GRINDING MEANS AND METHOD FOR PRODUCING THE GRINDING MEANS

Abstract

The invention relates to a grinding means (1) for grinding workpieces, comprising: a carrier (2), e.g., a carrier disk or a carrier strip, abrasive grains (4) applied to the carrier (2), and a binder (6) applied to the carrier (2).

To enable material saving and energy efficient production nanoparticles (8) are held in the binder (6) which comprise a superparamagnetic, ferrimagnetic and/or ferromagnetic material which can be excited by means of one or more of the following measures: an alternating electric induction field, an alternating magnetic field microwave radiation, where the nanoparticles (8) can be heated by means of the excitation, and where the binder (6) thermally cures.

Furthermore, a method for producing is provided.

Claims

1-34. (canceled)

35. A grinding means for grinding workpieces, the grinding means comprising: a carrier, abrasive grains applied to the carrier, and at least one binder applied to the carrier, wherein nanoparticles are held in the binder, the nanoparticles comprise a superparamagnetic, ferromagnetic, and/or ferromagnetic material which can be excited by means of one or more of the following measures: an alternating electric induction field, an alternating magnetic field, microwave radiation, where the nanoparticles can be heated by means of the excitation, and whereby the binder thermally cures.

36. The grinding means of claim 35, wherein the binder is endogenously thermally cured, at least in part, by means of the heating of the nanoparticles, e.g., by means of a polarity switch of the nanoparticles.

37. The grinding means of claim 35, wherein the nanoparticles are made exclusively from a material which can be excited in an alternating electric or magnetic field for switching the polarity, whereby heat energy can be induced in the binder.

38. The grinding means of claim 35, wherein a concentration of the nanoparticles in the binder lies in the range from 1 to 30% by weight, e.g., 5 to 25 Ge % by weight, preferably 10 to 20% by weight, in relation to the total weight of the binder layer.

39. The grinding means of claim 38, wherein the binder includes a resin component and, in particular, further substances, e.g., fillers, where the concentration of the nanoparticles (8) relative to the resin component lies at 3 to 30% by weight, preferably 10 to 25% by weight.

40. The grinding means of claim 35, wherein at least one binder layer including the binder is applied to the carrier, and abrasive grains are held in the binder layer, in particular, in a lower binder layer applied directly on the carrier.

41. The grinding means of claim 35, wherein the binder including the nanoparticles is applied as a top layer on one or more lower layers, e.g., a lower layer including abrasive grains.

42. The grinding means of claim 35, wherein a plurality of binder layers are provided, e.g., one lower binder layer and one or more top layers, where the plurality of binder layers exhibit different concentrations of nanoparticles and/or different Curie temperatures of their nanoparticles.

43. The grinding means of claim 43, wherein one or more of the binder layers, in particular, a top layer, is formed without nanoparticles.

44. The grinding means of claim 35, wherein the magnetic material of the magnetic nanoparticles is one or more of the following materials: a metal oxide, in particular, Mn.sub.xZn.sub.1-xFe.sub.2O.sub.4, where x=0.2 to 0.6, e.g., 0.3 to 0.5 and an iron oxide, in particular, Fe.sub.3O.sub.4 and/or Fe.sub.2O.sub.3.

45. The grinding means of claim 35, wherein the magnetic nanoparticles have a primary particle size of 2 to 200 nm, in particular, 10 nm to 150 nm, in particular, 10 to 100 nm, preferably 10 to 30 nm.

46. The grinding means of claim 35, wherein the abrasive grains are shaped abrasive grains.

47. The grinding means of claim 46, wherein the abrasive grains are formed plane-parallel and with a triangular upper side and underside, and stand on an edge on the carrier, with their tips pointing upwards and/or pointing upwards at an angle of inclination.

48. The grinding means of claim 35, wherein the abrasive grains are formed flaky and/or plane-parallel.

49. The grinding means of claim 35, wherein the abrasive grains are aligned in parallel in such a manner that their tips are arranged at about the same level above the carrier.

50. The grinding means of claim 35, wherein the abrasive grains are made from one or more of the following materials: zirconia alumina, alpha-alumina, silicon carbide, diamond, and crushed cubic boron nitride (CBN).

51. The grinding means of claim 35, wherein the carrier is formed from a disc or a band, e.g., made from a textile fabric, paper, plastics.

52. The grinding means of claim 35, wherein a Curie temperature of the nanoparticles lies above a curing temperature of the binder, in particular, within a range of 20? C., preferably 10? C., above the curing temperature of the binder, to avoid overheating of the binder.

53. The grinding means of claim 35, wherein the binder is formed by mixing one or several resins and one or several hardening agents, where the resin is selected, e.g., from the following group: epoxy resins, acrylates, phenolic resins, and polyurethanes.

54. A method for producing a grinding means, wherein at least one binder layer and abrasive grains are applied onto a carrier, and a binder of the binder layer is cured, wherein nanoparticles are held in the binder, and, upon curing of the binder and/or after the curing of the binder, the nanoparticles are excited and/or alternatingly polarized thereby heating up, whereby the binder, by virtue of the heating of the nanoparticles, is cured, at least in part, and/or is post-cured after curing.

55. The method of claim 54, comprising at least the following steps: providing the carrier, the abrasive grains, the binder, and the nanoparticles, applying the abrasive grains and the binder onto the carrier, curing and/or post-curing of the binder, at least in part, by activating and/or exciting the nanoparticles thereby producing heat, where the binder, at least in part, is cured by the heat generated by the nanoparticles and/or post-cured.

56. The method of claim 55, wherein at first the binder including the nanoparticles is applied onto the carrier and subsequently the abrasive grains are introduced into the binder by scattering.

57. The method of claim 55, wherein the binder is applied with abrasive grains contained therein, e.g., by means of a brush coating method or brush application.

58. The method of claim 54, wherein the nanoparticles are introduced, e.g., mixed in, into the binder in advance.

59. The method of claim 54, wherein the binder is applied as a binder layer, e.g., as lower binder layer, for holding the abrasive grains, and/or as top layer and/or as second top layer.

60. The method of claim 54, wherein the binder is cured and/or post-cured, at least in part, by means of an alternating magnetic field, for activating the nanoparticles, in particular, with the characteristics: frequency 100 to 1.000 kHz and field strength 4.000 to 21.000 A/m.

61. The method of claim 54, wherein the binder is cured and/or post-cured, at least in part, by means of microwave radiation, e.g., in a range from 1 to 10 GHz.

62. The method of claim 54, wherein the binder is cured and/or post-cured, at least in part, by means of an electric induction field, e.g., in a range from 500 to 1500 kHz.

63. The method of claim 54, wherein the step of aligning the abrasive grains happens by means of one or more of the following aligning methods: electrostatic alignment in an applied constant electrostatic field (E) and/or alternating field, gravitatively by scattering.

64. The method of claim 54, wherein upon curing of the binder, additionally or exclusively, thermal energy is fed, e.g., in a furnace.

65. The method of claim 54, wherein the magnetic nanoparticles lose their magnetic properties upon reaching their Curie temperature thereby providing an upper limit for a process temperature, where the Curie temperature lies above the curing temperature of the binder.

66. The method of claim 65, wherein the Curie temperature lies below a critical upper temperature at which the grinding means can suffer damage.

67. The method of claim 54, wherein for curing the binding the amount of energy is regulated, where the regulated amount of energy at least covers the energy fed in by the excitation of the nanoparticles.

68. The method of claim 67, wherein for regulating the amount of energy a surface temperature, e.g., of the binder layer, is measured, and the amount of energy introduced is deduced from a process time and the measured surface temperature.

Description

[0117] The invention is further illustrated in the following by means of the accompanying drawings by example of certain embodiments. It is shown in:

[0118] FIG. 1 a grinding means according to an embodiment of the invention;

[0119] FIG. 2 an enlarged representation of the grinding means;

[0120] FIG. 3 a flow chart of the method according to the invention.

[0121] A grinding means 1 comprises a carrier 2, e.g., a carrier strip or a carrier disk, e.g., made from a fabric material, technical paper, in particular, fiber, or plastic material, further a binder layer 3 applied onto the carrier 2, abrasive grains 4 and, preferably, a top layer 5 partially drawn in FIG. 1. The abrasive grains 4 are, in particular, ceramic abrasive grains, e.g., on the basis of ?-alumina. The abrasive grains 4 may be, in particular, shaped abrasive grains 4, e.g., as shown, with a triangular, in particular, triangular and plan-parallel shape. Thus, the abrasive grains 4 are aligned on the carrier 2 and fixed in their position and orientation by the binder layer 3.

[0122] The binder layer 3 comprises a thermally curing binder 6, in particular, epoxy resin, e.g., a bisphenol A resin, e.g., Hexion Epikote Resin 828, Ipox ER 1022, and/or a bisphenol F resin, e.g.,: Hexion Epikote Resin 862 or Ipox 1054 (Bisphenol A/F Resin).

[0123] In the thermally curing binder 6 magnetic nanoparticles 8 are evenly distributed, e.g., made of Mn.sub.xZn.sub.1-xFe.sub.2O.sub.4, e.g., where x=0.1 to 0.5, preferably 0.2 to 0.5. Further materials of the magnetic nanoparticles 8 may also be made even without manganese/zinc, e.g., on the basis of iron oxide, e.g., as Fe.sub.3O.sub.4 or alternatively as Fe.sub.2O.sub.3. Thus, the abrasive grains 4 are held in the binder layer 3 by the regions which are their lower regions in the direction of the orientation, i.e., upwards in the Figures, their respective underside 4a being in contact with the carrier 2, their tips 4b projecting upwards. Their orientation may be parallel, as shown in the Figures; in principle, however, they may be aligned in a manner with their upper sides and undersides non-parallel with one another. Furthermore, the abrasive grains 4 may also be arranged inclined in relation to the vertical, in particular, uniformly tilted in a preferred direction to facilitate abrasive operation in this direction.

[0124] FIG. 2 shows an embodiment with binder layer 3;

[0125] FIG. 4 shows a corresponding embodiment with binder layer 3 and additional top layer 5, whereby the top layer 5 in turn includes a binder 6 and nanoparticles 8, and

[0126] FIG. 5 shows an embodiment with binder layer 3, additional first top layer 5 and a second top layer 7, the first top layer 5 and the second top layer 7 each in turn including a binder 6 and nanoparticles 8.

[0127] In the three layers 3, 5, 7 different or equal binders 6 may be provided. Further, in the three layers 3, 5, 7 equal or different concentrations of nanoparticles 8 may be provided, where, e.g., in one of the layers 3, 5, 7 a concentration of zero may be provided, and/or in the three layers 3, 5, 7 nanoparticles 8 with equal or different Curie temperatures T8 may be provided.

[0128] In FIG. 4, by way of example, the concentration of nanoparticles 8 in the top layer 5 is lower than in the binder layer 3. In FIG. 5, by way of example, in the second top layer a concentration of the nanoparticles 8 or zero is provided.

[0129] The production of the grinding means 1 happens according to the method shown in FIG. 3:

[0130] Step ST1 of providing or producing the starting materials: The nanoparticles 8 may be produced, e.g., by means of a modified hydrothermal method which is known as such, e.g., from Chaudhary, Ramanujan, Steele, Applied Materials today-Magnetocuring of temperature failsafe epoxy adhesives, 2020.

[0131] As binder 6, in particular, epoxy resins with DICY (dicyandiamide) can be utilized.

[0132] According to Step ST2 the nanoparticles 8 are introduced or mixed in respectively into the binder 6 to attain an even distribution.

[0133] In Step ST3 the binder layer 3 is applied onto the carrier 2. To that end, the binder layer 3 may be applied, e.g., using a squeegee, e.g., knife-over-cylinder or knife-over-air, or roll coating, or even by spraying, e.g., compressed air spraying or even airless. The applied amount may be, e.g., 20 to 300 g/m.sup.2, depending on the grain size of the abrasive grains 4 to be introduced later, or, in the case of a cream mass, even 200 to 1.600 g/m.sup.2, depending on the grain size.

[0134] In Step ST4 the abrasive grains 4 are applied, i.e., grain scattering. The abrasive grains 4 may be applied gravimetrically and/or electrostatically, i.e., as electrostatic scattering. In the case of electrostatic scattering and electrostatic alignment an constant or alternating electric field E is applied.

[0135] According to Step ST5 the abrasive grains 4 are aligned. Hereby, the Steps ST4 and ST5 may be carried out in a combined fashion, i.e., the abrasive grains 4 are scattered in an aligned manner.

[0136] Upon aligning the abrasive grains 4 in Step ST5, advantageously, the positioning of the abrasive grains 4 on an edge as underside 4a is attained, as shown in FIGS. 1, 2. Thus, in particular in the case of the shaped abrasive grains 4 shown here, for one thing, a firm support on the edges, and, for another, a consistent length is attained so that the tips 4b are arranged or extend respectively at about equal distances from the carrier 2 thereby achieving simultaneous abrasive action when processing workpieces.

[0137] In Step ST6 the binder 6 is cured, thereby forming the solid binder layer 3. The curing of the binder 6 for forming the binder layer 3 happens by applying an alternating magnetic field 10, which principally may initially have any direction or orientation respectively. Thus, the direction or orientation respectively of the magnetic field may even change.

[0138] By virtue of the alternating magnetic field 10 the nanoparticles 8 are heated directly thereby creating heat, whereby, therefore, the entire binder layer 3 ism heat from the inside. This cures the binder 6 so that the solid binder layer 3 is formed.

[0139] The alternating magnetic field 10 may be formed, in particular, using a tunnel magnetizer. The frequency may be, e.g., 100 to 1.000 kHz. The field strength may be, e.g., 4.000 to 21.000 A/m.

[0140] Upon magnetic curing the process temperature T reached may preferably by determined by the Curie temperature T8 of the magnetic nanoparticles 8. As soon as the temperature T exceeds the Curie temperature T8 the magnetic nanoparticles 8 become non-magnetic or, respectively, will no longer be ferromagnetic, ferrimagnetic or superparamagnetic, in particular, the nanoparticles 8 become paramagnetic, and, therefore, will no longer continue to heat the binder or at least not to a relevant extent.

[0141] Further, however, even when using the alternating magnetic field process can be controlled by means of regulating the amount of energy so that possibly the Curie temperature T8 may be no longer applicable or not to a relevant extent.

[0142] Hereby, according to an embodiment the regulation the amount of energy may be carried out by measuring a surface temperature, e.g., that of the binder layer, e.g., in that the currently introduced energy is deduced from the surface temperature, and the introduced amount of energy is deduced from a process time and the measured surface temperature.

[0143] In order to attain a sufficient dwell time an array of multiple magnetic coils may be provided.

[0144] According to an embodiment alternative hereto the curing of the binder layer 3 happens not by means of an alternating magnetic field but, rather, by means of microwave radiation 11, e.g., in a frequency range from 1 to 5 GHZ, e.g., at 2.4 GHZ. By virtue of the microwave radiation 11, which, thereby, constitutes electromagnetic radiation in this frequency range, it is possible, in particular, to attain an induced excitation and thereby polarity shift of the nanoparticles 8 which, thereby, in turn leads to a heating of the nanoparticles 8 themselves as well as of the binder 6.

[0145] When using microwave radiation 11 power can be controlled process-based, and/or for a controlling function the temperature of the binder 6 may be measured, e.g., by means of an infrared sensor.

[0146] Subsequently, in a Step ST7 according to FIG. 4, a top layer 5 may be applied so that subsequently the grinding means 1 is finished. Alternatively, or possible in addition, this top layer 5 may be equipped with nanoparticles 8. In this case the endogenous curing happens in a manner equivalent as described above with respect to the previous layers.

[0147] Furthermore, in Step ST7 according to FIG. 5, even a plurality of top layers, e.g., two top layers 5, 7, may be applied which, e.g., may also exhibit different concentrations of nanoparticles 8 so that they, e.g., are heated differently and/or successively. Correspondingly, the plurality of top layers 5, 7 may even exhibit different nanoparticles 8 with different Curie temperatures T8. Thus, in this case, in FIG. 1, multiple top layers 5, 7 are then applied instead of the top layer 5 shown here.

[0148] In the case of the variant involving grain scattering by gravitation, the abrasive grains 4 are scattered from above into the carrier 2 with the binder layer 3. Thus, the abrasive grain 4 will align rather arbitrarily. Such embodiments are relevant for grain agglomerates or even stabilizing grain scattering, where part of the abrasive grains 4 serves as stabilizing grains for the further abrasive grains 4.

[0149] Hereby, e.g., in addition, smaller abrasive grain particles may be introduced in-between the abrasive grains 4 as so-called gravel which, in particular, supports the shaped abrasive grains 4.

[0150] In the alternative or in addition to a magnetic curing of the binder layer 3 holding the abrasive grains 4, even another binder layer, e.g., a top layer 5, 7 or, respectively, top layers may be magnetic cured. Thus, it is possible, to selectively cure one or more layers 3, 5, 7, e.g., even with different Curie temperatures T8, the process-related regulation of the energy amount, and/or even with different concentrations of the nanoparticles 8.

LIST OF REFERENCE NUMERALS

[0151] 1 grinding means [0152] 2 carrier, e.g., carrier strip, carrier belt or carrier disk [0153] 3 binder layer [0154] 4 abrasive grains [0155] 5 top layer, first top layer [0156] 6 binder, e.g., epoxy resin, the binder layer 3 [0157] 7 second top layer [0158] 8 magnetic nanoparticles [0159] 10 variable magnetic field, alternating magnetic field [0160] 11 microwave radiation [0161] 16 alternating electric induction field [0162] E constant or alternating electric field for alignment [0163] T temperature [0164] T8 Curie temperature [0165] ST1 providing starting materials [0166] ST2 introducing or mixing in respectively the nanoparticles 8 into the adhesive material 6 [0167] ST3 applying the binder layer 3 [0168] ST4 grain scattering [0169] ST5 aligning the abrasive grains 4 [0170] ST6 curing the binder layer 3 [0171] ST7 applying the top layer 5 and/or the plurality of top layers 5, 7.