EMAX cracks

[Marcusthegladiator CDT]

When the furnace opens, dont blow on it.

 

[Patrick Coon]

Nor pick it up with metal tongs and rinse under cold water.

 

[MasterCeramist]

The only cracks we have ever gotten with emax have been when we had to adjust on the inside of the crown to seat, The cracks didn't seem to show up until after glaze cycle. We have gotten much more diligent with blocking out undercuts and the like and haven't had any issues for a long time.

 

[Arkhalon]

We are getting cracks in our emax after it is fired for stain and glaze. We are using Vacumat 6000.
Starting temp: 403 C
6 min dry time
50 rise
Vacuum comes on at 453
Final temp 735 C
Hold 1 min

We are at wits end trying to figure out what is going on. Don't know if they might be too thin or a thick and thin spot together.

I have a Vacumat 6000MP take this program, i use at onlay, full contur emax crowns for glaze:
450C
6 min dry (25% - 44% - 62%)
Vacum start 450 C
rise 60 C
final is 800 C
Hold 1 min
Slow cool 80% 550 C

I always use Easy Fix! http://www.zubler.de/de/produkte/verbrauchsmaterial/easy-fix

 

[Patrick Coon]

That's when they usually crack in these situations. They have several firings in there thermal history and the stress builds, then releases in that glaze firing.

Again, in these situations with thick-to-thin-to-thick geometries, add a long term cooling to at least the glaze cycle. If you can control by temperature, cool to 500C; if you control by time, 5-7 minutes will usually do it.

 

[Affinity]

ive done hundreds and never had one crack in the lab, only a couple in the mouth... I know that doesnt help, but this sounds like more than an oven cooling issue.. are you rapid cooling the ring? This could build up some unwanted stress.. especially if its happening more than once.. and I dont slow cool my emax, maybe 2 min cool

 

[Mjr]

I am
Gay so who cares


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[user name]

CRACKS!!! We don't press any thinner than .3. We detail the anatomy with carbides, and quench the rings to keep things moving. I don't know whats going on?!!? Good thing we reuse all our old ingots!



Just kidding.

 

[Mjr]

Drunk friend if mine. Sorry. Makes for a laugh though


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