Composite machining: Diamond or Diamondlike coating? 2

[plvachon]

Hello all,

I need to make some machining on carbon/epoxy composite parts, so i have to buy some diamond-coated endmills. I found two types of coatings in the catalogs: diamond and diamondlike coatings, with diamondlike being half the price of diamond. Has anyone already tried diamondlike-coated tools and if so, were you satisfied with it? Should I prefer the diamond-coated tools? Thanks for your input!

 

[RPstress]

You will probably get better tool life from PCD (poly-crystalline diamond) coatings. However, a lot depends on the base material and the coater.

If it's a tungsten carbide tool being coated then the coating process can damage the cobalt binder, which results in a lack of sharpness and the resulting tool can start to give unexceptable results before the base carbide one, or tool breakages may increase. It's important for the base carbide manufacturer and the coater to be close (or the same entity).

A lot also depends on what exactly you're machining. Not only is carbon a bit worse than glass fiber (and both are a lot harder on cutters and drills than any monolithic metal workpiece), but apparently small details of the composite like the exact resin can make a significant difference. A weaker resin may well make it easy for the cutter to rip the material apart.

I suspect that the only way to tell for sure what your tool wear rates are is try it and see.

Alas, I can't share numbers, but PCD has been preferred for some operations where thickness has been being reduced (rather than a profile being machined) on a cost basis.

 

[MSSandvik]

generally speaking... Diamond like can be redressed and coated. true diamond cannot.

this is a cost-per-hole type problem as i find coatings make very little difference to quality.

You may have to buy some of each and compare prices accordingly.