Speaking of Precision Blog

Speaking of Precision

Speaking of Precision is a knowledge preservation and thought leadership blog covering the precision machining industry, its materials and services. With over 36 years of hands on experience in steelmaking, manufacturing, quality, and management, Miles Free (Milo) Director of Industry Research and Technology at PMPA helps answer "How?" "With what?" and occasionally "Really?"

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Monocrystalline Diamond Tool Inserts For Brilliant Machining

Posted May 31, 2011 10:00 AM by Milo

Monocrystalline diamonds make the coating question "moot."

Recently, we were asked, "Why all the fuss about tool coatings? The base material and the tool geometry do the work."

Coatings can make the impossible possible.

We agree that the tool material and geometry are important determinants of success in production machining. See our original post here. But tool coatings can play a critical role in assuring successful machining by:

  • Significantly increasing tool life by minimizing wear;
  • Control built up edge (BUE);
  • Contol heat build up;
  • Increase the edge hardness.

To me, and I hope to you, 'successful machining' means "more parts produced per day at lower cost per part." Coatings help achieve this by increasing tool life (reducing tool cost component per part); by keeping machines running longer between changes (more parts per shift because more uptime per shift); and reducing variability of parts produced (BUE and thermal variation requiring machine adjustments).

Advancing the idea from Diamond Coatings (polycrystalline) to a Monocrsytalline Tool Insert, the folks at Paul Horn and H10 worldwide make the coating material into the tool material- to make the impossible possible. The photo above shows an aluminum workpiece machined to a maximum surface deviation of Ra 0.010 μm; Rz 0.014 μm. It is an optical component machined from a single piece of aluminum, that I photographed at Paul Horn Technology Days last month.

Or how about this plastic workpiece- absolutely no tool marks or 'frosting':

Monocrystalline Diamond Coating Makes a Difference!

Polycrystalline diamond coatings are widely available. This monocrystalline diamond tooling was first shown to us by Horn USA at our 2010 National Technical Conference. While diamonds are a non-starter for ferrous workpieces, they can be your key for 'brilliant machining' on other workpiece materials such as aluminum, copper, brass and bronze, nickel, precious metals, and plastics like PVC, polycarbonate, acrylic.

But I guess it isn't quite correct to call it a coating.

Mirror, Mirror from the cutoff...

Editor's Note: CR4 would like to thank Milo for contributing this blog entry, which originally appeared here.

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#1

Re: Monocrystalline Diamond Tool Inserts For Brilliant Machining

05/31/2011 2:27 PM

Very nice.

A good follow up to the previous thread. Thanks, Milo, for removing the 'frosting' from a few spots.

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#2

Re: Monocrystalline Diamond Tool Inserts For Brilliant Machining

06/01/2011 1:04 AM

Diamonds Are a Girl's Best Friend!

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#3

Re: Mono-crystalline Diamond Tool Inserts For Brilliant Machining

06/01/2011 3:20 AM

http://www.medidia-diamond-tools.com/page/index.php?menu=200

Still better for high precision are single crystal diamond tools, I bought the tools for turning and fly-cutting at the above company.

Better because sharper cutting edge, smoother adjacent surfaces, higher heat conduction - but cost more and to be handled with great care. You may damage the cutting edge by touching with your fingernails if the direction of touch is generating bending stress in the diamond.

Photo: first signs of wear, visible only with an interference microscope as only a very few nanometers are worn.

Magnification (lateral) is 200x, wear is near 10nm, polishing marks visible (3nm deep), and one defect. Diamond will not tolerate any hard inclusion in the material to be cut.

The maximum depth of wear is somewhat behind the cutting edge as there is the rubbing of the chips most intense.

These tools were used to cut aluminum and brass and OF-Cu - aircraft-grade is advisable. The graininess (crystals) of the metals is limiting the obtainable roughness near 10nm Rt. This is not at all visible by naked eye but as stray light without problems if tested with a collimated laser-beam.

Here a 200x magnification of such a surface: same interference microscope.

The steps (10nm) at the grain boundaries are clearly to be seen, not so clear are the ripple marks that were generated by a self excited vibration at 3MHz with 5 nmpp amplitude.

In the upper left region some intentionally made deformation: individual sliding bands, deformation starts in discrete planes.

RHABE

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