EP1893384B1 - Method and device for grinding ceramic spheres - Google Patents

Method and device for grinding ceramic spheres Download PDF

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Publication number
EP1893384B1
EP1893384B1 EP06706173.9A EP06706173A EP1893384B1 EP 1893384 B1 EP1893384 B1 EP 1893384B1 EP 06706173 A EP06706173 A EP 06706173A EP 1893384 B1 EP1893384 B1 EP 1893384B1
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Prior art keywords
grinding
abrasive grain
diamond
grinding wheel
precious
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German (de)
French (fr)
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EP1893384A1 (en
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Michael Pötzsch
Walter Karb
Michael Haubert
Karl-Otto Stock
Marco Weber
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Atlantic GmbH
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Atlantic GmbH
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B11/00—Machines or devices designed for grinding spherical surfaces or parts of spherical surfaces on work; Accessories therefor
    • B24B11/02—Machines or devices designed for grinding spherical surfaces or parts of spherical surfaces on work; Accessories therefor for grinding balls
    • B24B11/04—Machines or devices designed for grinding spherical surfaces or parts of spherical surfaces on work; Accessories therefor for grinding balls involving grinding wheels
    • B24B11/06—Machines or devices designed for grinding spherical surfaces or parts of spherical surfaces on work; Accessories therefor for grinding balls involving grinding wheels acting by the front faces, e.g. of plane, grooved or bevelled shape

Definitions

  • the present invention relates to a method and apparatus for grinding ceramic balls.
  • the grinding of ceramic balls to achieve low surface roughness and high grades is currently generally performed with devices such as are used to machine metal balls.
  • the ceramic balls are not ground in the true sense, but lapped. While in the machining of metallic balls, first coarse grinding and then fine grinding with grinding wheels with bonded abrasive grain is provided and possibly thereafter the lapping present in paste form Abrasive grain is practiced, ceramic balls are not machined with grinding wheels, but lapped over the entire removal process.
  • the abrasive grain present in the abrasive paste is generally diamond.
  • the abrasive grain consists of more than 50% diamond and less than 5% Cr 2 O 3 .
  • high removal rates can be achieved with little wear on the grinding wheel or abrasive pad.
  • the abrasive grain is free of Cr 2 O 3 and in particular if the abrasive grain consists of pure diamond. In this case, a nearly tenfold removal rate is achieved compared with the closest prior art, while the average surface roughness is greater by a factor of 10 than in the prior art.
  • the proportion of diamond in the abrasive grain is thus more than 50%, in particular more than 90% and particularly preferred is an abrasive grain of 100% diamond.
  • the synthetic resin bond is a hot-pressed phenolic resin bond or polyimide bond, wherein preferably the pore volume is close to zero.
  • Abrasive wheels are subject in use a small deformation when attached as abrasive coating on a carrier plate, in particular are cemented. The wear is further reduced when a honing oil is added as a cooling lubricant.
  • Another embodiment of the invention provides that two grinding wheels are used in the stone-to-stone process, wherein in particular the two grinding wheels are substantially identical.
  • FIG. 1 illustrates the principle of ball grinding on machines with vertical drive axle.
  • the FIG. 1 shows a schematic representation of the device for ball grinding in a plan view and in a side view.
  • a fixed guide plate 1 is preferably made of cast steel.
  • the guide disk 1 has circumferential guide grooves on its underside, in which a plurality of balls 2 to be ground are guided.
  • a carrier plate 3 is provided with an abrasive coating 3a arranged thereon, which is to be rotated by a drive shaft.
  • a ball inlet and outlet 4 is provided for loading and unloading the device.
  • FIG. 2 shows a grinding machine similar to that in the FIG. 1 was presented.
  • the fixed guide plate 1 is also provided with an abrasive pad 1 a, which is disposed opposite to the abrasive pad 3 a of the rotating support plate 3.
  • the balls 2 to be ground are arranged between the two grinding wheels 1a and 3a.
  • a pressure P is exerted on the stationary guide disk 1 from the upper side.
  • the support plate 3 is rotated by a drive, so that the balls 2 roll in the guide grooves.
  • the speed differences in the various regions of the guide grooves cause a relative movement of the abrasive coating to the surface of the ceramic ball.
  • the abrasive grain located in the abrasive coating then leads to abrasion of the surface of the ball and thus to an improvement in the surface quality and the spherical shape.
  • the method according to the invention can be carried out both on a ball grinding machine with a vertical drive shaft and on a ball grinding machine with a horizontal drive shaft.
  • Zirconia (ZrO 2 ) spheres in a round shape having a starting dimension of 5.96 mm to 6.03 mm were machined. In a batch were about 140 bullets. The achieved final dimension was 5.50 mm. The removal was 504 ⁇ m with a grinding time of 4 hours. The removal rate was thus about 125 ⁇ m per hour. The depth of the grooves in the grinding wheel after completion of the experiment was 0.5 mm.
  • Balls made of ZrO 2 in barrel form with a starting dimension of 5.72 mm x 5.25 mm were processed. In total, the batch comprised 300 blanks. The gauge was 5.15 mm. The mean removal was 570 ⁇ m with a grinding time of 3.75 hours. This corresponds to an average removal rate of 152 ⁇ m per hour. The groove depth in the grinding wheel after completion of the experiment was 0.94 mm.
  • Silicon nitride balls (Si 3 N 4 ) with a starting dimension of 5.34 mm were machined. There were 300 blanks in a batch. The gauge was 5.16 mm. The average abrasion was 180 ⁇ m with a grinding time of 3.5 hours.
  • the average removal rate was 51 ⁇ m per hour.
  • the groove depth in the grinding wheel after completion of the experiment was 1.10 mm.
  • the indicated groove depths are based on the same grinding wheel, since the same disk was used successively in all three experiments.
  • the trial 2 thus already started with a groove depth of 0.5 mm, while the trial 3 already started with a groove depth of 0.94 mm.
  • the groove depth has therefore increased, for example, only by 0.16 mm in Experiment 3.
  • Silicon nitride (Si 3 N 4 ) balls with a starting diameter of 6.12 mm were machined. In a total of 340 pieces were processed. The grinding time was 9 hours. The final diameter reached was 5.956 mm. This corresponds to a removal of up to 120 ⁇ m in 9 hours.
  • the surface roughness Ra achieved is 0.05 ⁇ m to 0.06 ⁇ m.
  • the good removal rate and the low wear of the grinding wheel or of the abrasive pad cemented to the support plate are due to the synthetic resin bond of the abrasive grain.
  • this bond unlike electrolytic bonding in the prior art, a slight elastic movement of the abrasive grain in the bonding matrix is ensured. Due to this elasticity, the abrasive grain can escape at peak loads, which can occur due to the extremely hard ceramic balls, in the microscopic range. The service life of the grinding wheel increases considerably.
  • the removal rate is also improved because the balls form grooves during the grinding process in the grinding wheel. The depth of the grooves is relatively low. But it is larger than electrolytically bonded grinding wheels that can form virtually no grooves.
  • the novel method and the novel apparatus for grinding ceramic balls not only allow high removal rates with good grinding results, but also a use of grinding machines that are accessible to modern rational methods.
  • the use of magazines for the ball feeder is possible.
  • the use of cooling lubricants provides the technological control of the grinding processes and allows the connection of appropriate filter devices, which makes the process extremely environmentally friendly.
  • the cleaning of the balls after grinding is particularly simple and can be carried out in conventional ball washing machines, since not forming the lapping typical adhesions of the grinding paste.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Polishing Bodies And Polishing Tools (AREA)
  • Grinding And Polishing Of Tertiary Curved Surfaces And Surfaces With Complex Shapes (AREA)

Description

Die vorliegende Erfindung betrifft ein Verfahren und eine Vorrichtung zum Schleifen von keramischen Kugeln.The present invention relates to a method and apparatus for grinding ceramic balls.

Unter keramischen Kugeln sollen im Zusammenhang dieser Patentanmeldung Kugeln aus keramischen Materialien wie zum Beispiel Oxidkeramik, Carbiden, Siliziumnitrid, Edel- und Halbedelsteinen, aber auch Glas verstanden werden.Ceramic balls in the context of this patent application balls of ceramic materials such as oxide ceramic, carbides, silicon nitride, precious and semi-precious stones, but also glass are to be understood.

Das Schleifen von keramischen Kugeln zur Erzielung niedriger Oberflächenrauigkeiten und hoher Güteklassen wird derzeit allgemein mit Vorrichtungen durchgeführt, wie sie auch zur Bearbeitung von Metallkugeln verwendet werden. Dabei werden die Keramikkugeln im eigentlichen Sinne nicht geschliffen, sondern geläppt. Während bei der Bearbeitung von metallischen Kugeln zunächst das Grobschleifen und dann das Feinschleifen mit Schleifscheiben mit gebundenem Schleifkorn vorgesehen ist und eventuell danach das Läppen mit in Pastenform vorliegendem Schleifkorn praktiziert wird, werden keramische Kugeln nicht mit Schleifscheiben bearbeitet, sondern über den gesamten Abtragungsvorgang geläppt. Das Schleifkorn, das in der Schleifpaste vorhanden ist, ist dabei im allgemeinen Diamant.The grinding of ceramic balls to achieve low surface roughness and high grades is currently generally performed with devices such as are used to machine metal balls. The ceramic balls are not ground in the true sense, but lapped. While in the machining of metallic balls, first coarse grinding and then fine grinding with grinding wheels with bonded abrasive grain is provided and possibly thereafter the lapping present in paste form Abrasive grain is practiced, ceramic balls are not machined with grinding wheels, but lapped over the entire removal process. The abrasive grain present in the abrasive paste is generally diamond.

Dieser Prozess ist technologisch außerordentlich schwierig durchzuführen, denn die Abtragsleistung liegt in der Größenordnung von maximal 100 µm pro Tag. Der zu realisierende Abtrag von 0,2 - 0,4 mm im Kugeldurchmesser entspricht der Dicke der inhomogenen Grenzschicht und wird z. T. erst in mehreren Tagen Bearbeitungszeit erreicht. Weiter sind nach dem Läppen die Keramikkugeln durch anhaftende Schleifpaste stark verschmutzt. Diese Schleifpaste ist bei den herkömmlichen Verfahren zum Waschen der Kugeln zum Teil nur sehr schwer entfernbar. Der Verschleiß der beiden Metallscheiben ist beim Läppen mit losem Diamantkorn extrem hoch. Schließlich bewirkt auch der sehr hohe Diamantverbrauch eine erhebliche Kostenbelastung des gesamten Verfahrens. In der Konsequenz hat sich die Verwendung von Keramikkugeln insbesondere im Bereich von Kugellagern deshalb nur dort durchgesetzt, wo die Kosten von untergeordneter Bedeutung sind.This process is technologically extremely difficult to perform because the removal rate is on the order of a maximum of 100 microns per day. The to be realized removal of 0.2 - 0.4 mm in the ball diameter corresponds to the thickness of the inhomogeneous boundary layer and z. T. reached processing time in several days. Further, after lapping, the ceramic balls are heavily soiled by adhering abrasive paste. This abrasive paste is very difficult to remove in the conventional method for washing the balls in part. The wear of the two metal discs is extremely high when lapping with loose diamond grain. Finally, the very high diamond consumption also causes a considerable cost burden for the entire process. As a consequence, the use of ceramic balls, especially in the area of ball bearings, has therefore only become established where the costs are of subordinate importance.

Einen Ansatz zur Verbesserung der Wirtschaftlichkeit findet man in der US-Patentschrift US 6,171,179 B1 . Bei der dort vorgestellten Schleifmaschine ist eine Schleifscheibe mit elektrolytisch gebundenem Schleifkorn vorgesehen. Die feststehende Führungsscheibe weist eine Anzahl von Führungsringen auf, die jeweils einzeln hydraulisch belastet sind, um einen möglichst gleichmäßigen Eindruck der Keramikkugeln an die Schleifscheibe zu gewährleisten. In der Praxis hat sich diese Vorrichtung nicht durchgesetzt. Es wird vermutet, dass die Standzeit der Schleifscheibe zu gering ist.One approach to improving economics can be found in the US patent US 6,171,179 B1 , In the grinding machine presented there, a grinding wheel with electrolytically bonded abrasive grain is provided. The fixed guide disk has a number of guide rings, which are each hydraulically loaded individually in order to ensure the most uniform possible impression of the ceramic balls to the grinding wheel. In practice, this device has not prevailed. It is believed that the service life of the grinding wheel is too low.

Aus der japanischen Patentanmeldung JP 05042467 A , die die Gundlage für den Oberbegriff der Ansprüche 1 und 11 bildet, ist ein Verfahren zum Polieren von Siliziumnitridkugeln bekannt, bei dem Polierscheiben mit einem Schleifkorn von 5 - 60 Volumenprozent Cr2O3 mit einem mittleren Teilchendurchmesser von 0,01 - 3 µm eingesetzt werden. Die Bearbeitung der Kugeln hinsichtlich der Abtragsgeschwindigkeit der Oberfläche ist sehr gering. In einem Versuch wurde ein Abtrag von 60 µm in 50 Stunden erzielt, also etwa 1 µm pro Stunde. Die Oberflächenrauhigkeit, die bei einem zweiten Versuch erzielt wurde, liegt bei Ra = 0,005 µm. Dieses Verfahren, bei dem auch vorgeschlagen wird, einen Teil des Cr2O3 durch Diamant zu ersetzen, ist zur Erzielung hoher Oberflächengüten geeignet, die Abtragsleistung ist aber zum Schleifen von Keramikkugeln nach wie vor unbefriedigend.From the Japanese patent application JP 05042467 A which forms the basis for the preamble of claims 1 and 11, a method for polishing silicon nitride balls is known, wherein the polishing wheels having an abrasive grain of 5-60 volume percent Cr 2 O 3 having an average particle diameter of 0.01 - 3 microns be used. The processing of the balls with regard to the removal rate of the surface is very low. In one experiment, a removal of 60 microns in 50 hours was achieved, ie about 1 micron per hour. The surface roughness obtained in a second trial is Ra = 0.005 μm. This method, in which it is also proposed to replace a part of the Cr 2 O 3 by diamond, is suitable for achieving high surface qualities, but the removal rate is still unsatisfactory for grinding ceramic balls.

Es ist deshalb Aufgabe der vorliegenden Erfindung, ein Verfahren und eine Vorrichtung zum Schleifen von keramischen Kugeln zu schaffen, die eine wirtschaftlichere Fertigung von keramischen Kugeln mit der erforderlichen Güte und einer geringen Streuung im Kugeldurchmesser erlaubt.It is therefore an object of the present invention to provide a method and an apparatus for grinding ceramic balls, which allows a more economical production of ceramic balls with the required quality and a low dispersion in the ball diameter.

Diese Aufgabe wird von einem Verfahren mit den Merkmalen des Anspruchs 1 und von einer Vorrichtung mit den Merkmalen des Anspruchs 11 gelöst.This object is achieved by a method having the features of claim 1 and by a device having the features of claim 11.

Weil das Schleifen mit einer Schleifscheibe mit Schleifkorn in Kunstharzbindung erfolgt, bei der das Schleifkorn zu mehr als 50 % aus Diamant besteht und zu weniger als 5 % aus Cr2O3, können hohe Abtragsleistungen bei geringem Verschleiß der Schleifscheibe oder des Schleifbelages erreicht werden. Vorteilhaft ist es, wenn das Schleifkorn frei von Cr2O3 ist und insbesondere wenn das Schleifkorn aus reinem Diamant besteht. Dabei wird gegenüber dem nächstkommenden Stand der Technik eine nahezu zehnfache Abtragsleistung erreicht, während die mittlere Oberflächenrauhigkeit um einen Faktor 10 größer ist als im Stand der Technik. Der Anteil an Diamant im Schleifkorn liegt also bei mehr als 50%, insbesondere bei mehr als 90% und besonders bevorzugt ist ein Schleifkorn aus 100% Diamant.Because grinding is done with a synthetic resin bonded abrasive wheel, where the abrasive grain consists of more than 50% diamond and less than 5% Cr 2 O 3 , high removal rates can be achieved with little wear on the grinding wheel or abrasive pad. It is advantageous if the abrasive grain is free of Cr 2 O 3 and in particular if the abrasive grain consists of pure diamond. In this case, a nearly tenfold removal rate is achieved compared with the closest prior art, while the average surface roughness is greater by a factor of 10 than in the prior art. The proportion of diamond in the abrasive grain is thus more than 50%, in particular more than 90% and particularly preferred is an abrasive grain of 100% diamond.

Vorteilhaft ist die Kunstharzbindung eine heiß gepresste Phenolharzbindung oder Polyimidbindung, wobei vorzugsweise das Porenvolumen nahe Null ist.Advantageously, the synthetic resin bond is a hot-pressed phenolic resin bond or polyimide bond, wherein preferably the pore volume is close to zero.

Die Schleifscheibe weist vorzugsweise eine Körnung von D181 (nach FEPA-Standard, mittlerer Teilchendurchmesser = 181 µm) bis D2 (mittlerer Teilchendurchmesser = 2 µm) auf, wobei für das Grobschleifen Körnungen von D181 bis D25 zum Einsatz kommen und für das Feinschleifen Körnungen von D15 bis D2 bevorzugt werden.The grinding wheel preferably has a grain size of D181 (according to FEPA standard, mean particle diameter = 181 μm) to D2 (average particle diameter = 2 μm), with grits of D181 to D25 being used for rough grinding and grains of D15 for fine grinding to D2 are preferred.

Schleifscheiben unterliegen im Einsatz einer geringen Verformung, wenn sie als Schleifbelag auf einem Trageteller befestigt, insbesondere aufgekittet sind. Der Verschleiß wird weiter verringert, wenn als Kühlschmierstoff ein Honöl zugegeben wird.Abrasive wheels are subject in use a small deformation when attached as abrasive coating on a carrier plate, in particular are cemented. The wear is further reduced when a honing oil is added as a cooling lubricant.

Eine andere Ausführungsform der Erfindung sieht vor, dass zwei Schleifscheiben im Stone-to-Stone-Verfahren verwendet werden, wobei insbesondere die beiden Schleifscheiben im wesentlichen baugleich sind.Another embodiment of the invention provides that two grinding wheels are used in the stone-to-stone process, wherein in particular the two grinding wheels are substantially identical.

Weil bei einer erfindungsgemäßen Vorrichtung zum Schleifen von keramischen Kugeln mit einer Schleifscheibe mit gebundenem Diamantschleifkorn vorgesehen ist, dass die Schleifscheibe eine Kunstharzbindung, insbesondere eine heiß gepresste Phenolharzbindung aufweist, ist das oben beschriebene Verfahren möglich. Dabei kann die Schleifscheibe auf einen Trageteller aufgekittet sein, so dass die mechanische Stabilität unter dem Verfahrensdruck gefördert und der Materialaufwand zur Herstellung der Scheibe minimiert wird.Since it is provided in a device according to the invention for grinding ceramic balls with a grinding wheel with bonded diamond abrasive grain that the grinding wheel has a synthetic resin bond, in particular a hot-pressed phenolic resin bond, the method described above is possible. In this case, the grinding wheel can be cemented onto a carrier plate, so that the mechanical stability is promoted under the process pressure and the material expenditure for producing the disk is minimized.

Erfindungsgemäß ist auch die Verwendung einer Schleifscheibe mit Diamantschleifkorn in Kunstharzbindung zum Schleifen von keramischen Kugeln, insbesondere in einer konventionellen Kugelschleifmaschine, wie sie zum Schleifen metallischer Kugeln bekannt ist.The use of a grinding wheel with diamond abrasive grain in synthetic resin bond for grinding ceramic balls, in particular in a conventional ball grinding machine, as known for grinding metallic balls, is also according to the invention.

Nachfolgend wird die vorliegende Erfindung anhand der Zeichnung sowie anhand von drei Beispielen beschrieben. Es zeigen:

Figur 1:
eine Vorrichtung zum Kugelschleifen mit einer Schleifscheibe und vertikaler Antriebsachse; und
Figur 2:
eine Vorrichtung zum Kugelschleifen im Stone-to-Stone-Verfahren mit vertikaler Achse.
Hereinafter, the present invention will be described with reference to the drawings and three examples. Show it:
FIG. 1:
a device for ball grinding with a grinding wheel and vertical drive axle; and
FIG. 2:
a device for ball grinding in the stone-to-stone process with a vertical axis.

In der Figur 1 ist das Prinzip des Kugelschleifens auf Maschinen mit vertikaler Antriebsachse veranschaulicht. Die Figur 1 zeigt in einer schematischen Darstellung die Vorrichtung zum Kugelschleifen in einer Draufsicht und in einer Seitenansicht. Dabei ist eine feststehende Führungsscheibe 1 vorzugsweise aus Stahlguss vorgesehen. Die Führungsscheibe 1 weist an ihrer Unterseite umlaufende Führungsrillen auf, in denen eine Vielzahl von zu schleifenden Kugeln 2 geführt werden. Von der Unterseite her ist ein Trageteller 3 mit einem darauf angeordneten Schleifbelag 3a vorgesehen, der durch eine Antriebswelle in Rotation zu versetzen ist. Ein Kugelein- und -austritt 4 ist zum Laden und Entladen der Vorrichtung vorgesehen.In the FIG. 1 illustrates the principle of ball grinding on machines with vertical drive axle. The FIG. 1 shows a schematic representation of the device for ball grinding in a plan view and in a side view. In this case, a fixed guide plate 1 is preferably made of cast steel. The guide disk 1 has circumferential guide grooves on its underside, in which a plurality of balls 2 to be ground are guided. From the underside, a carrier plate 3 is provided with an abrasive coating 3a arranged thereon, which is to be rotated by a drive shaft. A ball inlet and outlet 4 is provided for loading and unloading the device.

Die Figur 2 zeigt eine Schleifmaschine ähnlich derjenigen, die in der Figur 1 dargestellt wurde. Bei dieser Schleifmaschine ist die feststehende Führungsplatte 1 ebenfalls mit einem Schleifbelag 1a versehen, der dem Schleifbelag 3a der rotierenden Trageplatte 3 gegenüber angeordnet ist. Die zu schleifenden Kugeln 2 sind zwischen den beiden Schleifscheiben 1a und 3a angeordnet.The FIG. 2 shows a grinding machine similar to that in the FIG. 1 was presented. In this grinding machine, the fixed guide plate 1 is also provided with an abrasive pad 1 a, which is disposed opposite to the abrasive pad 3 a of the rotating support plate 3. The balls 2 to be ground are arranged between the two grinding wheels 1a and 3a.

Zum Schleifen wird in beiden Ausführungsformen von der Oberseite her ein Druck P auf die feststehende Führungsscheibe 1 ausgeübt. Die Trageplatte 3 wird durch einen Antrieb in Rotation versetzt, so dass die Kugeln 2 sich in den Führungsrillen abwälzen. Die Geschwindigkeitsunterschiede in den verschiedenen Bereichen der Führungsrillen bewirken eine Relativbewegung des Schleifbelags zu der Oberfläche der Keramikkugel. Das in dem Schleifbelag befindliche Schleifkorn führt dann zu einer Abrasion der Oberfläche der Kugel und damit zu einer Verbesserung der Oberflächenqualität und der Kugelform.For grinding, in both embodiments, a pressure P is exerted on the stationary guide disk 1 from the upper side. The support plate 3 is rotated by a drive, so that the balls 2 roll in the guide grooves. The speed differences in the various regions of the guide grooves cause a relative movement of the abrasive coating to the surface of the ceramic ball. The abrasive grain located in the abrasive coating then leads to abrasion of the surface of the ball and thus to an improvement in the surface quality and the spherical shape.

Das erfindungsgemäße Verfahren kann dabei sowohl auf einer Kugelschleifmaschine mit vertikaler Antriebswelle als auch auf einer Kugelschleifmaschine mit horizontaler Antriebswelle ausgeführt werden.The method according to the invention can be carried out both on a ball grinding machine with a vertical drive shaft and on a ball grinding machine with a horizontal drive shaft.

Während des Schleifvorgangs wird als Kühlschmierstoff ein Honöl zugegeben, welches zum einen das Schleifkorn und die keramische Kugel umspült und welches zum anderen auch aus der Oberfläche der Schleifscheiben ausgebrochene Schleifkörner, Bindungspartikel und Kugelabschliff weg transportiert, so dass letztere nicht an der Kugeloberfläche anhaften und den Schleifprozess negativ beeinflussen können.During the grinding process, a honing oil is added as a cooling lubricant, which on the one hand surrounds the abrasive grain and the ceramic ball and which, on the other hand, also transports abrasive grains, binding particles and spherical abrasions that have broken out of the surface of the grinding wheels, so that the latter does not adhere to the spherical surface and the grinding process can affect negatively.

Die mit dem erfindungsgemäßen Verfahren erzielten Ergebnisse sollen nachfolgend anhand von drei Versuchsbeispielen beschrieben werden.The results obtained by the method according to the invention will be described below with reference to three experimental examples.

Bei den Versuchen 1-3 wurde eine Schleifscheibe mit einem Durchmesser von 200 mm und einer Dicke von 4 mm verwendet. Die Schleifscheibe wurde aufgekittet auf einen Trageteller aus Stahl. Als Kühlschmierstoff wurde das Hohnöl EMOL®-O-HON 920 NV des Herstellers ML Lubrication GmbH zugegeben. Die Druckplatte bestand aus Stahl und wies fünf umlaufende Rillen auf. Das Schleifen erfolgte ohne Magazin auf einer Schleifmaschine mit vertikaler Achse.In experiments 1-3, a grinding wheel with a diameter of 200 mm and a thickness of 4 mm was used. The grinding wheel was cemented onto a steel carrying plate. The cutting oil EMOL ® -O-HON 920 NV from the manufacturer ML Lubrication GmbH was added as cooling lubricant. The pressure plate was made of steel and had five circumferential grooves. Grinding was done without a magazine on a vertical axis grinder.

Versuch 1:Trial 1:

Kugeln aus Zirkonoxid (ZrO2) in runder Form mit einem Ausgangsmaß von 5,96 mm bis 6,03 mm wurden bearbeitet. In einer Charge befanden sich etwa 140 Kugeln. Das erzielte Endmaß betrug 5,50 mm. Der Abtrag betrug 504 µm bei einer Schleifzeit von 4 Stunden. Die Abtragsleistung betrug folglich etwa 125 µm pro Stunde. Die Tiefe der Rillen in der Schleifscheibe nach Beendigung des Versuchs betrug 0,5 mm.Zirconia (ZrO 2 ) spheres in a round shape having a starting dimension of 5.96 mm to 6.03 mm were machined. In a batch were about 140 bullets. The achieved final dimension was 5.50 mm. The removal was 504 μm with a grinding time of 4 hours. The removal rate was thus about 125 μm per hour. The depth of the grooves in the grinding wheel after completion of the experiment was 0.5 mm.

Versuch 2:Trial 2:

Kugeln aus ZrO2 in Tonnenform mit einem Ausgangsmaß von 5,72 mm x 5,25 mm wurden bearbeitet. Insgesamt umfasste die Charge 300 Rohlinge. Das Endmaß betrug 5,15 mm. Der mittlere Abtrag betrug 570 µm bei einer Schleifzeit von 3,75 Stunden. Dies entspricht einer durchschnittlichen Abtragsleistung von 152 µm pro Stunde. Die Rillentiefe in der Schleifscheibe nach Beendigung des Versuchs betrug 0,94 mm.Balls made of ZrO 2 in barrel form with a starting dimension of 5.72 mm x 5.25 mm were processed. In total, the batch comprised 300 blanks. The gauge was 5.15 mm. The mean removal was 570 μm with a grinding time of 3.75 hours. This corresponds to an average removal rate of 152 μm per hour. The groove depth in the grinding wheel after completion of the experiment was 0.94 mm.

Versuch 3:Trial 3:

Kugeln aus Siliziumnitrid (Si3N4) mit einem Ausgangsmaß von 5,34 mm wurden bearbeitet. Es befanden sich 300 Rohlinge in einer Charge. Das Endmaß betrug 5,16 mm. Der durchschnittliche Abtrag betrug 180 µm bei einer Schleifzeit von 3,5 Stunden.Silicon nitride balls (Si 3 N 4 ) with a starting dimension of 5.34 mm were machined. There were 300 blanks in a batch. The gauge was 5.16 mm. The average abrasion was 180 μm with a grinding time of 3.5 hours.

Die durchschnittliche Abtragsleistung betrug 51 µm pro Stunde. Die Rillentiefe in der Schleifscheibe nach Beendigung des Versuchs betrug 1,10 mm.The average removal rate was 51 μm per hour. The groove depth in the grinding wheel after completion of the experiment was 1.10 mm.

Die angegebenen Rillentiefen sind auf die gleiche Schleifscheibe bezogen, da die gleiche Scheibe bei allen drei Versuchen nacheinander verwendet wurde. Der Versuch 2 begann folglich bereits mit einer Rillentiefe von 0,5 mm, während der Versuch 3 bereits mit einer Rillentiefe von 0,94 mm begann. Die Rillentiefe hat sich deshalb beispielsweise im Versuch 3 nur um 0,16 mm vergrößert.The indicated groove depths are based on the same grinding wheel, since the same disk was used successively in all three experiments. The trial 2 thus already started with a groove depth of 0.5 mm, while the trial 3 already started with a groove depth of 0.94 mm. The groove depth has therefore increased, for example, only by 0.16 mm in Experiment 3.

Versuch 4:Trial 4:

Kugeln aus Siliziumnitrit (Si3N4) mit einem Ausgangsdurchmesser von 6,12 mm wurden bearbeitet. Es wurden in einem Versuch insgesamt 340 Stück bearbeitet. Die Schleifzeit betrug 9 Stunden. Der erreichte Enddurchmesser betrug 5,956 mm. Dies entspricht einem Abtrag von bis zu 120 µm in 9 Stunden. Die erzielte Oberflächenrauheit Ra liegt bei 0,05 µm bis 0,06 µm.Silicon nitride (Si 3 N 4 ) balls with a starting diameter of 6.12 mm were machined. In a total of 340 pieces were processed. The grinding time was 9 hours. The final diameter reached was 5.956 mm. This corresponds to a removal of up to 120 μm in 9 hours. The surface roughness Ra achieved is 0.05 μm to 0.06 μm.

Die Versuche zeigen, dass auch bei geringer Rillentiefe bereits eine gute Abtragsleistung erzielt wird. Normalerweise beginnt der Abtrag beim Kugelschleifen erst bei Rillentiefen von etwa 20 % des Kugeldurchmessers. Üblicherweise ist auch bei geringen Rillentiefen wie bei den vorliegenden drei Versuchen die Kugelgeometrie relativ schlecht. Die Ergebnisse der drei Versuche zeigen aber, dass bereits bei der sehr geringen Tiefe der Rillen in der Schleifscheibe ein sehr hoher Abtrag, eine gute Rundheit und eine ausgezeichnete Durchmesserstreuung erzielt werden konnte. Der Verschleiß der Schleifscheibe ist im Vergleich mit den hohen Abtragswerten sehr gering. Bemerkenswert ist, dass sich die länglichen, tonnenförmigen Rohlinge im Versuch 2 ebenso gut bearbeiten ließen wie runde Kugelrohlinge.The tests show that even at low groove depth a good removal rate is already achieved. Normally, the removal of the ball grinding begins only at groove depths about 20% of the ball diameter. Usually, even at low groove depths as in the present three experiments, the ball geometry is relatively poor. However, the results of the three tests show that even with the very small depth of the grooves in the grinding wheel a very high removal, a good roundness and an excellent diameter spread could be achieved. The wear of the grinding wheel is very low in comparison with the high removal rates. It is noteworthy that the elongated, barrel-shaped blanks in experiment 2 worked just as well as round ball blanks.

Die gute Abtragsleistung und der geringe Verschleiß der Schleifscheibe bzw. des auf die Trageplatte aufgekitteten Schleifbelags sind auf die Kunstharzbindung des Schleifkorns zurückzuführen. Bei dieser Bindung wird im Gegensatz zu der elektrolytischen Bindung im Stand der Technik eine geringfügige elastische Bewegung des Schleifkorns in der Bindungsmatrix gewährleistet. Durch diese Elastizität kann das Schleifkorn bei Spitzenbelastungen, wie sie durch die ausgesprochen harten keramischen Kugeln auftreten können, im mikroskopischen Bereich ausweichen. Die Standzeit der Schleifscheibe erhöht sich dadurch erheblich. Die Abtragsleistung wird ebenfalls verbessert, weil die Kugeln während des Schleifvorgangs in der Schleifscheibe Rillen ausbilden. Die Tiefe der Rillen ist relativ gering. Sie ist aber größer als bei elektrolytisch gebundenen Schleifscheiben, die praktisch keine Rillen ausbilden können.The good removal rate and the low wear of the grinding wheel or of the abrasive pad cemented to the support plate are due to the synthetic resin bond of the abrasive grain. In this bond, unlike electrolytic bonding in the prior art, a slight elastic movement of the abrasive grain in the bonding matrix is ensured. Due to this elasticity, the abrasive grain can escape at peak loads, which can occur due to the extremely hard ceramic balls, in the microscopic range. The service life of the grinding wheel increases considerably. The removal rate is also improved because the balls form grooves during the grinding process in the grinding wheel. The depth of the grooves is relatively low. But it is larger than electrolytically bonded grinding wheels that can form virtually no grooves.

Schließlich ist bei elektrolytisch gebundenem Diamantschleifkorn auf einer metallischen Trägerplatte zu erwarten, dass eine Beschädigung der Bindung zu einem Ausbrechen ganzer Bereiche der Bindung und damit zum Ausfall der Schleifscheibe führt, was bei einer Schleifscheibe in Kunstharzbindung, bedingt durch ihren Selbstschärfmechanismus, nicht der Fall ist. Im Ergebnis waren die geschliffenen Kugeln von der Rundheit und der Durchmesserstreuung her gut. Die Abtragsleistung liegt um mindestens eine Größenordnung über den Abtragsleistungen bei bekannten Verfahren. Die Oberflächenrauhigkeit wurde nur in einem Fall untersucht. Hier kann vorgesehen sein, dass nach dem Grob- und Feinschleifen noch ein Läppen vorzusehen ist.Finally, with electrolytically bonded diamond abrasive grain on a metal backing plate, damage to the bond is expected to result in breakage of entire areas of the bond and consequent failure of the abrasive wheel, which is not the case for a resin bonded abrasive wheel due to its self-sharpening mechanism. As a result, the ground balls were good in roundness and diameter dispersion. The removal rate is at least one order of magnitude above the removal rates in known methods. The surface roughness was examined only in one case. Here it can be provided that lapping is still to be provided after coarse and fine grinding.

Das neuartige Verfahren und die neuartige Vorrichtung zum Schleifen von keramischen Kugeln ermöglichen nicht nur hohe Abtragsleistungen bei guten Schleifergebnissen, sondern auch eine Verwendung von Schleifmaschinen, die den modernen rationellen Methoden zugänglich sind. So ist zum Beispiel die Verwendung von Magazinen für die Kugelzuführung möglich. Der Einsatz von Kühlschmierstoffen bewirkt die technologische Beherrschbarkeit der Schleifprozesse und erlaubt das Zuschalten entsprechender Filtereinrichtungen, wodurch das Verfahren äußerst umweltfreundlich gestaltet werden kann. Auch die Reinigung der Kugeln nach dem Schleifen ist besonders einfach und kann in konventionellen Kugelwaschmaschinen durchgeführt werden, da sich nicht die für das Läppen typischen Anhaftungen der Schleifpaste ausbilden.The novel method and the novel apparatus for grinding ceramic balls not only allow high removal rates with good grinding results, but also a use of grinding machines that are accessible to modern rational methods. For example, the use of magazines for the ball feeder is possible. The use of cooling lubricants provides the technological control of the grinding processes and allows the connection of appropriate filter devices, which makes the process extremely environmentally friendly. Also, the cleaning of the balls after grinding is particularly simple and can be carried out in conventional ball washing machines, since not forming the lapping typical adhesions of the grinding paste.

Claims (13)

  1. Method for grinding spheres made from ceramic materials such as oxide ceramics, carbides, silicone nitride, precious and semi-precious stones and/or glass in a sphere grinder, wherein the grinding is carried out by means of a grinding wheel (3a) with an abrasive grain bound in a synthetic resin, characterised in that more than 50% of the abrasive grain consists of diamond and less than 5% of the abrasive grain consists of Cr2O3.
  2. Method according to Claim 1, characterised in that more than 90% of the abrasive grain consists of diamond.
  3. Method according to one of the preceding claims, characterised in that 100% of the abrasive grain consists of diamond.
  4. Method according to one of the preceding claims, characterised in that the synthetic resin bond is a hot-pressed phenolic resin bond or a polyimide bond.
  5. Method according to one of the preceding claims, characterised in that a steel disc or cast iron disc is used as a guide washer (1).
  6. Method according to one of the preceding claims, characterised in that the grinding wheel (3a) features a grain size between D181 and D2.
  7. Method according to one of the preceding claims, characterised in that the grinding wheel (3a) is mounted on a support plate (3).
  8. Method according to one of the preceding claims, characterised in that a honing oil or grinding emulsion is added as a cutting fluid.
  9. Method according to one of the preceding claims, characterised in that two grinding wheels (3a, 1 a) are used in the stone-to-stone method.
  10. Method according to Claim 9, characterised in that both of the grinding wheels (3a, 1 a) are essentially structurally identical.
  11. Device for grinding spheres made from ceramic materials such as oxide ceramics, carbides, silicone nitride, precious and semi-precious stones and/or glass featuring a grinding wheel with bound diamond abrasive grain, characterised in that the grinding wheel (3a) features a synthetic resin bond, in particular a hot-pressed phenolic resin bond, wherein more than 50% of the abrasive grain consists of diamond and less than 5% of the abrasive grain consists of Cr2O3.
  12. Device according to Claim 11, characterised in that the grinding wheel (3a) is mounted on a support plate (3).
  13. Use of a grinding wheel (3a) with a diamond abrasive grain bound in a synthetic resin for grinding spheres made from ceramic materials such as oxide ceramics, carbides, silicone nitride, precious and semi-precious stones and/or glass, wherein more than 50% of the abrasive grain consists of diamond and less than 5% of the abrasive grain consists of Cr2O3.
EP06706173.9A 2005-01-27 2006-01-06 Method and device for grinding ceramic spheres Active EP1893384B1 (en)

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DE102005004038A DE102005004038A1 (en) 2005-01-27 2005-01-27 Method for grinding spheres of ceramic material uses grinding disc with diamond grinding grains embedded in plastics resin binding
PCT/EP2006/000075 WO2006079444A1 (en) 2005-01-27 2006-01-06 Method and device for grinding ceramic spheres

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KR (1) KR20070100904A (en)
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RU2007126372A (en) 2009-03-10
JP5294637B2 (en) 2013-09-18
WO2006079444A1 (en) 2006-08-03
EP1893384A1 (en) 2008-03-05
BRPI0607081A2 (en) 2009-08-04
PL1893384T3 (en) 2016-09-30
DE102005004038A1 (en) 2006-08-03
JP2008528304A (en) 2008-07-31
US20080171492A1 (en) 2008-07-17
US7722440B2 (en) 2010-05-25
RU2396160C2 (en) 2010-08-10
CN101107096A (en) 2008-01-16

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