CNC (Computer Numerically Controlled) Cut Diamonds

[pang_k]

Hi all,

Curious, why do we have humans hand cutting and polishing diamonds? Why subject such beautiful diamond roughs to the jitters of a humans touch when grinding down diamonds?

CNC technology using programming in computers to cut widgets have been around for a long time. Why can't this technology be applied to diamond cutting? Imagine programming in AGS Triple Zero and/or H&A ideal proportion parameters to yield one after another perfect diamonds.

I've ask this question to a few cutters and retailers and they say you need humans to adjust cuts to accommodate 'grains' or something like that.

Come on now...we have machines/robots that make everything from cars to coins and paper currency. Can you imagine needing a human to hand stencil dollar bills for you and hand make every car? The end product would probably be so costly with so much labor involved. Perhaps the cost of diamonds would drop drastically with automation. Is it for this reason why the cutters don't want to answer my question with a straight face for fear of obsolecense?

One day I'd like to buy my lady a diamond necklace with several H&A linked diamonds at a smidgen of what it would cost today.

What are your thoughts everyone?

 

[diamondloveaffair]

For an engineer, you are thinking far too simply.

If you think that everything is so achievable with CNC, you might want to consider getting "hearts and arrows" CZ. It will save you all the pain and costs. Why begin with diamonds to start with? Even modern machinery doing mass production can't achieve a properly cut CZ stone. Bear in mind, if you are cutting a diamond, which is many many times harder than that, things become complicated. How much would your cutting tool cost? What do you think can cut diamond and give it the nice polished surface finish? The standard silicon carbide tool used in CNC machines can't simply do the job.

Next, the real reason lies in the state of the diamond rough and costs. Put your engineering brain behind a business mind. If every single rough diamond that came out of the ground is exactly the same and has no inclusions, everything would be much simpler. They don't.

More importantly, economics is more important for the rough stone owners. Even if they have a rough stone that they can cut into an ideal cut diamond, they won't do that.

Here's an example: If you are a business owner and you are faced with a rough diamond of say 2 carat size. Would you want to make MORE money creating a 1.3 carat diamond with just a Very Good cut or make LESS money creating an ideal cut diamond of 0.8 carat with 100% perfectly crafted arrows?

 

[kenny]

CNC is a great labor-saving tool for wood or metal, but with diamond rough too much money is at stake.

Diamond has grain and internal stress from feathers knots, twinning wisps etc.
These may affect mechanical stability when a diamond is under mechanical and heat stress on the polishing wheel.
You don't want the diamond to explode on the wheel.

As the polishing progresses a human can observe these diamond properties and imperfections and make decisions that can minimize the chance of the diamond destructing.

CNC can follow directions precisely but can't think and make decisions as well at a skilled human.

 

[JulieN]

It can already be done. Computers can't innovate.

 

[smitcompton]

Hi,

I saw a TV show that showed DEBeers using a machine to cut reds and pinks . It is computer programed while someone watches the cutting process. So, they already do it with some stones. So, Mr. Engineer, you are right.


Annette

 

[bunnycat]

CNC is a great labor-saving tool for wood or metal, but with diamond rough too much money is at stake.

Diamond has grain and internal stress from feathers knots, twinning wisps etc.
These may affect mechanical stability when a diamond is under mechanical and heat stress on the polishing wheel.
You don't want the diamond to explode on the wheel.

As the polishing progresses a human can observe these diamond properties and imperfections and make decisions that can minimize the chance of the diamond destructing.

CNC can follow directions precisely but can't think and make decisions as well at a skilled human.

I agree with Kenny. It's nice in theory, but maybe not in practice.

Last year, one of the cutters for Lazare was at the local jewelers I go to in town showing how diamonds were cut. It was fascinating. He showed me the computer modeling they do and how the computer gives various optimal options for different diamond cuts based on the particular rough they are working on, but all the cutting work is done by hand. This does save them some time with the computer modeling but the main work still has to be done with the cutter judegment.

I got to cut on a really nappy stone. I was so excited. (It was really hard.)

 

[TC1987]

Hi,

I saw a TV show that showed DEBeers using a machine to cut reds and pinks . It is computer programed while someone watches the cutting process. So, they already do it with some stones. So, Mr. Engineer, you are right.


Annette

^That it was already being done was my guess. "How do you know it's not already being done?" was going to be my reply, lol.

 

[ame]

There are actually some brands that use lasers for cutting.

 

[John P]

Curious, why do we have humans hand cutting and polishing diamonds? Why subject such beautiful diamond roughs to the jitters of a humans touch when grinding down diamonds?

It's a logical question...and the answer 10 years ago would be different than the answer now. Technology doesn't stand still.

But as the hardest known natural substance (emphasis on natural) of high value, with limited supply, there are three obstacles:

A. Although the hardest substance, diamonds have softer/harder spots, variable graining and highly variable internal characteristics.
B. Diamond cannot efficiently be "forced" to comply with a mechanical plan due to the factors in A, without risk.
C. Diamantaires will not take such risk: Losing a small percentage of source material annually may be negligible in other substances, but to a diamond production the implications are massive (see my final Yield Note).

There are currently four general applications for mechanical "cutting."

1. Rotary-Sawing and Girdling: The rotary saw has been in use since 1899 with little fundamental change. It allows us to efficiently get (commonly) two diamonds out of a single piece of rough. In the top images image a carbon blade coated with diamond grit saws through a 10-grain (2.50ct) octahedron. Finished yield for the primary stone here is planned circa 1.05ct, with a circa 0.45ct "toppie" or secondary stone. This piece of rough will require 6-8 hours to saw. The sawyer will inspect the process every few minutes, along with dozens of other saws, monitoring and adjusting as needed.

Girdling (also known as Bruting) is the process of shaping the diamond girdle. This was first done by cementing two diamonds onto sticks and literally rubbing them together to create the total outline, including the "finished" facets (for very antique cuts). The bottom-left image below shows an old girdling machine which produces a bruted girdle. The bottom-right two images show a modern girdling machine with a water-cooled scaife which produces a finely-finished girdle - smoothly grained, but neither bruted or faceted.



2. Blocking of common-sized diamonds: After sawing comes blocking, which polishes the initial eight facets onto crown and pavilion for a standard round brilliant. This Octopus machine handles diamonds in common sizes and can be programmed for a range of primary angles. Following the initial stages of sawing, girdling and blocking, workers handle the details of cross-working and brillianteering, placing the lower halves, stars, upper girdle facets and culet (as needed). This is where human experience and feel is relied-on to adjust things that might have gone out of tune in blocking.



3. Production of small diamonds: Many factories have introduced machines which finish melee, due to the minute-scale and lower-value implications of obstacle C above. But the tradition of human labor remains strong. In Surat and Mumbai India human workers finish millions of carats of melee annually, including diamonds smaller than 0.01ct. Factories I have visited in Surat sometimes have up to four workers on a single polishing wheel, producing at an enviable rate. As a footnote; it is possible to produce finished larger diamonds by machine, but it's not common at high values for the reasons given above.



4. Laser-Sawing: Some pieces of rough are not suitable for straightforward rotary-sawing. This can be due to breakage, internal strain, difficult inclusion situations, a plan for multiple diamonds from the crystal or other factors. Laser-sawing has become very useful and, while extremely expensive, it's very practical for tricky crystals - and much faster than rotary sawing.



Ultimately, in the same way the human hand is preferred to finish productions of common-sized diamonds, rotary sawing is often preferred by manufacturers because it separates the crystal at a molecular level and leaves grit-residue, rather than vaporizing material as the laser does. While some loss is associated with both, the grit suitable for re-use in sawing/polishing is desirable to have.

Yield Note: I realize the loss-difference between mechanical and traditional may seem trivial, so I'd like to put it in perspective: Let's imagine that using a laser-saw and robot-polishing (instead of rotary sawing and hand finishing) results in only -0.005 average yield than traditional methods. A half-percent is not a big deal, right? It means your 1.15 carat diamond becomes a 1.145... But now multiply 0.005 by a four-million carat annual production, and you're talking about losing 20,000 carats per year to the vaporizer and robot-polisher. That can equate to millions of dollars left on the cutting room floor! I might add that my loss-prediction is conservative, according to the manufacturers I work with.

In my opinion the real strides-forward (technologically) are occurring in upstream rough-analysis. From internal scan technology which maps the most minute internal characteristics and calculates optimal cutting-plans - to the immersion of rough crystals in liquid with the same refractive index as diamond; empowering extremely clean viewing to the same end, there is amazing technology in-use at the top-end of the process. Long strides have also happened downstream in fundamental optical assessment of finished diamonds in the past decade: Specific credit to OctoNus and AGS Laboratories, among others. I can only expect further developments to continue as we approach the technological singularity (Ray Kurzweil, anyone?).

It's a great question and a cool topic. I hope the information here is interesting.

Cheers,

 

[Modified Brilliant]

Thanks John. Interesting information indeed!

 

[John P]

Thanks John. Interesting information indeed!

Thanks for the thanks Jeff. I'm glad someone read it.

 

[alisonia333]

This is a really interesting topic. My engagement ring stone is an early OEC and the idea that someone cut and polished this by hand amazes me. It's interesting to know how much is still being done by "hand" today. I love technology as much as the next 90s kid, but diamond cutting seems like an art as much as a science, to me. Thank you John and pang!

 

[Draco]

Curious, why do we have humans hand cutting and polishing diamonds? Why subject such beautiful diamond roughs to the jitters of a humans touch when grinding down diamonds?

It's a logical question...and the answer 10 years ago would be different than the answer now. Technology doesn't stand still.

But as the hardest known natural substance (emphasis on natural) of high value, with limited supply, there are three obstacles:

A. Although the hardest substance, diamonds have softer/harder spots, variable graining and highly variable internal characteristics.
B. Diamond cannot efficiently be "forced" to comply with a mechanical plan due to the factors in A, without risk.
C. Diamantaires will not take such risk: Losing a small percentage of source material annually may be negligible in other substances, but to a diamond production the implications are massive (see my final Yield Note).

There are currently four general applications for mechanical "cutting."

1. Rotary-Sawing and Girdling: The rotary saw has been in use since 1899 with little fundamental change. It allows us to efficiently get (commonly) two diamonds out of a single piece of rough. In the top images image a carbon blade coated with diamond grit saws through a 10-grain (2.50ct) octahedron. Finished yield for the primary stone here is planned circa 1.05ct, with a circa 0.45ct "toppie" or secondary stone. This piece of rough will require 6-8 hours to saw. The sawyer will inspect the process every few minutes, along with dozens of other saws, monitoring and adjusting as needed.

Girdling (also known as Bruting) is the process of shaping the diamond girdle. This was first done by cementing two diamonds onto sticks and literally rubbing them together to create the total outline, including the "finished" facets (for very antique cuts). The bottom-left image below shows an old girdling machine which produces a bruted girdle. The bottom-right two images show a modern girdling machine with a water-cooled scaife which produces a finely-finished girdle - smoothly grained, but neither bruted or faceted.



2. Blocking of common-sized diamonds: After sawing comes blocking, which polishes the initial eight facets onto crown and pavilion for a standard round brilliant. This Octopus machine handles diamonds in common sizes and can be programmed for a range of primary angles. Following the initial stages of sawing, girdling and blocking, workers handle the details of cross-working and brillianteering, placing the lower halves, stars, upper girdle facets and culet (as needed). This is where human experience and feel is relied-on to adjust things that might have gone out of tune in blocking.



3. Production of small diamonds: Many factories have introduced machines which finish melee, due to the minute-scale and lower-value implications of obstacle C above. But the tradition of human labor remains strong. In Surat and Mumbai India human workers finish millions of carats of melee annually, including diamonds smaller than 0.01ct. Factories I have visited in Surat sometimes have up to four workers on a single polishing wheel, producing at an enviable rate. As a footnote; it is possible to produce finished larger diamonds by machine, but it's not common at high values for the reasons given above.



4. Laser-Sawing: Some pieces of rough are not suitable for straightforward rotary-sawing. This can be due to breakage, internal strain, difficult inclusion situations, a plan for multiple diamonds from the crystal or other factors. Laser-sawing has become very useful and, while extremely expensive, it's very practical for tricky crystals - and much faster than rotary sawing.



Ultimately, in the same way the human hand is preferred to finish productions of common-sized diamonds, rotary sawing is often preferred by manufacturers because it separates the crystal at a molecular level and leaves grit-residue, rather than vaporizing material as the laser does. While some loss is associated with both, the grit suitable for re-use in sawing/polishing is desirable to have.

Yield Note: I realize the loss-difference between mechanical and traditional may seem trivial, so I'd like to put it in perspective: Let's imagine that using a laser-saw and robot-polishing (instead of rotary sawing and hand finishing) results in only -0.005 average yield than traditional methods. A half-percent is not a big deal, right? It means your 1.15 carat diamond becomes a 1.145... But now multiply 0.005 by a four-million carat annual production, and you're talking about losing 20,000 carats per year to the vaporizer and robot-polisher. That can equate to millions of dollars left on the cutting room floor! I might add that my loss-prediction is conservative, according to the manufacturers I work with.

In my opinion the real strides-forward (technologically) are occurring in upstream rough-analysis. From internal scan technology which maps the most minute internal characteristics and calculates optimal cutting-plans - to the immersion of rough crystals in liquid with the same refractive index as diamond; empowering extremely clean viewing to the same end, there is amazing technology in-use at the top-end of the process. Long strides have also happened downstream in fundamental optical assessment of finished diamonds in the past decade: Specific credit to OctoNus and AGS Laboratories, among others. I can only expect further developments to continue as we approach the technological singularity (Ray Kurzweil, anyone?).

It's a great question and a cool topic. I hope the information here is interesting.

Cheers,

John,

I think this is excellent information, thank-you for the time and effort you put forth into putting this together very informative.
I have thought the barriers to use of CNC in diamond cutting come down to variations in rough and graining and the lack of ability to make fine adjustments during the cutting process to get better precision and tuning amongst the facets.

From a cost perspective though the loss of diamond dust versus the additional cost of labour do these factors balance each other out?
Would CNC make sense for average quality mass produced rounds that were/are produced in assembly line fashion? (I.e. one person doing the same facets on multiple stones at once and then passing it off to another.) Is this even done like it is for colored gems?

 

[chrono]

In the coloured stone world, mass cut stones are done in factory houses in an assembly line fashion. The cut isn't great but the labour cost is extremely inexpensive. Stones of finer quality (ie above average colour) is cut by their better lapidaries. Precision cutting is modeled on computer first, then machine cut by hand.

 

[John P]

John,

I think this is excellent information, thank-you for the time and effort you put forth into putting this together very informative.
I have thought the barriers to use of CNC in diamond cutting come down to variations in rough and graining and the lack of ability to make fine adjustments during the cutting process to get better precision and tuning amongst the facets.

From a cost perspective though the loss of diamond dust versus the additional cost of labour do these factors balance each other out?
Would CNC make sense for average quality mass produced rounds that were/are produced in assembly line fashion? (I.e. one person doing the same facets on multiple stones at once and then passing it off to another.) Is this even done like it is for colored gems?

Draco,

You're welcome. I'm glad it's useful. I think it's a cool topic.

Chrono addressed colored stones. What's key here is that the hardest colored gemstone material is still a world away from the hardness of diamond.

We frequently use the Mohs scale (where diamond is 10) but it doesn't truly communicate how far-above every other natural known substance diamond is in hardness. To refresh, Quartz is 7, Topaz is 8, Corundum is 9, Diamond is 10... But put into perspective, diamond is much farther away than "9" to "10."

As it relates to CNC, we can look at the relative "scratch hardness" of materials as a reference point. Per Vickers, some people say corundum is around 400 and diamond is around 1600. But Vickers is nearly 100 years old and our methods have evolved. Here's a NanoScan example of a modern scratch-hardness test: http://nanoscan.info/eng/modes/scratch-hardness-test/

Quartz, topaz and corundum range from 11-23 GPa. The value for diamond shoots all the way up to 137! Put into (abstract) human perspective, we know there are athletes who can curl 230 pounds - although it's close to the world record - but there are not yet athletes who can curl 1,370 pounds. Returning to the topic, there is no doubt machines will evolve faster than humans. But, for now, the pure crystallography of natural diamond remains of of nature's most impressive creations. It still commands our respect.

Just as Chrono noted that human laps are still used for fine quality colored stones (which are soft by comparison), it's only logical that diamonds of any value are given human attention after sawing/blocking. Humans can inspect/anticipate the natural inclusions and feel the grain as they go. While machines could certainly "force" issues by-the-numbers, graining, internal strain or natural characteristics present could cause a forced diamond to burn, cleave or even 'explode...' And even small diamonds have enough value that producers won't typically risk them in that manner.

Comparatively, I believe there is more machining fashioning going on with industrial diamonds, where value is not such a factor. No doubt GQ producers will take cues from that sector as things evolve.

Cheers,

 

[Smith1942]

John, all that info was amazing. Thanks! It's fascinating to see images of diamonds being cut.