muffle cracks with 3D print pattern

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Hi

I am printing full anatomical crowns in asiga's supercast material. I am investing these and attempting to press in emax. But muffle keeps cracking badly due to expansion of supercast under heat. So far tried press vest speed. Then tried formula 1 with very slow temp increase. Even tried letting it set under pressure for denser mix.

No luck
Any ideas?
 
gdallc

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Hi

I am printing full anatomical crowns in asiga's supercast material. I am investing these and attempting to press in emax. But muffle keeps cracking badly due to expansion of supercast under heat. So far tried press vest speed. Then tried formula 1 with very slow temp increase. Even tried letting it set under pressure for denser mix.

No luck
Any ideas?
Use Shofu Ceravety Press and Cast, Burnout at 1700 deg.F for 45min. I also use the Asiga but have not used supercast yet as I still have some plascast however I have tried a lot of investments with different prints from different machines, Ceravety has never failed but others do.
 
Patrick Coon

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I would check the content of your printing material. Some have too high of a resin content to be able to use a quick set investment and fast burnout. I would recommend you use a regular investment (PressVest) and a two stage burnout from a cold oven (Heat rise of 5C/41F to 250C/482F and hold for 30 minutes, then heat rise of 5C/41F to 850C/1562F hold for 45minutes for 100g ring or hold for 1 hour for 200g ring. Of course if burning out more than two rings at a time increase your high temp hold 15mins per ring.

To keep this from greatly affecting my production times I would always wax and invest throughout the day and put all rings in the burnout furnace before leaving for the day. I would set the furnace to start around 2:30am and when I arrived at 7am everything was ready to press or cast. This has the added advantage of using the most energy when electricity prices are the lowest (off-peak hours).

I hope this helps.

Also, per Asiga's web site: "Offering excellent strength, build speed and resolution, SuperCAST is designed for direct-investment casting. Processing under a 12 hour burnout cycle, SuperCAST burns beautifully leaving no ash or residue." Of course this is for a gypsum bonded investment, not a phosphate bonded investment.

https://www.asiga.com/media/main/files/SuperCAST_us_en.pdf
 
Affinity

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Having the same problem with milled wax.. not bad cracking but fins nonetheless.. A 12 hr burnout is out of the question.. We might as well be sintering zirconia.. I would just try putting it into a cooler oven.. ~350-400c then slowly ramp it up... 2 stage like noted above.
 
gdallc

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Having the same problem with milled wax.. not bad cracking but fins nonetheless.. A 12 hr burnout is out of the question.. We might as well be sintering zirconia.. I would just try putting it into a cooler oven.. ~350-400c then slowly ramp it up... 2 stage like noted above.
Seriously, give this a try. Use Shofu Ceravety Press and Cast, Burnout at 1700 deg.F for 45min
 
Patrick Coon

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Having the same problem with milled wax.. not bad cracking but fins nonetheless.. A 12 hr burnout is out of the question.. We might as well be sintering zirconia.. I would just try putting it into a cooler oven.. ~350-400c then slowly ramp it up... 2 stage like noted above.


I was DEFINITELY NOT recommending a 12 hour burnout, but that was a quote on there website for casting jewelry in a gypsum bonded investment. I think the two stage burnout that I offered would be the best option. Any time you are using a pattern with a resin content that is too high (as in some 3D printers or milled wax/plastic) it will give you this issue as the resin expands too much before it starts to melt and burnout.
 
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Raise to 750-800F and hold for 30-60 minutes (depending on how many rings)

then climb to high temp as usual......hold....cast.
 
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Thanks for the advice.

Far as burn out time goes, no matter how slow the climb, doesn't seem to help. I am going to go with getting some Shofu ceravety.

Only catch is nobody sells it in this country. Gonna have to order it in myself :(

Hope it works as the prints are beyond my expectations.
 
Patrick Coon

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Another question... How long are you mixing your pressvest speed for? I know some people are only mixing it for about 1.5 minutes, or less. The instructions call for a mix of 2.5 minutes at ~350 rpms. This material really needs the 2.5 minute mix time to develope its' full strength.
 
Toast

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Thanks for the advice.

Far as burn out time goes, no matter how slow the climb, doesn't seem to help. I am going to go with getting some Shofu ceravety.

Only catch is nobody sells it in this country. Gonna have to order it in myself :(

Hope it works as the prints are beyond my expectations.

What country are you in? For some reason SHOFU doesn't sell cerevety through distributors at least here in the states. You have to order it direct from SHOFU. It is a nice investment, a bit expensive but worth it for the results. I mentioned in another thread I accidentally put a ring of full contour printed crowns in a hot oven and they pressed great. I can't say it was because I invested with Cerevety but from then on I always went into a hot (1562 C) oven and pressed without any issues. I wish I had the same luck with some of the resin/wax milling discs.
 
DMC

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Thanks for the advice.

Far as burn out time goes, no matter how slow the climb, doesn't seem to help. I am going to go with getting some Shofu ceravety.

Only catch is nobody sells it in this country. Gonna have to order it in myself :(

Hope it works as the prints are beyond my expectations.


You have to HOLD at 800F for a while. (30-45 minutes)

nothing else matters that you are trying....

Trust me. I talk with many industries and know a whole bunch of people printing and casting.
I have owned over Twenty printers myself, and have Four here now with me.
 
Zubler USA

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Sorry I'm late to the party. It's been a while. I know this is something most technicians refuse to believe, but cracked rings are rarely the result of the press oven. They are usually the result of investing issues. Although I am sure you are an experienced technician, I deal with many that do not understand how the investment is affected by certain procedures during the investing process. One thing that Mr. Coon pointed out is the mix speed & time, this is crucial for setting the investment up properly, but if the investment is not bench set long enough, then it makes no difference. Keep in mind the following:

1. De-bubblizer, Vasoline and other chemicals will keep the investment from setting up properly.
2. Proper mixing is crucial, being able to control the mix speed (RPM) and time are both important
3. Vacuum must be maintained well, check you machine from time to time
4. BENCH SET GIVES YOUR RING THE STRENGTH IT NEEDS!!! When your investment is mixed, the friction and chemical reaction both cause the heat in the ring you feel - obvious. However, the faster you mix the investment, the hotter it gets. Most investments have an RPM range. This dictates the efficiency at which any moisture is evaporated from the investment during the bench set time, it also dictates the working time. If you tend to mix at the lowest setting, you should bench set longer. You can even bench set a little longer than the maximum time in the instructions typically, (not much) but a little.
5. Sometimes cracked rings can be the result of improper burnout. One side of the ring being to close to the heating element, rings not being spaced properly through the burnout oven.
6. Some times reusable alox plungers will cause cracking, but this is usually passed to the ceramic itself and not usually the cause of the ring cracking. This is a topic for another time.

Large labs are my favorite - They want to mix 600 grams of investment at one time. They need more working time so they mix at the lowest speed, they want the rings processed faster so they bench set the shortest time, They shove too many rings in a burnout oven to one side too close the the heating elements and they have cracked rings like crazy and blame it on the equipment.

Rings crack because of procedures. Very rarely because of press ovens. You may see the cracking more evidently in one oven over the other based on the type of press, pressure used and program used (longer shorter press times etc),but it is only the place where the final result is shown, not where the problem stems from.

NOW, on to the milling and printed materials - these materials were not made for use in this industry. They have caused numerous problems and tend to be problematic when pressing. A couple things to remember when working with these materials:

1. The more resin in the material, the more of a pain it's going to be. You will have to watch the burnout time carefully. Times vary depending on the material. Some of the original resins take more than a couple of hours to completely burnout. The good news for those of you milling is that new discs are being manufactured that address these issues and are readily available....(like ours - sorry, I had to - I know it's shameless, and opportunistic, but I haven't mentioned our other products throughout this whole thing..)

2. If you do not burnout long enough, the burnout will be completed in your pressing oven, causing a decreased life in your heating element and contamination in your insulation.

Good luck. I hope this helps.
 
Old Navy Tech

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I'm late to the party too, stumbled onto this thread while searching the google for how high possible to burnout Ceravety by Shofu.

I agree with Glick Dental Labs 100%, I have in my 25 years of being a lab tech, not found a better investment than Ceravety... I use it to press lithium disilicate, and
to cast my CrCo frames for acrylic retention/support for implant supported full dentures. I use a variety of modeling materials, from light cure plastics/waxes to GC pattern resin and
regular waxes.. I've been doing a slow burn for the CrCo, and take it all the way to 950 for 45 minute hold, then down to 920 to cast... for LD using wax only, it goes into a 820 C degree oven
ramped up to 950C for 30 min and back to 860 to press.
I had an old boss that told me that cooking the bjesus out of high heat investments, made the silica fuse etc and makes for a smoother casting. Whether there is any real science to it, I
haven't researched... all I know is it works, I even use HH investment to cast full gold crowns with surface texture like Cristobalite.

My molds do have a few micro fissures when I use pattern resins (more with the lightcure stuff) but it seems to fuse harder than hammered cat**** and I don't see to often "fins"

The reason I was "researching" just how high I can take the Ceravety, I was having a "discussion" with my Swiss technician wife about having the other employees following the instructions
with the pink metal opaquer, doing it in layers, rather than clumping it all on in one go, and she brought up that I don't follow the instructions of the investment, which say max 900 C, tho I read
that part as to the max you can put a 20 min bench set fast burnout ring in. ;-)
Anyways, Happy New Year and successful casting !
 
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Another question... How long are you mixing your pressvest speed for? I know some people are only mixing it for about 1.5 minutes, or less. The instructions call for a mix of 2.5 minutes at ~350 rpms. This material really needs the 2.5 minute mix time to develope its' full strength.
This is a great point we always mix 1.5min I think I’ve over looked this , if it adds strength I’m doing it 👍👍🦷🦷
 
Patrick Coon

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This is a great point we always mix 1.5min I think I’ve over looked this , if it adds strength I’m doing it 👍👍🦷🦷
DentalDen, this post was from 7 years ago, and things have changed. If using Ivoclar Investment, it is now a 1.5 min mix @350rpms. If you mix for 2 minutes it will likely set before you finish investing. Always read and follow the manufacturers instructions on any material for the best results.
 
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Indeed things have changed, Patrick... What an innocent world it was, back then...
I’m gona read instructions soon that’s only been a few years I’ve been using it I’m slowly getting there 😂👍👍🦷🏴󠁧󠁢󠁳󠁣🏴󠁧󠁢󠁳󠁣󠁴🏴󠁧
 
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