Indian Patents. 258643:METHOD AND DEVICE FOR GRINDING CERAMIC SPHERES

Title of Invention	METHOD AND DEVICE FOR GRINDING CERAMIC SPHERES
Abstract	The invention relates to a method for grinding ceramic spheres using a sphere grinder. The method is especially effective because the grinding is carried out using a grinding wheel with abrasive diamond grains bound in a synthetic resin.

Full Text	1 Method and device for grinding ceramic spheres The present invention relates to a method and a device for grinding ceramic spheres. The term "ceramic spheres" is to be understood in the context of the present patent application as referring to spheres made of ceramic materials such as, for example, oxide ceramics, carbides, silicon nitride, precious and semiprecious stones but also glass. Currently, the grinding of ceramic spheres for achieving low degrees of surface roughness and high quality classes is generally carried out using devices such as are also used for the machining of metal spheres. The ceramic spheres are in this case not actually ground but rather lapped. Whereas in the machining of metallic spheres there is provided initially coarse grinding and then fine grinding using grinding wheels with bound abrasive grains and lapping is optionally practised thereafter with abrasive grains present in paste form, ceramic spheres are not machined using grinding wheels but rather lapped over the entire abrasion process. The abrasive grains present in the grinding paste are in this case generally in diamond form. Technologically, this process is exceptionally difficult to carry out, for the abrasion rate is in the order of magnitude of at most 100 um per day. The abrasion to be realised of from 0.2 to 0.4 in sphere diameter corresponds to the thickness of the inhomogeneous boundary layer and is in some cases achieved only in a machining time of several days. In addition, after the lapping process, the ceramic spheres are markedly soiled by adhering grinding paste. In the conventional methods for washing the spheres, this grinding paste is in some cases very difficult to remove. The degree of wear of the two metal discs is extremely high during lapping with loose diamond grains. Finally, the very high consumption of diamonds greatly increases the costs of the method as a whole. As a result, the use of ceramic spheres has become established, especially in the field of ball bearings, only in applications in which costs are of secondary importance. An attempt to improve the cost-effectiveness is found in US patent specification US 6,171,179 Bl. In the grinder provided in said document, a grinding wheel is provided with electro lyrically bound abrasive grains. The fixed guide disc has a number of guide rings which are each hydraulically loaded individually to ensure optimally uniform pressing of the 2 ceramic spheres against the grinding wheel. This device has not proven successful in practice. It is believed that the service life of the grinding wheel is too short. Japanese patent application JP 05042467 A discloses a method for the polishing of silicon nitride spheres using polishing discs having abrasive grains of from 5 to 60 per cent by volume of Cr2O3 with an average particle diameter of from 0.01 to 3 urn. The machining of the spheres is very low with regard to the speed of abrasion of the surface. In a test, abrasion of 60 um was achieved over 50 hours, i.e. approximately 1 urn per hour. The degree of surface roughness achieved in a second test is Ra = 0.005 urn. This method, which also proposes replacing a portion of the Cr2O3 with diamond, is suitable for achieving high surface qualities, although the abrasion rate is still unsatisfactory for the grinding of ceramic spheres. The object of the present invention is therefore to provide a method and a device for grinding ceramic spheres allowing more economical manufacture of ceramic spheres having the requisite quality and low divergence in the diameter of the spheres. This object is achieved by a method having the features of claim 1 and by a device having the features of claim 9. Because the grinding is carried out using a grinding wheel with abrasive grains bound in a synthetic resin, wherein the abrasive grains consist of more than 50% diamond and less than 5% Cr2O3, high abrasion rates can be achieved with a low degree of wear of the grinding wheel or the abrasive lining. It is advantageous if the abrasive grains are free from Cr2O3 and, in particular, if the abrasive grains consist of pure diamond. This allows an abrasion rate almost ten times higher than that of the closest prior art, whereas the average degree of surface roughness is greater by a factor of 10 than in the prior art. The diamond content of the abrasive grains is therefore greater than 50%, in particular greater than 90% and particularly preferred are abrasive grains consisting of 100% diamond. Advantageously, the synthetic resin bonding is a hot-pressed phenolic resin bonding or polyimide bonding, the pore volume preferably being close to zero. The grinding wheel preferably has a grain size of from D181 (in accordance with the FEPA standard, average particle diameter =181 um) to D2 (average particle diameter = 2 um), grain 3 sizes of from D181 to D25 being used for coarse grinding and grain sizes of from D15 to D2 being preferred for fine grinding. During use, grinding wheels undergo slight deformation if they are fastened, in particular attached using putty, to a support plate as an abrasive lining. The degree of wear is further reduced if the cooling lubricant added is a honing oil. Another embodiment of the invention provides for two grinding wheels to be used in a stone- to-stone process, the two grinding wheels being, in particular, of substantially identical construction. The above-described method is possible as a result of the fact that provision is made, in a device according to the invention for grinding ceramic spheres using a grinding wheel with bound abrasive diamond grains, for the grinding wheel to have a synthetic resin bonding, in particular a hot-pressed phenolic resin bonding. The grinding wheel can in this case be attached to a support plate using putty, thus promoting the mechanical stability under the process pressure and minimising the material costs for the manufacture of the wheel. Also in accordance with the invention is the use of a grinding wheel with abrasive diamond grains bound in a synthetic resin for the grinding of ceramic spheres, especially using a conventional sphere grinder, such as is known for the grinding of metallic spheres. The present invention will be described hereinafter with reference to the drawings and also with reference to three examples. In the drawings: Fig. 1 shows a device for the grinding of spheres with a grinding wheel and a vertical drive axis; and Fig. 2 shows a device for the grinding of spheres in a stone-to-stone process with a vertical axis. Fig. 1 illustrates the principle of the grinding of spheres on machines with a vertical drive axis. Fig. 1 is a schematic plan view and side view of the device for grinding spheres. A fixed guide disc, made preferably of cast steel, is provided in this case. The guide disc 1 has on its 4 underside peripheral guide grooves in which a large number of spheres 2 to be ground are guided. Provided from the underside is a support plate 3 which has an abrasive lining 3 a arranged thereon and can be caused to rotate by a drive shaft. A sphere inlet and outlet 4 is provided for loading and unloading the device. Fig. 2 shows a grinder similar to that illustrated in Fig. 1. In the case of this grinder, the fixed guide plate 1 is also provided with an abrasive lining la arranged opposing the abrasive lining 3a of the rotating support plate 3. The spheres 2 to be ground are arranged between the two grinding wheels la and 3a. In both embodiments, for the purposes of grinding, a pressure P is exerted on the fixed guide disc 1 from the upper side. The support plate 3 is caused to rotate by a drive, so the spheres 2 roll off in the guide grooves. The differences in speed in the various regions of the guide grooves cause movement of the abrasive lining relative to the surface of the ceramic sphere. The abrasive grains located in the abrasive lining then lead to abrasion of the surface of the sphere and thus to improvement of the surface quality and the spherical shape. The method according to the invention can be carried out in this case both on a sphere grinder comprising a vertical drive shaft and on a sphere grinder comprising a horizontal drive shaft. During the grinding process, the cooling lubricant added is a honing oil which both rinses around the abrasive grains and the ceramic sphere and removes abrasive grains, bonding particles and ground-off spheres broken out of the surface of the grinding wheels, so such elements do not adhere to the surface of the sphere and adversely affect the grinding process. The results achieved using the method according to the invention will be described hereinafter with reference to three test examples. Tests 1 to 3 used a grinding wheel having a diameter of 200 mm and a thickness of 4 mm. The grinding wheel was attached to a steel support plate using putty. The cooling lubricant added was the honing oil EMOL®-O-HON 920 NV from ML Lubrication GmbH. The pressure plate consisted of steel and had five peripheral grooves. The grinding was carried out without a hopper on a grinder having a vertical axis. 5 Test 1: Round spheres made of zirconium oxide (ZrO2) and having starting dimensions of from 5.96 mm to 6.03 mm were machined. A batch contained approximately 140 spheres. The final dimensions achieved were 5.50 mm. The abrasion was 504 um over a grinding time of 4 hours. The abrasion rate was therefore approximately 125 um per hour. The depth of the grooves in the grinding wheel after completion of the test was 0.5 mm. Test 2: Barrel-shaped spheres made of ZrO2 and having starting dimensions of 5.72 mm x 5.25 mm were machined. In total, the batch comprised 300 blanks. The final dimensions were 5.15 mm. The average abrasion was 570 um over a grinding time of 3.5 hours. This corresponds to an average abrasion rate of 152 um per hour. The depth of the grooves in the grinding wheel after completion of the test was 0.94 mm. Test 3: Spheres made of silicon nitride (Si3N4) having starting dimensions of 5.34 mm were machined. A batch contained 300 blanks. The final dimensions were 5.16 mm. The average abrasion was 180 um over a grinding time of 3.5 hours. The average abrasion rate was 51 um per hour. The depth of the grooves in the grinding wheel after completion of the test was 1.10 mm. The specified groove depths are based on the same grinding wheel, as the same wheel was used in all three successive tests. Test 2 accordingly started with a groove depth of 0.5 mm, whereas Test 3 started with a groove depth of 0.94 mm. The groove depth therefore increased in size, for example, in Test 3 merely by 0.16 mm. Test 4: Spheres made of silicon nitride (S13N4) having starting dimensions of 6.12 mm were machined. A total of 340 items were machined in a test. The grinding time was 9 hours. The 6 final diameter achieved was 5.956 mm. This corresponds to abrasion of up to 120 \|im over 9 hours. The achieved degree of surface roughness Ra is from 0.05 urn to 0.06 urn. The tests reveal that a good abrasion rate is achieved even at a low groove depth. Normally in the grinding of spheres abrasion does not commence until groove depths of approximately 20% of the diameter of the sphere. At low groove depths, as in the present three tests, the geometry of the spheres is usually also relatively poor. However, the results of the three tests reveal that high abrasion, good roundness and outstanding divergence in diameter could be achieved even at a very low depth of the grooves in the grinding wheel. Compared to the high abrasion values, the degree of wear to the grinding wheel is very low. It is noteworthy that the elongate, barrel-shaped blanks in Test 2 can be machined just as well as round spherical blanks. The good abrasion rate and the low degree of wear to the grinding wheel or the abrasive lining attached to the support plate using putty are due to the bonding of the abrasive grains in a synthetic resin. This bonding, in contrast to the electrolytic bonding in the prior art, ensures low resilient movement of the abrasive grains in the bonding matrix. This resilience allows the abrasive grains to deflect in the microscopic range in the event of peak loads such as can be caused by the extremely hard ceramic spheres, thus greatly increasing the service life of the grinding wheel. The abrasion rate is also improved because the spheres form grooves in the grinding wheel during the grinding process. The depth of the grooves is relatively low. It is, however, greater than in the case of electrolytically bound grinding wheels which are able to form almost no grooves. Finally, it is to be expected, in the case of electrolytically bound abrasive diamond grains on a metallic carrier plate, that damage to the bonding will lead to breaking-out of entire regions of the bonding and thus to falling-out of the grinding wheel, and this is not the case in a grinding wheel bound in a synthetic resin, as a result of its self-sharpening mechanism. As a result, the ground spheres were good in terms of roundness and the divergence in diameter. The abrasion rate is greater than the abrasion rates of known methods by at least one order of magnitude. The degree of surface roughness was examined merely in one case. Provision may be made in this regard for lapping to be provided after the coarse and fine grinding. 7 The novel method and the novel device for grinding ceramic spheres allow not only high abrasion rates with good grinding results but also the use of grinders accessible to modern streamlined methods. The use of hoppers for supplying the spheres is thus, for example, possible. The use of cooling lubricants allows the grinding processes to be technologically controlled and corresponding filter means to be connected, as a result of which the method can be made extremely environmentally friendly. The cleaning of the spheres after the grinding process is also particularly simple and can be carried out in conventional sphere washers as there is no adhering grinding paste as is typical for lapping. 8 Claims 1. Method for grinding spheres made of ceramic materials such as, for example, oxide ceramics, carbides, silicon nitride, precious and semiprecious stones and/or glass using a sphere grinder, characterised in that the grinding is carried out using a grinding wheel (3a) with abrasive grains bound in a synthetic resin, the abrasive grains consisting of more than 50% diamond and less than 5% Cr2O3. 2. Method according to claim 1, characterised in that the abrasive grains consist of more than 90% diamond. 3. Method according to any one of the preceding claims, characterised in that the abrasive grains consist of 100% diamond. 4. Method according to any one of the preceding claims, characterised in that the synthetic resin bonding is a hot-pressed phenolic resin or polyimide bonding. 5. Method according to any one of the preceding claims, characterised in that the guide disc (1) used is a steel or cast disc. 6. Method according to any one of the preceding claims, characterised in that the grinding wheel (3a) has a grain size of from D181 to D2. 7. Method according to any one of the preceding claims, characterised in that the grinding wheel (3a) is fastened to a support plate (3). 8. Method according to any one of the preceding claims, characterised in that the cooling lubricant added is a honing oil or a grinding emulsion. 9. Method according to any one of the preceding claims, characterised in that two grinding wheels (3a, la) are used in a stone-to-stone process. 10. Method according to claim 9, characterised in that the two grinding wheels (3a, la) are of substantially identical construction. 9 11. Device for grinding spheres made of ceramic materials such as, for example, oxide ceramics, carbides, silicon nitride, precious and semiprecious stones and/or glass using a grinding wheel with bound abrasive diamond grains, characterised in that the grinding wheel (3a) has a synthetic resin bonding, in particular a hot-pressed phenolic resin bonding. 12. Method according to claim 11, characterised in that the grinding wheel (3a) is fastened to a support plate (3). 13. Use of a grinding wheel (3a) with abrasive diamond grains bound in a synthetic resin for the grinding of spheres made of ceramic materials such as, for example, oxide ceramics, carbides, silicon nitride, precious and semiprecious stones and/or glass. The invention relates to a method for grinding ceramic spheres using a sphere grinder. The method is especially effective because the grinding is carried out using a grinding wheel with abrasive diamond grains bound in a synthetic resin.

Full Text

1
Method and device for grinding ceramic spheres
The present invention relates to a method and a device for grinding ceramic spheres.
The term "ceramic spheres" is to be understood in the context of the present patent
application as referring to spheres made of ceramic materials such as, for example, oxide
ceramics, carbides, silicon nitride, precious and semiprecious stones but also glass.
Currently, the grinding of ceramic spheres for achieving low degrees of surface roughness and
high quality classes is generally carried out using devices such as are also used for the
machining of metal spheres. The ceramic spheres are in this case not actually ground but
rather lapped. Whereas in the machining of metallic spheres there is provided initially coarse
grinding and then fine grinding using grinding wheels with bound abrasive grains and lapping
is optionally practised thereafter with abrasive grains present in paste form, ceramic spheres
are not machined using grinding wheels but rather lapped over the entire abrasion process.
The abrasive grains present in the grinding paste are in this case generally in diamond form.
Technologically, this process is exceptionally difficult to carry out, for the abrasion rate is in
the order of magnitude of at most 100 um per day. The abrasion to be realised of from 0.2 to
0.4 in sphere diameter corresponds to the thickness of the inhomogeneous boundary layer and
is in some cases achieved only in a machining time of several days. In addition, after the
lapping process, the ceramic spheres are markedly soiled by adhering grinding paste. In the
conventional methods for washing the spheres, this grinding paste is in some cases very
difficult to remove. The degree of wear of the two metal discs is extremely high during
lapping with loose diamond grains. Finally, the very high consumption of diamonds greatly
increases the costs of the method as a whole. As a result, the use of ceramic spheres has
become established, especially in the field of ball bearings, only in applications in which costs
are of secondary importance.
An attempt to improve the cost-effectiveness is found in US patent specification US
6,171,179 Bl. In the grinder provided in said document, a grinding wheel is provided with
electro lyrically bound abrasive grains. The fixed guide disc has a number of guide rings
which are each hydraulically loaded individually to ensure optimally uniform pressing of the

2
ceramic spheres against the grinding wheel. This device has not proven successful in practice.
It is believed that the service life of the grinding wheel is too short.
Japanese patent application JP 05042467 A discloses a method for the polishing of silicon
nitride spheres using polishing discs having abrasive grains of from 5 to 60 per cent by
volume of Cr2O3 with an average particle diameter of from 0.01 to 3 urn. The machining of
the spheres is very low with regard to the speed of abrasion of the surface. In a test, abrasion
of 60 um was achieved over 50 hours, i.e. approximately 1 urn per hour. The degree of
surface roughness achieved in a second test is Ra = 0.005 urn. This method, which also
proposes replacing a portion of the Cr2O3 with diamond, is suitable for achieving high surface
qualities, although the abrasion rate is still unsatisfactory for the grinding of ceramic spheres.
The object of the present invention is therefore to provide a method and a device for grinding
ceramic spheres allowing more economical manufacture of ceramic spheres having the
requisite quality and low divergence in the diameter of the spheres.
This object is achieved by a method having the features of claim 1 and by a device having the
features of claim 9.
Because the grinding is carried out using a grinding wheel with abrasive grains bound in a
synthetic resin, wherein the abrasive grains consist of more than 50% diamond and less than
5% Cr2O3, high abrasion rates can be achieved with a low degree of wear of the grinding
wheel or the abrasive lining. It is advantageous if the abrasive grains are free from Cr2O3 and,
in particular, if the abrasive grains consist of pure diamond. This allows an abrasion rate
almost ten times higher than that of the closest prior art, whereas the average degree of
surface roughness is greater by a factor of 10 than in the prior art. The diamond content of the
abrasive grains is therefore greater than 50%, in particular greater than 90% and particularly
preferred are abrasive grains consisting of 100% diamond.
Advantageously, the synthetic resin bonding is a hot-pressed phenolic resin bonding or
polyimide bonding, the pore volume preferably being close to zero.
The grinding wheel preferably has a grain size of from D181 (in accordance with the FEPA
standard, average particle diameter =181 um) to D2 (average particle diameter = 2 um), grain

3
sizes of from D181 to D25 being used for coarse grinding and grain sizes of from D15 to D2
being preferred for fine grinding.
During use, grinding wheels undergo slight deformation if they are fastened, in particular
attached using putty, to a support plate as an abrasive lining. The degree of wear is further
reduced if the cooling lubricant added is a honing oil.
Another embodiment of the invention provides for two grinding wheels to be used in a stone-
to-stone process, the two grinding wheels being, in particular, of substantially identical
construction.
The above-described method is possible as a result of the fact that provision is made, in a
device according to the invention for grinding ceramic spheres using a grinding wheel with
bound abrasive diamond grains, for the grinding wheel to have a synthetic resin bonding, in
particular a hot-pressed phenolic resin bonding. The grinding wheel can in this case be
attached to a support plate using putty, thus promoting the mechanical stability under the
process pressure and minimising the material costs for the manufacture of the wheel.
Also in accordance with the invention is the use of a grinding wheel with abrasive diamond
grains bound in a synthetic resin for the grinding of ceramic spheres, especially using a
conventional sphere grinder, such as is known for the grinding of metallic spheres.
The present invention will be described hereinafter with reference to the drawings and also
with reference to three examples. In the drawings:
Fig. 1 shows a device for the grinding of spheres with a grinding wheel and a vertical drive
axis; and
Fig. 2 shows a device for the grinding of spheres in a stone-to-stone process with a vertical
axis.
Fig. 1 illustrates the principle of the grinding of spheres on machines with a vertical drive
axis. Fig. 1 is a schematic plan view and side view of the device for grinding spheres. A fixed
guide disc, made preferably of cast steel, is provided in this case. The guide disc 1 has on its

4
underside peripheral guide grooves in which a large number of spheres 2 to be ground are
guided. Provided from the underside is a support plate 3 which has an abrasive lining 3 a
arranged thereon and can be caused to rotate by a drive shaft. A sphere inlet and outlet 4 is
provided for loading and unloading the device.
Fig. 2 shows a grinder similar to that illustrated in Fig. 1. In the case of this grinder, the fixed
guide plate 1 is also provided with an abrasive lining la arranged opposing the abrasive lining
3a of the rotating support plate 3. The spheres 2 to be ground are arranged between the two
grinding wheels la and 3a.
In both embodiments, for the purposes of grinding, a pressure P is exerted on the fixed guide
disc 1 from the upper side. The support plate 3 is caused to rotate by a drive, so the spheres 2
roll off in the guide grooves. The differences in speed in the various regions of the guide
grooves cause movement of the abrasive lining relative to the surface of the ceramic sphere.
The abrasive grains located in the abrasive lining then lead to abrasion of the surface of the
sphere and thus to improvement of the surface quality and the spherical shape.
The method according to the invention can be carried out in this case both on a sphere grinder
comprising a vertical drive shaft and on a sphere grinder comprising a horizontal drive shaft.
During the grinding process, the cooling lubricant added is a honing oil which both rinses
around the abrasive grains and the ceramic sphere and removes abrasive grains, bonding
particles and ground-off spheres broken out of the surface of the grinding wheels, so such
elements do not adhere to the surface of the sphere and adversely affect the grinding process.
The results achieved using the method according to the invention will be described hereinafter
with reference to three test examples.
Tests 1 to 3 used a grinding wheel having a diameter of 200 mm and a thickness of 4 mm.
The grinding wheel was attached to a steel support plate using putty. The cooling lubricant
added was the honing oil EMOL®-O-HON 920 NV from ML Lubrication GmbH. The
pressure plate consisted of steel and had five peripheral grooves. The grinding was carried out
without a hopper on a grinder having a vertical axis.

5
Test 1:
Round spheres made of zirconium oxide (ZrO2) and having starting dimensions of from
5.96 mm to 6.03 mm were machined. A batch contained approximately 140 spheres. The final
dimensions achieved were 5.50 mm. The abrasion was 504 um over a grinding time of 4
hours. The abrasion rate was therefore approximately 125 um per hour. The depth of the
grooves in the grinding wheel after completion of the test was 0.5 mm.
Test 2:
Barrel-shaped spheres made of ZrO2 and having starting dimensions of 5.72 mm x 5.25 mm
were machined. In total, the batch comprised 300 blanks. The final dimensions were
5.15 mm. The average abrasion was 570 um over a grinding time of 3.5 hours. This
corresponds to an average abrasion rate of 152 um per hour. The depth of the grooves in the
grinding wheel after completion of the test was 0.94 mm.
Test 3:
Spheres made of silicon nitride (Si3N4) having starting dimensions of 5.34 mm were
machined. A batch contained 300 blanks. The final dimensions were 5.16 mm. The average
abrasion was 180 um over a grinding time of 3.5 hours. The average abrasion rate was 51 um
per hour. The depth of the grooves in the grinding wheel after completion of the test was
1.10 mm.
The specified groove depths are based on the same grinding wheel, as the same wheel was
used in all three successive tests. Test 2 accordingly started with a groove depth of 0.5 mm,
whereas Test 3 started with a groove depth of 0.94 mm. The groove depth therefore increased
in size, for example, in Test 3 merely by 0.16 mm.
Test 4:
Spheres made of silicon nitride (S13N4) having starting dimensions of 6.12 mm were
machined. A total of 340 items were machined in a test. The grinding time was 9 hours. The

6
final diameter achieved was 5.956 mm. This corresponds to abrasion of up to 120 |im over 9
hours. The achieved degree of surface roughness Ra is from 0.05 urn to 0.06 urn.
The tests reveal that a good abrasion rate is achieved even at a low groove depth. Normally in
the grinding of spheres abrasion does not commence until groove depths of approximately
20% of the diameter of the sphere. At low groove depths, as in the present three tests, the
geometry of the spheres is usually also relatively poor. However, the results of the three tests
reveal that high abrasion, good roundness and outstanding divergence in diameter could be
achieved even at a very low depth of the grooves in the grinding wheel. Compared to the high
abrasion values, the degree of wear to the grinding wheel is very low. It is noteworthy that the
elongate, barrel-shaped blanks in Test 2 can be machined just as well as round spherical
blanks.
The good abrasion rate and the low degree of wear to the grinding wheel or the abrasive
lining attached to the support plate using putty are due to the bonding of the abrasive grains in
a synthetic resin. This bonding, in contrast to the electrolytic bonding in the prior art, ensures
low resilient movement of the abrasive grains in the bonding matrix. This resilience allows
the abrasive grains to deflect in the microscopic range in the event of peak loads such as can
be caused by the extremely hard ceramic spheres, thus greatly increasing the service life of
the grinding wheel. The abrasion rate is also improved because the spheres form grooves in
the grinding wheel during the grinding process. The depth of the grooves is relatively low. It
is, however, greater than in the case of electrolytically bound grinding wheels which are able
to form almost no grooves.
Finally, it is to be expected, in the case of electrolytically bound abrasive diamond grains on a
metallic carrier plate, that damage to the bonding will lead to breaking-out of entire regions of
the bonding and thus to falling-out of the grinding wheel, and this is not the case in a grinding
wheel bound in a synthetic resin, as a result of its self-sharpening mechanism.
As a result, the ground spheres were good in terms of roundness and the divergence in
diameter. The abrasion rate is greater than the abrasion rates of known methods by at least
one order of magnitude. The degree of surface roughness was examined merely in one case.
Provision may be made in this regard for lapping to be provided after the coarse and fine
grinding.

7
The novel method and the novel device for grinding ceramic spheres allow not only high
abrasion rates with good grinding results but also the use of grinders accessible to modern
streamlined methods. The use of hoppers for supplying the spheres is thus, for example,
possible. The use of cooling lubricants allows the grinding processes to be technologically
controlled and corresponding filter means to be connected, as a result of which the method
can be made extremely environmentally friendly. The cleaning of the spheres after the
grinding process is also particularly simple and can be carried out in conventional sphere
washers as there is no adhering grinding paste as is typical for lapping.

8
Claims
1. Method for grinding spheres made of ceramic materials such as, for example, oxide
ceramics, carbides, silicon nitride, precious and semiprecious stones and/or glass using a
sphere grinder, characterised in that the grinding is carried out using a grinding wheel (3a)
with abrasive grains bound in a synthetic resin, the abrasive grains consisting of more than
50% diamond and less than 5% Cr2O3.
2. Method according to claim 1, characterised in that the abrasive grains consist of more
than 90% diamond.
3. Method according to any one of the preceding claims, characterised in that the
abrasive grains consist of 100% diamond.
4. Method according to any one of the preceding claims, characterised in that the
synthetic resin bonding is a hot-pressed phenolic resin or polyimide bonding.
5. Method according to any one of the preceding claims, characterised in that the guide
disc (1) used is a steel or cast disc.
6. Method according to any one of the preceding claims, characterised in that the
grinding wheel (3a) has a grain size of from D181 to D2.
7. Method according to any one of the preceding claims, characterised in that the
grinding wheel (3a) is fastened to a support plate (3).
8. Method according to any one of the preceding claims, characterised in that the cooling
lubricant added is a honing oil or a grinding emulsion.
9. Method according to any one of the preceding claims, characterised in that two
grinding wheels (3a, la) are used in a stone-to-stone process.
10. Method according to claim 9, characterised in that the two grinding wheels (3a, la) are
of substantially identical construction.

9
11. Device for grinding spheres made of ceramic materials such as, for example, oxide
ceramics, carbides, silicon nitride, precious and semiprecious stones and/or glass using a
grinding wheel with bound abrasive diamond grains, characterised in that the grinding wheel
(3a) has a synthetic resin bonding, in particular a hot-pressed phenolic resin bonding.
12. Method according to claim 11, characterised in that the grinding wheel (3a) is fastened
to a support plate (3).
13. Use of a grinding wheel (3a) with abrasive diamond grains bound in a synthetic resin
for the grinding of spheres made of ceramic materials such as, for example, oxide ceramics,
carbides, silicon nitride, precious and semiprecious stones and/or glass.

The invention relates to a method for grinding ceramic spheres using a sphere grinder. The
method is especially effective because the grinding is carried out using a grinding wheel with
abrasive diamond grains bound in a synthetic resin.

Documents:

02353-kolnp-2007-abstract.pdf

02353-kolnp-2007-claims.pdf

02353-kolnp-2007-correspondence others 1.1.pdf

02353-kolnp-2007-correspondence others 1.2.pdf

02353-kolnp-2007-correspondence others 1.3.pdf

02353-kolnp-2007-correspondence others.pdf

02353-kolnp-2007-description complete.pdf

02353-kolnp-2007-drawings.pdf

02353-kolnp-2007-form 1.pdf

02353-kolnp-2007-form 2.pdf

02353-kolnp-2007-form 3.pdf

02353-kolnp-2007-form 5.pdf

02353-kolnp-2007-international publication.pdf

02353-kolnp-2007-international search report.pdf

02353-kolnp-2007-pct request form.pdf

02353-kolnp-2007-priority document.pdf

02353-kolnp-2007-translated copy of priority document.pdf

2353-KOLNP-2007-(08-08-2012)-ABSTRACT.pdf

2353-KOLNP-2007-(08-08-2012)-AMANDED CLAIMS.pdf

2353-KOLNP-2007-(08-08-2012)-DESCRIPTION (COMPLETE).pdf

2353-KOLNP-2007-(08-08-2012)-DRAWINGS.pdf

2353-KOLNP-2007-(08-08-2012)-EXAMINATION REPORT REPLY RECEIVED.pdf

2353-KOLNP-2007-(08-08-2012)-FORM-1.pdf

2353-KOLNP-2007-(08-08-2012)-FORM-2.pdf

2353-KOLNP-2007-(08-08-2012)-FORM-3.pdf

2353-KOLNP-2007-(08-08-2012)-OTHERS.pdf

2353-KOLNP-2007-(08-08-2012)-PETITION UNDER RULE 137.pdf

2353-KOLNP-2007-(18-09-2013)-AMANDED CLAIMS.pdf

2353-KOLNP-2007-(18-09-2013)-CLAIMS.pdf

2353-KOLNP-2007-(18-09-2013)-CORRESPONDENCE.pdf

2353-KOLNP-2007-(18-09-2013)-DRAWINGS.pdf

2353-KOLNP-2007-(21-12-2012)-ABSTRACT.pdf

2353-KOLNP-2007-(21-12-2012)-CORRESPONDENCE.pdf

2353-KOLNP-2007-(21-12-2012)-DRAWINGS.pdf

2353-KOLNP-2007-(21-12-2012)-FORM 1.pdf

2353-KOLNP-2007-(21-12-2012)-FORM 2.pdf

2353-KOLNP-2007-(21-12-2012)-FORM 5.pdf

2353-kolnp-2007-form 18.pdf

abstract-02353-kolnp-2007.jpg

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Patent Number

258643

Indian Patent Application Number

2353/KOLNP/2007

PG Journal Number

05/2014

Publication Date

31-Jan-2014

Grant Date

27-Jan-2014

Date of Filing

26-Jun-2007

Name of Patentee

ATLANTIC GMBH

Applicant Address

GARTENSTRASSE 7-17 53229 BONN

Inventors:

#	Inventor's Name	Inventor's Address
1	POTZSCH, DR. MICHAEL	BURGGASSE 7 53757 ST. AUGUSTIN
2	HAUBERT, MICHAEL	SANDORFSTR. 13 53225 BONN, GERMANY
3	STOCK, KARL-OTTO	AM SCHERENSTUCK 79 53757 ST. AUGUSTIN, GERMANY
4	WEBER, MARCO DR.	AUF DER WEIDE 15A 52134 HERZOGENRATH, GERMANY
5	KARB, WALTER	JUDENHOF 14, 97525 SCHWEBHEIM, GERMANY

PCT International Classification Number

B24B 11/06

PCT International Application Number

PCT/EP06/000075

PCT International Filing date

2006-01-06

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	102005004038.1	2005-01-27	Germany