RSX-M Series High Friability Diamond Micron Powders
Clearly the Best for: Ceramics, Electronics, and Cemented Carbides
By: Roy A. Wagner, Technical Director, SAT SuperAbrasive Techniques, Inc.
ç Copyright SAT Inc. 1999, All rights reserved.
Friable Resin Diamond Micron Powders:
The same Cutting Properties which have made RSX Series Mesh Diamond be the number one choice of Resin Bond Grinding Wheels users are now available in a full range of RSX-M Diamond Micron Powders. ( 0 - 80: m)
The Friable, Self Sharpening RSX crystals which work so well for the Grinding of ceramics and for Cemented Carbides has now been shown to produce superior workpiece surface finishes in the RSX Diamond Micron Powder sizes. Even in the Sub-Micron sizes such as 0.5-1.0: the friable diamond crystals continued to offer the consistently superior surface finishes which are characteristic with these free-cutting, friable diamond crystals.
Friable Diamond Particles Cut Best !!
Fine Grinding and Polishing Ceramics and Cemented Carbides require diamond properties that allow the crystals to remain sharp and Free-Cutting throughout their entire cutting life. Unfortunately, the abrasive processes when grinding super hard ceramics and cemented carbides tend to polish the crystals cutting edges, reducing the crystals cutting effectiveness. This is where the friable crystal characteristics of RSX diamond do their best work. Rather than becoming polished and requiring frequent dressing, the friable crystals tend to micro-fracture as their primary wear mode, continually presenting sharp new cutting edges to the workpiece throughout the grinding or polishing operation.
There are several ways to approach the need for a friable diamond crystal, but they ultimately involve:
The Intrinsic Crystal strength is determined by the type, the level, and the location of inclusions and the overall crystal defect structure. Ideally, for Resin Bond Diamond Micron Powder to work effectively, the inclusions will be spread throughout the crystal to allow a progressive micro-fracturing action. As a cutting edge begins to become polished it leads to a slight build-up of cutting forces that cause a small portion of the crystal to break off or "Micro-Fracture", presenting a new sharp cutting edge that will then continue the grinding or polishing operation. The lower the force required to achieve this micro-fracture, the more friable the crystal is said to be.
In the coarser sizes, this ideal crystal "defect structure" is easily recognized when microscopically examining the RS4-M crystals against a white background with reflected light. Alternately, transmitted light will also demonstrate the crystal inclusions which lead to this highly desirable wear mechanism even though the overall Crystal Shape is relatively full-bodied and blocky.
For the Bonded-Abrasive market (i.e. grinding wheels and pellets) or RSX-M Diamond Slurry user, this blocky shaped friable crystal enhances the possibility of Positive Performance Duplication.
Crystal Shape Factor:
In general, Crystal shapes are said to be "more Friable" when they are more angular shapes. The most angular product would be one with a high proportion of needles or platelets contained within the crystal mix. However, while the angular shape does encourage some progressive breakdown of the crystals as they begin to dull, this shape factor is typically much less predictable than the blocky crystals with the intrinsic crystal structure as described above.
An extreme example of attempting to achieve friability with shape is seen when transparent metal bond synthetic diamond (MSX Series) or even natural diamond crystals (SNAT Series) are processed to be highly angular in an attempt to achieve the micro-fracture wear mechanism. The limitations of this practice become obvious when considering the probability that the angular crystals will be oriented perfectly within the slurry or bond to use the shapes friable cutting edges. Improperly oriented "Friable shape" crystals are less useable with the results being inconsistent wear, inconsistent surface finishes, and generally shorter useable life.
In the most extreme case, if a tough full-bodied Blocky crystal were being used in a resin bond diamond grinding wheel, the force necessary to Micro-fracture or to Macro-fracture the crystal would be so high that the crystal would quickly pop out of the bond rather than to fracture.
Wheel life would be low, surface finishes would be poor, and the thoughtful engineers would quickly change to a more friable diamond crystal.
For Slurries, the tough crystal would simply show up as a scratched or destroyed workpiece.
The Solution = RSX-M Friable Diamond Micron Powder.
Uniform Diamond Characterization:
The "Uniform Diamond Characterization" value, (UDC values ranging from 1 to 5), is designed to improve understanding of the uniformity of the crystal make-up within the RSX-M diamond product. A UDC of 1 would mean that the particles have uniform intrinsic properties, while a UDC of 5 would mean that the crystals are widely different from each other.
Many of the diamond micron powder products which have come to be the "Standards of the Industry" are based on Blending Practices which worked "well enough" 25 or 40 years ago, and which have not been revisited often enough since then. In the extreme case, defining a diamond product by its "Friability" or by its "Toughness Index" could lead to the proportional blending of two widely disparate materials, neither one of which would fall within the "Toughness" specification. This could result in a product which technically meets the specification, but with a UDC value of 5.
So what does it mean to Micron Powder performance?
Many unexplained failures to achieve the required Polishing surface finishes on structural ceramics work-pieces or in the electronics industry could be traced to these blending practices. This would entail blending some minute or even not minute percentage (5%, 10%, 15%, 25%, or whatever) of tougher metal diamond into the friable resin bond diamond micron powder product as a cost saving extender, a "Cost Improvement"!
Now after many years, these practices which worked without being noticed in 1975 are the reasons for the failures which are attributed to other causes such as "Oversized Particles" or surface chemistry rather than being attributed to the real cause which is "Over-Strong particles". In todays vernacular, perhaps it could best be described as a 5% enriched product, with 5% of the crystals being on steroids!
Your workpieces will notice the difference Immediately!! ..
.You will notice the difference when you inspect the workpiece!
Uniform Crystal Strength è Optimal Finish
The RS4-M Diamond products are composed of statistically uniform strength crystals (UDC1). This is the key to optimizing Resin Bond Diamond Micron Powders for Ceramics and other precision work-pieces.
In actual practice, RS4-M is the number one choice for the polishing of ceramics since it has the most desired properties and it is available in the full range of sizes. Other Product Designations in the RSX-M series are reserved for Future special micron applications.
Particle Size Distribution:
The best known designation and yet the most subjective aspect of Diamond Micron Powders is the Particle Size Definition and the Particle Size Distribution.
Especially in the finer micron sizes, it is rather easy to over-specify the micron powder size, thereby making it unnecessarily difficult for the micron powder supplier to provide the most useful product at the most cost effective price.
For this reason, we typically request that the user provide an approximate estimate of the desired size range and a visual sample of material which is currently working or which is giving results which are nearest to the desired surface finish, Material Removal Rates, workpiece Geometry, and overall workpiece characteristics. A good visual and size sample, combined with a verbal description of the desired workpiece requirements will help design the most cost effective RSX-M Diamond solution to your micron powder needs.
SAT SuperAbrasive Techniques Inc.
886 East College Avenue
WESTERVILLE OH 43081-2505 USA
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