulley is relatively small.

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 a high torque, which is inefficient and causes a large amount of heat to be generated.

Another disadvantage of the belt drives used is that the mass inertia of the drive increases quadratically with each gear ratio. If the grinding/polishing plate or the grinding/polishing head suddenly becomes blocked, this can cause the belt drive to slip, which can accelerate wear or even lead to failure.

Furthermore, due to the unfavorable wrap angle and small drive pulley diameters explained above, the belt must be dimensioned larger in order to be able to transmit the required torque. This in turn causes significant deformation and thus flexing work, which in turn can accelerate the wear of the belt.

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 tensioned too much, this can lead to bearing damage on the drive motor. If the belt is tensioned too little, it can slip, which in turn can lead to wear and complete failure. With disc grinders/polishing machines, the belt should be re-tensioned 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 much. This can result in the bearings being overloaded, and even a possible failure of the drive motor due to bearing damage, which leads to an expensive service call on site at the customer's premises.

In the practical application of grinding/polishing machines, the belt drive is repeatedly replaced at certain intervals, which is not without problems on site. On the one hand, the device has to be partially dismantled and on the other hand, there is often no measuring device available on site to accurately determine the belt tension, which in turn can lead to the consequential damage described.

The known belt drives also have disadvantages in terms of design. Firstly, a tensioning option is required, which is typically achieved by moving the electric motor transversely. The belts used here require n drives for the electric motor and the adjustment range for the belt tension require appropriate installation space in the device.

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

Furthermore, with the well-known disc grinding/polishing devices - either with individual pressure or with central pressure - the samples are pressed against the rotating grinding/polishing plate with a defined pressure force to ensure that the samples to be prepared are removed accordingly. 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 the 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 due to contamination.

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

The invention therefore has the task of providing a disc grinding/polishing device which guarantees high-quality grinding and polishing results.

Another aspect of the task 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 removal.

A further aspect of the task is to provide a disc grinding/polishing device which 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.

A further aspect of the task is to provide a disc grinding/polishing device which makes optimal use of 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.

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

The object of the invention is solved by the subject matter of the independent claims. Advantageous developments of the invention are defined in the subclaims.

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 structural examination of the ground and polished underside of the in particular embedded samples.

The disk grinding/polishing device has a grinding/polishing head with a sample holder for inserting one or more embedded or non-embedded samples. The sample holder can, for example, comprise a receiving disk with several, e.g. six, sample holders distributed symmetrically around the axis of rotation for inserting one embedded or non-embedded sample each.

Grinding and polishing of embedded samples is carried out in materialographic analysis, e.g. after separating sample pieces with a separating machine and then embedding the sample pieces in embedding material to give the embedded samples a more or less standardized shape, e.g. in the form of cylinders with diameters in the range between 25 mm and 50 mm. In the professional world, this is also referred to as metallographic embedding. The disc grinding/polishing device is particularly suitable as a laboratory device for such embedded samples. The disc grinding/polishing device 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.

The disc grinding/polishing device also includes a lower housing with a collecting tray for collecting grinding and/or polishing suspension. During grinding, cooling is typically carried out with water, so that the suspension of grinding material and water is collected in the collecting tray and can be drained off via a drain in the collecting tray. Polishing is carried out using polishing suspensions, e.g. diamond suspensions, which are applied to the polishing disc or polishing cloth before and/or during the polishing process. The polishing suspension can be collected in the collecting tray and drained away via the drain.

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 grinding 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 ever finer level. 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-adhesively, with a vacuum and, if necessary, with other 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 embedded or non-embedded materialographic samples can be first ground (if necessary with different abrasive grains) and then immediately polished (if necessary with polishing suspensions of different fineness) using the same disc grinding and polishing device, without having to remove the samples from the adapted sample holder. A cleaning station can also be provided if necessary.

The disc grinder/polishing device includes an upper first electric drive motor arranged in the grinding/polishing head for rotatingly driving the sample holder.

The disc grinding/polishing device further includes a lower second electric drive motor arranged in the lower housing for rotating the grinding/polishing disc.

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 in a form-fitting or friction-fitting manner to the first rotor and extends in particular coaxially through the first rotor and the first stator, such that the first electric drive motor forms a first coaxial direct drive for the sample holder with the first drive spindle. The sample holder is in particular coaxially attached, preferably detachably, to a lower end of the first drive spindle.

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 forms a second coaxial direct drive for the grinding/polishing plate with the second drive spindle. The grinding/polishing plate is in particular coaxially attached to an upper end of the second drive spindle, preferably detachably.

The disc grinding/polishing device can therefore have its own coaxial direct drive, as defined above, either for the sample holder or for the grinding/polishing disc, or preferably for both.

The speed of the first electric drive motor is preferably in the range between 20 min ^-1 and 200 min ^-1 . The speed of the second electric drive motor is preferably in the range between 50 min ^-1 and 600 min ^-1 . The speeds can in particular be controllable.

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.

Instead of conventional asynchronous motors with belt drives, torque motors are used as direct drives, for example. 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 supplied with the appropriate current, generate magnetic fields which the associated rotor follows. The torque motors can generate a very high torque from a standstill up to the maximum speeds required here (approx. 200 min ^-1 or 600 min ^-1 ) and are used as direct drives, i.e. without a belt drive or gearbox. The respective rotor can be mounted directly coaxially on 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 associated drive spindle can be made, for example, by form-fitting, e.g. with a feather key, or by friction. Transverse forces exerted on the spindle by belts in conventional disc grinding/polishing machines are eliminated, which reduces the bearing load and thus wear is significantly reduced. Furthermore, the drive is almost silent and completely maintenance-free, which means that on-site service work at the customer's premises is no longer necessary. The drive units can be constructed compactly overall, resulting in a slim design despite the high torque.

The disc grinding/polishing device preferably has a vertical motor-driven lifting mechanism, by means of 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 enables a high level of precision for the desired removal of material.

Preferably, the lifting mechanism has at least one, preferably at least two vertical guides, a rotating spindle, e.g. a ball screw, and a rotating spindle drive motor. Preferably, the rotating spindle drive motor rotates the rotating spindle and the spindle nut or rotating guide (e.g. ball screw guide of the ball screw) relative to each other in order to effect the vertical lifting movement of the grinding/polishing head along the vertical guides. This moves the grinding/polishing head up and down, and thus the samples in the sample holder can be fed precisely during grinding and/or polishing.

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

According to a preferred embodiment, the grinding/polishing head is suspended from an L-shaped suspension, which has 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 on the rear of the lower housing. The horizontal bridge section is in turn suspended from the vertical tower section and extends horizontally over 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 axially elastically resiliently from rigid areas of the grinding/polishing head.

The first drive spindle can be mounted above and below the first rotor. 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 in order to remove bearing play.

Furthermore, the upper bearing of the first drive spindle can be designed as a floating 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.

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

For surface grinding and/or polishing with central pressure, the samples are clamped firmly in the sample holder. By moving the entire grinding/polishing head including the first electric drive motor, a defined pressure force _FA is exerted on the sample holder as central pressure via the first drive spindle.

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

Preferably, the contact pressure acting on the first drive spindle of the direct drive relative to the grinding/polishing head is measured with a force measuring device, in particular 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 the grinding/polishing head is lowered onto the grinding/polishing plate. The force measuring device measures the contact pressure F _A in particular between the first drive spindle and rigid areas of the suspension of the grinding/polishing head, in particular in response to the elastically springy axial movement of the first drive spindle caused by the contact pressure relative to rigid areas of the suspension.

With central pressure, the force on the samples is preferably not applied by pneumatic pistons, but by an electric motor, e.g. with a spindle drive. The force can be measured using the force measuring device and the drive motor for the lifting mechanism in the closed loop can be controlled using this signal, which in turn rum, for example, the feed movement can be applied with exactly the right load via the ball screw. Likewise, the electromotor spindle drive of the lifting mechanism can be used to output the exact path length by calculating the motor position, e.g. using the rotary encoder. This also makes it possible to achieve a precisely defined removal of the samples with a precisely defined feed force.

The grinding/polishing device preferably also has a device for determining the zero point, with which the contact of the lower sample surface with the grinding/polishing plate or the grinding pad can be detected. This makes it possible to determine the exact zero point, i.e. the surface of the sample from which the material removal is measured. To determine the zero point, the impact of the samples on the grinding/polishing plate is detected when the grinding/polishing head is lowered. This advantageously makes it possible to precisely determine the material removal of the samples during the grinding process. This can be determined or set in the hundredth to a few thousandths of a millimeter range, which can be advantageous for penetrating certain layers of the samples.

Precise adjustment of the material removal is possible in particular with the electromotive lifting mechanism, as this enables a rigid feed drive to be achieved, which, in comparison to pneumatic force application, avoids unknown friction forces in the system and inaccuracies, e.g. due to the compressibility of the air. The zero point determination therefore has a special synergistic effect in combination with the electromotive lifting mechanism.

To determine the zero point, i.e. to detect the contact with the sample surface, the force measuring device can be used in particular, as described above, since it emits a measurable signal even at the slightest contact of the sample with the grinding/polishing plate.

The force measuring device can comprise one or more force sensors, e.g. strain gauges, which change their electrical resistance when stretched. The at least one force sensor or strain gauge can be applied to a spring element of the force measuring device, e.g. to a leaf spring element. The leaf spring elements can be arranged around the first drive spindle, preferably under the first drive motor.

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 F _G acting upwards on the first drive spindle via the sample holder during central pressure 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 connected in an axially elastic manner to the suspension of the grinding/polishing head, for example with the particularly radial leaf spring elements on which the at least one or more force sensors, particularly with strain gauges, can be attached, in order to measure the pressure force F _A with the strain gauges via the strain gauges that strain during central pressure due to the axial movement of the first drive spindle relative to the suspension.

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 on 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 carried out by means of the force measuring device. The force measuring device is preferably generally ring-shaped 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.

In order to obtain an unadulterated signal from the force measuring device, it is extremely advantageous if no transverse forces, e.g. from a drive belt, are introduced into the force measuring device. This can be achieved in particular 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 has a special synergy effect, especially in combination with the coaxial force measuring device.

The rotor and the stator of the first direct drive motor are preferably axially displaceable relative to one another in order to absorb the axial elastic movement of the first drive spindle when the samples are pressed against the grinding-polishing plate, in particular in the central pressure method. The bearing of the first drive spindle can also absorb the axial elastic movement when the samples are pressed against the grinding-polishing plate, e.g. by means of a cylindrical roller bearing.

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 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 measurement value measured by the force measuring device to the set pressure force setpoint.

Preferably, the sample holder is designed as a multiple sample holder with several sample holders that are arranged symmetrically around the rotation 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 apply force individually to the samples that are each inserted into the associated sample holder.

The sample holder is designed, for example, to hold 6 samples that are arranged symmetrically around the rotation axis of the first drive motor or the first drive spindle in order to grind and/or polish several samples at the same time. For individual pressure, the samples are placed into the sample holders from above. With central pressure, the samples are additionally clamped firmly in the sample holders in order to exert the desired pressure force 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 introduced into the first drive spindle via a compressed air connection that can be rotated 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. In the first drive spindle, for example, there is an axial compressed air channel that can guide the compressed air axially through the first rotor and the first stator to an air distributor that rotates with the first drive spindle under the first electric drive motor. The air distributor can then distribute the compressed air radially to the individual pressure pistons through distribution channels in order to actuate them pneumatically. The air pressure can be adjusted by a pressure control valve so that the required pressure force is exerted on the grinding/polishing plate.

• ein Untergehäuse mit einer Auffangwanne zum Auffangen von Schleif- und/oder Poliersuspension,
• einen horizontalen Schleif-/Polierteller, der in der Auffangwanne angeordnet ist und um eine vertikale Rotationsachse rotiert, wobei auf der Oberseite des Schleif-/Poliertellers wahlweise unterschiedliche Schleifpads, z.B. Schleifpapier, Schleiffolie, dünne Schleifscheiben, unterschiedlicher Körnung, z.B. Korund, Diamant etc., Polierpads und/oder Poliertücher anhaftbar sind, um mit dem jeweiligen Schleifpad, Polierpad bzw. Poliertuch die Unterseite der von oben auf den Schleif-/Polierteller aufgedrückten Proben plan zu schleifen und/oder zu polieren, wobei im Betrieb Schleif- und/oder Poliersuspension in der Auffangwanne aufgefangen und über einen Suspensionsauslass der Auffangwanne abgeführt werden können,
• einen Schleif-/Polierkopf mit einem Probenhalter zum Einsetzen einer oder mehrerer Proben,
• eine sich vertikal in dem Schleif-/Polierkopf erstreckende erste Antriebsspindel, wobei der Probenhalter koaxial mit einem unteren Ende der ersten Antriebsspindel verbunden ist, um mit der ersten Antriebsspindel den Probenhalter zentral rotierend anzutreiben,
• einen in dem Schleif-/Polierkopf angeordneten ersten elektrischen Antriebsmotor zum Antreiben der Rotation der ersten Antriebsspindel, ggf. mit variabler Drehzahl,
• wobei der erste elektrische Antriebsmotor einen ersten Stator und einen ersten Rotor umfasst, wobei die erste Antriebsspindel koaxial, z.B. form- oder reibschlüssig, mit dem ersten Rotor verbunden ist und sich koaxial in dem ersten Rotor und dem ersten Stator erstreckt, derart dass der erste elektrische Antriebsmotor mit der ersten Antriebsspindel einen ersten koaxialen Direktantrieb für den Probenhalter bildet.

The invention also relates to a disk 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 with a horizontally rotating grinding/polishing disk, 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 disk 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 plate which is arranged in the collecting tray and rotates about a vertical axis of rotation, whereby different grinding pads, e.g. sandpaper, grinding foil, thin grinding discs, different grain sizes, e.g. corundum, diamond etc., polishing pads and/or polishing cloths can be attached to the top of the grinding/polishing plate in order to use the respective grinding pad, polishing pad or polishing cloth to grind and/or polish the underside of the samples pressed onto the grinding/polishing plate from above, whereby grinding and/or polishing suspension can be collected in the collecting tray during operation 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 centrally in rotation 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, optionally at a variable speed,
• wherein the first electric drive motor comprises a first stator and a first rotor, wherein the first drive spindle is coaxially connected, 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.

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 at the same time as the sample holder. The rotations can be in the same direction or in opposite directions.

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 of 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 forms a second coaxial direct drive for the grinding/polishing plate with the second drive spindle.

There are also simple disc grinding/polishing machines without a grinding/polishing head and automatic pressure mechanism, in which the sample is ground and polished manually.

• ein Untergehäuse mit einer Auffangwanne zum Auffangen von Schleif- und/oder Poliersuspension,
• einen horizontalen Schleif-/Polierteller, der in der Auffangwanne angeordnet ist und um eine vertikale Rotationsachse rotiert, wobei auf der Oberseite des Schleif-/Poliertellers wahlweise unterschiedliche Schleifpads, z.B. Schleifpapier, Schleiffolie, dünne Schleifscheiben, unterschiedlicher Körnung, z.B. Korund, Diamant etc., Polierpads und/oder Poliertücher anhaftbar sind, um mit dem jeweiligen Schleifpad, Polierpad bzw. Poliertuch die Unterseite der von oben auf den Schleif-/Polierteller aufgedrückten Proben plan zu schleifen und/oder zu polieren, wobei im Betrieb Schleif- und/oder Poliersuspension in der Auffangwanne aufgefangen und über einen Suspensionsauslass abgeführt wird,
• eine sich vertikal aus dem Untergehäuse in die Auffangwanne durch eine Bodenöffnung in der Auffangwanne erstreckende zweite Antriebsspindel, wobei der Schleif-/Polierteller in der Auffangwanne an einem oberen Ende der zweiten Antriebsspindel verbunden ist, um mit der zweiten Antriebsspindel den Schleif-/Polierteller von unten rotierend anzutreiben,
• einen in dem Untergehäuse angeordneten zweiten elektrischen Antriebsmotor zum Antreiben der Rotation der zweiten Antriebsspindel, ggf. mit variabler Drehzahl,
• wobei der zweite elektrische Antriebsmotor einen zweiten Stator und einen zweiten Rotor umfasst, wobei die zweite Antriebsspindel koaxial, z.B. form- oder reibschlüssig mit dem zweiten Rotor verbunden ist und sich koaxial in dem zweiten Rotor und dem zweiten Stator erstreckt, derart dass der zweite elektrische Antriebsmotor mit der zweiten Antriebsspindel einen zweiten koaxialen Direktantrieb für den Schleif-/Polierteller bildet.

It is also conceivable to use the drive described for the grinding/polishing plate in these simple disc grinding/polishing devices. Therefore, the subject of the invention is also a disc grinding/polishing device for surface grinding and/or polishing the sample surface on the underside of the samples, in particular 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/polishing device comprises:

• a lower housing with a collecting tray for collecting grinding and/or polishing suspension,
• a horizontal grinding/polishing plate which is arranged in the collecting tray and rotates about a vertical axis of rotation, whereby different grinding pads, e.g. sandpaper, grinding foil, thin grinding discs, different grain sizes, e.g. corundum, diamond etc., polishing pads and/or polishing cloths can be attached to the top of the grinding/polishing plate in order to use the respective grinding pad, polishing pad or polishing cloth to grind and/or polish the underside of the samples pressed onto the grinding/polishing plate from above, whereby grinding and/or polishing suspension is collected in the collecting tray during operation 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 a rotating manner 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 variable speed,
• wherein 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 forms a second coaxial direct drive for the grinding/polishing plate with the second drive spindle.

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

Short description of the characters

• 1 eine dreidimensionale Darstellung eines Teller-Schleif-/Poliergeräts gemäß einem Ausführungsbeispiel der Erfindung mit aufgeschnittenem Schleif-/Polierkopf,
• 2 einen vertikalen Querschnitt durch den Schleif-/Polierkopf des Teller-Schleif-/Poliergeräts aus 1,
• 3 eine dreidimensionale Darstellung einer Kraftmesseinrichtung gemäß einem Ausführungsbeispiel der Erfindung,
• 4 eine Draufsicht auf die Kraftmesseinrichtung aus 3
• 5 einen Schnitt durch die Kraftmesseinrichtung entlang der Linie A-A in 4
• 6 eine Explosionsdarstellung des Schleif-/Polierkopfes und der Aufhängung,
• 7 einen vertikalen Querschnitt durch den Hubmechanismus für den Schleif-/Polierkopf,
• 8 eine teilweise aufgeschnittene Ansicht von vorne des Teller-Schleif-/Poliergeräts aus 1,
• 9 einen vertikalen Querschnitt durch den Schleif-/Polierteller mit Auffangwanne und Antrieb des Teller-Schleif-/Poliergeräts aus 1,
• 10 eine Explosionsdarstellung des Schleif-/Poliertellers mit Auffangwanne und Antrieb.

Show it:

• 1 a three-dimensional representation of a disc grinding/polishing device according to an embodiment of the invention with a cut-away grinding/polishing head,
• 2 a vertical cross-section through the grinding/polishing head of the disc grinding/polishing machine 1 ,
• 3 a three-dimensional representation of a force measuring device according to an embodiment of the invention,
• 4 a top view of the force measuring device 3
• 5 a section through the force measuring device along the line AA in 4
• 6 an exploded view of the grinding/polishing head and the suspension,
• 7 a vertical cross-section through the lifting mechanism for the grinding/polishing head,
• 8th a partially cutaway view from the front of the disc grinder/polisher 1 ,
• 9 a vertical cross-section through the grinding/polishing plate with collecting tray and drive of the plate grinding/polishing device 1 ,
• 10 an exploded view of the grinding/polishing plate with collecting tray and drive.

Detailed description of the invention

Referring to 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 speed of the sample holder, speed of the grinding/polishing disc, contact pressure, grinding removal, 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 ( 9 ). The user can optionally attach various grinding pads, polishing pads or polishing cloths to the top side 18a of the grinding/polishing plate 18. Grinding pads can be designed as silicon carbide or diamond grinding discs, as sandpaper or sanding foils, for example.

If necessary, a magnetic foil can also be used as an adhesive carrier. For polishing, polishing pads or polishing cloths can be attached to the top side 18a, which are used for polishing 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 water 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 attached to the drive spindle 66 of the grinding/polishing head 30, wherein the sample holder 34 can rotate about a rotation axis 21 ( 2 ) of the grinding/polishing head 30. This sample holder 34 is designed as an 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 operated individual pressure piston 38 is provided above each sample holder 36, with which the samples inserted 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 with a defined pressure force F _A onto the grinding/polishing plate 18 or to adjust the axial feed of the grinding/polishing head 30, in particular in order to achieve a defined removal during the grinding process.

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 on the lifting mechanism 44 is moved downwards by means of the lifting mechanism 44 in order to bring about the pressure force for the grinding or polishing process. The lifting mechanism 44 therefore 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 brings about the vertical stroke via a rotation of a ball screw 50. The suspension 32 and 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 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 rotation drive of the sample holder 34 is therefore carried out by means of 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 feather key 68. Thus, the upper torque motor 60 forms an upper coaxial direct drive 61 for the sample holder 34 which is connected coaxially at the lower end to the upper drive spindle 66.

The upper drive spindle 66 is mounted below and above the rotor 62, whereby the lower bearing 70 is designed as a fixed bearing and can comprise angular contact ball bearings or normal deep groove ball bearings. In the present 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 remove the bearing play. Both ball bearings 70a, 70b are spaced apart by an intermediate ring 74 and clamped internally by means of a clamping nut 76.

A force measuring device 80 is arranged on the upper drive spindle 66, which in the present example 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 force by the upper drive spindle 66, in the present example via the lower bearing 70, when the counterforce F _G of the pressing force F _A 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 removal 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 removal 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 transfer ring 86 is supported, for example, on a rigid area of the grinding/polishing head 30. A force sensor 87 is attached to the leaf spring section 84, in the exemplary embodiment on one of the leaf springs 85, e.g. a strain gauge 88 is glued on, which changes its ohmic resistance when stretched, so that the stretch of the associated leaf spring 85 or the leaf spring section 84 can be measured when the upper drive spindle 66 is axially displaced relative to rigid components of the grinding/polishing head 30 or against the spring tension. Strain gauges can also be attached or glued on several, e.g. two or all (here four) leaf springs 85, which can further improve the accuracy of the force measurement. The measuring signals of the strain gauge(s) 88 can be amplified with a measuring amplifier 89 and transmitted to the control device of the disc grinding/polishing device 10, in particular in order to regulate the contact force F _A. 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 cast therein if necessary.

During central pressure, the grinding/polishing head 30 is moved axially downwards via the lifting mechanism 44 until the samples clamped in the sample holder 34 touch the grinding/polishing plate 18. During further vertical feeding with central pressure, the samples are pressed against the grinding/polishing plate 18 with a pressing force F _A , whereby a corresponding counterforce F _G acts axially or vertically upwards on the upper drive spindle 66. This counterforce F _G causes a deformation of the leaf springs 85 and thus an expansion of the strain gauge 88, whereby the pressing force F _A can be measured.

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 downwards against the preload of the return springs 39 against an upper side of the respective sample (not shown). To pneumatically actuate 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 can be rotated relative to the upper drive spindle 66 and directs the compressed air downwards 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, e.g. six, individual pressure pistons 38.

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 attached to the lower end of the upper drive spindle 66. The sample holder 34 can be attached to the bottom of the upper drive spindle 66, for example with a quick-release fastener 104.

In central pressure, the samples are firmly clamped in the sample holder 34 and the pressure force F _A is adjusted by moving the entire Grinding/polishing head 30 is applied to the sample holder 34 via the upper drive spindle 66, the contact pressure F _A being 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, the control device actively controlling the contact pressure F _A in a closed control loop in response to this measurement signal. In other words, the contact pressure F _A is measured via the force measuring device 80 or the force sensor 87 and, by feeding back to the control device, is controlled in a closed control loop to a contact pressure setpoint that can be entered via the input device 14.

The upper bearing 106 of the upper drive spindle 66 forms the floating bearing and in the present example is designed as a cylindrical roller bearing in order to compensate for the axial deformation of the force measuring device 80 during central pressure through its axial free mobility. A sealing ring 108 seals the upper drive spindle 66 or the upper rotor 62 against a non-rotating cover plate 110.

Referring to 7 and 8th the tower section 42 is suspended, for example, from the back of a device foot 112, which forms the device base in the lower housing 12. Two vertical guide rods 53a, 53b are suspended from the device foot 112 as part of the linear guides 52a, 52b. The bridge section 46, to the front end of which the grinding/polishing head 30 is rigidly attached, has guide sleeves 54a, 54b that slide vertically on the guide rods 52a, 52b at its end opposite the grinding/polishing head 30. 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 be able to precisely control the vertical lifting movement of the grinding/polishing head 30, the stepper motor 48 can have a rotary encoder (not shown).

The tower section 42 can also be suspended from the device base 112 so that it can move horizontally. For this purpose, the tower section 42 including the lifting mechanism 44 can be connected to the device base 112 so that it can move horizontally and linearly using 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 disk 18. The horizontal displacement mechanism 244 can be driven by a spindle drive 249, e.g. with a ball screw 250 with an electric motor 248. The horizontal movement takes place, for example, transversely to the horizontal bridge section 46. This can generate a horizontal pendulum movement of the samples when grinding the samples on the grinding/polishing disk 18. This has the advantage that the grinding or polishing discs wear evenly.

Referring to 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 rotation drive of the grinding/polishing plate 18 is thus carried out 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 feather 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.

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. The lower torque motor 160 with the lower drive spindle 166 thus forms the lower coaxial direct drive 161 for the grinding/polishing plate 18 which is coaxially connected to the lower drive spindle 166.

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.

The lower drive spindle 166 is supported axially above and below the lower gate by means of a lower bearing 170 and an upper bearing 172. quemotors 160. The bearings 170, 172 can be designed as deep groove or angular contact ball bearings, for example.

The grinding/polishing plate 18 is also seated on a plate holder 19, which is screwed coaxially from above to the lower drive spindle 166 and which enables easy removal of the grinding/polishing plate 18. The grinding/polishing plate 18 can be held magnetically and in a form-fitting manner on the plate holder 19, for example.

An annular splash guard can optionally be attached to the upper edge of the collecting tray 16 (not shown). 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 coaxially to the bottom opening 176. The collecting tray 16 can be emptied via an outlet 178 and a drain 180.

It is clear 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. It is also 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 (23)

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 with a rotating grinding/polishing disc (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 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 can be detachably attached to the upper side (18a) of the grinding/polishing disc (18) in order to flatly grind and/or polish the underside of the samples pressed onto the grinding/polishing disc (18) from above with the respective grinding pad, polishing pad or polishing cloth, a grinding/polishing head (30) arranged first electric drive motor (60) 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). Disc grinder/polishing machine (10) to Claim 1 , wherein the speed of the first electric drive motor (60) is in the range between 20 min ^-1 and 200 min ^-1 and/or the speed of the second electric drive motor (160) is in the range between 50 min ^-1 and 600 min ^-1 . Disc grinding/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. 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 disc (18) for surface grinding and/or polishing the samples. Disc grinder/polishing machine (10) to Claim 4 , wherein the lifting mechanism (44) has at least one vertical guide (52a, 52b), a circulating spindle (50) and a circulating spindle drive motor (48), wherein the circulating spindle drive motor (48) rotates the circulating spindle (50) in a spindle nut or circulating guide (118) to effect a vertical lifting movement of the grinding/polishing head (30) along the at least one vertical guide (52a, 52b). Disc grinder/polishing machine (10) to Claim 5 , wherein the rotary spindle drive motor (48) is designed as a stepper motor with rotary encoder. Disc grinding/polishing device (10) according to one of the 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 suspended from the vertical tower section (42) and extends horizontally over the lower housing (12) to the grinding/polishing head (30), and wherein the grinding/polishing head (30) is suspended from 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). Disc grinding/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). Disc grinding/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 floating 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), Disc grinding/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. Disc grinding/polishing device (10) according to one of the preceding claims, wherein the samples for surface grinding and/or polishing can be firmly clamped in the sample holder (34) with central pressure and by advancing the entire grinding/polishing head (30) including the first electric drive motor (60) via the first drive spindle (66) a defined pressing force (F _A ) is exerted as central pressure on the sample holder (34). Disc grinding/polishing device (10) according to one of the preceding claims, comprising a zero point determination device which detects the contact of the lower sample surface with the grinding/polishing disc (18). Disc grinding/polishing device (10) according to one of the preceding claims, wherein a force measuring device (80) is included which measures the pressing force (F _A ) 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). Disc grinder/polishing machine (10) to Claim 13 , 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 the Claims 13 - 14 , wherein the force measuring device (80) comprises a force distribution ring (82) which extends around the first drive spindle (66), wherein the counterforce (F _G ) acting upwards on the first drive spindle (66) arising 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 (F _A ) can be measured. Disc grinding/polishing device (10) according to one of the Claims 13 - 15 , wherein a control device is included into which a pressing force target value can be entered, wherein the control device controls the lifting mechanism (44) and defines a closed control loop in which the pressing force (F _A ) exerted by the lifting mechanism (44) on the sample holder (34) on the grinding/polishing plate (18) is actively regulated to the set pressing force target value in response to the pressing 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 several sample receptacles (36) which are arranged around the rotation 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 grinder/polishing machine (10) to Claim 17 , 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) under 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) for flat 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 tray (16) and rotates about a vertical axis of rotation (20), wherein different grinding pads, polishing pads and/or polishing cloths can be detachably attached to the upper side (18a) of the grinding/polishing plate (18) in order to flatly grind and/or polish the underside of the samples pressed onto the grinding/polishing plate (18) from above with the respective grinding pad, polishing pad or polishing cloth, 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), 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) 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). Disc grinder/polishing machine (10) to Claim 19 , further comprising a second electric drive motor (160) for the grinding/polishing plate (18) arranged in the lower housing (12). Disc grinder/polishing machine (10) to Claim 20 , 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). Disc grinding/polishing device (10) for flat grinding and/or polishing the sample surface on the underside of the samples with a rotating grinding/polishing disc (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 disc (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 attached to the upper side (18a) of the grinding/polishing disc (18) in order to flatly grind and/or polish the underside of the samples pressed onto the grinding/polishing disc (18) from above with the respective grinding pad, polishing pad or polishing cloth, a vertically extending from the lower housing (12) into the collecting tray (16) extending second drive spindle (166), 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) forms a second coaxial direct drive (161) for the grinding/polishing plate (18) with the second drive spindle (166). Disc grinder/polishing machine (10) to Claim 22 , 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 connected coaxially 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).

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