Patent Application
20210031332
The invention concerns a support body for a grinding tool, and a grinding tool having such a support body and an abrasive layer which has abrasive means, in particular superabrasive means, and which is arranged on a preferably circumferential support surface of the support body. The abrasive layer is formed from a continuous abrasive ring or individual abrasive segments. The invention further concerns a method of producing a support body as noted above, and a method of producing a grinding tool having such a support body.
Support bodies for grinding tools should be as far as possible stable, light and with a damping action in particular in so-called centerless grinding tools.
It is known from the state of the art to produce support bodies from a phenolic moulding material by hot pressing and hardening. Then either mixtures of synthetic resin, fillers and superabrasive means are pressed hot on to those supports or ceramic superabrasive layers are adhesively bonded in place. A support body produced in that way is light and damps vibrations in the grinding process so that wear of the layers in comparison for example with layers with aluminium supports in grinding use is reduced and the surface quality of the ground components is improved, this being manifested by a lower degree of roughness, lesser break-outs and the absence of chatter marks.
It will be noted, however, that those support bodies suffer from the disadvantage that a relatively great uncontrolled wastage occurs in the production of the supports, and only a limited spectrum of support bodies in regard to the dimensions thereof can be produced. In addition, cracking occurs in the grinding operation. The maximum working highest speed is limited to about 63 m/s.
U.S. Pat. No. 2,069,116 discloses a grinding tool having a support body formed from layers of a fibrous layer material. The grinding tool is produced jointly with the support body in a press of fixed dimensions, wherein the individual layers of the layer material have to be successively laid in the press. That manufacturing procedure is highly time-consuming. In addition, only grinding tools of the fixed size can be produced by means of the press so that it is not possible to produce a grinding tool of differing dimensions.
It is further known from the state of the art to produce support bodies from a carbon fibre-reinforced plastic. That material makes it possible to produce light and at the same time dimensionally stable support bodies. However that involves very complicated production and very high manufacturing costs.
The object of the present invention is to at least partially overcome the disadvantages of the state of the art and to provide a support body which is lighter and improved in relation thereto as well as a grinding tool having such a support body. A further object is to provide a method of producing a support body and a grinding tool having such a support body, in which the method is in particular distinguished in that support bodies and grinding tools of differing dimensions can be flexibly produced, more specifically in a short time and at reasonable production costs.
The support body substantially comprises an abrasive means-free composite material comprising a plurality of mutually superposed layers of a natural fibre material and which are connected together by plastic, preferably phenolic resin.
The term ‘abrasive means’ in connection with the present invention is used to denote hard material grains which are used to achieve removal of material from a workpiece. In that respect, natural grain materials (flint, quartz, corundum, emery, granite, natural diamond) and synthetic grain materials (corundums, silicon carbides, chromium oxides, cubic boron nitride, diamonds) are differentiated.
The term ‘superabrasive means’ is used to denote professional diamond and cubic boron nitride.
If there are no abrasive or superabrasive means present in a material then they are of an abrasive means-free nature in accordance with the present invention.
Abrasive means-free composite materials comprising a plurality of mutually superposed layers of a natural fibre material which are connected together by plastic, preferably phenolic resin, wherein the natural fibre material is a cotton fabric or paper, are known from the technical field of the production of electrical and thermal insulation components for machine and equipment construction—in the case of cotton fabric—as hard cotton fabric and—in the case of paper—in the form of hard papers.
In comparison with the support bodies known from the state of the art and comprising a phenolic moulding material the support body according to the invention has an approximately 30% higher flexural breaking stress, an elongation at break which is about three times greater and a higher elasticity, and is about 15% lighter. Higher operational speeds are possible, for example 125 m/s and more.
In addition, in the production of the support body or a grinding tool having such a support body, no or markedly reduced wastage occurs.
When an abrasive layer mixture for producing an abrasive ring is pressed on to the support body, a lower pressure is required for that purpose in the pressing operation. The grinding tool is markedly easier to remove from the mould as the support body does not expand after the hot pressing operation. Pressing without a flange is also easier, thereby subsequently giving a potential saving in a machining operation.
The use of the composite material also makes it possible to produce support bodies in a wider range of sizes. Thus, support bodies for example up to a diameter of 1050 mm and a height of 100 mm can be readily produced.
The composite material further has the advantage that it can be more easily machined with carbide metal. Usually expensive tools with PCD cutting edges have to be used in comparison therewith for machining the materials used in the state of the art. Furthermore the composite material can be very well combined with other materials like for example carbon fibre reinforced plastic, glass fibre reinforced plastic, Al or steel, for example by glueing or screwing.
Advantageously, the composite material used in the present invention is thermosetting, that is to say it is no longer deformable after setting.
By virtue of the fact that the support body has a first, preferably cylindrical or hollow-cylindrical body and at least one further, preferably cylindrical or hollow-cylindrical body, wherein the bodies are connected together, preferably by glueing, it is possible in a flexible fashion to construct light support bodies of complex shapes, as could be achieved in the state of the art only with carbon fibre-reinforced plastic, but in a markedly shorter time and at markedly lower cost.
According to advantageous embodiments the natural fibre material is a cotton fabric or paper.
In regard to its physical properties it has proven to be advantageous if the composite material is of a density of 1.0 to 2.0 g/cm3, preferably 1.4 g/cm3 (for example measured in accordance with the testing standard ISO 1183) and/or has a water absorption of 1.5 to 7.5%, preferably 2.4% or 5.2% (for example measured in accordance with the testing standard ISO 62).
In regard to the thermal properties it has proven to be advantageous if the composite material has a length extension coefficient of 20 to 40×10−6 K−1, preferably 30×10−6 K−1 (for example measured in accordance with the testing standard DIN 51045) and/or thermal conductivity of 0.1 to 0.3 W/mK, preferably 0.2 W/mK (for example measured in accordance with the testing standard DIN 52612).
The temperature of use can be continuously or temporarily 110° C. or 180° C.
In regard to the mechanical properties, it is appropriate if the composite material has a compressive strength at 23° C. of 200 to 400 N/mm2, preferably 300 N/mm2 or 320 N/mm2 (for example measured in accordance with the testing standard ISO 604) and/or a flexural strength at 23° C. of 50 to 150 N/mm2, preferably 100 N/mm2 or 135 N/mm2 (for example measured in accordance with the testing standard ISO 178) and/or a modulus of elasticity (from a bending test) of 6000 to 8000 N/mm2, preferably 7000 N/mm2 (for example measured in accordance with the testing standard ISO 178) and/or a tensile strength of 50 to 150 N/mm2, preferably 80 N/mm2 or 120 N/mm2 (for example measured in accordance with the testing standard ISO 527) and/or a splitting force of 1500 to 3500 N, preferably 1900 N or 3000 N (for example measured in accordance with the testing standard DIN 53463).
In regard to the electrical properties, the composite material can have a tracking resistance CTI 100 (for example measured in accordance with the testing standard IEC 112) and/or an electrical dielectric strength (perpendicular) of 1.5 KV/3 mm or 10 KV/3 mm (for example measured in accordance with the testing standard IEC 243-1) and/or an electrical dielectric strength (parallel) of 1.0 KV/25 mm or 10 KV/25 mm (for example measured in accordance with the testing standard IEC 243-1).
According to a preferred embodiment of the invention, the support body has at least one side surface which is separate from the support surface for the abrasive layer and at which a layer of the composite material is arranged flat.
It is further appropriate if the support body has a central coupling region, preferably with a central bore, for connection to a rotary drive for rotating the support body or a grinding tool formed therewith about an axis of rotation extending through the coupling region and/or the support body is of a substantially rotationally symmetrical configuration.
It has proven to be advantageous if the first and the at least one further body are cylindrical or hollow-cylindrical bodies which are connected together at side surfaces, preferably in which axes of symmetry of the bodies are substantially congruent. The support bodies or grinding tools which can be produced in that way are particularly well suited for example for grinding camshafts.
It has further proven to be desirable if the support body has an adaptor for connecting the support body or a grinding tool formed therewith to a rotary drive connected, preferably glued to at least one of the bodies, preferably wherein the adaptor substantially comprises a metal and/or is of a substantially hollow-cylindrical configuration.
In this connection, it is appropriate if the support body has a central bore, and the adaptor is at least region-wise arranged in the central bore. Preferably, the adaptor extends only over a part of the length of the central bore, and particularly preferably the central bore has a funnel-shaped insertion opening. A funnel-shaped insertion opening makes it easier to clamp the support body.
A grinding tool has a support body according to the invention and an abrasive layer which has abrasive means, in particular superabrasive means, and which is arranged on the preferably circumferential support surface of the support body. Preferably, the abrasive layer is formed from a continuous abrasive ring or individual abrasive segments.
Furthermore, a method of producing a support body for a grinding tool is provided. The support body includes a preferably circumferential support surface for an abrasive layer having abrasive means, in particular superabrasive means, and substantially comprises an abrasive means-free composite material comprising a plurality of mutually superposed layers of a natural fibre material which are connected together by plastic, preferably phenolic resin, preferably wherein the natural fibre material is a cotton fabric or paper. The abrasive means-free composite material is provided in the form of a plate in a first method step and in a second method step a preferably cylindrical or hollow-cylindrical body is cut out of the plate with predetermined dimensions preferably by water jet cutting or by means of a band saw.
According to an advantageous configuration, in the course of the second method step at least one further, preferably cylindrical or hollow-cylindrical body is cut out of the plate with predetermined dimensions and connected to the first body, preferably by adhesive.
In this connection, it is appropriate if the first and the at least one further body is cylindrical or hollow-cylindrical bodies, the bodies being connected together at side surfaces, preferably wherein axes of symmetry of the bodies are brought substantially into congruent relationship.
It has proven to be advantageous if in a third method step the body or bodies is or are re-worked, preferably by cutting machining and/or balancing and/or by fitting a central bore.
It has proven to be desirable if at least one of the bodies in a further method step which follows the second method step or the third method step is connected to an adaptor for connecting the support body or a grinding tool formed therewith to a rotary drive, preferably by adhesive. Preferably, the adaptor substantially comprises a metal and/or is of a substantially hollow-cylindrical configuration.
In addition, protection is claimed for a method of producing a grinding tool having a support body which includes a preferably circumferential support surface for an abrasive layer having abrasive means, in particular superabrasive means, and substantially comprises an abrasive means-free composite material comprising a plurality of mutually superposed layers of a natural fibre material, which are connected together by plastic, preferably phenolic resin. The natural fibre material is a cotton fabric or paper, and an abrasive layer which has abrasive means, in particular superabrasive means and which is arranged on the preferably circumferential support surface of the support body. Preferably, the abrasive layer is formed from a continuous abrasive ring or individual abrasive segments. Firstly, a support body preferably produced by means of the method for production of the support body is provided, and then an abrasive layer having abrasive means, preferably superabrasive means, is arranged on a preferably circumferential support surface of the support body, preferably by pressing thereon and/or adhesive bonding, and preferably the abrasive layer is formed from a continuous abrasive ring or individual abrasive segments.
Further details and advantages of the invention will be described more fully hereinafter by means of the specific description with reference to the drawings in which:
The support body 1 substantially comprises an abrasive means-free composite material 6 comprising a plurality of mutually superposed layers 7 of a natural fibre material connected together by plastic 8. That is diagrammatically indicated in the view on an enlarged scale of the portion in
Directly adjacent layers 7 can be at a very small spacing relative to each other and even at least region-wise touch. The layers 7 are oriented substantially parallel to side surfaces.
Two embodiments have proven to be particularly advantageous in relation to the composite material 6.
In the first embodiment the natural fibre material is a cotton fabric. In that case the composite material 6 is of a density of 1.4 g/cm3 and has water absorption of 2.4%. In addition the composite material 6 has a length extension coefficient of 30×10−6 K−1 and a thermal conductivity of 0.2 W/mK. And finally the composite material 6 has a compressive strength at 23° C. of 320 N/mm2, a flexural strength at 23° of 100 N/mm2, a modulus of elasticity of 7000 N/mm2, a tensile strength of 80 N/mm2 and a splitting force of 3000 N.
In the second embodiment the natural fibre material is paper. In that case the composite material 6 is of a density of 1.4 g/cm3 and has water absorption of 5.2%. In addition the composite material 6 has a length extension coefficient of 30×10−6 K−1 and a thermal conductivity of 0.2 W/mK. And finally the composite material 6 has a compressive strength at 23° C. of 300 N/mm2, a flexural strength at 23° of 135 N/mm2, a modulus of elasticity of 7000 N/mm2, a tensile strength of 120 N/mm2 and a splitting force of 1900 N.
The support body 1 has two oppositely disposed side surfaces 9 which are separate from the support surface 3 for the abrasive layer 5 and at which a respective layer 7 of the natural fibre material is arranged flat (see also
The support body 1 includes a central coupling region 10 having a central bore 11 for connection to a rotary drive for rotating the support body 1 or a grinding tool 2 formed therewith about an axis of rotation 12 extending through the coupling region 10. The axis of rotation 12 extends through the centre 25 of the central bore 11 and is oriented substantially normal to the side surfaces 9.
The dimensions of the support body 1 can be characterised by its diameter 17, its thickness 18 and the diameter 19 of the central bore 11.
The grinding tool 2 shown in
The abrasive layer 5 can be formed from a continuous abrasive ring or, as indicated in the lower region of the grinding tool 2, individual abrasive elements 13.
In the grinding tool 2 shown in
To improve the rotary characteristic of the grinding tool 2 the support body 1 can have balancing bores 22 and/or a step 23.
Particularly preferred embodiments of the method of producing a support body and the method of producing a grinding tool are illustrated by reference to the flow chart shown in
In the method 14 of producing a support body 1 in a first method step 15 the abrasive means-free composite material 6 comprising a plurality of mutually superposed layers 7 of a natural fibre material, that are connected together by plastic 8, preferably phenolic resin, is provided in the form of a plate.
In a second method step 16 a body is cut out of the plate with predetermined dimensions 17, 18, 19 (see
In a third method step 20 the body is re-worked, preferably by cutting machining and/or balancing.
That method 14 can be expanded to constitute a method 21 of producing a grinding tool 2 insofar as, in a further method step 28, an abrasive layer 5 having abrasive means 4, preferably superabrasive means, is arranged on a preferably circumferential support surface 3 of the support body 1, preferably by pressing and/or adhesive bonding thereon, preferably wherein the abrasive layer 5 is formed from a continuous abrasive ring or individual abrasive segments 13.
The third method step 20 can optionally also be carried out only after the abrasive layer 5 is arranged on the support surface 3 of the support body 1.
The support body 1 has an adaptor 34 for connecting the support body 1 or the grinding tool 2 formed therewith to a rotary drive which is adhesively secured to the bodies 32 and 33. The adaptor 34 can also be connected to more than two or only to one of the bodies 29, 30, 31, 32, 33, in particular in dependence on the stiffness to be achieved for the grinding tool 2.
The adaptor 34 can substantially comprise a metal and, as in the illustrated case, can be substantially hollow-cylindrical.
As in the illustrated case the adaptor 34 can have bores 37 for receiving fixing means, by way of which the adaptor 34 can be connected to a machine spindle.
The support body 1 has a central bore 11. The adaptor 34 is arranged in the central bore 11, with the adaptor 34 extending only over a part of the length 35 of the central bore 11. The central bore 11 has a funnel-shaped insertion opening 36.
A respective abrasive disc 5 is circumferentially arranged on the bodies 29 and 31.
For producing the support body 1 it is appropriate in a first method step 15 to provide a plate of a thickness 18 and in a second method step 16 to cut out of the plate with predetermined dimensions 17, 18, 19, three cylindrical or hollow-cylindrical bodies 30, 32 and 33, preferably by water jet cutting or by means of a band saw.
It is also appropriate in the course of the first method step 15 to provide a further plate of a differing thickness 18 and in the course of the second method step 16 to cut out of the plate two cylindrical or hollow cylindrical bodies 29 and 31, of predetermined dimensions 17, 18, 19, preferably by water jet cutting or by means of a band saw.
In the course of the second method step 16 the bodies 29, 30, 31, 32, 33 are connected together after they have been cut out of the plates at side surfaces 9, wherein axes of symmetry 12 of the bodies 29, 30, 31, 32, 33 are brought substantially into coincident relationship.
In a third method step 20 the bodies 29, 30, 31, 32, 33 are re-worked by cutting machining, in particular to impart predetermined dimensions to the central bore 11.
In a further method step the bodies 32, 33 are connected to the adaptor 34.
| Number | Date | Country | Kind |
|---|---|---|---|
| A 50455/2018 | Jun 2018 | AT | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/AT2019/060146 | Apr 2019 | US |
| Child | 17073842 | US |
