Abstract
A shaped ceramic abrasive grain, in particular based on alpha-Al.sub.2O.sub.3, includes two substantially parallel base surfaces with a polygonal base shape, said surfaces being connected by means of at least one stand surface, which is arranged substantially perpendicularly to the base surfaces, in order to position the abrasive grain on an abrasive article underlay. The abrasive grain has at least one cutting element which is arranged substantially opposite the at least one stand surface, wherein the cutting element includes at least one facet which is oriented obliquely to the base surfaces. The disclosure additionally relates to an abrasive article with abrasive grain and to a method for producing such abrasive grain.
Claims
1. A shaped ceramic abrasive grain comprising: two essentially parallel main faces which have a polygonal geometry; at least one standing face joining the two main faces and arranged essentially perpendicularly to the main faces, the at least one standing face configured for standing the abrasive grain upright on an abrasive article substrate; and at least one cutting element arranged essentially opposite the at least one standing face, the at least one cutting element including at least one facet oriented at an oblique angle to the two main faces.
2. The shaped ceramic abrasive grain as claimed in claim 1, wherein the at least one facet forms essentially an angle of from 115° to 170° to an adjoining one of the two main faces.
3. The shaped ceramic abrasive grain as claimed in claim 1, wherein the abrasive grain is delimited by the at least one facet in such a way that the at least one cutting element forms at least one point and/or at least one edge.
4. The shaped ceramic abrasive grain as claimed in claim 3, wherein: the at least one edge is formed by an intersection line of one of the two main faces and the at least one facet; and/or the at least one point is formed by an intersection point of one of the two main faces and the at least one facet.
5. The shaped ceramic abrasive grain as claimed in claim 1, further comprising: a further facet oriented at an oblique angle to the two main faces, wherein the abrasive grain is delimited by the further facet in such a way that the at least one cutting element forms at least one edge and/or a point, and wherein (i) the at least one edge is formed by an intersection line of the at least one facet and the further facet and/or (ii) the at least one point is formed by an intersection point of the at least one facet and the further facet.
6. The shaped ceramic abrasive grain as claimed in claim 5, wherein the at least one further facet essentially forms an angle of from 110° to 170° to an adjoining one of the two main faces.
7. The shaped ceramic abrasive grain as claimed in claim 3, wherein the at least one edge is arranged essentially parallel to the two main faces.
8. The shaped ceramic abrasive grain as claimed in claim 3, wherein the at least one edge is arranged essentially parallel to the at least one standing face.
9. The shaped ceramic abrasive grain as claimed in claim 3, wherein the at least one edge is arranged essentially at an angle of 45° relative to the at least one standing face.
10. The shaped ceramic abrasive grain as claimed in claim 5, wherein the at least one edge is arranged in a plane which lies essentially parallel to the two main faces centrally between the two main faces.
11. The shaped ceramic abrasive grain as claimed in claim 1, wherein the two essentially parallel main faces having a polygonal geometry are congruent.
12. The shaped ceramic abrasive grain as claimed in claim 1, wherein the two essentially parallel main faces having a polygonal geometry are not congruent.
13. The shaped ceramic abrasive grain as claimed in claim 1, wherein there is a spacing of less than 2000 μm between the at least one cutting element and the at least one standing face.
14. An abrasive article comprising: a plurality of shaped ceramic abrasive grains, each of which comprises: two essentially parallel main faces which have a polygonal geometry; at least one standing face joining the two main faces and arranged essentially perpendicularly to the main faces, the at least one standing face configured for standing the abrasive grain upright on an abrasive article substrate; and at least one cutting element arranged essentially opposite the at least one standing face, the at least one cutting element including at least one facet oriented at an oblique angle to the two main faces.
15. The abrasive article as claimed in claim 14, further comprising: an abrasive article substrate on which the plurality of shaped ceramic abrasive grains are arranged in such a way that each of the plurality of shaped ceramic abrasive grains stands on the at least one standing face.
16. The abrasive article as claimed in claim 14, further comprising: an abrasive article substrate on which the shaped ceramic abrasive grains are arranged in such a way that the two main faces of each of the plurality of abrasive grains are oriented parallel to a direction of use of the abrasive article.
17. A casting mold for producing shaped ceramic abrasive grains as claimed in claim 1, comprising a plurality of mold cavities that have a form complementary to the shape of the abrasive grain.
18. A process for producing shaped ceramic abrasive grains comprising: producing shaped ceramic abrasive grains having two essentially parallel main faces which have a polygonal geometry; at least one standing face joining the two main faces and arranged essentially perpendicularly to the main faces, the at least one standing face configured for standing the abrasive grain upright on an abrasive article substrate; and at least one cutting element arranged essentially opposite the at least one standing face, the at least one cutting element including at least one facet oriented at an oblique angle to the two main faces.
19. The shaped ceramic abrasive grain as claimed in claim 1, wherein the shaped ceramic abrasive grain is based on alpha-Al.sub.2O.sub.3.
20. The shaped ceramic abrasive grain as claimed in claim 2, wherein the angle formed by the at least one facet to the adjoining one of the two main faces is from 140° to 150°.
Description
DRAWINGS
[0042] The invention will now be illustrated in the following description with the aid of working examples depicted in the drawings. The drawings, the description and the claims contain numerous features in combination. A person skilled in the art will advantageously also look at the features individually and combine them to give useful further combinations. Identical reference numerals in the figures designate identical elements.
[0043] The figures show:
[0044] FIG. 1 a schematic view of one embodiment of a ceramic shaped abrasive grain according to the prior art;
[0045] FIG. 2 a schematic view of a first embodiment of a ceramic shaped abrasive grain according to the invention having at least one cutting element, where the cutting element comprises at least one facet oriented at an oblique angle to the main faces;
[0046] FIG. 3 a schematic view of a second embodiment of a ceramic shaped abrasive grain according to the invention;
[0047] FIG. 4 a schematic view of a third embodiment of a ceramic shaped abrasive grain according to the invention;
[0048] FIG. 5 a schematic view of a fourth embodiment of a ceramic shaped abrasive grain according to the invention;
[0049] FIG. 6 a schematic view of a fifth embodiment of a ceramic shaped abrasive grain according to the invention;
[0050] FIG. 7 a schematic view of a sixth embodiment of a ceramic shaped abrasive grain according to the invention;
[0051] FIG. 8 a schematic view of a seventh embodiment of a ceramic shaped abrasive grain according to the invention;
[0052] FIG. 9 a schematic view of an eighth embodiment of a ceramic shaped abrasive grain according to the invention;
[0053] FIG. 10 a schematic view of a ninth embodiment of a ceramic shaped abrasive grain according to the invention;
[0054] FIG. 11 a section of a schematic sectional view of an embodiment of the abrasive article according to the invention;
[0055] FIG. 12 a section of a schematic sectional view of an alternative embodiment of the abrasive article according to the invention with directionally positioned abrasive grains;
[0056] FIG. 13 a flow diagram to illustrate the process steps for producing a shaped ceramic abrasive grain according to the invention.
[0057] FIG. 1 schematically shows (in particular not true to scale) an illustrative embodiment of a shaped ceramic abrasive grain 210 as is known from the prior art. The geometric shape of the abrasive grain 210 is formed by a regular three-sided upright prism having the side edges 212 and the height edges 212a with the height 214. The main face 216 and the covering face 218 are accordingly each formed by three side edges 212 of equal length. The main face 216 and the covering face 218 have the same size and are spaced from one another by the height 214. The three side faces 220 are formed by rectangles and are of essentially the same size. In the illustrative embodiment of FIG. 1, the side edges 212 have a length 222 of 1400 μm. The height 214 is 410 μm. The ceramic abrasive grain 210 is produced based on alpha-Al.sub.2O.sub.3.
[0058] In the following, embodiments of the shaped ceramic abrasive grain 10, 10a-i according to the invention for an abrasive article 50 are presented. The proposed shaped ceramic abrasive grain 10, 10a-i is likewise produced based on alpha-Al.sub.2O.sub.3 in these examples and has two essentially parallel main faces 12a, 12b which have a polygonal geometry and are joined by at least one standing face 14 arranged essentially perpendicularly to the main faces 12a, 12b for standing the abrasive grain 10, 10a-i upright on an abrasive article substrate 52. The abrasive grain 10, 10a-i has at least one cutting element 16, 16a-i which is arranged essentially opposite the at least one standing face 14, where the cutting element 16, 16a-i comprises at least one facet 18 oriented at an oblique angle to the main faces 12a, 12b. The size of the abrasive grains 10, 10a-i depicted is in the range from 100 μm to 2000 μm (for example determined as diameter of a circle which can be fitted into the abrasive grain 10, 10a-i), depending on the desired fineness of a grinding result to be achieved.
[0059] FIG. 2 depicts an illustrative embodiment of the ceramic shaped abrasive grain 10, 10a of the invention. The abrasive grain 10, 10a has a first main face 12a and a second main face 12b which each have a hexagonal geometry. The main faces 12a, 12b are congruent and are joined at each of three non-contacting edges 20a of the main faces 12a, 12b by one in each case (i.e. three in total) standing face 14 which is arranged essentially perpendicularly to the main faces 12a, 12b for standing the abrasive grain 10, 10a upright on an abrasive article substrate 52 (cf. FIG. 11). Adjoining the main faces 12a, 12b, a respective cutting element 16, 16a is formed on in each case a further three non-contacting edges 20b of the main faces 12a, 12b, where each cutting element 16, 16a comprises two facets 18 which are oriented at an oblique angle to the main faces 12a, 12b and contact one another in a common edge 22. The facets 18 each form an external angle 24 of about 206° (internal angle about) 154° to an adjoining main face 12a, 12b. The respective edge 22 is arranged essentially parallel to the main faces 12a, 12b and essentially parallel to the standing face 14 arranged opposite. In particular, the edge 22 is arranged in a plane (not shown in more detail here, but cf. FIG. 6, there reference numeral 28) which lies essentially parallel to the main faces 12a, 12b centrally between the main faces 12a, 12b. Thus, the abrasive grain 10, 10a in this working example has three symmetric (in respect of a mirror plane arranged centrally between the two main faces 12a, 12b and parallel to these) cutting elements 16, 16a, each having an edge 22. An envelope of the abrasive grain 10, 10a (not shown in more detail here, but cf. FIG. 6) is triangular, with each side face of the abrasive grain 10, 10a adjoining the envelope representing a standing face 14. The edge length of the envelope is 2.1 mm, and the thickness of the abrasive grain 10, 10a (i.e. the spacing of the main faces 12a, 12b) is 340 μm. The abrasive grain 10, 10a has three-fold rotational symmetry.
[0060] Similarly to the abrasive grain 10, 10a of FIG. 2, the abrasive grain 10, 10b in FIG. 3 has a first main face 12a and a second main face 12b which each have a hexagonal geometry. The main faces 12a, 12b are congruent and are joined at in each case three non-contacting edges 20a of the main faces 12a, 12b by a respective standing face 14 arranged essentially perpendicularly to the main faces 12a, 12b for standing the abrasive grain 10, 10b upright on an abrasive article substrate 52. Adjoining the main faces 12a, 12b, there is formed a respective cutting element 16, 16b at each of a further three non-contacting edges 20b of the main faces 12a, 12b, where each cutting element 16, 16b comprises two facets 18 which are arranged at an oblique angle to the main faces 12a, 12b and contact one another in a common point 26.
[0061] The facets 18 each form an external angle 24 of about 194° (internal angle about 166°) to an adjoining main face 12a, 12b. The respective point 26 is arranged in a plane (not shown here, but cf. FIG. 6) which lies essentially parallel to the main faces 12a, 12b centrally between the main faces 12a, 12b. The abrasive grain 10, 10b thus has three symmetric (in respect of a mirror plane arranged centrally between the two main faces 12a, 12b and parallel to these) cutting elements 16, 16b, each having a point 26. An envelope of the abrasive grain 10, 10b (not shown in more detail here, but cf. FIG. 6) is likewise triangular, with each side face of the abrasive grain 10, 10b adjoining the envelope representing a standing face 14. The edge length of the envelope is 2.1 mm, and the thickness of the abrasive grain 10, 10b is 340 μm. The abrasive grain 10, 10b has three-fold rotational symmetry.
[0062] The abrasive grain 10, 10c of the depiction in FIG. 4 has two main faces 12a, 12b which do not have a congruent geometry, although both main faces 12a, 12b in each case have a hexagonal shape. The main faces 12a, 12b are joined at each of three non-contacting edges 20a of the main faces 12a, 12b by a respective standing face 14 arranged essentially perpendicularly to the main faces 12a, 12b for standing the abrasive grain 10, 10c upright on an abrasive article substrate 52. Adjoining the main faces 12a, 12b there is formed a respective cutting element 16, 16c at each of a further three non-contacting edges 20b of the main faces 12a, 12b, where each cutting element 16, 16c comprises a facet 18 which is oriented at an oblique angle to the main faces and forms at least one edge 22 as intersection line of the main face 12b and the facet 18 (it may be pointed out that the edge 20b corresponds to the edge 22 based on the main face 12b).
[0063] The facets 18 each form an external angle 24 of about 224° (internal angle about 136°) to the adjoining main face 12a. The respective edge 22 is arranged essentially parallel to the main faces 12a, 12b and essentially parallel to a standing face 14 arranged correspondingly opposite. However, in this case the edge 22 is not arranged in a plane (not shown in more detail here, but cf. FIG. 6) which lies essentially parallel to the main faces 12a, 12b centrally between the main faces 12a, 12b. The abrasive grain 10, 10c thus has three asymmetric, in respect of this plane, cutting elements 16, 16c each having an edge 22. An envelope of the abrasive grain 10, 10c (not shown in more detail here, but cf. FIG. 6) is once again triangular, with each side face of the abrasive grain 10, 10c adjoining the envelope representing a standing face 14. The edge length of the envelope is 2.1 mm, and the thickness of the abrasive grain 10, 10c is 340 μm. The abrasive grain 10, 10c has three-fold rotational symmetry.
[0064] In the working example of the abrasive grain 10, 10d depicted in FIG. 5, one main face 12a has a hexagonal geometry while the second main face 12b has a triangular geometry. The hexagonal main face 12a is joined at three non-contacting edges 20a to in each case a standing face 14 arranged essentially perpendicularly to the main faces 12a, 12b for standing the abrasive grain 10, 10d upright on an abrasive article substrate 52 and the triangular main face 12b. Here, a respective cutting element 16, 16d is formed adjoining the hexagonal main face 12a at in each case a further three non-contacting edges 20b of the main face 12a, where each cutting element 16, 16d has a respective facet 18 which is oriented at an oblique angle to the main faces 12a, 12b and forms a common point 26 with the triangular main face 12b. The facets 18 each form an external angle 24 of about 206° (internal angle about 154°) to the adjoining main face 12a. The respective point 26 is therefore in this case likewise not arranged in a plane (not shown in more detail here, but cf. FIG. 6) which lies essentially parallel to the main faces 12a, 12b centrally between the main faces 12a, 12b. The abrasive grain 10, 10d has an asymmetric cutting element 16, 16d with a point 26, where the two main faces 12a, 12b are not congruent to one another. The abrasive grain 10, 10d is thus likewise arranged asymmetrically in respect of a mirror plane arranged centrally between the two main faces 12a, 12b and parallel to these. The abrasive grain 10, 10d thus has three cutting elements 16, 16d each having a point 26. An envelope of the abrasive grain 10, 10d (not shown in more detail here, but cf. FIG. 6) is likewise triangular, with each side face of the abrasive grain 10, 10d adjoining the envelope representing a standing face 14. The edge length of the envelope is 2.1 mm, and the thickness of the abrasive grain 10, 10d is 340 μm. The abrasive grain 10, 10d has three-fold rotational symmetry.
[0065] Similarly to the abrasive grain 10, 10b of FIG. 3, the working example of the abrasive grain 10, 10e of FIG. 6 has a first main face 12a and a second main face 12b which each have a hexagonal geometry. The main faces 12a, 12b are congruent and are joined at in each case three non-contacting edges 20a of the main faces 12a, 12b by a respective standing face 14 arranged essentially perpendicularly to the main faces 12a, 12b for standing the abrasive grain 10, 10e upright on an abrasive article substrate 52. A cutting element 16, 16e is respectively formed adjoining the main faces 12a, 12b at in each case a further three non-contacting edges 20b of the main faces 12a, 12b, where each cutting element 16, 16e comprises two facets 18 which are oriented at an oblique angle to the main faces 12a, 12b and contact one another at a respective common point 26. The respective point 26 is, however, not arranged in a plane 28 which lies essentially parallel to the main faces 12a, 12b centrally between the main faces 12a, 12b. The abrasive grain 10, 10e thus has three asymmetric (in respect of this plane) cutting elements 16, 16e each having a point 26. An envelope 30 of the abrasive grain 10, 10e is likewise triangular, with each side face of the abrasive grain 10, 10e adjoining the envelope representing a standing face 14. The edge length of the envelope is 2.1 mm, and the thickness of the abrasive grain 10, 10e is 340 μm. The abrasive grain 10, 10e has three-fold rotational symmetry.
[0066] The working examples of FIGS. 7 to 10 concern abrasive grains 10, 10f-i whose envelope (not shown in more detail here, but cf. in principle FIG. 6) has a rectangular shape, in particular square shape. FIG. 7 depicts an illustrative embodiment of the ceramic shaped abrasive grain 10, 10f according to the invention in which the abrasive grain 10, 10f has a first main face 12a and a second main face 12b which each have an octagonal geometry. The main faces 12a, 12b are congruent and joined at in each case four non-contacting edges 20a of the main faces 12a, 12b by a respective standing face 14 arranged essentially perpendicularly to the main faces 12a, 12b for standing the abrasive grain 10, 10f upright on an abrasive article substrate 52. Adjoining the main faces 12a, 12b, a respective cutting element 16, 16f is formed at in each case a further four non-contacting edges 20b of the main faces 12a, 12b, where each cutting element 16, 16f comprises two facets 18 which are oriented at an oblique angle to the main faces 12a, 12b and contact one another in a common edge 22. The facets 18 each form an external angle 24 of about 223° (internal angle about 137°) to an adjoining main face 12a, 12b. The respective edge 22 is oriented essentially parallel to the main faces 12a, 12b and at an angle of essentially 45° to the standing face 14 arranged opposite. In particular, the edge 22 is arranged in a plane (not shown in more detail here, but cf. FIG. 6) which lies essentially parallel to the main faces 12a, 12b centrally between the main faces 12a, 12b. The abrasive grain 10, 10f thus has four cutting elements 16, 16f which are symmetric in respect of this plane and each have an edge 22. An envelope of the abrasive grain 10, 10f (not shown in more detail here, but cf. FIG. 6) is square, with each side face of the abrasive grain 10, 10f adjoining the envelope representing a standing face 14. The edge length of the envelope is 1.8 mm, and the thickness of the abrasive grain 10, 10f (i.e. the spacing of the main faces 12a, 12b) is 400 μm. The abrasive grain 10, 10f has four-fold rotational symmetry.
[0067] FIG. 8 depicts an embodiment of the abrasive grain 10, 10g in which each cutting element 16, 16g comprises at least two facets 18 which are oriented at an oblique angle to the main faces 12a, 12b and contact one another in a common point 26. The facets 18 each form an external angle 24 of about 205° (internal angle about 155°) to an adjoining main face 12a, 12b. The point is arranged in a plane (not shown in more detail here, but cf. FIG. 6) which lies essentially parallel to the main faces 12a, 12b centrally between the main faces 12a, 12b. The abrasive grain 10, 10g thus has four cutting elements 16, 16f which are symmetric in respect of this plane and each have a point 26. Here too, the envelope of the abrasive grain 10, 10g (not shown in more detail here, but cf. FIG. 6) is square, with each side face of the abrasive grain 10, 10g adjoining the envelope forming a standing face 14. The edge length of the envelope is 1.8 mm, and the thickness of the abrasive grain 10, 10g is 400 μm.
[0068] The abrasive grain 10, 10h of the depiction in FIG. 9 has two main faces 12a, 12b which do not have a congruent geometric shape, but each of the two main faces 12a, 12b has an octagonal shape. The main faces 12a, 12b are joined at in each case four non-contacting edges 20a of the main faces 12a, 12b by a respective standing face 14 arranged essentially perpendicularly to the main faces 12a, 12b for standing the abrasive grain 10, 10h upright on an abrasive article substrate 52. Adjoining the main faces 12a, 12b, a respective cutting element 16, 16h is formed at in each case a further four non-contacting edges 20b of the main faces 12a, 12b, where each cutting element 16, 16h comprises a facet 18 which is oriented at an oblique angle to the main faces 12a, 12b and forms at least one edge 22 as intersection line of the main faces 12b and the facet 18 (it may be pointed out that the edge 20b corresponds to the edge 22 in respect of the main face 12b). The facets 18 each form an external angle of about 242° (internal angle about 118°) to an adjoining main face 12a. The respective edge 22 is oriented essentially parallel to the main faces 12a, 12b and at an angle of essentially 45° to the standing face 14 arranged opposite. However, the edge 22 is in this case not arranged in a plane (not shown in more detail here, but cf. FIG. 6) which lies essentially parallel to the main faces 12a, 12b centrally between the main faces 12a, 12b. The abrasive grain 10, 10h thus has four cutting elements 16, 16h which are asymmetric in respect of this plane and each have an edge 22. An envelope of the abrasive grain 10, 10h (not shown in more detail here, but cf. FIG. 6) has a quadrilateral geometry, with each side face of the abrasive grain 10, 10h adjoining the envelope representing a standing face 14. The edge length of the envelope is 2.1 mm, and the thickness of the abrasive grain 10, 10h is 340 μm. The abrasive grain 10, 10h has four-fold rotational symmetry.
[0069] In the case of the working example of the abrasive grain 10, 10i, depicted in FIG. 10, one main face 12a has an octagonal geometry while the second main face 12b has a quadrilateral geometry. The octagonal main face 12a is joined at four non-contacting edges 20a to a respective standing face 14 arranged essentially perpendicularly to the main faces 12a, 12b for standing the abrasive grain 10, 10i upright on an abrasive article substrate 52 and to the quadrilateral main face 12b. Here, a cutting element 16, 16i is respectively formed adjoining the octagonal main face 12a at in each case a further four non-contacting edges 20b of the main faces 12a, where each cutting element 16, 16i comprises a respective facet 18 which is oriented at an oblique angle to the main faces 12a, 12b and forms a common point 26 with the quadrilateral main face 12b. The facets 18 each form an external angle 24 of about 223° (internal angle about) 137° to the adjoining main face 12a. The respective point 26 is therefore likewise not arranged in a plane (not shown in more detail here, but cf. FIG. 6) which lies essentially parallel to the main faces 12a, 12b centrally between the main faces 12a, 12b. The abrasive grain 10, 10i therefore has four cutting elements 16, 16i which are asymmetric in respect of this plane and each have a point 26, with the two main faces 12a, 12b not being congruent to one another. The abrasive grain 10, 10i is thus likewise asymmetric. An envelope of the abrasive grain 10, 10i (not shown in more detail here, but cf. FIG. 6) is likewise quadrilateral, in particular square, with each side face of the abrasive grain 10, 10i adjoining the envelope forming a standing face 14. The edge length of the envelope is 2.1 mm, and the thickness of the abrasive grain 10, 10i is 340 μm. The abrasive grain 10, 10i has four-fold rotational symmetry.
[0070] FIG. 11 shows a section of an illustrative embodiment of an abrasive article 50 according to the invention with abrasive grains 10, 10a-i in a schematic sectional view. In the embodiment depicted, the abrasive article 50 is a coated abrasive article 50 having an abrasive article substrate 52 made of vulcanized fiber. The abrasive article substrate 52 composed of vulcanized fiber serves as flexible substrate for the abrasive grains 10, 10a-i. Vulcanized fiber is a composite material comprising cellulose, in particular cotton fibers or cellulose fibers, and is adequately known to a person skilled in the art as flexible substrate for abrasive articles from the prior art. The abrasive grains 10, 10a-i are fixed by means of a base binder 54, for example composed of phenolic resin, to the abrasive article substrate 52. The layer of base binder 54 and abrasive grains 10, 10a-i is coated with a covering binder 56, for example composed of phenolic resin. It may be pointed out that the abrasive grains 10, 10a-i are not positioned with a preferential orientation in this working example.
[0071] FIG. 12 depicts an abrasive article 50 according to the invention having an advantageous arrangement of the abrasive grains 10, 10d (cf. for abrasive grain 10d FIG. 5 and associated passage in the text; equivalent embodiments also apply to abrasive grains 10, 10a-i) on an abrasive article substrate 52. In this variant of the abrasive article 50, the proportion of shaped ceramic abrasive grains according to the invention is about 100% based on the total amount of abrasive grains. The shaped ceramic abrasive grains 10, 10d are arranged oriented on the abrasive article substrate 52 of the abrasive article 50 in such a way that they stand on at least one standing face 14 for standing the abrasive grain 10, 10d upright on the abrasive grain substrate 52. Here, a cutting element 16, 16d arranged essentially opposite the standing face 14 faces away from the abrasive article substrate 52, toward a workpiece to be machined. Furthermore, the abrasive grains 10, 10d are arranged on the abrasive article 50 in such a way that the main faces 12a, 12b are oriented parallel to a direction 58 of an intended use of the abrasive article 50. It can be seen from the abrasive grain 10, 10d shown by way of example in an enlarged depiction that the standing face is advantageously oriented so that the longitudinal direction of the standing face is aligned in the direction 58 of the intended use of the abrasive article 50. The abrasive grain 10, 10d can thus optimally counter the force “F” which acts. The abrasive grains 10, 10d have a particularly stable seat.
[0072] The process of the invention for producing shaped ceramic abrasive grains is illustrated with the aid of the flow diagram of FIG. 13. The production process 100 comprises the following steps. In a first step 110, a slip comprising at least an alpha-Al.sub.2O.sub.3 powder and a dispersant is produced, with a solids content in the slip being from 50% by weight to 90% by weight and an average particle size being from 0.1 μm to 8 μm. In one embodiment of the process, it is additionally possible to use a ZrO.sub.2 powder. In a second step 120, the slip is introduced into depressions in a casting mold (not shown in more detail), where the depressions have a defined geometry. The casting mold has, in particular, a plurality of mold cavities, where the plurality of mold cavities comprises a lower mold surface, a mold side wall and a depth between the lower mold surface and the surface of the casting mold. The plurality of cavities has a form which is complementary to the shape of the abrasive grain 10, 10a-i. In a third step 130, drying of the slip in the depressions is then carried out to give abrasive grain precursors, with a solids content of the abrasive grain precursors being from 85% by weight to 99.9% by weight. After drying of the slip, the abrasive grain precursors are removed from the depressions in a fourth step 140. Furthermore, sintering of the abrasive grain precursors is carried out in a fifth step 150 to give abrasive grains which are based on alpha-Al.sub.2O.sub.3 and have a content of ZrO.sub.2 of from 5% by weight to 30% by weight and a density of from 92% to 99.9% of theoretical density, where the alpha-Al.sub.2O.sub.3 has an average crystallite size of from 0.5 μm to 3 μm and the ZrO.sub.2 has an average crystallite size of from 0.25 μm to 8 μm.
