WO2019220373A1

WO2019220373A1 - Grinding wheel

Info

Publication number: WO2019220373A1
Application number: PCT/IB2019/054039
Authority: WO
Inventors: Marijke VAN DER MEER
Original assignee: 3M Innovative Properties Company
Priority date: 2018-05-16
Filing date: 2019-05-15
Publication date: 2019-11-21
Also published as: EP3793774A1; US20210069867A1; CN112135711A; EP3569360A1

Abstract

The invention relates to a grinding wheel for the material-removing machining of at least one workpiece, preferably a grinding wheel for the simultaneous material-removing machining of at least two flat workpieces, wherein the grinding wheel is provided with a base body and a grinding layer arranged thereon for the grinding machining of the at least one workpiece, and wherein the grinding layer comprises a plurality of surface segments, wherein, in each case, a plurality of surface segments is provided both in the circumferential direction and in the radial direction. In order to specify a grinding wheel with which both harder and softer workpieces can be machined with good machining results and good wear behavior of the grinding wheel, the grinding layer should comprise at least two different types of surface segments with different degrees of hardness.

Description

GRINDING WHEEL

The invention relates to a grinding wheel for the material-removing machining of at least one workpiece, preferably a grinding wheel for the simultaneous material- removing machining of at least two flat workpieces, wherein the grinding wheel is provided with a base body and a grinding layer arranged thereon for the grinding machining of the at least one workpiece, and wherein the grinding layer comprises a plurality of surface segments, wherein, in each case, a plurality of surface segments is provided both in the circumferential direction and in the radial direction.

Such grinding wheels, in which the hardness of the surface segments is matched to the respective application, are known from practice. In this respect, grinding wheels with harder surface segments for machining hard workpieces, such as hardened steel, and grinding wheels with less hard surface segments for machining less hard

workpieces, such as copper, are known.

In this application, "hardness" is used as the term for the modulus of elasticity of the material, since the modulus of elasticity correlates with the "hardness" (in the linguistic sense) of a grinding tool as a measure of wear resistance. In this respect, the term "harder" is understood as a higher modulus of elasticity value and "less hard" or "softer" designates a lower modulus of elasticity value.

For the application relevant in this case, the modulus of elasticity should be in the range of 40 GPa to 120 GPa, preferably 70 GPa to 105 GPa.

In this respect, the modulus of elasticity for determining such values is determined using the resonance method, also known as acoustic hardness testing. The elasticity modulus is determined in accordance with DIN EN 843-2 (2006). The natural frequency of a test specimen is used in conjunction with sample dimensions and additional material properties (density) to calculate the modulus of elasticity. For this purpose, the test specimen is brought into direct contact with a piezo transducer and continuously vibrated over a fixed frequency spectrum (at most between 100 Hz and 100 kHz) [DIN EN 843-2 (2006)]. If the excitation frequency corresponds to the fundamental frequency of the sample, resonance oscillation with maximum amplitude occurs. In this manner, the natural frequency can be determined with the assistance of another piezoelectric sensor. The natural frequency is used for a subsequent calculation of the modulus of elasticity according to DIN EN 843-2 (2006). The measuring instalment used for this can, for example, be a ZVUK 130 (supplier: ABRASIV, a.s., Pod Borkem 312, 293 01 Mlada Boleslav, Czech Republic).

A disadvantage of the previously known grinding wheels is that, in practice, situations arise in which, in a short time sequence, hard workpieces and less hard workpieces have to be machined in alternation. This means that either different grinding wheels are used and, in this respect, the grinding machine used has to be modified accordingly. In addition to the increased financial expenses for holding the various grinding wheels available, the set-up times also lead to a reduced useful life of the grinding machine, which also constitutes a financial impairment.

If, instead, only one grinding wheel with a higher hardness is used for machining hard and less hard workpieces, it must be sufficiently hard for machining the hard workpieces. In practice, however, when machining less hard workpieces with such a grinding wheel, material inclusions occur increasingly on the surface segments of the grinding wheel, which lead to an adverse effect on the grinding pattern. The material inclusions are workpiece dust, for example metallic particles, which adhere to the surface segments. A hard grinding wheel tends to form plateaus when the surface segments are worn; this leads to increased frictional heat in certain areas, which can cause particles to adhere to the surface segments.

The object of the invention is to avoid the aforementioned disadvantages and to specify a grinding wheel with which both harder and softer workpieces can be machined with good machining results and good wear behavior of the grinding wheel.

This object is achieved with a generic grinding wheel in that the grinding layer comprises at least two different types of surface segments, which have different degrees of hardness. The different surface segments of the grinding wheel are of the same height when the grinding wheel is unused, and remain at the same height as a result of uniform wear of the surface segments. This means that two different grinding wheels or grinding wheel sets (with a simultaneous double-sided machining of the workpieces) are not required and the corresponding loss of time due to conversion of the grinding machine is eliminated. At the same time, the performance in terms of removal is virtually unchanged, with only a slight increase in wear on the grinding wheel. The roughness of the workpiece surface produced, which is also negatively affected by scratches from material inclusions in the grinding layer of the grinding wheel, is improved compared to a grinding wheel that only has surface segments with the high degree of hardness. Preferably, at least a first group of harder surface segments and a second group of softer surface segments can be provided. The hardness of the respective surface segments is influenced by the bond (usually by means of glass frit) and the type and proportion of the grain size (for example, diamond or CBN), as well as by the proportion of the binder (for example, glass frit) and the proportion of a secondary grain, for example aluminum oxide.

In this respect, the ratios of the differently hard surface segments to each other can be arbitrary; for example, a distribution of harder surface segments / softer surface segments of 20%/80% up to 80%/20% is possible. Preferably, the distribution can amount to 30%/70% up to 70%/30%. With more than 2 different hard types of surface segments, other divisions are also possible. Advantageously, the proportion of harder surface segments can always be higher than the proportion of softer surface segments or vice versa.

According to the invention, the harder surface segments can have a hardness that is at least 5% harder than the hardness of the softer surface segments, preferably 10% to 20% harder than the hardness of the softer surface segments.

Advantageously, at least some of the surface segments can be either circular or annular, or even hexagonal. Thus, the entirety of the surface segments can form a total surface without a high proportion of free spaces between the surface segments.

In this respect, at least some of the surface segments can also be quadrangular with straight and/or curved side edges.

Preferably, at least two adjacent surface segments may be separated from one another by a recessed area, for example in the form of a groove. The recessed areas can also be used, for example, for the intake/removal of coolants and/or lubricants.

Viewed in the radial direction, at least one recessed area can extend over the entire radial extension of the grinding wheel and/or, viewed in the radial direction, at least one recessed area can extend only over a partial area of the radial extension of the grinding wheel.

Alternatively, adjacent surface segments can be arranged directly adjacently to each other (that is, "butt jointed").

Furthermore, at least one recessed area can extend radially or in the form of an involute.

In a preferred exemplary embodiment of the invention, at least one recessed area, preferably each recessed area, may be filled, at least partially, preferably completely, with a filling material, such as epoxy resin. According to the invention, at least one recessed area, preferably each recessed area, may have a width of at least 1 mm, preferably 3 mm to 5 mm.

Preferably, at least one harder surface segment and at least one softer surface segment can be provided at each radial position of the grinding wheel when viewed in the circumferential direction. This ensures that the desired machining result can be achieved with every radial position of the grinding wheel. At any radial position of the grinding wheel when viewed in the circumferential direction, the proportion occupied by the at least one harder surface segment and the proportion occupied by the at least one softer surface segment can advantageously be of approximate uniform size.

Advantageously, the material thickness of the surface segments can be at least 3 mm, preferably 5 mm to 10 mm. In this respect, the depth of the recessed areas can correspond to the material thickness of the surface segments, or at least be slightly smaller.

The invention also relates to a grinding wheel set with two grinding wheels for the simultaneous material -removing machining of both sides of at least two flat workpieces.

An additional object of the invention in this respect is to avoid the disadvantages mentioned above and to specify a grinding wheel set with which both harder and softer workpieces can be machined with good machining results and good wear behavior of the grinding wheels of the grinding wheel set.

This object is achieved with a generic grinding wheel set in that at least one grinding wheel is a grinding wheel according to the invention, and preferably each of the grinding wheels is a grinding wheel according to the invention.

In the following, an exemplary embodiment of the invention shown in the drawing is explained. The only figure shows a grinding wheel 1, which has a base body and a grinding layer arranged thereon for the grinding machining of at least one workpiece not shown in the drawing.

The grinding layer comprises a plurality of surface segments 2, 3, which are hexagonal in the exemplary embodiment shown, wherein, in each case, a plurality of surface segments is provided both in the circumferential direction and in the radial direction.

In each case, adjacent surface segments 2, 3 are separated from each other by a recessed area 4 in the form of a groove. In this respect, the recessed area 4, viewed in the radial direction, extends over the entire radial extension of the grinding wheel 1.

The grinding wheel 1 also comprises a base body 5, to which the surface segments 2, 3 are preferably attached by gluing. The surface elements 2, 3 of the grinding layer are divided into two different types of surface segments 2, 3, which have different degrees of hardness, and comprise a first group of harder surface segments 2 and a second group of softer surface segments 3.

Claims

1. Grinding wheel (1) for the material-removing machining of at least one workpiece, preferably a grinding wheel (1) for the simultaneous material-removing machining of at least two flat workpieces, wherein the grinding wheel (1) is provided with a base body (5) and a grinding layer arranged thereon for the grinding machining of the at least one workpiece, and wherein the grinding layer comprises a plurality of surface segments (2, 3), wherein, in each case, a plurality of surface segments (2, 3) is provided both in the circumferential direction and in the radial direction, characterized in that the grinding layer comprises at least two different types of surface segments (2, 3) which have different degrees of hardness.

2. Grinding wheel (1) according to the preceding claim, characterized in that at least a first group of harder surface segments (2) and a second group of softer surface segments (3) are provided.

3. Grinding wheel (1) according to the preceding claim, characterized in that the harder surface segments (2) have a hardness that is at least 5% harder than the hardness of the softer surface segments (3), preferably 10% to 20% harder than the hardness of the softer surface segments (3).

4. Grinding wheel (1) according to one of the preceding claims, characterized in that at least some of the surface segments (2, 3) are either circular or annular, or even hexagonal.

5. Grinding wheel (1) according to one of the preceding claims, characterized in that at least some of the surface segments (2, 3) are quadrangular with straight and/or curved side edges.

6. Grinding wheel (1) according to one of the preceding claims, characterized in that at least two adjacent surface segments (2, 3) are separated from one another by a recessed area (4), for example in the form of a groove.

7. Grinding wheel (1) according to the preceding claim, characterized in that, viewed in the radial direction, at least one recessed area (4) extends over the entire radial extension of the grinding wheel (1) and/or, viewed in the radial direction, at least one recessed area (4) extends only over a partial area of the radial extension of the grinding wheel (1).

8. Grinding wheel (1) according to claim 6 or 7, characterized in that at least one recessed area (4) extends radially or in the form of an involute.

9. Grinding wheel (1) according to one of claims 6 to 8, characterized in that at least one recessed area (4), preferably each recessed area, is at least partially, preferably completely, filled with a filling material, such as epoxy resin.

10. Grinding wheel (1) according to one of claims 6 to 8, characterized in that at least one recessed area (4), preferably each recessed area, has a width of at least 1 mm, preferably 3 mm to 5 mm.

11. Grinding wheel (1) according to one of the preceding claims, characterized in that at least one harder surface segment (2) and at least one softer surface segment (3) are provided at each radial position when viewed in the circumferential direction.

12. Grinding wheel (1) according to one of the preceding claims, characterized in that the material thickness of the surface segments (2, 3) is at least 3 mm, preferably 5 mm to

10 mm.

13. Grinding wheel set having two grinding wheels (1) for the simultaneous material- removing machining of both sides of at least two flat workpieces, characterized in that at least one grinding wheel (1) is formed as a grinding wheel (1) according to one of the preceding claims, and preferably each of the two grinding wheels (1) is formed as a grinding wheel (1) according to one of the preceding claims.