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UKAM Industrial Superhard Tools

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Diamond Pellets

UKAM Industrial Superhard Tools

Diamond Pellets

Diamond Pellets provide quick material removal with precision finishing.. Diamond pellets are suited for superfine glass, sapphire, ceramics, semiconductor materials, ultra hard & brittle materials and other glass like materials. It is recommended that pellets be used with on our SMART CUT® coolants to maximize efficiency and surface finish.

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Advantages

Materials Used on:

Sintered (metal bond)

Resin Bond

Hybrid Bond

Vitrified Bond

Sintered (metal bond)
diamond pellets

have high retention of diamond crystals inside the bond matrix. Provide excellent cutting rates, form retention, and long life.

Resin Bond Diamond
Pellets

organic bond matrix this is formed by high pressure and high temperature. Offers fast cutting speeds, minimum heat generation, self sharpening characteristic, and best surface finish. The resin bond pellets are typically used for hard materials, glass and optics.

Hybrid Bond Diamond
Pellets

combines the benefits of metal bonded tools (cutting performance, endurance and good cooling properties) and resin bonded tooling (homogeneous scratch-free surfaces, very low sub surface damage, optically measurable after grinding, reduced polishing times).

Diamond Pellets:

Specifications Available:

Our Diamond Pellets are used for:

Bond Types Available:

Bond Types Available:

Application:

Diamond

Guide Pellets Selectiong

Diamond-impregnated lappingpellets (also known as plugs or buttons) have been successfully used for a number of years to cut and lap glass materials. However, many lapping machine operators have been disappointed with the results obtained when using these pellets on extremely hard materials, such as quartz, tungsten carbide, alumina or sapphire. Conventional diamond pellets were typically supplied as a “one-size-fits-all” solution, with little consideration for the requirements of the application. As a result, they often added significant costs while providing few, if any, benefits. Additionally, some of the pellets used poor-quality diamond powders that scratched the product’s surface or wore down quickly. For these reasons, many manufacturers of hard materials have continued using loose abrasives in their cutting and polishing operations.

Recently, however, new diamond pellets have been developed that incorporate higher quality diamond crystals and stronger bond formulations in carefully balanced compositions. With the availability of these custom-engineered, high-performance diamond pellets, manufacturers of hard materials can significantly increase their cutting and lapping efficiency and quality.

Diamond Pellets:

Technical Specifications

Diamond pellets advantages

Overview

Diamond-impregnated SMART CUT Diamond Grinding Pellets can be fabricated in several shapes and sizes, with varying diameters and heights.  Most commonly, they are cylindrical disks 3/8" to 1" in diameter and 1/8" to 3/8" in thickness (height).  They can also be manufactured with spherical surfaces of specified (+/-) radius.

The binding material of the pellets can be Metallic (M), or Organic/Resin (R), depending on the nature of the work to be performed.

The diamond powder used in the pellets can be varied from ultra-fine (Lap-Polish) to Extra Course, depending on the type of grinding to be performed and the material being worked.  Note that not all diamond grain sizes are appropriate for all binder materials.

Pellet Size Table

Pellet Size

Binder

Volume (cc)

1

3/8" x 1/8"

Metal (M)

0.151

2

3/8" x 3/16"

Organic (R)

0.227

3

1/2" x 1/4"

M or R

0.804

4

1/2" x 3/8"

M or R

1.207

5

5/8" x 3/16"

Organic (R)

0.943

6

5/8" x 1/4"

Organic (R)

1.257

Diamond Grain Table

It should be noted that diamond abrasive suppliers are often not in agreement on the distribution of sizes within a batch of powder.  The values listed below are those for which Gator Diamond strives.  Pellets with other specific grain sizes can be made to order.

Grade

Coarseness

Diamond Grain Sizes (Approx.)
in Micrometers

Concentration

0

Extra Coarse

~ 167 µ

100% (+)

1

Coarse

~ 100 µ

100%

2

Medium

~ 67 µ

85%

3

Medium Fine

~ 45 µ

75%

4

Fine

~ 30 µ

50%

5

Extra Fine

~ 15 µ

35% (+)

6

Pre-Polish

~ 7 µ

25%

7

Lap-Polish

~ 4 µ

20%

Binder Selection Chart

The following table is provided to illustrate some typical work pieces that require different pellet binder grades.  WE  can provide assistance in determining the optimum binder grade and coarseness for specific types of grinding and polishing applications.

Material

Hardness

Recommended Binder Material

Glass

530 Knoop

Metallic/Organic Resin

Quartz

820 Knoop

Metallic/Organic Resin

Silicon

1150 Knoop

Metallic/Organic Resin

Tungsten Carbide

1500 Knoop

Organic Resin

Alumina Ceramic

2100 Knoop

Metallic/Organic Resin

Grinding is the removal of a stock material, or "work," by abrading against a harder material - usually called a "stone."

Lapping is a process where a slurry containing a hard grain is trapped between the work and a lapping or pressure plate.

Technically, the use of pellets is a grinding process with lapping equipment. Results using pellets approach those of lapping in terms of flatness because the plate containing the pellets can be kept true or flat, like the lapping plate. The efficiency of the pellet process as measured by the work-stock removal rates approaches that of grinding because the cutting points are held firmly in place, and each point is used until it begins to dull.

Diamond Pellets:

Parameters Affecting Pellet Selection

The engineer/supervisor over the lapping process must consider several factors when selecting a system of pellets, just like selecting any other grinding or lapping abrasives. A proper selection of pellet parameters will affect rate and quality of the grinding, as well as the useful life of the grinding pellets. Consider the following:

As the work is ground away by the pellets, the pellets are also ground away by the work, but desirably at a much lower rate. There are two actions on the pellets of which the operator must remain aware. The pellet matrix is being worn away exposing new diamond points, and simultaneously some existing diamond points are being worn flat.

Under normal usage, the two actions are in equilibrium. However, if the pellets are used on a harder material than that for which they were designed, the matrix will not wear as fast as it should. The outcome is that the points will become dulled. The operator will know this is happening because more pressure will be required to achieve the same results.

As an example, when the pellets which contain 50 micron diamond particles are first applied to the surface generated by the pellets which contain 75 micron diamond particles, grinding effectiveness will appear large at the beginning and slowly decrease. This occurs because the rougher surface wears the pellet matrix faster, exposing a constant supply of new diamond points. As the work surface becomes smoother, effectiveness will decrease due to lack of wear on the matrix.

This diamond-point-flattening can also occur when a pellet is used for too long on a given work piece. Because this can occur in normal operations, a loose grain may be applied to the grind surface to wear away pellet matrix and thus expose sharp diamond points. However, the applied grain must be a specific match to the diamond particle size in the pellet in use. Doing this occasionally is not harmful to the pellets, but care must be used to apply the correct loose abrasive to the matching pellets for the sake of the pellet and the work.

Pellet Matrix or Binder

Two different types of diamond are used to make pellets: friable and hard.

A metal binder (matrix) is used to encase the hard diamond, and an organic/carbonaceous binder is used to encase the friable diamond. For many materials, either is a good choice. The metal bonded pellet is a more aggressive grinder (tolerates higher pressure), but it does create more subsurface damage. The friable diamond in the organic pellet provides less aggressive grinding action.

A process could start with metal bonded pellets and, when needed, finish with organic bonded pellets - all prior to polishing. Very sensitive optics, such as those used with lasers, might require the use of organic bonded pellets throughout.

Pellet Hardness or Grade

The same pellet system used to lap glass will not effectively lap ceramic, and vice versa.

When pellets are used on material softer than that for which they were designed, the matrix (binder) will erode away too fast reducing grinding efficiency (sometimes dramatically), and causing excessive pellet wear.

When pellets are used on material harder than that for which they were designed, the diamond points will wear flat and thereby greatly reduce the effectiveness of the pellets.

Diamond Pellets:

Lapping Plate Layout

The standard lapping plate is flat. The pellets are glued or epoxied to the plate in any reasonable design. A layout design may depend on how pressure is applied to the plate and how the work rotates against the plate. The layout of pellets may, for example, be evenly distributed or slightly more dense nearer the center.

Theoretically, the maximum population density of cylindrical pellets on a flat plat will be about 91%, but this would not allow for an even flow of the lubricating fluid. If the pellets are spaced too far apart, the likelihood that one of them would catch an edge on the work, causing it to be popped off, is increased. A density of sixty percent, plus or minus ten percent, seems to work fine.

Lapping plates with concave or convex surfaces are possible. Please contact us for more information.

The pellets are supplied either mounted onto a plate (customer’s plate or a plate supplied by us) or as loose pellets ready for the customer to mount onto his own plate. An epoxy kit can be supplied with the pellets if the customer desires to mount the pellets.

Improving the Diamond Composition

DEVELOPING

New Pellets

To improve the performance of diamond-impregnated pellets, researchers evaluated many different diamond and bond compositions on a variety of materials and made extensive measurements in five different areas: the surface roughness (Ra), the material removal rate (mrr), the pressure required for operation, the amount of loading or dulling incurred over a period of time, and the lifetime or grinding ratio (G-ratio, defined as the volume of product removed divided by the volume of pellet lost) of the pellets. They found that these five characteristics are frequently interrelated. For example, increasing the operating pressure typically increased the mrr. Pellet compositions engineered to have a larger mrr also showed a higher Ra, while pellets designed to have a larger G-ratio generally exhibited lower mrr, a lower Ra and a shorter loading time. Most changes in composition to enhance one characteristic degraded another. However, researchers discovered that they could improve the overall performance of the pellets by using the newer high-quality diamond powders with high-strength bonds, and by carefully adjusting the composition and concentration of the separate components.

The test data also showed that the mrr generally declined over time, with the decline becoming progressively worse after just a few minutes of lapping. This decline could be quantified by a decay constant (D), which was unique to each combination of pellet and lapped material. Frequently, the mrr approached zero as the lapping process continued, at which point the pellets had to be redressed to restore the original mrr. When the lapping process was resumed, the decay of the mrr was repeated. Again, researchers discovered that by using the newer high-quality diamond powders with high-strength bonds, and by carefully adjusting the composition and concentration of the separate components, they could slow the speed of decay. The high-performance fixed abrasives developed through these tests range from very aggressive lapping to fine cutting. Using the refined pellets, glass and quartz can be lapped up to 80 microns per minute on existing lapping machines—significantly faster than with conventional pellets or loose abrasives. Additionally, while the pellets have been successfully tested in pressures as high as 45 psi, they also work well with the lower pressure constraints often found in glass and ceramic lapping. Unlike conventional pellets, which required pressures of 4-6 psi and higher, the new pellets can operate at 1-3 psi—and even lower, in some cases. For example, glass lapping pellets are available that operate successfully down to 3⁄4 psi.

The new pellets also produced satisfactory results on hard materials.

Figure 1 shows the test results on fused quartz using a test plate with new pellets engineered specifically for quartz lapping. In this instance, quartz straight from a high-quality saw was lapped in preparation for polishing. The saw left an Ra of 150 µ-in, and the final Ra after lapping with the medium grade quartz pellet test plate was 9 to 10 µ-in. A total of 0.020 in. of material was removed in this run. In this example, several hours of lapping with loose abrasives of three different grits was replaced with pellet lapping for only a few minutes. Because of the excellent Ra created by the pellets, the subsequent polish time was also reduced from about two hours to about 45 minutes. In addition, the abrasive waste (swarf) was reduced from several pounds to a few ounces.

Figure 2 shows the results obtained from a new medium-grade sapphire pellet on c-axis sapphire

In this test, three 2-in. wafers were run with 33 lbs of dead weight at 80 rpm on a 12-in. SpeedFam lapping machine. The average pressure (always measured on the surface of the pellet) was 5.4 psi, and the test plate contained 202 pellets. The resulting population density (the area of the pellet to the area of the plate) was 64%. As can be seen from Figure 2, the average mrr was about 3.5 microns per minute, and the final Ra after 35 minutes of lapping was 13 µ-in. This operation to remove 0.005 in. of material replaced a 12-hour lap with loose abrasives. The same pellets exhibited similar results on hard alumina. In yet another test, a more aggressive sapphire pellet yielded an mrr of 7 microns per minute with an Ra of 20+ on c-axis sapphire and much faster lapping on a-axis sapphire and alumina.

Efficient Lapping

Considerable progress has been made in the last few months in pellet performance on hard materials. With the availability of improved diamond powders and stronger bonds, pellets have been developed that work well with glass, quartz, silicon, ceramics, sapphire (including c-axis) and many metals. Advantages of the new pellets in these applications include:

Pellets are also under development for extremely hard ceramic materials, such as silicon carbide and tungsten carbide.

With today’s high-performance fixed abrasives, ceramic manufacturers can reduce their polishing and lapping times and increase their manufacturing efficiency.

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ITS WHAT YOU CANT SEE THAT MAKES ALL THE DIFFERENCE

SMART CUT® technology

CBN Crystal
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Comprehensive Source Of Information On Diamond Tools

The more you understand about what we can do for you the better our partnership will be. Here you will find most comprehensive source of information and optimizing and improving your cutting, drilling, grinding and polishing on the web. Find everything you ever wanted to know about diamond tools.

Large Inventory & Custom Manufacturing

We have the largest variety of diamond tools available in stock. we regularly produce custom diamond tools to better fit customers specific needs & specifications. Just about any diamond tool can be designed and manufactured per customer drawing or specifications.

Umatched Technical Support

WE ARE A PARTNER IN YOUR SUCCESS

Developing close ties with our customers is the foundation of our business. At the core of our company is a team of world class engineers, knowledgeable customer service personnel here to serve you. Whether is designing or manufacturing a special solution. We will go out of our way to optimizing your process to ultimate level of efficiency.

Advanced
Technology

AMERICAN MANUFACTURER
As one of the few remaining independent U.S.Diamond Tool & machine builders. We have the experience & tradition to help you remain at frontier of technology Our experience has been further enhanced by acquiring assets and processes from some of the oldest American tool manufacturers, along with their decades of experience and R& D. This has positioned us as one of the most experienced companies in the industry.

Superior Quality & Consistency

Different Product
Different Company
Different Technology

Our unique bond formulations, tool designs, stringent requirements, and utilization of exceptionally high-quality diamonds and raw materials ensure top-notch products that adhere to strict ISO 9000 standards. Our proprietary technology allow us to control and regulate the dozens of variable that affect toolife, quality, & consistency

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Experience Makes All The Difference

"ONE OF THE MOST EXPERIENCED COMPANIES IN THE INDUSTRY"
With a team of highly knowledgeable and experienced engineers, we possess a deep understanding of the challenges you encounter when cutting, drilling, grinding and polishing. This expertise is gained from decades of experience manufacturing sophisticated and high precision tools and equipment for advanced industries and complex applications. Unlike other companies that exclusively focus on tools for the stone and construction industries, we offer unique solutions that surpass their capabilities and expertise.

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