I need help with short margin

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I think you are pressing at to high a temperature
That could very well be. Id double check the burnout temp, and make sure its at or under 850. If youre getting reaction layer, your press temp is too high, and at least with the Zubler...if you raise your regulator pressure, youre not increasing your press-power.
 
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Brian Chahs

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I think you are pressing at to high a temperature
High temp? I am pressing at 700Celsius and my burn out oven is set 850.

Should i increase the temp? Or decrease?

Should I start decreasing burn out oven for how much? Or start with zubler 700 to 670?

...
 
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High temp? I am pressing at 700Celsius and my burn out oven is set 850.

Should i increase the temp? Or decrease?

Should I start decreasing burn out oven for how much? Or start with zubler 700 to 670?

...
No youre not. Your 100 gm ring should be pressing in the 910 to 920 range.
 
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Brian Chahs

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I have jubler 300 pressing furnace and the final pressing temperature is 885.

Should I raise temp 5 Celsius? And see what happen?
 
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ztech

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If you are pressing at 885, your calibration is off. The Emax pressing range is 900-940 C. I have the 300 and press at 921 for the 100 gm ring. Without seeing photos of the internal aspect of the crowns I suspect that this may be investment breakdown at the point of the prep. Your margin, although rough, they seem the same shape as the die margin. I think if you illuminate the coping you will see some opaque spots that will indicate investment in the press, but then I could be wrong.
 
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MasterCeramist

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The margins are rough but seem to follow shape of the die. Looks like they are tight on the die or may have an undercut issue keeping them from seating. Have you adjusted any internally to see if they will seat or used any type of fit checker .
 
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martintay

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The margins are rough but seem to follow shape of the die. Looks like they are tight on the die or may have an undercut issue keeping them from seating. Have you adjusted any internally to see if they will seat or used any type of fit checker .
Agreed - doesn`t look like a press issue to me ! Cast another die , and if necessary trim the occlusal and axial walls and see if margins are accurate ??
 
LA Ceramics

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If you don't take the ring out of the oven immediately, or even worse,..if you allow the ring to be taken back up into the oven then the material can be drawn back toward the plunger/pellet. I always take it out as soon as it beeps and place it on the cooling rack with the furnace tongs propped on the plunger. Yes ,...I know that last part about the tongs is a bit much but it's a quirk that works,...or maybe I'm just kidding myself,..oh no,...now I'm starting to sound kinda flaky,..darn it!!!HahahaBanghead
 
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fadlm

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According to the pictures I can diagnose, with a high degree of certainty, that the issue you are having is, in fact, one of short margins.
 
Marcusthegladiator CDT

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The margins are rough but seem to follow shape of the die. Looks like they are tight on the die or may have an undercut issue keeping them from seating. Have you adjusted any internally to see if they will seat or used any type of fit checker .
They are not seated. The op lifted them off the die so we can get a better view.


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Zubler USA

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ztech - Lithium disilicate (E.max) melts at between 880C & 885C. The Temperatures typically used in traditional press programs are high in order to compensate for the thermal mass they must get through to melt the ingots sufficiently to press. Thus when you complete the press, some areas of the press have more reaction layer than others. The programs in the Vario Press 300.e are different. What Brian's display is showing him is correct.

All - The problem Brian is experiencing I suspect is not furnace related, however I will leave you to decide. Here are a couple Brian sent me for troubleshooting purposes. Those of you that have posted so far let me know what you think the problem might be and maybe together we can get Brian set.

20140527_102227.jpg 20140527_102222.jpg
 
Mike2

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use some fit check or take off the top of the die I thinks it's either investment breakdown from die lube or more so an issue of expansion liquid ratio is off. I thinks that seat with a little/ lot of internal adjustment, only because it follows the mg contour too well. My two cents
 
Zubler USA

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Do you think it's the oven? at all?
 
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No. It was an insufficient prep for an e.max to begin with; needs more material at the margin. It should still have pressed, but is doomed to fail in the mouth. Im guessing when the investment is poured, its lifting residual die lube or cleaner to the margins and because of surface tension, its being left there creating either a void or corrupted investment. I don't like the looks of the rest of the crown as Im seeing it either. Almost honeycombed with a faint crystal spyderwebing. Im guessing a reused ingot(?),quenched to cool? Burn out oven way too hot?
 
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ztech

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Chris, I saw in another thread where he was using the newer Vario Press 300 and I know from talking to you and Kurt that you have programmed in a different way to handle the thermal mass. I just could never find the thread to post an update to my post. After looking at these photos, I will first say that what is visible is a lot of chips and fractures on both the margins and the sprue leads. Another obvious defect besides the short margins is the scallop fracture areas along the axial surfaces of the margins. This still doesn't account for the failure to fully seat. I would start with the investment and things that can effect its integrity, but from the other defects it seems it may be in the burnout or press parameters. A simple test would be to have him send another lab an invested pattern. That would either confirm investment problems or point you to an oven (burnout or pressing) problem.
 
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LamPlusLab

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First always use a high powered microscope to view any bubbles that can accumulate inside the crown. If only a portion of the margin is gone, increase your hold time and add 30 seconds to your press time. It's always a function of hold and press time and temperature, so any one of these alterations may affect the crown margins.


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sidesh0wb0b

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that looks like an incomplete burnout and possible a hot press either from too hot of a burnout or the press itself. not to mention the lack of a proper shoulder (but as username mentioned, it should have pressed)
 
Mike2

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I have to agree with the die lube factor.. I'd seen this over the years, especially with alcohol based die lubes. Which lube are u using? Make sure all die lube is removed from the pattern before investing. I don't think it is suck back as it would be rounded also and less uniform.. My money is on die lube, change back to what u were using, or try new bottle of lube. When they sit for long time it can become concentrated. In addition with summer months you may want to increase bench set for rings as they take longer to set in humid environment.
On a separate note, change only one thing at a time to pinpoint. My 2cents.
 

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