DE102020113324A1 - Laboratory Disc Grinder, Procedure, Replacement Grinding Wheel, and Using a Grinding Wheel - Google Patents

Abstract

The invention relates to a laboratory disc grinder and a method for surface grinding an underside of, in particular, embedded samples as well as a replacement grinding wheel for the laboratory disc grinder and the use of a grinding wheel in a laboratory disc grinder, the grinding wheel (16) being in a peripheral annular first surface area ( 42) and a central second surface area (44) arranged within the peripheral annular first surface area (42), the upper side (62b) of the carrier disk (62) with the abrasive (46) only in the peripheral annular first surface area (42) is occupied, so that a rubbing peripheral annular first surface area (42) and a passive central second surface area (44) are formed.

Description

Field of invention

The invention relates to a material-removing device on a laboratory scale for grinding samples, in the form of a laboratory disc grinder, a method for surface grinding an underside of particularly embedded samples and a replacement grinding wheel for the laboratory disc grinder and the use of a grinding wheel in a laboratory disc grinder.

Background and general description of the invention

In order to carry out material tests on samples, smaller sample pieces are often embedded in a cylindrical body made of plastic material. The diameter of such embedded samples is, for example, 40 mm. Such embedded samples are then ground flat and, if necessary, polished in order to be able to carry out material examinations, e.g. hardness test measurements or structure analyzes, on the flat ground and possibly polished surface of the material sample. For plane grinding and, if necessary, polishing of the embedded samples, laboratory disc grinders with rotating grinding wheels are typically used, such as those known from ATM Qness GmbH under the brand names Saphir and Rubin, see www.qatm.com. Such laboratory disc grinders are often designed as combined grinding and polishing devices, i.e. the laboratory disc grinders can also be equipped with a polishing disc to provide an additional polishing function. Such laboratory disc grinders are therefore typically used for surface grinding and, if necessary, polishing of the underside of embedded samples in material testing, in particular hardness testing or structural analysis.

Such laboratory disc grinders are available either with one or more spindles. Manual laboratory disc grinders essentially have a housing with a tub, a drive motor and a grinding disc. With these simple devices, the embedded sample can be pressed and ground by hand. Automatic grinding devices also have a device head, sometimes referred to as a polishing head, with a pressure stamp in which a sample holder can be mounted, which rotates. The sample can either lie loosely in the sample holder and be pressed against the grinding plate by individual pressure pins (individual sample pressure), or it is firmly clamped in the sample holder and the sample holder is pressed as a whole against the grinding plate (central pressure)

The grinding wheels for such laboratory disc grinders are typically designed over the entire surface, i. H. The abrasive with a certain grain size and a certain spread is distributed over the entire surface of the grinding wheel, possibly in a certain pattern, from the inside to the outside over the entire surface of the grinding wheel.

However, the peripheral speed of the grinding wheel decreases towards the center. Due to the decreasing peripheral speed, the pressure on the sample increases towards the center of the disk. Typically, no work is carried out in the middle of the disc, since the peripheral speed is zero and no material is removed. Therefore, primarily the outer area of the disc is used and the inner area is not used. After long-term use, this leads to different levels of wear, so that the grinding wheel is no longer flat after long-term use, which in turn can have a detrimental effect on the flatness of the specimen, which is basically aimed for.

These disadvantageous effects are counteracted by regularly honing the grinding wheel with a grindstone, typically by hand, which, however, disadvantageously causes additional effort. In addition, abrasives are wasted, resulting in unnecessary costs.

These effects are even more problematic in automatic laboratory disc grinders in which one or more samples are fastened in a sample holder which is automatically pressed onto the grinding wheel by means of a pressure ram that is rotatably fastened to a device head. The samples are typically always ground on the same radius of the grinding wheel, which leads to uneven wear of the abrasive on the grinding wheel, namely in an outer ring area in which the sample or samples are primarily ground. Since the specimen, or in the case of several specimens the entirety of the specimens, always remains in about the same radius interval despite its own radial rotation, a difference in height of the grinding surface, i.e. the grinding body between the radially outer area and the central area of the grinding wheel, can arise during long-term use. since there is less to no wear and tear on the abrasive in the central area.

If such an unevenly worn grinding wheel is not regularly honed with a grindstone, this can even cause the abrasive to form regular steps at a certain radius, which can lead to a fundamentally undesirable rounding of the lower outer edge of the embedded sample.

It is therefore an object of the present invention to provide a laboratory disc grinder, a method, a replacement grinding wheel and a use of a grinding wheel which avoid or at least reduce the disadvantages described above.

Another aspect of the object of the present invention is to provide a laboratory disc grinder, a method, a replacement grinding wheel and a use of a grinding wheel, in which, on the one hand, the need for honing the grinding wheel is eliminated or at least reduced and in which the The underside of the ground, embedded samples has a high degree of evenness, in particular rounding on the edge of the sample being avoided or at least reduced, while the grinding wheel has a long service life at the same time.

The object of the invention is achieved by the subject matter of the independent claims. Preferred embodiments are the subject of the dependent claims.

The invention relates to a laboratory-scale disc grinder with a rotating grinding wheel for surface grinding of an underside of, in particular, embedded samples, wherein the laboratory disc grinder can also be designed as a combined grinding and polishing device. It comprises a device housing with a grinding wheel mounting plate and a drive motor, by means of which the grinding wheel mounting plate is set in rotation. The speed of rotation of the grinding wheel can preferably be regulated and can be regulated, for example, between 30 min ^-1 and 600 min ^-1 .

A particularly thin grinding wheel can be attached, e.g. attached, to the grinding wheel mounting plate, which essentially consists of a backing disk and an abrasive layer in the form of abrasive grains or abrasive particles bonded to the backing disk as an abrasive. The abrasive grains are bonded preferably by means of a synthetic resin bond or a metal bond, e.g. a nickel bond, in which the abrasive grains are embedded.

The backing disk of the grinding wheel has an upper side and an underside and the underside is detachably attached to the grinding wheel mounting plate, e.g. by means of an adhesive, so that the grinding wheel as a consumable material can easily be exchanged after it has worn out or for grinding with a different grain size. For this purpose, the grinding wheel can be attached to the grinding wheel mounting plate, e.g. magnetically, i.e. by means of magnetic adhesion of the carrier disk to the grinding wheel mounting plate or by means of a carrier disk with an adhesive underside, e.g. with a gel-like surface coating. The grinding wheel is in particular considerably larger than the sample to be ground flat, the diameter of which is typically in the range from 30 mm to 60 mm.

According to one aspect of the invention, the grinding wheel is subdivided into a peripheral annular first surface region and a central second surface region arranged within the peripheral annular first surface region, the upper side of the carrier disk being covered with the abrasive grains as an abrasive only in the peripheral annular first surface region, see above that a grinding peripheral annular first surface area and a passive, non-grinding central second surface area are formed. In other words, the grinding wheel has a grinding peripheral ring area which is covered with grinding material, and a clearance in the inner ring area in which the grinding material was cut out, that is to say that the backing disk of the grinding wheel is present in the passive, non-grinding central second surface area, but is essentially not covered with abrasive grains as an abrasive. Alternatively, it is also conceivable to additionally cut out the grinding wheel mounting plate and the carrier disk in the non-grinding central second surface area and to provide an outlet for the coolant in the grinding wheel mounting plate. The abrasive layer on the backing wheel, i.e. the actively grinding surface of the grinding wheel, is designed as an annular surface and encloses a bare, non-grinding central area of the backing wheel. The abrasive layer is accordingly designed in the shape of a ring with a recess in the center around the axis of rotation of the grinding wheel.

The radial width of the grinding peripheral ring area or the radial width of the ring-shaped abrasive layer is preferably adapted to the size of the sample or samples, in such a way that the sample or samples with their edge area encompass the grinding peripheral ring area, in particular permanently or at least regularly, radially overflow inwards, so that no surface areas remain in the central area of the grinding wheel that do not, in particular permanently or at least regularly, participate in the grinding of the sample or samples. In other words, the entire surface of the abrasive layer grinds the underside of the sample or samples without there being any areas of the abrasive layer that are not overrun by the sample or samples. In other words, the diameter of the non-grinding central second surface area is large enough that the sample or the samples are permanent or at least regularly radial run inwards into the passive, non-abrasive central second surface area.

Different wear of the abrasive or the abrasive layer, especially in the central inner region of the grinding wheel, can thus advantageously be avoided, since there is preferably no abrasive at all.

This enables a synergistic double benefit to be achieved. On the one hand, the regular honing of the grinding wheel can be dispensed with or at least significantly reduced and a level grinding result for the underside of the specimen or specimens is still ensured, even if the grinding wheel has already reached a certain degree of wear. On the other hand, it is possible to avoid or at least reduce the waste of abrasive material in places where the peripheral speed of the grinding wheel is too low to achieve an optimal grinding result.

In addition, uneven wear of the abrasive can preferably also be avoided on the radial outside of the grinding wheel, in that the sample or samples also radially outward over the grinding peripheral ring area, i.e. protrude radially outward beyond the grinding peripheral ring area.

In the abrasive peripheral ring area or the ring-shaped abrasive layer, the abrasive grains are bonded to the backing disk as an abrasive with a certain grain size and a certain degree of dispersion by means of a binder. For example, epoxy resin or nickel can be used as a binding agent. For example, industrially produced diamond in the form of diamond particles with the desired grain size is used as the abrasive, whereby the diamond particles are bound in synthetic resin with a desired hardness (soft, medium, hard). The abrasive particles are preferably printed as a powder, e.g. a diamond powder, using a printing process with the synthetic resin on the surface of the carrier disk and thereby locally bound. The abrasive grains are accordingly preferably printed on in the abrasive, peripheral annular first surface area with binder in a predefined pattern. The screen printing process is particularly suitable for this. Alternatively, the abrasive particles can also be bonded to the backing disk by means of a metal bond, e.g. a nickel bond.

As a result, a surface of the annular abrasive layer is formed in the cross section of the grinding wheel by the abrasive grains embedded in the binder, which in the grinding peripheral annular first surface area define a common annular grinding first surface of the grinding wheel. The backing disk of the grinding wheel forms a central, non-grinding second surface of the grinding wheel in the passive, non-grinding central second surface area, since the central second surface area of the backing disk is not covered with abrasive grains or because the abrasive layer is cut out there. In a fresh, unused state of the grinding wheel, the common annular grinding first surface of the grinding wheel is higher than the central non-grinding second surface of the grinding wheel, so that a height difference or a step between the common annular grinding first surface and on the inner radius of the annular abrasive layer the central non-grinding second surface is formed and the sample or the samples run into the passive non-grinding central second surface area and there, due to the height difference, have an axial distance from the grinding wheel.

The difference in height of the step between the common annular abrasive first surface or the surface of the annular abrasive layer and the central non-abrasive second surface or the thickness of the abrasive layer can be between 50 µm and 5 mm, preferably between 100 µm and 3 mm, depending on the grinding wheel mm, preferably between 200 μm and 1.5 mm. Suitable grain sizes for the grinding peripheral annular first surface area have grain sizes of 3 µm, 6 µm, 15 µm, 30 µm, 60 µm, 125 µm or 250 µm or grain sizes of 80, 120, 180, 240, 320, 600, 800, 1000, 1200, 2500, whereby the grain size corresponds to 25.4mm (1 inch) / grain. E.g. the grain size for a 1000 grain size is 25.4mm / 1000 = 0.025 mm or for an 80 grain size 25.4 mm / 80 = 0.32 mm. Grains below 80 are rather uncommon for laboratory disc grinders, so that the largest grain size is preferably around 0.32 mm or 0.25 mm.

The abrasive grains are preferably bonded in several layers, preferably in 3 to 200 layers, preferably in 5 to 100 layers, so that in the multi-layer abrasive layer on average about 3 to 200 layers are bonded in the abrasive, peripheral annular first surface area with the binder on the upper side of the backing disk , preferably about 5 to 100 abrasive particles are bound axially one above the other.

More preferably, the multi-layer abrasive layer is designed to be self-sharpening, for example in such a way that abrasive grains that have become dull, for example diamond particles, break out during the grinding process and thus fresh abrasive grains, for example Diamond particles from an underlying layer come to the surface of their own accord.

On the one hand, this has the advantage that the grinding wheel in the laboratory disc grinder has a long service life and a large number of embedded samples can be ground one after the other before the grinding wheel has to be replaced. On the other hand, a combination of such a grinding wheel with a plurality of layers of abrasive grains bonded one on top of the other, which are successively removed, and the recess of the abrasive layer in the inner area of the grinding wheel, provides a synergistic advantage, since without the present invention the resulting height difference, especially with multi-layer self-sharpening grinding wheels is particularly large due to the wide range of wear and tear.

In other words, the difference in height between the grinding peripheral annular first surface area and the passive, non-grinding central second surface area preferably does not correspond to the size of the abrasive bodies, but is considerably larger than the size of the abrasive grains, since the bond, preferably a synthetic resin bond with diamond particles, eg by means of a screen printing process, is applied in several layers, and thus differences in height of eg up to 1 mm can be applied even with smaller grain sizes. This significantly increases the service life of the grinding wheel, even if the abrasive grains become dull relatively quickly. In the case of a multi-layer bond of the abrasive grains, as already explained above, if an abrasive grain is blunt, it breaks with the bedding due to the high cutting force, and the fresh and still sharp abrasive grains underneath come to the surface and develop their abrasive effect. This enables a long service life to be achieved.

The grinding wheel is preferably (circular) round and / or has an outer diameter between 100 mm and 500 mm, preferably between 150 mm and 400 mm, preferably 300 mm +/- 50 mm.

The grinding peripheral annular first surface area or the annular abrasive layer preferably has an inside diameter D_i and an outside diameter D_a, with half of the difference between the inside diameter D_i and the outside diameter D_a defining the radial width B_r of the annular abrasive layer and between 240 mm and 20 mm, preferably between 180 mm and 25 mm, preferably 30 mm +/- 10 mm or 125 mm +/- 50 mm. For grinding a single sample, the radial width B_r of the ring-shaped abrasive layer can be 30 mm +/- 10 mm or between 5% and 50% narrower than the diameter of the embedded sample and for a sample holder with several samples, the radial width B_r can be annular abrasive layer 125 mm +/- 50 mm or between 150% and 400% of the diameter of a single embedded sample.

According to a preferred embodiment, the grinding peripheral annular first surface area or the ring-shaped abrasive layer has an inner diameter D_i and an outer diameter D_a, the inner diameter D_i corresponding to the outer diameter of the passive, non-grinding central second surface area and the inner diameter D_i preferably between 20 mm and 450 mm mm, preferably between 30 mm and 300 mm, preferably 50 mm +/- 30 mm for a sample holder with several samples or 250 mm +/- 50 mm for a single sample and / or the outer diameter D_a is preferably between 100 mm and 500 mm , preferably between 150 mm and 400 mm, preferably in the range of 300 mm +/- 50 mm.

The carrier disk is preferably designed as a particularly rigid sheet metal. Sufficient rigidity of the carrier disk is an advantage for the grinding parameters relevant in a laboratory disc grinder. The sheet metal is preferably a metal sheet, but it can also be a plastic sheet. The thickness of the sheet is preferably between 0.1 mm and 3 mm. For example, a metal sheet with a thickness of 0.5 mm is suitable. Magnetizable metal sheets, e.g. magnetizable steel sheets, are particularly suitable, since these can be magnetically attached directly to the grinding wheel mounting plate if the grinding wheel mounting plate contains magnets.

The abrasive grains are preferably diamond particles, which in turn has a positive effect on the service life of the grinding wheel.

The abrasive grains are preferably bonded to the backing disk by means of a synthetic resin bond. Alternatively, a nickel bond can be used. The abrasive grains are embedded in the binder. The binding is done e.g. with a screen printing process.

The abrasive grains or diamond particles can even be bonded directly to the sheet metal with the binder. Alternatively, the grinding wheel can comprise a textile intermediate layer on which the abrasive grains or diamond particles are bound with the binder. The latter can have advantages in terms of production technology. In this case, the textile backing and the abrasive layer form a flexible sanding pad, which in turn is then applied to the sheet metal is glued on so that the sheet metal, together with the textile intermediate layer, forms the carrier disk in order to obtain a stiff grinding wheel.

According to a preferred embodiment, the grinding wheel has adhesive with which the lower side of the grinding wheel is attached in a removable adhesive manner on the grinding wheel mounting plate. The adhesion can be achieved, for example, by means of magnetic force or a gel-like adhesive layer. This allows the user to change the grinding wheel easily and conveniently, e.g. to change the grain size or when the grinding wheel has reached the end of its service life.

The grinding wheel mounting plate and thus the grinding wheel preferably rotate in a collecting trough which collects the abrasive material and, if necessary, the cooling liquid. This allows the grinding wheel to be cooled with a coolant, e.g. water, and the abrasive material to be washed away.

According to a preferred embodiment, the laboratory disc grinder has a preferably exchangeable sample holder, which can be designed, for example, as a plate for inserting several samples or as a gripper for a single sample, the sample or samples being inserted into the sample holder, and by means of the sample holder can be pressed against the grinding wheel by individual pressure or by central pressure. In the case of individual contact pressure, the specimen is or are simply inserted into the specimen holder and in the case of central contact pressure, they are or are firmly clamped. Furthermore, in addition to the rotation of the grinding wheel, the sample holder with the inserted sample or with the inserted samples rotates during the grinding process and during the opposite or in the same direction double rotation of the grinding wheel and the sample holder, an edge area of the sample or the samples runs inside and possibly additionally radially on the outside beyond the grinding peripheral annular first surface area or the annular abrasive layer and runs radially on the inside into the passive, non-abrasive central second surface area. This ensures that there is no abrasive in the central inner area of the grinding wheel that is not worn evenly by the sample or samples.

In other words, i) in the case of an individual sample, the sample defines an outer diameter and the sample protrudes during the grinding process with its outer diameter inward and possibly outward beyond the grinding peripheral annular first surface area or the annular abrasive layer, and ii ) in the case of a specimen holder with several inserted specimens, the totality of the specimens defines a total outside diameter in relation to the rotation of the specimen holder and the total outside diameter protrudes radially during the grinding process inside and possibly outside over the grinding peripheral annular first surface area or the annular abrasive layer and into the passive non-abrasive central second surface area.

According to a preferred embodiment of the invention, the laboratory disc grinder is designed as an automatic laboratory disc grinder and has a device head with a pressure stamp for attaching a sample holder. The pressure ram at the lower end of which the specimen holder for inserting the specimen or specimens is attached is driven by a rotary drive and positioned vertically against the grinding wheel by means of a linear drive, e.g. a spindle drive. The pressure ram automatically presses the samples inserted in the sample holder against the grinding wheel with a predefined pressure force in order to effect the grinding process with a defined pressure force, whereby individual pressure or central pressure can be used. With individual contact pressure, each sample is pressed individually against the grinding wheel by means of a single pressure pin and is not fixed in the sample holder, but is taken along, but can be moved axially in the sample holder. With central contact pressure, the specimens are firmly clamped in the holder, e.g. by means of a radial clamping screw. The rotation of the pressure ram and / or the pressure force against the grinding wheel can be preselected by the user by means of a user interface and the rotation and / or the pressure force caused by the pressure ram is then automatically controlled by a control device. With double rotation, namely rotation of the grinding wheel and rotation of the specimen holder, grinding takes place in opposite directions or in the same direction, which enables a particularly uniform grinding result.

The sample holder can, for example, be designed as a disk-shaped holder in which several samples are inserted next to one another, but it can also be designed as a gripper, which in particular grips and holds a single sample. Such a gripper as a sample holder can be designed as a three-finger gripper, for example.

The laboratory disc grinder preferably has at least one coolant nozzle for spraying coolant onto the grinding wheel. The coolant is then typically collected in the drip pan and can be drained off together with the abrasive material via a drain. Especially when the laboratory disc grinder is used as a combined grinding and polishing device is formed, several nozzles can be provided in order to also be able to apply diamond suspensions of different grain sizes or polycrystalline or monocrystalline grain sizes during polishing. Furthermore, both the manual and the automatic version of the laboratory disc grinder can be single-spindle or multi-spindle, ie it can comprise one or more grinding stations arranged next to one another, each with a grinding wheel mounting plate.

The grinding peripheral annular first surface area or the annular abrasive layer has an inner diameter D_i and an outer diameter D_a, with half of the difference between inner diameter D_i and outer diameter D_a defining the radial width B_r of the grinding peripheral annular first surface area or the annular abrasive layer. This radial width B_r is preferably adapted i) in the case of an individual sample to the diameter of the sample or ii) in the case of several samples arranged next to one another to the diameter of the totality of the samples. In this case, i) in the case of a single sample, the radial width B_r of the grinding, peripheral annular first surface area is preferably chosen so that the diameter of the sample protrudes inwardly beyond the inner diameter D_i and / or outwardly beyond the outer diameter D_a, permanently or temporarily by radial displacement or oscillation of the rotating sample during the grinding process, and ii) in the case of a sample holder with several samples inserted next to one another, the totality of the samples, based on the rotation of the sample holder, defines a total outer diameter D_g (circular envelope) and the radial width B_r of the grinding peripheral annular first surface area or the annular abrasive layer is selected so that the total outer diameter D_g (circular envelope) protrudes inwardly beyond the inner diameter D_i and / or outwardly beyond the outer diameter D_a, namely permanently or temporarily through radia le displacement or oscillation of the rotating sample during the grinding process. In both cases, the specimen or specimens can overflow the grinding, peripheral annular first surface area or the annular abrasive layer radially on the inside and / or radially on the outside, thereby avoiding abrasive areas without wear. In other words, the grinding wheel does not have any places that are on the one hand covered with abrasive but on the other hand are not overrun by the sample or samples, so that there are no places on the surface of the grinding wheel that are covered with abrasive and where the abrasive does not pass through the grinding of the sample or samples will be removed.

One aspect of the invention also relates to a method for surface grinding the underside of, in particular, embedded samples with the rotating grinding wheel, in particular with the laboratory disc grinder described above. The grinding wheel has a backing disk and abrasive grains bonded to the backing disk with a binding agent, or consists of this, possibly with a textile intermediate layer, for example, and is considerably larger than a sample to be ground flat. The grinding wheel is further subdivided into a peripheral ring-shaped first surface area and a central second surface area arranged within the peripheral ring-shaped first surface area, the top side of the carrier disk only being covered with the abrasive grains as abrasive in the peripheral ring-shaped first surface area, so that a grinding peripheral ring-shaped first surface area or an annular abrasive layer and a passive, non-abrasive central second surface area can be formed. The one or more samples are inserted into a sample holder, which can also be designed as a sample gripper, and are optionally pressed against the grinding wheel by machine. In addition to the rotation of the grinding wheel, the specimen holder with the specimen or specimens rotates during the grinding process and an edge area of the specimen or specimens runs radially inside and, if necessary, outside over the grinding peripheral annular first surface area or the annular abrasive layer an area without abrasives, in particular permanently or through radial oscillation of the specimen holder or the specimen.

In other words, i) in the case of a single sample, the sample defines an outer diameter and the sample rotates during the grinding process and hangs with its outer diameter radially on the inside and, if necessary, on the outside over the grinding peripheral annular first surface area or the annular abrasive layer, and ii) In the case of a specimen holder with several inserted specimens, the specimen holder rotates and the totality of the specimens defines a total outside diameter based on the rotation of the specimen holder and during the grinding process the total outside diameter hangs radially on the inside and, if necessary, on the outside over the grinding peripheral annular first surface area or the annular abrasive layer in order to ensure even wear of the abrasive over the entire surface of the grinding wheel that is covered with abrasive in the long term.

One aspect of the invention also relates to the grinding wheel as a replacement grinding wheel consisting of a carrier disk and abrasive grains bonded to the carrier disk with a binding agent as an abrasive, for the laboratory disc grinder Flat grinding of an underside of, in particular, embedded samples as described above, wherein the grinding wheel is considerably larger than the sample to be ground flat, wherein the carrier disk of the grinding wheel has an upper side and a lower side, and the lower side of the grinding wheel can be releasably adhered to the grinding wheel mounting plate,
wherein the grinding wheel is subdivided into a peripheral annular first surface area and a central second surface area arranged within the peripheral annular first surface area, wherein the upper side of the carrier disk is only covered with the abrasive grains as an abrasive surface in the peripheral annular first surface area, so that a grinding peripheral annular first surface area or an annular abrasive layer is formed on the carrier disk and a passive, non-abrasive central second surface area of the carrier disk.

One aspect of the invention also relates to the use of the replacement grinding wheel described in the said laboratory disc grinder.

The invention is explained in more detail below using exemplary embodiments and with reference to the figures, with identical and similar elements in some cases being provided with the same reference numerals and the features of the various exemplary embodiments being able to be combined with one another.

Figure list

• 1 eine dreidimensionale Darstellung einer Ausführungsform des Labor-Tellerschleifgeräts,
• 2 eine vergrößerte Darstellung der Schleifscheibe sowie des Probenhalters aus 1,
• 3 einen Querschnitt durch eine eingebettete Probe,
• 4 eine Draufsicht von oben auf die Schleifscheibe mit dem Probenhalter aus 2,
• 5 einen Querschnitt entlang der Linie 5-5 in 4,
• 6 eine Ausschnittsvergrößerung des Bereichs A aus 5,
• 7 eine weitere Ausführungsform des Labor-Tellerschleifgeräts,
• 8 eine schematische Querschnittsdarstellung durch den Probenhalter und die Schleifscheibe aus 7,
• 9 eine dreidimensionale Darstellung durch den Gerätekopf aus 7 ohne Gerätekopfgehäuse,
• 10 einen vertikalen Schnitt durch den Gerätekopf aus 9,
• 11 eine Querschnittsdarstellung der ungleichmäßigen Abnutzung einer herkömmlichen Schleifscheibe.

Show it:

• 1 a three-dimensional representation of an embodiment of the laboratory disc grinder,
• 2 an enlarged view of the grinding wheel and the specimen holder 1 ,
• 3 a cross section through an embedded sample,
• 4th a plan view from above of the grinding wheel with the sample holder 2 ,
• 5 is a cross section taken along line 5-5 in 4th ,
• 6th an enlarged section of area A. 5 ,
• 7th another embodiment of the laboratory disc grinder,
• 8th a schematic cross-sectional view through the sample holder and the grinding wheel 7th ,
• 9 a three-dimensional representation through the device head 7th without device head housing,
• 10 a vertical section through the device head 9 ,
• 11th a cross-sectional representation of the uneven wear of a conventional grinding wheel.

Detailed description of the invention

Referring to the 1 shows the laboratory disc grinder 10 a device housing 12th on, in the present example a free-standing housing for placing on a laboratory bench. Above the device housing 12th there is a device head 14th , in the present example designed as a cantilever arm, which extends over the grinding wheel 16 extends. The grinding wheel 16 rotates in a collecting tray 18th in the device housing 12th . From the device head 14th a rotating pressure ram extends 20th down and at the bottom 22nd of the pressure stamp 20th is a sample holder 24 , in the present example in the form of a plate, with a connecting pin 26th ( 2 ) attached. In the sample holder 24 or the sample holder are six embedded samples in the present example 30th used. The illustrated embodiment works with central contact pressure. Alternatively, it is also possible to work with individual contact pressure, with the samples 30th are pressed against the grinding wheel with their own pressure stamp and not axially fixed in the specimen holder 24 be clamped (not shown).

The sample holder 24 and the six embedded samples inserted therein 30th rotate around the axis of rotation AK of the pressure ram 20th or the connection pin 26th . This describes the six embedded samples 30th a circular movement around the axis AK and thereby define an overall outer circumference 31 with a total outside diameter D_g of about 130 mm in the present example ( 4th ).

For grinding the samples 30th the grinding wheel now rotates on the one hand 16 around the grinding wheel axis AS and on the other hand the sample holder 24 about the axis AK of the pressure stamp 20th , whereby the axis AK of the rotation of the specimen holder is laterally offset parallel to the axis AS of the rotation of the grinding wheel ( 4th , 5 ). In particular, the overall scope 31 outside the grinding wheel axis AS, which is advantageous since the peripheral speed of the grinding wheel on its own axis of rotation AS is equal to zero.

In the example device head 14th with central pressure there is a pressure mechanism, for example with a linear guide 78 ( 9 , 10 ), which the sample holder 24 with the embedded samples 30th with a predefined pressing force F during the opposite or in the same direction rotation of the grinding wheel 16 and the sample holder 24 against the grinding wheel 16 presses to the grinding process of the undersides 30a of the samples by abrasion by means of the on top 16b to effect the abrasive layer of abrasive or abrasive grains located on the grinding wheel.

Referring to the 3 is the test 30th an embedded sample, which consists of the actual sample material to be examined 32 , for example a piece of a metallic test object, for example for later carrying out a hardness test measurement or structural analysis with a microscope, and a cylindrical block made of plastic embedding material in which the sample material is made 32 is embedded. The sample material 32 is particularly in the plastic block 34 embedded to be more manageable. In the present example, the plastic block consists of two different plastics 34a , 34b to optimize costs. Bakelite, epoxy resins, thermosetting plastics, thermoplastics or acrylic resins, for example, are used as embedding materials for transparent embedding.

Referring to the 4th is the grinding wheel 16 into a peripheral ring area 42 and a central area located in the peripheral ring area 44 divided. The grinding wheel is only covered with abrasive in the peripheral ring area 44 , in the present example with hexagonal abrasive grain coverage. The abrasive is in the central inner area 46 recessed so that an annular dividing line 48 the peripheral ring area covered with abrasive 42 from the central, non-abrasive interior area 44 separates. In other words, it is the abrasive layer 47 ring-shaped with a recessed central inner area 44 . The distance between the axes of rotation AK and AS is now selected so that the entire circumferential line is 31 of the embedded samples 30th with the dividing line 48 between the peripheral ring area 42 and the central interior 44 , i.e. with the inner diameter D_i of the annular abrasive layer 47 cuts. In other words, the embedded samples are running 30th during the rotation of the grinding wheel 16 and the sample holder 24 over the peripheral ring area covered with abrasive 42 inwards into the interior area not covered with abrasives 44 . As a result, there is no area on the grinding wheel that is covered with abrasive 16 not from the embedded samples 30th is run over, whereby an even wear of the abrasive is guaranteed.

The same applies to the outer edge 16c the grinding wheel 16 , since the radial offset between the axes AK and AS is chosen so that the samples 30th also over the outer edge 16c the grinding wheel 16 run outwards.

In the present example is the grinding wheel 16 in a hexagonal pattern with abrasive 46 proven, but this is not mandatory. Other occupancy patterns are also possible. Both the covering pattern and the ring shape of the abrasive layer can be produced in one step using screen printing. By means of the screen printing process, the binder with the abrasive grains are applied as a powder to the surface of the grinding wheel 16 , in the present example directly on a metal sheet, which is the rigid carrier disk 62 forms, printed so that the abrasive grains are embedded locally in the binder where desired on the grinding wheel 16 are bound. The carrier disk 62 can, however, also comprise a textile intermediate layer (not shown) on which the abrasive grains are bonded.

Referring to the 5 and 6th can be seen even more precisely, like the sample currently on the inside 30th over the peripheral ring area covered with abrasive 42 or over the dividing line 48 inwards into the interior area not covered with abrasives 44 the grinding wheel 16 runs out. By the fact that the sample holder 24 in addition to the grinding wheel 16 rotates, it is still ensured that all samples 30th also on their scope 30c be ground flat, just not at the moment when they are in the interior 44 or the circular abrasive recess in the interior of the annular abrasive layer 47 immerse.

In other words, it is the grinding wheel 16 not completely cover their entire surface with the abrasive 46 occupied, but only ring-shaped on the outside. By having the samples 30th always a minimum distance from the axis AS of the grinding wheel during the double rotation during the grinding process 16 adhere to, a minimum peripheral speed of the abrasive remains relative to the samples 30th preserved in every turning position. This means that the samples to be ground 30th inside over the peripheral ring area covered with abrasive 42 will result in both the abrasive 46 in the peripheral ring area 42 as well as the bottom 30a the sample 30th removed flat, so that a pulling off of the grinding wheel 16 is no longer necessary. This initially saves the user the time it takes to withdraw the sample. However, the cost of the abrasive can be added as an additional benefit 46 can be reduced as there are fewer abrasives 46 for the grinding wheel 16 is needed.

Would the interior too 44 abrasives, as is typically the case in the prior art, would be in the area around the axis of rotation AS of the grinding wheel 16 there is no material removal from the abrasive, which resulted in a non-planar wear behavior of the grinding wheel. Therefore, the grinding wheel had to be peeled off from time to time so that it was flat again. Otherwise, with uneven wear, a certain transition occurred at a radius r_s of the grinding wheel, at which the entire circumference 31 ends inside, which led to the rehearsals 30th at the edge 30c tended to round off during grinding and were not flat. 11th shows this problem of rounding 33 as it occurred with earlier grinding machines or grinding wheels.

Back to the in 1-6 illustrated embodiment of the invention, has the abrasive peripheral ring area 42 an outer diameter D_a and an inner diameter D_i, the outer diameter D_a = 300 mm and the inner diameter D_i = 50 mm in this example. These dimensions are adapted to the in 4th sample holder shown 24 in the form of a sample holder, which contains six embedded samples 30th clamped in an annular arrangement around the axis AK and itself has a diameter of 140 mm. In the present example, the samples 30th a diameter of 40 mm and the total outside diameter D_g of the total circumference 31 is about D_g = 130 mm. The overlap area or overflow area 43 of the samples 30th in the passive indoor area 44 is therefore a few millimeters in this example.

The principle of the ring-shaped design of the actively grinding surface area 42 the grinding wheel 16 however, it is not limited to specimen holders 24 with multiple samples 30th but can also be used when grinding a single sample 30th are used. In this regard, the 7th until 10 Referring to the a laboratory disc sander 10 ' show which one device head 14th having several grinding stations 15th each with its own grinding wheel 16 served. In this example the device head is 14th along the direction 52 movable on the housing 12th attached to alternately several grinding stations 15th to be able to operate. Each grinding wheel rotates here 16 in their own catch basin 18th . The laboratory disc grinder 10 ' also has two separate polishing stations 54 on.

Referring to the 8th assigns each grinding station 15th a grinding wheel holder 58 on, which can be designed as a stable metal plate, for example. The grinding wheel holder 58 is driven by a grinding wheel drive 60 rotates around the axis AS. On the grinding wheel holder 58 is the grinding wheel 16 releasably adhered, for example by means of a magnetic holder, but other techniques for adherence are also possible.

The grinding wheel 16 in turn consists of a rigid carrier disk 62 and the one on the carrier disk 62 bonded abrasives 46 in the form of abrasive grains of a certain grain size that are embedded in the binder, creating the abrasive layer 47 is formed. The abrasive grains are applied in several layers to the backing disc to create a self-sharpening grinding disc 16 to build. For this purpose, the abrasive grains are applied to the grinding wheel as a powder, for example by means of a screen printing process with synthetic resin binder 16 , in this example directly on the top 62b the carrier disk 62 imprinted. Depending on the grain size, this means that about 3 to 100 layers of abrasive grains on the backing disc 62 can be bound in the binder. The thickness of the abrasive layer created in this way 47 depends on the grinding wheel 16 about 0.2 mm to 1 mm. By means of the screen printing process, on the one hand, a desired sanding pattern, for example hexagonal as in 2 shown, as well as the subdivision into the peripheral ring area covered with abrasive 42 and the interior area not covered with abrasives 44 can be generated in one step. Due to the subdivision into the peripheral ring area covered with abrasive 42 and the interior area not covered with abrasives 44 arises at the ring-shaped dividing line 48 between the peripheral ring area covered with abrasive 42 and the interior area not covered with abrasives 44 a step 64 , the height of which is the thickness of the abrasive layer 47 corresponds to, for example, about 0.2 mm to 1 mm. The stage 64 that of the peripheral ring area 42 in the interior 44 down, ensures that even with significant wear and tear on the abrasive 46 in the peripheral ring area 42 the sample 30th a sufficient axial distance from the top 62b the carrier disk 62 and in particular from the peripheral ring area 42 in the interior 44 no undesirable step upwards can arise, as is the case with conventional grinding wheels, if the grinding means in the central area of the grinding wheel is not worn by the sample or samples. Regular honing to plan the grinding wheel can therefore be dispensed with. The carrier disk 62 is with their bottom 62a to the top 58b of the grinding wheel support plate 58 stuck.

In the in 7th until 10 The example shown is the sample holder 24 as a sample gripper 72 educated. The sample gripper 72 has three gripping arms 74 which can automatically pick up a single sample in order to automatically grind it. Using several nozzles 76 can for example automatically use water as a coolant and / or for rinsing or diamond suspensions in different grain sizes on the grinding wheel 16 be injected.

Referring to the 9 and 10 indicates the device head 14th a linear drive mechanism 78 on, by means of which the sample holder 24 and with it the sample 30th or the samples 30th with a defined force F against the grinding wheel 16 be employed, the pressure stamp 20th rotates at the same time.

It is obvious to a person 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 protection of the claims. Furthermore, it can be seen 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. All features that are disclosed in connection with the laboratory disc grinder, the method, the replacement grinding wheel and the use, of course, also apply to the objects of the respective other categories as disclosed and the features of one exemplary embodiment also apply to another exemplary embodiment. In the present case, this applies in particular to the two exemplary embodiments in FIG 1-6 on the one hand and 7-10 on the other hand.

Claims (18)

Laboratory disc grinding device (10, 10 ') with rotating grinding wheel (16) for surface grinding of an underside (30a) of, in particular, embedded samples (30), comprising: a device housing (12) with a grinding wheel mounting plate (58) and a drive motor (60) by means of which the grinding wheel mounting plate (58) can be set in rotation, a grinding wheel (16) with a backing wheel (62) and an abrasive (46) which is bonded with a binding agent on an upper side (62b) of the backing wheel (62), the backing wheel (62) of the grinding wheel (16) having an upper side ( 62b) and an underside (62a), and with the underside (62a) of the grinding wheel (16) being releasably attachable to the grinding wheel mounting plate (58), wherein the grinding wheel (16) is divided into a peripheral annular first surface region (42) and a central second surface region (44) arranged within the peripheral annular first surface region (42), the upper side (62b) of the carrier disk (62) only in the peripheral annular first surface area (42) is covered with the bonded abrasive (46), so that an abrasive peripheral annular first surface area (42) and a passive central second surface area (44) are formed. Laboratory disc grinder (10, 10 ') Claim 1 wherein the abrasive means (46) is formed by abrasive grains and, in the cross section of the grinding wheel (16), the abrasive grains (46) in the grinding peripheral annular first surface region (42) define a common annular grinding first surface of the grinding wheel (16) and the carrier disk ( 62) of the grinding wheel (16) in the passive central second surface area (44) forms a central non-grinding second surface of the grinding wheel (16), and wherein in a fresh, unworn condition of the grinding wheel (16) the common annular grinding first surface of the grinding wheel is higher than the central non-abrasive second surface of the grinding wheel (16). Laboratory disc grinder (10, 10 ') Claim 2 , wherein the height difference between the common annular abrasive first surface and the central non-abrasive second surface is in the range between 50 µm and 5 mm. Laboratory disc grinder (10, 10 ') according to one of the preceding claims, wherein the abrasive (46) is formed by abrasive grains and in the abrasive, peripheral annular first surface region (42) the abrasive grains are bonded with the binder in several layers, preferably in 3 to 100 layers, on the upper side (62b) of the carrier disk (62) . Laboratory disc grinder (10, 10 ') Claim 4 , the abrasive layer being designed to be self-sharpening in multiple layers, in such a way that abrasive grains that have become blunt break out during the grinding process and, as a result, fresh abrasive grains automatically come to the surface from an underlying layer. Laboratory disc grinder (10, 10 ') according to one of the preceding claims, wherein the abrasive (46) is formed by abrasive grains and is printed in the abrasive peripheral annular first surface area (42) with a binder in a predefined pattern. Laboratory disc grinder (10, 10 ') according to one of the preceding claims, wherein the grinding wheel (16) is round and has an outer diameter between 100 mm and 500 mm, preferably between 150 mm and 400 mm, preferably 300 mm +/- 50 mm having. Laboratory disc grinder (10, 10 ') according to one of the preceding claims, wherein the grinding peripheral annular first surface region (42) has an inner diameter D_i and an outer diameter D_a, half of the difference between inner diameter D_i and outer diameter corresponding to the radial width B_r of the grinding peripheral annular first surface region (42) and between 240 mm and 20 mm , preferably between 180 mm and 25 mm, preferably 30 mm +/- 10 mm or 125 mm +/- 50 mm. Laboratory disc grinder (10, 10 ') according to one of the preceding claims, wherein the grinding peripheral annular first surface area (42) has an inner diameter D_i and an outer diameter D_a, the inner diameter D_i between 20 mm and 450 mm, preferably between 30 mm and 300 mm, preferably 50 mm +/- 30 mm or 250 mm + / - 50 mm and / or the outer diameter D_a between 100 mm and 500 mm, preferably between 150 mm and 400 mm, preferably in the range of 300 mm +/- 50 mm. Laboratory disc grinder (10, 10 ') according to one of the preceding claims, wherein the carrier disk (62) comprises a sheet metal, in particular a metal sheet or a plastic sheet, and / or wherein the grinding means (46) consists of diamond particles. Laboratory disc grinder (10, 10 ') according to one of the preceding claims, wherein the underside of the grinding wheel (16) can be attached to the grinding wheel mounting plate (58) in a removable and adhesive manner. Laboratory disc grinder (10, 10 ') according to one of the preceding claims, wherein the device housing (12) has a collecting trough (18) for coolant and grinding debris, the grinding wheel receiving plate (58) rotating in the collecting trough (18). Laboratory disc grinder (10, 10 ') according to one of the preceding claims, wherein one or more samples (30) are inserted into a sample holder (24) and pressed against the grinding wheel (16), and wherein in addition to the rotation of the grinding wheel (16) the sample holder (24) with the sample (30) or with the samples (30) rotates during the grinding process and during the rotation of the grinding wheel (16) and the sample holder (24) an edge area of the The sample (30) or the samples (30) extends radially on the inside beyond the grinding peripheral annular first surface area (42). Laboratory disc grinder (10, 10 ') according to one of the preceding claims, wherein the laboratory disc grinder has a device head (14) with a pressure stamp (20) for attaching a sample holder (24), with which one or more samples (30) which are inserted in the sample holder (24) are applied with a predefined pressing force the grinding wheel (16) are pressed on, and the specimen holder (24) can in particular be rotated in order to achieve a rotation of the specimen holder (24) during the grinding process in addition to the rotation of the grinding wheel (16), the axes of rotation (AS, AK ) of the grinding wheel (16) and the specimen holder (24) run parallel to one another. Laboratory disc grinder (10, 10 ') according to one of the preceding claims, wherein the grinding peripheral annular first surface region (42) has an inner diameter D_i and an outer diameter D_a, and wherein half of the difference between the inner diameter D_i and the outer diameter D_a defines the radial width B_r of the grinding peripheral annular first surface region (42) and i) in the case of a single sample, the radial width B_r of the grinding, peripheral annular first surface area (42) is selected so that the diameter of the sample (30) protrudes inside beyond the inner diameter D_i, in particular permanently or temporarily through radial displacement of the rotating sample during the grinding process, or ii) in the case of a specimen holder (24) with several inserted specimens (30), the totality of the specimens, based on the rotation of the specimen holder, defines a total outer diameter D_g and the radial width B_r of the grinding, peripheral annular first surface area (42) is selected such that the total outside diameter D_g protrudes on the inside beyond the inside diameter D_i, in particular permanently or temporarily due to radial displacement of the rotating sample during the grinding process. Method for plane grinding of an underside of, in particular, embedded samples (30) with a rotating grinding wheel (16), in particular with the laboratory disc grinder (10, 10 ') according to one of the preceding claims, wherein: a grinding wheel (16) with a carrier disk (62 ) and an abrasive (46) which is bonded with a binding agent on an upper side (62b) of the carrier disk (62) is used, and wherein the carrier disk (62) of the grinding wheel (16) has an upper side (62b) and an underside (62a ), wherein the grinding wheel (16) is considerably larger than the sample (30) to be ground flat, the grinding wheel (16) being divided into a peripheral annular first surface region (42) and a first inside the peripheral annular Surface area (42) arranged central second surface area (44) is divided, wherein the upper side (62b) of the carrier disk (62) is only covered in the peripheral annular first surface area (42) with the grinding means (46), so that a grinding peripheral ring-shaped first surface area (42) and a passive central second surface area (44) are formed, wherein one or more samples (30) are inserted into a sample holder (24) and are pressed against the grinding wheel (16), and in addition to the rotation of the grinding wheel the specimen holder (24) with the specimen (30) or with the specimens (30) rotates during the grinding process and during the rotation during the grinding process edge areas of the specimen (30) or the specimens (30) inside over the grinding peripheral annular first Run out surface area (42) and run into the passive central second surface area (44). Replacement grinding wheel (16) consisting of a backing disk (62) and abrasive grains bonded to the backing disk with a binding agent, prepared for use in the laboratory disc grinder (10, 10 ') for surface grinding an underside (30a) of, in particular, embedded samples (30 ) according to one of the Claims 1 - 15th , wherein the grinding wheel (16) is considerably larger than the sample (30) to be ground flat, wherein the carrier disk (62) of the grinding wheel (16) has an upper side (62b) and an underside (62a), and wherein the carrier disk (62 ) with the underside (62a) on a grinding wheel receiving plate (58) of the laboratory disk grinding device (10, 10 ') can be releasably adhered, and wherein the grinding wheel (16) is divided into a peripheral annular first surface area (42) and an inside the peripheral annular first Surface area (42) arranged central second surface area (44) is divided, wherein the upper side (62b) of the carrier disk (62) is covered with the abrasive grains as abrasive (46) only in the peripheral annular first surface area (42), so that an abrasive peripheral annular first surface area (42) and a passive central second surface area (44) are formed. Use the replacement grinding wheel (16) after Claim 17 in the laboratory disc grinder (10, 10 ') according to one of the Claims 1 - 15th .

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