EP0763403B1 - Grinding tool and method and apparatus for manufacturing the same - Google Patents

Description

The invention relates to a grinding tool the preamble of claim 1. it also relates to a method for producing the grinding tool according to the invention and to a device for producing the grinding tool according to the invention the preamble of claim 10.

A grinding tool with the extremely hard diamond abrasives or cubic-crystalline boron nitride usually settles from a rotationally symmetrical body and a grinding surface together. The basic body, the static and dynamic strength of the grinding wheel, can for example be made of aluminum, synthetic resin Fillers, steel or ceramic exist. The grinding surface is made up of one grit and one Binding. The abrasive grit consists, for example, of diamond or boron nitride crystals based on their grain size be distinguished. Allow coarse grain sizes high chip removal rate, low wear and cause great roughness. Fine grain sizes allow a small roughness, result in a larger one Wear and leave only a smaller chip removal volume to. There are different types of binding, such as for example synthetic resin bonds from phenolic and polyimide resins, sintered metal bonds, for example bronze bonds, Steel bonds, ceramic bonds or also Carbide bonds. Within the series of binding types are the individual bonds by different compositions the basic components, e.g. Tin and Copper in bronzes, as well as by different fillers, such as. Silicon carbide or corundum in phenolic resin, and their proportionate amounts to the required grinding behavior customized. Metal bonds are generally more wear-resistant than synthetic resin bonds, usually grind harder and slower and generate more grinding heat than resin-bonded grinding wheels. There are also galvanic ones Bindings known.

In addition to ring or cylindrical grinding surfaces often also grinding wheels with profiled abrasive coating used. Depending on the design of the abrasive coating, this has in the axial direction of Seen basic body or a different extent in the feed direction. The profile or its dimension largely depends on the profile of the material to be ground Workpiece. It turns out that certain areas of the abrasive coating more subject to wear than others. Exceptions to this are workpieces, which have a preformed profile, which by a in the feed direction Grinding wheel is marked uniform oversize. Appropriate preprocessing However, the workpiece is complex and therefore only rarely in practice encountered. The stability of such grinding wheels naturally depends on it how long the most stressed areas of the abrasive coating have been used can be.

From US-A-4 131 436 a profile grinding wheel is known according to the preamble of claim 1, which has a diamond grinding surface with metal binding. It is used to grind glasses and plastic lenses. The abrasive coating is designed so that the concentration of the Diamond grit in the center of the grinding wheel is larger than towards the front. This can improve the stability of the grinding wheel.

The invention is also based on the object of a grinding tool with a To create abrasive coating, its service life with uneven load in individual Areas of the abrasive coating can be increased by even wear can.

This object is achieved by the features of patent claim 1. claim 8 defines a method for producing the tool according to the invention. Anspunch 10 defines a device for producing the tool according to the invention.

As already mentioned, the concentration of diamond grains in the grinding wheel surface is known to adapt to the different grinding loads on a workpiece.

In the grinding tool according to the invention, further physical properties and / or the volume fractions of the covering components in the axial direction chosen differently so that they are different in the axial direction Grinding load are adjusted. The more stressed areas of the abrasive coating have different compositions and nature of their proportions than less contaminated zones. The composition of the covering components or the distribution the Kömungs size is therefore differentially adapted to the load in the axial direction. It is essential that there are no clear boundaries between the zones or There are stages in terms of quality, but a continuous transition from Z. B. the concentration of the abrasive grain on another. In one embodiment the nature of the invention could change continuously if also the load changes continuously, the change in the course of Change in load is adjusted. However, zones of one can also be used certain nature be present, but what for the concentration of Abrasive grit is known from US-A-4 131 436, the transitions between the Zones can be "flowing" so that no abrupt change between the Zones takes place.

In the invention, i.a. based on the known knowledge that the Wear of a unit area of an abrasive coating depends largely on how as long as it is in engagement with the workpiece or which volume fraction of the workpiece he has to grind. For grinding tools with a profiled abrasive coating the area of the abrasive coating which has been in engagement with the workpiece the longest and has to remove the largest volume fraction, which is radial or in the feed direction on farthest outside.

In the solution according to claim 1, the stability or the chip removal rate influenced by the fact that a different grain size is provided in the axial direction is. Coarse grain sizes result in a high volume of chips, low Wear and great roughness. Finer grain sizes result in small roughness, greater wear and smaller chip removal rates. According to the invention is therefore the Grain size of the abrasive coating was chosen differently in the axial direction, for example in the area where the grinding wheel has the largest volume has to grind on the workpiece, have a larger grain size, the Grain size decreases in the direction of lower loads in the axial direction. Because of The grain size cannot be arbitrarily given a usually predetermined maximum roughness be chosen high.

For the attainable chip removal volume, the nature of the binding is also of Importance. Synthetic resin bonds, for example with phenolic or polyimide resins, are considered soft, fast and cool grinding, result in only low grinding forces and leave a wide scope for adaptation. Close sintered bronze bonds in the direction of greater bond hardness to the synthetic resin bonds. Even harder act steel and hard metal bonds. Grind metal-bonded grinding wheels usually harder, slower and generate more grinding heat than synthetic resin-bonded Grinding wheels. Ceramic bonds have the ability to produce large amounts of material and high wear resistance. They enable free grinding through porosity and self-sharpening as well as good coolant transport into the contact zone. In the embodiment according to claim 2, the composition of the binding components different in the axial direction.

Within the individual types of binding there is further adjustment to the respective one Grinding task further variants.

It is known to fill materials or additives of the generic type add lubricating, for example graphite. This will make the Grinding forces and temperatures reduced; however, increases in most Cases of wear. It is also known to be wear-reducing, essentially wear-reducing additives, for example cobalt. wear-reducing Additives require a higher grinding force, but lead to one Reduction of wear. For example, in the zone of the largest Load increases the wear resistance by such additives according to the invention, it is in turn possible to approximate one over the entire profile of the grinding wheel to get even wear with sufficient chip removal volume. Concentration in the configurations according to patent claim 3 or 4 the fillers with a lubricating effect or those that influence wear Additions differ in the axial direction.

According to an embodiment of a grinding tool according to the invention, the grain concentration is different in the axial direction.

The concentration information indicates the volume fraction of diamond or boron nitride in the abrasive coating. Concentration is one of the most important features of a diamond or boron nitride grinding wheel. It influences the grinding forces, grinding temperatures, roughness and wheel life to a large extent. The concentration must be matched to the other parameters of the grinding tool, the grinding process and the operating conditions. The concentration is usually given in carats per cm ³ . In order to increase the service life of the grinding wheel, the concentration in the entire grinding surface could be increased proportionally. However, this leads to the grinding forces and grinding temperatures also increasing, which under certain circumstances leads to dimensional and shape deviations and to the structural influence of the surface. One embodiment of the invention therefore provides that the concentration in such covering zones is increased where there is increased wear, whereas, in contrast, in covering zones with lower loads the concentration may even be reduced so that the grinding forces and grinding temperatures do not increase beyond the permissible level ,

By a corresponding distribution of the concentration in the axial direction in Dependence on the radial distance of the surface from the disc axis can therefore over the entire measurement of the section to be ground Uniform wear for the grinding surface can be achieved. This results in a significantly longer service life for the grinding tool as a whole receive; ideally, the entire grinding surface can be used up without reworking become.

In one embodiment of the invention it is provided that the volume fraction of the Abrasive grit and / or the lubricating filler and / or the wear-reducing Addition and / or the composition of the basic components, the binding and / or the grit size of the grinding grit depends on the Size of the radius changed so that the grinding wheel at the largest radius has the greatest wear resistance. The change can be done in stages or continuously take place, however, between stages (or zones) a gradual Transition takes place. It is preferably to the profile of the abrasive coating or Adapted workpiece.

If the cutting surface is linear, the change can also be linear respectively. If, however, there is a profile with a different course, it can, for example have a progressive or a degressive course.

It is possible to manufacture a grinding wheel by making a ring from the Abrasive coating is produced. In a press mold with an annular mold space a mixture of abrasive grain and powdered binder and possibly filled with lubricating and / or wear-reducing substances and then pressed into a ring. The inner boundary of the mold space can be determined by the Basic body. After the ring-shaped blank has been completed, it must be be processed accordingly if the abrasive coating has a profile shall be. For the production of the grinding wheel according to the invention described procedures made use of. This happens because during the filling of the mold space the grain size of the abrasive grain and if necessary the volume fraction of the abrasive grain, the proportion of lubricating and / or wear-changing Additions and still given the composition of the basic components of the binder is changed depending on how the radial extension of the Changes the grinding profile over the fill level. During the pressing process becomes the height or diameter of the material significantly reduced in the mold space. The relative distribution however, the concentration does not change.

The molds for making the described Abrasive pads usually have a first molded part, the limited a cylindrical mold space. In the mold cavity the base body is inserted, which with the wall of the Cavity forms the annular mold space. A second The molded part is ring-shaped and is used to press the filled Surfacing material. The filling of the covering material happens in such a way that the shape is rotated, whereby the annular mold space on a stationary Feeding device for the topping mixture, in particular binder and abrasive grain is passed. A Dosing device doses the mixture into the mold space, whereby the amount of the mixture depending on the time or also e.g. of the turns of the shape is chosen. To manufacture the grinding wheel according to the invention for example at least one further stationary feed device provided with its own dosing device. The feeders are made with a mixture Abrasive grit, binders and fillers supplies that in a given but different one Mixing ratio or in different, the removal behavior influencing nature is present. To e.g. the values for the lower and the upper concentration for It is therefore necessary to maintain the abrasive grit that the feeder providing the low concentration is supplied with a mixing ratio that the lowest concentration value for the abrasive grain equivalent. The other variable feeder Dosage is supplied with a mixture that adds to the lowest concentration value the highest concentration level equivalent. By an appropriate dosage of Mixtures such as those from the feeders into the mold space can be entered depending on the Time between the given concentration values each set any. However, it is also conceivable to do more than to provide two feeders, each with one Covering mix can be supplied that a different Have a concentration of abrasive grit. Ensprechendes applies to the attitude of others, the grinding and Parameters determining wear behavior: grain size, Binder composition and proportions of lubricating and / or wear-changing additives.

The invention thus provides a grinding tool that is optimally adapted to the respective load case, by the coating components influencing the wear behavior over the grinding wheel width accordingly can be varied. For example, also in the edge area "Edge reinforcement" can be made to the increased Counteracting stress in this area.

An improvement is already achieved in the invention, if a parameter influencing the grinding behavior according to the profile of the grinding wheel over their Width is changed accordingly. It is understood that a change also with regard to further or part of the Parameters can take place additionally or alternatively. in this connection is certainly to be considered that for example a coordination between grain size and binder hardness he follows. The use of an inactive filler, for example pore builder, is not least also adapt to the workpiece material.

Fig. 1

zeigt schematisch den Schnitt durch ein Schleifwerkzeug nach der Erfindung.

Fig. 2

zeigt ein Diagramm für die Verteilung der Schleifkörnung in dem Schleifbelag des Werkzeugs nach Fig. 1.

Fig. 3

zeigt schematisch eine Vorrichtung zur Herstellung eines Schleifbelags für ein Werkzeug nach Fig. 1.

Fig. 4

zeigt schematisch eine Draufsicht auf den Formraum der Vorrichtung nach Fig. 3.

The invention is explained in more detail below with reference to drawings.

Fig. 1

shows schematically the section through a grinding tool according to the invention.

Fig. 2

1 shows a diagram for the distribution of the abrasive grain in the abrasive coating of the tool according to FIG. 1.

Fig. 3

shows schematically an apparatus for producing an abrasive coating for a tool according to FIG. 1.

Fig. 4

shows schematically a top view of the mold space of the device according to FIG. 3.

1 shows a grinding wheel 10 with a base body 12 made of a suitable material, such as steel, Aluminum or plastic, for example a suitable one Thermoset. On the base body 12 is a cross section triangular abrasive coating 14 applied. The grinding surface 14 is constructed in a conventional manner. It exists from boron nitride or diamond crystals or grains in a desired size. This depends on the application parameters but also across the width of the disc 10 varied. The abrasive grains are in a binder bound which is a metal, e.g. Bronze, can be or a suitable plastic material, for example polyimide. Such a grinding wheel can be used, for example to grind hollow glass, for example Form grooves, grooves or the like.

In Fig. 1, the abrasive grains in the covering 14 are indicated by points. It can be seen that the distribution of the grains is different in the axial direction. It is provided on the outermost edge 16 at maximum radius with a maximum concentration that decreases in the direction of the facing sides. With a triangular profile, as shown in FIG. 1, the decrease in concentration can be linear. This is shown in Fig. 2. The coating side B _s is plotted on the ordinate and the concentration in carats per cm ³ on the abscissa. It can be seen that the concentration in the axially central region is approximately 4.4 ct / cm ³ , while it is approximately 0.3 ct / cm ³ directly next to the facing sides. The distribution therefore corresponds to a straight line towards the two facing sides. With a correspondingly differently shaped profile, the course of the concentration in the axial direction is also different. It is selected in any case so that the wear behavior of the covering 14 is adapted to the oversize of the workpiece to be ground. The wear is dependent on the engagement time of the different covering sections 14 in relation to the total engagement time or the volume portion to be removed from the total volume.

The teaching described is independent of the grain size and which binder is used. There, as described above, the grain size and also that Binder has an influence on the grinding and wear behavior of the abrasive coating can vary this parameter, for example by different Binding composition, also an adaptation to the 10 different across the width of the grinding wheel Load can be achieved. The same applies to the choice grinding-inactive additives such as pore formers, lubricants or other wear-changing additives. According to the invention the grit size of the abrasive grit is continuously varied in the axial direction.

It goes without saying that they are also suitable for multi-profile panes applies, for example, where two or more ring-shaped Abrasive pads corresponding to that of FIG. 1 are provided are.

Fig. 3 shows very schematically a device for Production of an abrasive coating. A first molded part 20 has a table-shaped section 22 and an annular one Section 24, which has a cylindrical cavity Limit 26. By using a blank of a basic body 28 of cylindrical shape becomes a ring cylindrical Forming space 30 formed. He is with a mixture 32 from abrasive grain, powdered binder and others Additives, e.g. grinding-inactive fillers, filled. The filling of the mixture 32 takes place during the Rotation of the molded part 20, as indicated by the arrow 32. A second molded part 34 has a cylindrical ring Molding section 36 that fits into the molding space 30 can be introduced. With its help, the mixture 32 in Molding space 30 in a known manner to a ring of about pressed together a third of the original height and heated. This creates a cylindrical grinding surface obtained, which is fixedly connected to the base body 28. The base body 28 is then set to the Width of the abrasive covering worked off. Also receives the grinding surface has the desired profile, for example the one shown in Fig. 1.

FIG. 4 shows the molding space 30 according to FIG. 3, arrow 38 indicating that the molding space 30 is set in rotation. A first schematically illustrated feed device 40 is located above the mold space 30. A second feed device 42 is located diametrically opposite the device 40, also above the mold space 30. The feed devices 40 and 42 are fed a mixture of abrasive grain and powdered binder in the desired mixing ratio, with the For example, the concentration of the abrasive grain of the mixture supplied to the device 40 is 0.3 ct / cm ³ , while the concentration of the abrasive grain of the mixture supplied to the device 42 is 4.1 ct / cm ³ or more. The feed devices 40, 42 are assigned metering devices 44 and 46, respectively, which are controlled by a processor 48. The processor 48 controls, via the metering devices 44, 46, the quantity which is supplied by the feed devices 40, 42 per unit of time. This allows the concentration of the abrasive grain to be varied as desired over the height of the material (see FIG. 3). It can therefore have the course shown in FIGS. 1 and 2. This means that there is a minimum concentration of the abrasive grain in the bottom and top layers, while it is maximum in the middle.

Claims (10)

1. A grinding tool for the grinding of profiles, said tool comprising a basic body (12) symmetrically with respect to rotation, and an annular grinding layer (14) deposited on the said basic body, said grinding layer being composed of grinding grains, bonding agent and occasionally filler and/or an additive influencing the grinding performance, the grinding layer being loaded irregularly in axial direction, e.g. in that the outer radius or the extension in feeding direction perpendicular to the axis of the basic body is different, the physical properties and/or the volume contents of the components of the grinding layer changing differentially in the direction of said axis of said grinding layer such that they are adapted to the grinding load in axial direction, characterized in that the size of the grains is different in axial direction and the change is continuous.
2. The grinding tool according to claim 1, wherein the composition of the components of the bonding agent is different in axial direction and in that the change of the composition in continuous.
3. The grinding tool of claim 1 or 2, wherein the concentration of the filler materials having a lubricating effect is different in axial direction and the change of the effect is continuous.
4. The grinding tool of one of the claims 1 to 3, wherein the concentration of additives influencing the wear is different in axial direction and the change is continuous.
5. The grinding tool of one of the claims 1 to 4, wherein the concentration of the abrasive grains in axial direction is different.
6. The grinding tool of one of the claims 1 to 5, wherein the volume contents of the grinding grains and/or of the lubricating filler and/or of wear-changing additives and/or the size of the grinding grains has a maximum at the largest radius of the grinding layer and changes in dependence on the amount of the radius such that it is smaller with smaller radius.
7. The grinding tool of one of the claims 1 to 6, wherein the change of the volume contents of the grinding grains and/or of the lubricating filler and/or of the wear-changing additive and/or of the composition of the components of the bonding agent and/or of the grain size is adapted to the profile of the grinding layer.
8. A method for the manufacture of a grinding tool of one of the claims 1 to 7, wherein a mixture (32) of grinding grains, powder-like bonding agent and occasionally fillers and/or wear-changing additives is filled into an annular molding cavity (26), the mixture thereafter is subject to a press molding and heating and wherein the grinding profile thereafter is made by machining, and wherein during the filling of the molding cavity the volume contents of the layer components and/or the layer constituents and continuously changed in view of their physical properties in dependence on the load on the grinding layer in axial direction.
9. The method of claim 8, wherein the volume contents of the grinding grains and/or the lubricating fillers and/or the wear-changing additives and/or the composition of the components of the bonding agent and/or the grain sizes of the grinding layer are changed continuously in dependence on the radial extension of the grinding profile relative to the filling height.
10. An apparatus to manufacture a grinding tool of one of the claims 1 to 7, wherein a mold has a first molding portion (20) forming a cylindrical cavity (26), a cylindrical basic body (28) being placed within said cavity, said basic body forming an annular cavity (30) with the wall of the first cavity and open to the top, a second annular molding portion (34) adapted to be introduced in the annular cavity (30) under pressure, supply means (40, 42) for the supply of a mixture of grinding grains and powder-like bonding agent (32), and proportioning means (44, 46) for the control of the supply of the mixture to said cavity (30), with the first molding part (20) being rotatably (32) driven about a vertical axis and the supply means (40, 42) being stationarily located, characterized in that at least a second stationary supply means (40, 42) are provided associated with it's own proportioning means (44, 46), with the supply means (40, 42) supplying said mixture of grinding grains and bonding agents and/or lubricating filler and/or wear-reducing additives in a given proportion of mixture which changes with the height of the filling within said cavity.

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