Getting the most out of your Diamond Wafering / Sectioning Operation

New improvements in diamond wafering blade manufacturing technology have expanded the use of diamond into many other applications and materials.

Cross Sectioning is the first and most important step in the sample preparation process. Getting the best results involves obtaining a smooth surface finish, minimum chipping, material deformation, without sacrificing cutting speed. Today, most laboratories, work  with dozens of materials. Frequently each material requires a different sectioning method and sample preparation approach. 

Selecting the right equipment, consumables, and parameters for your specific material/application will significantly affect your sectioning operation. Save you time and money, as well as set the stage for the rest of your specimen preparation process. The ever increasing variety of  ultra hard, new generation, composite, engineered, highly metallic content and exotic materials, transform the way we look at cross sectioning. And set many age old conventional sectioning equipment and consumables obsolete. New materials require different technology & sample preparation methods.

Many laboratory technicians still spend days and even weeks, experimenting with different consumables, cut off wheels, coolants, RPM’s and many other variables. An expensive and time consuming trial and error process, witch can be avoided with proper understanding of your material, consumables and objectives you need to accomplish.

New Generation diamond wafering blades have been engineered to change they way sectioning and specimen preparation process is handled. This article deals with new developments in diamond wafering blade manufacturing, technologies and several misconceptions regarding their use. The following information have come from years of experience inesearch, development and manufacturing of precision diamond products, as well as years of personal experience and observation. New improvements in diamond wafering blade manufacturing technology have expanded the use of diamond, into many other application, traditionally sectioned by other types of cut off blades. Historically Laboratories, R & D, and manufacturing facilities have found the high cost of using diamond wafering blades prohibitive. Relying on abrasive cut off blades to observe brunt of their sectioning work, including application where use of diamond could be advantages. 

Diamond can be used to section very hard materials, than switch to cutting soft materials, while still maintain consistent performance and cutting speed. SMART CUTä technology recently developed by UKAM Industrial Superhard Tools has made use of diamond wafering blades more economically feasible on broader variety of materials & applications. Materials such as:  

·          Plastic

·          Very soft metals

·          Non-ferrous soft metals  

·          Very ductile metals

·          (Ti) Soft ferrous metals

·          Medium soft ferrous metals

·          Medium hard  ferrous metals Hard ferrous metals  

·          Very hard ferrous metals

·          Extremely hard ferrous metals

·          Sintered carbides

·          Hard ceramics

·          Minerals and ceramics  

Have been successfully sectioned utilizing new generation metal bond diamond wafering blades with SMART CUTä technology.   

How Diamond Wafering Blades Work

Simply, a  diamond blade wafering blade is a cutting tool which has  exposed diamond particles captured in a metal matrix each with a  small cutting edge. 1A1R wafering blade is made of a steel core with an Inside Diameter (ID) usually ½” or other size, that rotates around a center shaft.

During the sectioning operation, the surface speed may reach 30 m/sec, if using a high speed sectioning saw. This is faster than most cars running on a highway. The cutting action is performed by accumulation of small chips scratched out by the numerous diamond particles impeded in the bond.

The  number  of  cutting  edges  which  is  determined  by  the  number  of  diamonds  (or concentration)  make  up  the  structure  of  the  diamond  blade,  along  with  its  matrix,  (metal  or  nickel  bond). The  size of  the  diamond  particle  will  have  a  direct  result  in  the  size  of  chip  you  can obtain. The  thickness  of  the  blade  (diamond particle  plus  matrix)  will  determine  the  width  of  the  cut. Therefore,  blade  selection  along  with  feed  rate,  cutting speed,  and  depth  of  cut  will  ultimately  determine  your sectioning  success

The following are some factors to consider when selecting the right diamond wafering/sectioning blade for your application:

Diamond Grit (Mesh Size)

According to U.S. Standards, mesh designates the approximate number of sieve meshes per inch. High Mesh Sizes mean fine grits, and low numbers indicate coarse grits.

Diamond Mesh Size plays a major role in determining the surface finish quality, smoothness, level of chipping you will obtain, and material microstructure damage you will obtain. Finer mesh size diamonds such as 220 and 320 grit are much smaller in size than coarser diamond particles. And will give you a very smooth surface finish, with minimal amount of chipping on edges. These mesh sizes are usually used for fine cutting of a full rage of materials such as:  LiNbO3, YVO4, GaAs, and optical materials. Courser diamond particles such as  80 and 100 grit are much larger in diameter and are frequently used fast cutting / material removal on more harder materials such as silicon carbide, zirconia, Al2O3, stainless steels, and other advanced ceramics and high metallic content materials. Witch do not require a very fine surface finish.

Diamond Mesh size does have considerable effect on cutting speed. Coarse Diamonds are larger than finer diamonds and will 

remove more material than finer diamond particles. This means that coarse diamond wheels are more aggressive for material removal than the finer diamond wheels and will cut faster. However, the tradeoff is increase in material micro damage. If you are cutting fragile, more delicate materials then finer mesh size diamond wafering blades are recommended. 

Diamond mesh size (grit size) should provide maximum removal rate at minimal acceptable finish. Often the desired finish cannot be achieved in a single step/operation. Lapping or polishing may be necessary to produce desired surface finish, as a secondary step in your sample preparation process.  

Diamond Wafering Blades & Cutting Speeds

High Speed vs. Low Speed

Sectioning can be performed either at low or high speeds. There are advantages and disadvantages of each process. Diamond may break at very high speeds, and fall out at very slow speeds. An optimum surface speed / RPM’s must be selected to balance out the two disadvantages. Diamond Wafering Blade life will usually increase at slower cutting speeds. However the increase in labor costs, utilities costs, depreciation of equipment and other overhead expenses. Will usually offset the saving blade life and other consumables. Cutting speed is often the most important consideration when selecting the right diamond wafering blade for your application. The operator mush choose a balance between life of the blades and their cutting rate.

Diamond has a higher impact strength than the material being machined. During the sawing operation, the diamond ruptures the material by impact. Each diamond is able to transfer the electrical power into momentum the breaks the material. 

By increasing power on your sectioning saw, your diamond wafering blade RPM’s and surface speed will increase as well. Hence, each diamond will chip off a smaller amount of material, reducing its impact force on material being machined. And reducing cutting resistance. In theory, by increasing surface speed / RPM’s, each diamond should receive a smaller impact force.

However, because impact is supported by a smaller volume, the impact force with this low volume is actually increased. There is a higher probability that the diamond particles will break or shatter. Hence, sectioning materials at very low surface speeds, creates a large impact force between diamond and material being machined. Although the diamond may not break, the risk that the diamond will be pulled out of diamond wafering blade and causing premature failure of the blade does increase.  

Diamond Effect of Sectioning at Low RPM’s

The proportion, and distribution of diamond abrasive particles, also known as “concentration” has an effect  on overall cutting performance and price of precision diamond blades. Usually concentration defined as: Concentration 100 = 4.4 ct per cm layer volume (mesh size + bond).

Based on this definition a concentration of 100 means that the diamond proportion is 25% by volume of diamond layer, assuming at diamond density is 3.52 g/cm3 and 1 ct = 0.2g. Nominal diamond concentration in precision diamond blades range from 0.5 ct/cm3 to 6 ct/cm3. This means diamond concentrations are available from 8 to 135).

Until recently Diamond Concentration has played a major role in Diamond Sectioning/Wafering Blade performance. A new technological process recently developed, called SMART CUTä technology, minimizes the effect of diamond concentration in your overall sectioning process. Selecting Optimum Diamond Concentration for your application will depend on a large number of factors, such as:

·         Material Being Cut

·         Bond Type and Hardness

·         Diamond Mesh Size

·         Cutting Speeds

·         Coolants being used

Diamond Concentration is still a factor in determining the life and cutting speed of your Diamond Sectioning/Wafering Blade. Higher diamond concentration is recommended and usually used for cutting softer and more abrasive types of materials. However, the trade off is significantly slower cutting speed. Low diamond concentration is recommended and widely used for cutting ultra hard and brittle materials.  

Predicting Diamond Wafering Blade Performance

Prediction of diamond wafering blade performance, when sectioning different types of materials, has always been a difficult and challenging process. Analytical approaches are often empirically based and build from previous successes and failures. It is not uncommon for a wafering blade to work for one application, and not work for another. Successful sectioning results depend on a large number of variables that often cannot be controlled. New techniques have been developed to better predict diamond wafering blade behavior. Successful sectioning results can be achieved by relying on the experience of the diamond wafering blade manufacturer and using two complementary diamond tool performance measurements:

1. Average chip height equation

2. Wear mechanism indicator

Average chip height equation

The average un-deformed chip height equation was introduced [1] to describe the theoretical maximum average chip height of a cutting particle. This height is described by the following geometric equation:

H_avg = Average un-deformed chip height

V_t = table speed (head speed)

V_s = blade peripheral speed,

λ = ratio of total segment length to blade circumference (partition of rim),

N_a = number of active grit particles per unit area,

r = chip ratio (ratio of chip width to thickness)

d = depth of cut,

One disadvantage of the chip height equation is it does not take the diamond strength and material properties into consideration. This disadvantage may be supplemented by using the Wear Mechanism Indicator or WMI [7]. Wear mechanism indicator is an excellent tool for qualitatively predicting diamond wafering blade wear and life.  This method is able to predict to some degree of accuracy when each diamond particle is contributing to the cutting action of the blade.

Each zone (region) of this diagram represents the cutting rate of each diamond particle.  In the yellow flat region each diamond particle is fully contributing to the cutting rate and remains the sharpest of the three stages.  In the blue (micro-fraction) region, diamond particles are beginning to form internal cracks and chip off from the blade bond. Operating in this stage may still provide successful sectioning, however the diamonds will wear at much faster rate. At the orange (extended wear flat region) of Wear Mechanism Indicator diagram, diamond wafering blade will exhibit the slowest cutting rate and performance. Frequently wafering blades at this stage in the life cycle require extensive dressing.

Both equations can be used to evaluate the effect of different diamond wafering blade parameters such as: diamond mesh size, diamond concentration, bond type and hardness on the behavior of wafering blade in application. Thus in situations where diamond wafering blade performance is unsatisfactory, it is possible to use these two evaluation techniques to examine the effect of varying parameters to produce a wafering blade that will achieve the expected level of performance.

Diamond Concentration & Cutting Performance

Today, most sectioning saw manufacturers and laboratory technicians recommend and use low concentration diamond wafering

for sectioning ceramics, glasses, silicon, carbides, sapphire, and other related semiconductor and optical materials. And use high concentration wafering blades should on metals such as stainless steel, aluminum, titanium, pc boards. A new technological breakthrough called SMART CUTä technology, in orienting diamonds inside the metal matrix, so that every diamond is better able to participate in cutting action, is making fundamental changes in these beliefs and setting new benchmarks on how diamond wafering blade performance is measured. 

By orienting diamonds, SMART CUTä technology makes diamond concentration only a minor factor in the overall sectioning equation. Studies and extensive testing shows that diamond concentration in wafering blades manufactured utilizing SMART CUTä technology plays a no major role in determining overall wafering performance. Large number of diamonds in a high concentration diamond wafeirng blade come in contact with material, creating friction, hence considerably slowing down material removal rate. It takes considerable dressing in order to rexpose the next diamond layer.

SMART CUTä technology resolves this problem  by making sure that every diamond is in the right place and at the right time, working where you need it most. You get maximum use of diamond and bond.  Before this technology was developed, orienting diamonds inside the wafering blade bond matrix was impossible. This was one of the main problems faced by diamond tool manufacturers worldwide. Over the decades there have been numerous attempts to solve the diamond and CBN distribution problem. Unfortunately, none of the attempts have been proven effective. Even today 99.8% diamond wafering blade manufacturers still have no way or technology to evenly control and distribute Diamond or CBN particles inside bond matrix, nor properly position them to maximize their machining efficiency.

Current Diamond Wafeirng Blade technologies are also inadequate to provide effective control of diamond mesh size (grit size) and concentration of variations on different parts of the same tool. Current technologies also do not allow diamond distribution to be factored in when manufacture a wheel specifically designed for individual material property and structure.

What  most  diamond  wafering blade  manufacturers  used  to do,  and  still   do  today  is  place  diamonds    inside  the  metal  matrix,  with  no  control  over diamond  distribution. The  problem  with  this   approach  is  inconsistent  diamond tool performance. Only  about 40%  of  these  diamonds  are  able  to  participate  in  the  cutting  action. The  rest  fall out,  become  dull, or  disintegrate  before  they have  a  chance  of  being  used. This  factor  causes the  following  problems:  

Problems with Conventional Diamond Wafering Blades

The distance between each Diamond or CBN particles determines the work load each diamond will perform. Improper spacing of diamond or CBN particles typically leads to premature failure of abrasive surfaces or structure. If diamond or CBN particles are too close to one another, some of these particles are redundant and provide little or no  assistance in cutting and sectioning. Excess diamonds particles increase the cost of manufacturing diamond tools, due to high cost diamond and CBN powder.

Yet have no effect in increasing performance. In fact  excess and non performing diamond or CBN particles reduce the diamond tools overall performance and efficiency by blocking up the passage of debris from material being machined. In many cases these excessive diamond particles play a major rule in decreasing the useful life of your diamond tool. Conventional diamond wafering blades and diamond tools have been suffering from these type of problems and inefficiencies for over 50 years.

Diamond Inefficiency / Ineffective Wafering Blade Performance

The performance of a diamond wafering blade depends on how diamonds are distributed and adhered in matrix. Diamond weak. 

If diamond particles are separated too far (the impact exerted by each diamond particle on material becomes excessive). The sparsely distributed diamond or CBN particles may be crushed or even dislodged from the matrix into which they are disposed. The damaged or missing diamond particles are unable to fully assist in the work load. Hence the workload is transferred on to the remaining diamond particles. The failure of each diamond particle causes a chain reaction, witch soon results in tool ineffective performance or complete pre-mature failure of the wafering blade.  

Inconsistent  Cutting Speed  &  Excessive Blade Dressing

Conventional diamond wafeirng blade usually exhibit the following behavior: After  a  few  dozen  cuts,  speed  of the wafering blade gradually  begins  to  slow  down. You  will notice  excessively  longer  cutting  speeds,  and equipment  motor  bug  downs. And  since only  a  few  diamonds  participate  in  the  machining action,  you  may  find  your self  applying  an increasing  amount  pressure  just  to  machine  the  same  amount  of  material. Without properly  orienting  the  diamonds,  conventional  wafering blades  quickly  become  dull,  out of round. With   further  cutting  requiring  constant  blade  dressing,  in  order  to  expose  new  diamonds.

Excessive Heat Generation & Loss of  straight cutting capability

By constantly dressing the wafering blade,  pressure put forth on material, causes the tool to overheat and loose its tension. The user may find themselves using excessive force and pressure just to cut a small amount of material.  

Frequently a metal bond diamond wafering blade requires different sizes of diamonds and different diamond concentrations to be distributed at different parts of the wafering blade bond. Most diamond wafering blades wear faster on the edge or in front than the middle. Higher diamond concentrations are preferred in these locations to prevent uneven wear and thus premature blade failure. By making the distribution of Diamond or CBN particles uniform and in a predetermined pattern, tailored to individual customer application. The work load can be evenly distributed to each diamond particle. As a result a diamond wafering blade with SMART CUT technology will machine material faster and its working life will be extended a considerable amount of time.

SMART CUT technology promotes not only even diamond distribution. But strong diamond retention as well. Allowing the diamond wafering manufacturer to use of smaller diamond particles. Small diamond particles will improve surface finish, and optimized performance of each diamond particle.

Sectioning Materials with High Metallic Content

Historically conventional Metal Bonded Diamond Wafering Blades had problems in cross sectioning  high metallic content specimens. It could take hours cross sectioning materials such as titanium and tungsten carbide with a diamond blade. Most laboratories use abrasive cut-off blades for this application. NEW GENERATION Sintered (metal bond) Diamond Wafering Blades - SMART CUTä technology actually do a good job on metals, not just ceramics. See graph below for comparison of cutting speeds on high metallic content materials. Here is an example of typical sectioning results obtained using the New Generation Sintered (metal bond) diamond wafering blade. 

Diamond Wafering Blades & Cutting Speeds Case Studies

New Generation Sintered (metal bond) diamond wheel with SMART CUTä  technology was tested against a conventional metal bond diamond wheel under similar conditions. Using three different materials, namely Aluminum, Brass, and Quartz, cuts were made to determine cutting times for all five diamond wheel types. Using a Model 650 Low Speed Diamond Wheel Saw, each diamond wheel blade was used for cutting the specified materials. Each specimen cut was a 12-millimeter diameter rod of material, helping maintain consistency during the cutting process. Specimens were first mounted onto a graphite plate, which was then mounted onto an aluminum mounting block. The entire system was then placed into the Model 65001 Single Axis Goniometer  

specimen mount of the Model 650. Specimens were mounted using MWH 135 low melting point wax (melting point at 100 degrees Celsius). The following diamond wheels were used in this experiment:

Conventional Diamond Wafering Blade, Sintered (metal bonded) 4. diameter; 0.012. thickness; Mesh Size: coarse; Diamond Concentration: High

New Generation, Sintered (metal bonded) Diamond Wafering Blade with SMART CUTä technology. 4. diameter; 0.012. thickness; Mesh Size: coarse  Diamond Concentration: High

Each diamond wheel was used to make three cuts on each sample, with a total of nine cuts total

per wheel. The diamond wheels were dressed with a silicon carbide dressing stick immediately

prior to cutting. The following cutting parameters were used for each of the cuts made. 

Cutting Parameters 

Load: 80 grams   Blade Dressing: Prior to each cut      Wheel Speed: 10 maximum on dial) 

Coolant Density: 30:1 

Each cut was timed and recorded, with each cut averaged for each sample and then plotted in a graph.

Results: New Generation, Sintered (metal bonded) Diamond Wafering Blades with SMART CUTä

technology cut substantially faster than Conventional Sintered (metal bond) diamond wafering

blades. For all three materials.  

Cutting Times of Various Materials Using Different Diamond Wheels

(All samples 12mm rods)

New Generation Metal Bond      Conventional Metal Bond

Diamond Wafering Blades        Diamond Wafering Blades

with SMART CUTä technology     

Material

Quartz        4.5 minutes                   10 minutes

Aluminum   26 minutes                    29.5 minutes

Brass         25.5 minutes                 33.5 minutes  

New Generation Metal Bond with SMART CUTä technology Conventional Metal Bond Diamonds are oriented and evenly distributed through the bond. So that every diamond is better able to participate in cutting action. Diamonds are placed inside bond with no control over diamond distribution or orientation. 100 concentration is used to make sure the blade will cut hard materials. Microstructure of New Generation Metal Bond with SMART CUT technology Microstructure of Conventional Metal Bond Wafering Blade Diamond concentration is dispersed to areas of bond, where its needed most. Every diamond works at the right place and at the right time. The sharpest part of the diamond particle almost always peruses from the bond, growing sharper with each cut. Some areas of diamond bond are filled with excessive number of diamond particles. In other bond layers, diamond particles are rarely sighted. In a few occasions material comes in contact with overly excessive number of diamonds. In other cases, there are almost no diamonds to be found. User must periodically dress blade, to rexpose bond layers. Until new diamonds can be found.

When using Abrasive, Carbide, and Other blade types

Diamond is an excellent alternative to abrasive, carbide, and vitrified bond blades.. 

Advantages over other blades:

• Cross application capabilities 

• Superior Long Life

• More Consistency in Performance

• More Durability

• Less Material Deformation

• No Contamination

Many users have found that  ONE  blade can last up to 100 abrasive or carbide blades put together. Is a Diamond Blade the right tool for your application? To find out, give our Engineering Department a call at Phone: (661) 257-2288.