Wet Milling Zirconia?

Bryce Hiller

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Are there pros and/or cons to wet milling zirconia instead of milling it dry? Thanks!
 
CoolHandLuke

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the only Pro is better control of your dust, but there are several big Cons.

you have to use pure distilled water because minerals in the water cause discolouration. you cannot share the machine with any other application that uses oil or alcohol based coolants, such as Ti or Emax. you have to clean your machine immediately post finish or else the liquid will cake on your surfaces and be difficult to remove. for the same reason you have to clean the milled units immediately after the cycle finishes. if it dries on a unit, it wont be easy to remove.

the alternative to milling presintered zirc, is milling fully densified zirc a la bruxzir anterior. so good luck with that.
 
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really dont mill it wet also if it is not completely dry you will get 5hitty colours if hand colouring and a lots of steam fractures .also when you wet mill it isnt just water coming out of the machines its a mix of water and milling lubricant which has oil and glycerine .god knows what that does to the inside of your furnace.
 
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reqvaa

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Working with KaVo Arctica - milling wet Zirconia, after milling washing and cleaning with steam, and after drying in the furnace with heating to 400 C for 30-60 min, for now this is the only way for us.
Its hard to paint well if not go through heating process. And yes, this is must be not cool for furnace.
 
2000markpeters

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You will just kill your mill with zirconia sludge. No advantage what so ever.
 
Bryce Hiller

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Well I guess I'll let the cat out of the bag...We are getting our first mill very soon, and its likely going to be a Versamill 5XS from Axsys. This is a wet mill, but can also be converted into a dry mill. I've been told by them that they recommend wet-milling our zirconia, and they even have that on their website. Could Brayks help me out with this?? Can someone tag him in this? I don't know how to do it....
 
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@brayks

Could you share some thoughts on this boss?
 
brayks

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I am currently traveling and will share my thoughts once I land and get sorted...
 
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I mill wet. It has it a few drawbacks like Luke mentioned. The switching coolant to water is probably the most inconvenient. I mostly do Zirconia so it's not that big of a deal.

If you had to switch all the time between Emax and Zirconia I could see it be a bit of a pain but then you just buy a separate tank for the coolant and hook it up.

Cleaning the mill is no big deal. Just a spray and a wipe down.

As far as the cleaning the units. Just place then in an Ultrasonic for a few minutes then dry off with a toaster oven for 20 minutes and your good to go.

Or use a camel hair brush and some compressed air and give it a good clean. Same as you would if you milled dry.

I like how quiet it is. No suction running all the time is actually quite nice.

And I don't know but it seems like milling wet should make tools last longer but I can't confirm that claim.

If you have any other questions please feel free to pm me.
 
CoolHandLuke

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the 5xS was built to mill everything and it is very capable of that. does ti as well as emax and plastics and soft stuff, but given the differences in coolant you should really consider segregating that; wet mill ti from one tank, emax from the other tank, and dry it off for doing zirc. the main thing will be "try not to switch often" given the pain in the butt it is to keep contaminant free.

its not going to hurt your ti milling to have contaminants. it IS going to hurt your emax, and it is definitely going to hurt your zirconia.

in practical terms you could fill both tanks with water and do emax with water coolant only, but you will use up tools like crazy.

why should you mill zirconia wet then, well for one i can speak to versamill zirconia procedure and i can tell you it is whisper quiet. like sit perfectly still and you will strain your ears to hear the cutters engage. specifically for versamill this means its a highly controlled method. yes you will need to clean your machine often and keep the pumps running so the sludge doesnt break the pumps. but acoustics alone arent a good reason. im certain steve has posted his reasons before ....
 
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I mill both wet and dry. If I were to purchase another mill I will buy a wet mill again. I use ultrasonic to clean all my units prior to putting them inside convection oven for drying. It is an extra step but the mill quality is so much better and the tools last longer.
 
Polarmolar

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If you mill Katana precoloured does it effect the colours much ?


Sent from my iPhone using Tapatalk
 
brayks

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Really nothing much really to add to what's already been covered, but OK, machining zirconia…

There are four basic principles that should be followed when machining zirconium (dental or other applications): slow speeds, high feed rates, climb cutting and a flood coolant.

Zirconia tends to compact and adhere to cutting tools and metal surfaces. It also tends to work harden, requiring higher than normal clearance angles on cutting tools to penetrate the work-hardened surface and cut a clean coarse chip. 12 to 15 degree positive radial rake give optimal surface finish and tool life.

techdat4.gif


Cutting rates ae from .005” to .010” per tooth at 150 to 250 SFM. Since small cutters are used with small step over values are used, small chips are created therefore Radial Chip Thinning adjustments must be made to cutting rates to avoid excessive tool wear, poor finishes and chipped margins - yet another reason for flood coolant as the heat generated by the machining process is typically not transferred to the chip (either due to inappropriate feeds/speeds or the fact that zirconia is a pretty good insulator) but instead remains in the cutting tool which tends to gall on the tool cutting and relief surfaces.

speed-feed-milling.png



Because of its brittleness, Heavy rigid machines and fixturing give best results and it is important to maintain a non-interrupted, constant load, climb cut when machining.

7515_orig.png

The machining “slurry” associated with dry machining zirconia is very fine, caustic and highly abrasive. Regardless of fine filters and massive vacuum systems it is very difficult to keep the dust from penetrating “sealed” areas of the machine (ballscrews, ways, transport mechanisms, electronic enclosures, etc.). This penetration will lead to premature wear on critical machine components and in many cases escapes the enclosed machining area and accumulates in the work environment.

There is also the noise and added expense and maintenance associated with filters and vacuum systems.

Since the zirconia tends to gall, it should not be left to dry and accumulate on metal machine surfaces for an extended period of time. Periodic rinsing of the machining compartment of the machine using a tube attached to the coolant nozzle while activating the coolant pump is a very quick and easy way to accomplish this. Also, a quick shot with an inexpensive steam cleaner into the machining “chamber” periodically will keep the area looking shiny and new. This whole process takes about 5 minutes or so.

Distilled water is best to use. We use it for both zirconia and glass-ceramics. Extended tool life can be obtained by utilizing a lubricant. We are currently testing a water soluble, residue-free coolant that looks very promising. As mentioned previously residual lubricant on zirconia or glass-ceramics is all bad.

Machining wet does add another dying step to the workflow as units with residual moisture can crack in sintering and cause color shades to appear lighter.

An inexpensive toaster oven works quite well. Drying times vary. See below.

Single (70°C)): 15 minutes+

Single (140°C)): 5-10 minutes

2-4 units (70 °C): 40 minutes+

2-4 units (140°C): 25 minutes+

5+ units (70°C): 50 minutes+

5+ units (140°): 25 minutes+

Our customers have found the machine cleaning (which should be done anyway),coolant swapping (if necessary) and drying are worthwhile trade-offs for increased tool life, lower operating expense, lower noise levels, cleaner working environment, extended machine life, higher quality and more aesthetic units.

End of report...
 
CoolHandLuke

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250? i run titanium faster than that. you guys change to 4fluted tools when i wasnt looking ?
 
brayks

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250? i run titanium faster than that. you guys change to 4fluted tools when i wasnt looking ?
Remember 250 is for full width cut. Factor in the RCTF and you have what we are running...
 
JMN

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Really nothing much really to add to what's already been covered, but OK, machining zirconia…

There are four basic principles that should be followed when machining zirconium (dental or other applications): slow speeds, high feed rates, climb cutting and a flood coolant.

Zirconia tends to compact and adhere to cutting tools and metal surfaces. It also tends to work harden, requiring higher than normal clearance angles on cutting tools to penetrate the work-hardened surface and cut a clean coarse chip. 12 to 15 degree positive radial rake give optimal surface finish and tool life.

techdat4.gif


Cutting rates ae from .005” to .010” per tooth at 150 to 250 SFM. Since small cutters are used with small step over values are used, small chips are created therefore Radial Chip Thinning adjustments must be made to cutting rates to avoid excessive tool wear, poor finishes and chipped margins - yet another reason for flood coolant as the heat generated by the machining process is typically not transferred to the chip (either due to inappropriate feeds/speeds or the fact that zirconia is a pretty good insulator) but instead remains in the cutting tool which tends to gall on the tool cutting and relief surfaces.

speed-feed-milling.png



Because of its brittleness, Heavy rigid machines and fixturing give best results and it is important to maintain a non-interrupted, constant load, climb cut when machining.

7515_orig.png

The machining “slurry” associated with dry machining zirconia is very fine, caustic and highly abrasive. Regardless of fine filters and massive vacuum systems it is very difficult to keep the dust from penetrating “sealed” areas of the machine (ballscrews, ways, transport mechanisms, electronic enclosures, etc.). This penetration will lead to premature wear on critical machine components and in many cases escapes the enclosed machining area and accumulates in the work environment.

There is also the noise and added expense and maintenance associated with filters and vacuum systems.

Since the zirconia tends to gall, it should not be left to dry and accumulate on metal machine surfaces for an extended period of time. Periodic rinsing of the machining compartment of the machine using a tube attached to the coolant nozzle while activating the coolant pump is a very quick and easy way to accomplish this. Also, a quick shot with an inexpensive steam cleaner into the machining “chamber” periodically will keep the area looking shiny and new. This whole process takes about 5 minutes or so.

Distilled water is best to use. We use it for both zirconia and glass-ceramics. Extended tool life can be obtained by utilizing a lubricant. We are currently testing a water soluble, residue-free coolant that looks very promising. As mentioned previously residual lubricant on zirconia or glass-ceramics is all bad.

Machining wet does add another dying step to the workflow as units with residual moisture can crack in sintering and cause color shades to appear lighter.

An inexpensive toaster oven works quite well. Drying times vary. See below.

Single (70°C)): 15 minutes+

Single (140°C)): 5-10 minutes

2-4 units (70 °C): 40 minutes+

2-4 units (140°C): 25 minutes+

5+ units (70°C): 50 minutes+

5+ units (140°): 25 minutes+

Our customers have found the machine cleaning (which should be done anyway),coolant swapping (if necessary) and drying are worthwhile trade-offs for increased tool life, lower operating expense, lower noise levels, cleaner working environment, extended machine life, higher quality and more aesthetic units.

End of report...
Copy, Paste, Print.

Thanks!

pdf of his post attached for those who want it.

[edit: whoa, Dude. I thought I had a small clue on machining until reading where that links. My clue is very very small indeed. Thanks again.]
 

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brayks

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Copy, Paste, Print.

Thanks!

pdf of his post attached for those who want it.

[edit: whoa, Dude. I thought I had a small clue on machining until reading where that links. My clue is very very small indeed. Thanks again.]

Thanks JMN.
Yeah, That's the Mastercam website. Mastercam is the world's most widely used CAM product. We have been one of their top 5 resellers worldwide, every year for nearly 25 years. We also live this stuff daily (www.axsysinc.com) in just about any application and machine tool you can think of.

 
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JMN

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Thanks JMN.
Yeah, That's the Mastercam website. Mastercam is the world's most widely used CAM product. We have been one of their top 5 resellers worldwide, every year for nearly 25 years. We also live this stuff daily (www.axsysinc.com) in just about any application and machine tool you can think of.


You're very welcome ;)

I knew heat management was a tricky beast when machining, making sure the cooled part after machining and work hardening is the correct size instead of cooling shrink to a incorrect size, but hadn't a clue how much chip size played into that.

Now I have all kinds of more stuff I thought I knew...
Thanks, y' turkey. Really. Seriously. Thanks.


Y' turkey.
 
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