Underwater machining ?

[RCaffin]

I will be doing some machining with diamond cutters on very hard materials. The diamond tooling is best used underwater.I have done a little diamond drilling underwater (drilling 1 mm holes in cubic zirconia and ruby), but that was on a manual mill. So ...

Has anyone much experience with diamond machining?

Has anyone done any CNC work underwater?

What have you used as a chuck or face plate underwater? (Steel will rust, and I cannot find any SS or Al chucks on the web.)

Cheers
Roger

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[Jim Dawson]

Would a standard flood coolant system work? Using standard machine coolant? I think the goal is to remove heat as well as the generated particles, pretty sure that would accomplish your goals.

[LeeWay]

I was thinking standard coolant as well, but if you do not want the lubricity, guys use a rust inhibitor in the water for plasma tables. I haven't used it before, but that may keep things from rusting.

[RCaffin]

The advice from the vendors of diamond tooling is that conventional flood coolant is not as good as water. They are all quite definite about using water. I think the idea is that water has lower viscosity and higher thermal mass.

I tried dry machining and trashed a drill within a few minutes. I tried machining under water and the drill lasted more than an hour without significant damage. And the wet machining was on ruby, which has a Moh hardness of 9. I wrote a review of that at
http://www.cnczone.com/forums/calibr...ml#post1956342

My machine is set up for MQL and has no flood coolant facilities at all. I don't want to go down the flood coolant rabbit hole.

Cheers
Roger

[LeeWay]

You can make a pan to hold the vise or chuck that is deep enough. Just need to make a nice rubber gasket for it where the bolts go through. Also no real high speed machining with a pan of water on the table.

[RCaffin]

Hi Lee

Of course. I probably will. But has anyone DONE it?

Footnote: once the cutter is underwater, it does not seem to spray at all. Very strange to watch.

Cheers
Roger

[LeeWay]

I haven't done that particularly, but the method seems sound. I do have a wet tile saw and basically the same principles would apply to both. I also think for the reason I mentioned about rapids, that flood coolant would be a better option. You can run the same rust inhibited water in that system too. A large enough pans would catch most of everything.

[underthetire]

I've seen it done with quartz, but they used vacuum to hold down the part.

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[RCaffin]

Hi Lee

There is a difference between flood coolant and machining underwater. With flood coolant you have almost zero fluid pressure at the cutter, so that in many cases there is actually no fluid at the cutting face. The spinning cutter flings any water away, which makes it worse. That lets the diamonds get very hot and fail. That is a well-known problem.

With underwater machining you do have positive pressure at the cutting face so the coolant is at the cutting edge - or perhaps one should say the grinding face. The same reasoning applies to drills and cutters with high-pressure internal coolant and to lathe tools with high-pressure jets right at the tool tip. Getting the coolant to the active zone is hard.

Tile saws are a special case in a way. You pour the coolant onto the blade and the motion of the blade forces the coolant into the grinding zone. That works, and I dare say spray coolant will also work with twin-spindle grinding machines.

In any event, I am not going to flood coolant. End of that story. Sorry.

Cheers
Roger

[LeeWay]

I understand that you do not want to use flood coolant, but you are not quite correct about the pressure at the tool. I would think a pool of water to be far less capable of removing debris from under the tool than a steady heavy stream of coolant.
Otherwise everybody would be machining everything underwater.

[underthetire]

All the rock guys prefer to cut underwater. Not dealing with chips, just powder. Our guys do add a spray mist concentrate to the water, not coolant.

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[RCaffin]

Hi Lee

Ah, but it is not about removing the debris in this case. There are no chips in this, and the fine dust spreads out in the water very easily.
Instead it is all about the cooling of the diamond chips on the surface of the cutter. It is worth repeating: diamond machining on hard crystaline materials is not about 'cutting'; it is a grinding. And grinding generates heat.

Yes, I have seen photos of machining quartz. That too is grinding.

Cheers
Roger

[LeeWay]

Certainly a different method with different needs.

[RCaffin]

Hi UnderTheTire

All the rock guys prefer to cut underwater. Not dealing with chips, just powder. Our guys do add a spray mist concentrate to the water, not coolant.
References???? Any info at all???? What spray mist concentrate?
Please!

Cheers
Roger

[CaptainVee]

I seem to remember that grease attracts diamond, as in, olive oil is used to coat cutting wheels for diamond so that the diamond dust adheres to the wheel.

I think that using oily compound as a coolant will get messy.

[RCaffin]

I really,really hope that I will NOT be generating any diamond dust! That could get very expensive very quickly.

I guess the solution is an under-water slow-speed lathe or 4-axis mill. Rust-FREE!

Cheers
Roger

[awerby]

How big are the cuts you plan to make? Fastening your material to the bottom of an aluminum tank that can be bolted down to your mill bed would be a feasible strategy if the parts were fairly small. But if you're cutting corundum windows for a space shuttle or something, constructing a machine that's hardened against abrasive slurry might be your best bet. You can get diamond tooling that's designed to dispense coolant through the tool and into the cut, but it takes a special spindle to run it.

[RCaffin]

Hi Andrew

Aluminium tank - I think so. But I need the 4th axis, so 'there are complications'.
Both the tailstock and the axle of the 4th axis headstock will have to go though seals. The tailstock should be simple as it does not move, but the headstock axle will need to be a shade more sophisticated as it is rotating. That also means the chuck has to be stainless or 7000-series aluminium. These are not commercially available. Fortunately, it will not be spinning fast.

How big? Dunno yet. I would like 150 mm x 150 mm x 100 mm, but I dare say somewhat smaller will be very usable.

I asked a major American mfr of diamond tooling for advice. Their reply was
We have never had any of our customers use our bits in a CNC machine before (that we know of). It might work, but we've never tried anything like that.

Odd, as I would have thought some mfrs of gravestones would have used basic CNC gear for shaping and lettering.

Cheers
Roger

[tc26]

I grind and drill technical glass all day long, every day of the week on HAAS and FADAL CNC milling machines.
Diamond core drills, ICE BLUE ULTRA coolant concentrate mixed with water, external coolant and through spindle coolant.
Generally the materials are fused silica (quartz), samarium doped glass and borofloat. I have worked with ruby on occasion.
To drill a flat sheet that is at finish thickness we stack it as follows;

.040" cover glass
work piece
.25" base glass
Aluminum base for clamping to machine.

Base glass and cover glass eliminate chipping as drill enters and exits work piece.
Everything in stack is heated and covered in wax prior to stacking

[RCaffin]

Hi tc26

Aha! Interesting.
Care to let me know what size drills, what brand drills, what spins and feeds?
Granite contains a lot of quartz, so your figures would be directly relevant.
I am in Australia and won't be working in the same area as you at all.

Cheers
Roger