METHODS OF USING AND MAKING SAME

Inventors: Srinivasan RAMANATH; Joseph E. SMITH, Jr.; Samuel Lyman

MUNSON, IV.

RELATED APPLICATION

This application claims the benefit of priority under PCT Article 8 of U.S. Provisional Patent Application No. 63/429,610 filed December 2, 2022, the contents of which are incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

The present invention, in some embodiments thereof, relates to the metalworking industry and, more particularly, but not exclusively, to an abrasive structure for grinding tools.

BACKGROUND OF THE INVENTION

Grinding of high speed steel such as M2 steel is typically done with a multilayer vitrified (or glass-bonded) wheel or a single layer electroplated CBN wheel, where the abrasives are held in place mechanically. While the vitrified wheel lasts for a long time due to the presence of several layers, the electroplated wheel could grind at higher removal rates due to its open structure.

Single layer brazed products have not been very successful in the past for a variety of reasons, including lack of precision in wheel roundness, grit covered with braze, non-uniformity of the abrasive grit distribution, loading of the wheel surface with grinding debris and more. Loading of the wheel face with grinding debris could be due to dull abrasives, lack of adequate space between abrasives or reactions between the grits and the work material. Most single layer brazed products consist of one layer of abrasives that are chemically bonded to a steel or carbide core with a braze. SUMMARY OF THE INVENTION

According to an aspect of some embodiments of the present invention there is provided a functionally graded abrasive structure with controlled variation in abrasive content in one or more directions ranging from 5% to 60% by volume, together with variation in porosity content ranging from 5% to 50% by volume, within the structure. The variation in abrasive content is achieved through packing efficiencies, mixture of different nominal size abrasives or through the use of fillers.

In an embodiment of the invention, the abrasive type could comprise of superabrasives such as diamond or cubic boron nitride or conventional abrasives such as aluminum oxide, silicon carbide, boron carbide, tungsten carbide, or zirconium oxide.

In an embodiment of the invention, the abrasive type could be a mixture of two different abrasive types.

In an embodiment of the invention, the abrasive size could vary from 1200 microns down to 5 microns.

In an embodiment of the invention, a filler when present could comprise of an oxide, nitride, boride, oxynitride, silicide or carbide.

In an embodiment of the invention, the bond holding the structure could be a metal or metal alloy.

In an embodiment of the invention, the bond holding the structure could be a glass or glass ceramic.

In an embodiment of the invention, the abrasive comprises of a finite number of layers such as 10 layers, optionally 5 layers, or optionally 2 layers.

Unless otherwise defined, all technical and/or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the invention, exemplary methods and/or materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be necessarily limiting. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS)

Some embodiments of the invention are herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example, are not necessarily to scale and are for purposes of illustrative discussion of embodiments of the invention. In this regard, the description taken with the drawings makes apparent to those skilled in the art how embodiments of the invention may be practiced.

In the drawings:

FIG. 1 is a schematic illustration of a prior art abrasive structure;

FIGS. 2-8 are schematic illustrations of functionally graded abrasive structures, in accordance with exemplary embodiments of the invention; and

FIG. 9 is a graph showing the spindle power as a function of parts ground, in accordance with experimental results acquired through use of the invention.

DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

The present invention, in some embodiments thereof, relates to the metalworking industry and, more particularly, but not exclusively, to an abrasive structure for grinding tools.

Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not necessarily limited in its application to the details of construction and the arrangement of the components and/or methods set forth in the following description and/or illustrated in the drawings and/or the Examples. The invention is capable of other embodiments or of being practiced or carried out in various ways.

The new invention addresses many of the problems in the metalworking field with respect to grinding tools and actually produces better results than could be expected. In an embodiment of the invention, after abrasives of one size are sprinkled onto a braze, abrasives of a smaller size are sprinkled onto the same surface to fill the gaps, followed by additional braze. Additionally in some embodiments, a “second” layer of abrasives of the first size is sprinkled above that (actually it becomes the “third” layer if you count the smaller abrasives as well). The tackiness of the sprayed braze keeps this new layer in place. After furnacing, there is a dense and porous layer of abrasives. When used as a grinding wheel, the dense layer is more durable and draws higher grinding forces and power.

In an embodiment of the invention, there is more than one layer of abrasives in the product of new invention. Additionally, alternatively and/or optionally, the abrasive concentration or amount varies with the layers which is termed by the inventors as a “functionally graded” abrasive structure. FIGS. 2-8 are schematic illustrations of functionally graded abrasive structures, in accordance with exemplary embodiments of the invention

In some embodiments of the invention, a corrosion resistant steel or tungsten carbide core or blank is coated with bronze- titanium hydride braze mixed with an organic binder for adhesion. A layer of CBN (large grits, size A) is sprinkled on the surface of the steel, in an exemplary embodiment of the invention. The spaces in between the CBN are filled with grits of a smaller size (smaller size B), in some embodiments of the invention, which optionally improves the bonding system/action. More braze is added to the grits to make it tacky, in some embodiments of the invention. Another layer of CBN grits of size A is optionally/additionally sprinkled on the grits at a desired spacing. With more braze added as needed, the composite is dried to remove the solvent in the binder and cure it at the same time, in some embodiments of the invention. It is then placed in a vacuum furnace at a temperature above the liquidus temperature of the braze to fully melt and bond to the abrasive grits. The product is cooled, inspected, marked and shipped for evaluation.

In some embodiments, the abrasive structure comprises “large” and “small” sized grits (e.g. FIGS. 2, 4, 6). In some embodiments, the abrasive structure comprises “large”, “medium” and “small” sized grits (e.g. FIG. 3, 5, 7). In some embodiments, the abrasive surface comprises “large” grits (e.g. FIG. 8), “medium” grits (not shown) or “small” grits (not shown). In some embodiments, the abrasive structure comprises “medium” and “small” sized or “medium” and “large” grits (not shown). As can be seen in the various FIGS., the grits can be arranged in any orientation with the understanding that orientation can be random or it can be intentional, or a combination of both.

It should also be understood that while in some embodiments, smaller grits are used to fill interstitial spaces between larger grits or grit layers, and sometimes this happens during “stacking” to automatically create layers, the smaller grits can also comprise their own layer or layers, depending on the desired performance of the abrasive structure. In some embodiments of the invention, “small” grits are used to intentionally space apart larger sized grits, to create stronger bonding within the abrasive structure. In a similar vein, the number of layers and/or the materials which are used for each layer is customizable to tailor the abrasive structure for a particular and intended purpose. The material of each grit is also customizable, in some embodiments of the invention. For example, a grit material could be chosen that matches to the underlying grinding wheel surface or material.

Of particular note, the inventors have observed that the spindle power actually drops with more parts ground, see the graph of FIG. 9. This is a surprising and unexpected result, which actually provides a superior performance than any grinding wheel currently available to the industry. Additionally, an abrasive structure is created that is intentionally different in densities to create a functionally graded abrasive structure.

In some embodiments of the invention, the number of layers is limited to a small finite number (e.g. a few layers or less), else it would approach a metal bonded structure with many layers.

In some embodiments of the invention, the layering can be in any axis.

In some embodiments of the invention, individual grit shapes are also customized. For example, they can be square, rectangular, irregular, round, ovoid, flat, triangular, angular, and the like.

In some embodiments of the invention, each layer wears uniformly and/or the layers wear uniformly with respect to each other.

In some embodiments of the invention, functionally graded and/or multi- sized particle layering enables the abrasive structure to fracture or exhibit friability. Optionally, the friable nature of the abrasive structure is customizable by selecting grit sizes, layers, materials, amounts of braze and/or adhesive.

Various embodiments and aspects of the present invention as delineated hereinabove and as claimed in the claims section below find experimental support in the following example. EXAMPLE

Reference is now made to the following example, which together with the above descriptions illustrate some embodiments of the invention in a non-limiting fashion.

The grinding wheel was used to grind flutes in high-speed steel (M2 tool steel) that had been hardened to 60 to 65 HRC. Such a material is considered difficult to grind and could wear out the abrasive grits in a short time. For example, an electroplated product would grind 40 to 80 parts before requiring its removal. Since there are more than one wheel of different shapes and sizes that are mounted on the same spindle, removal and replacement is a costly affair.

When a test wheel of the new invention was mounted and used without any prior truing or dressing, it started to produce good quality parts. The power required to grind was about 64% of the total power available which is common. After grinding a load of 73 parts, the power actually dropped to 54% and then to 51% and finally to 41%. Figure 1 shows the spindle power as a function of parts ground. Normally one would expect the power to increase with parts ground due to formation of wear flats and/ or contact with increased number of abrasives. This was an unexpected result for a brazed product. It was also noted that there was no wheel loading leading to work piece “burn”. Burn takes place due to oxidation of the surface and degrades the properties of the work material.

The grinding wheel continued to perform well, overtaking the 80 parts that the current electroplated wheel produced, and gradually over several days astoundingly resulted in over 500 parts. The grinding wheel was still capable of grinding well at the conclusion of this experiment. The wheel was removed for examination and another similar wheel mounted to check for consistency. The second wheel produced a total of 603 parts before wearing out.

FIG. 9 is a graph showing the spindle power as a function of parts ground, in accordance with experimental results acquired through use of the invention.

It is expected that during the life of a patent maturing from this application many relevant brazes and wheel materials will be developed and the scope of the term brazes and wheel materials is intended to include all such new technologies a priori.

The terms "comprises", "comprising", "includes", "including", “having” and their conjugates mean "including but not limited to". The term “consisting of’ means “including and limited to”.

The term "consisting essentially of' means that the composition, method or structure may include additional ingredients, steps and/or parts, but only if the additional ingredients, steps and/or parts do not materially alter the basic and novel characteristics of the claimed composition, method or structure.

The term “plurality” means “two or more”.

As used herein, the singular form "a", "an" and "the" include plural references unless the context clearly dictates otherwise. For example, the term "a compound" or "at least one compound" may include a plurality of compounds, including mixtures thereof.

Throughout this application, various embodiments of this invention may be presented in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

Whenever a numerical range is indicated herein, it is meant to include any cited numeral (fractional or integral) within the indicated range. The phrases “ranging/ranges between” a first indicate number and a second indicate number and “ranging/ranges from” a first indicate number “to” a second indicate number are used herein interchangeably and are meant to include the first and second indicated numbers and all the fractional and integral numerals therebetween.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination or as suitable in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements.

Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.

All publications, patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention. To the extent that section headings are used, they should not be construed as necessarily limiting.