loose castings

amadent

amadent

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All my castings seem to be on the loose side. They are not retentive. I have tried using more water, less liquid in my investment. It does not seem to help. I am using galaxy II from talladium. For my np I went from 3 water, 20 liquid to 6 water, 17 liquid. the copings still are not tight enough. On my noble I use 7 water,and 16 liquid. What else can I try to get better fitting castings?
 
SiKBOY

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Keep upping the water to liquid ratio.
 
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Have your fittings suddenly become loose, or gradually? New box of investment? Fresh bottle of liquid? Do you store your stuff in a temp stable location? If its kept in a cabinet next to an exterior wall you can have some variable fittings. Double check your burnout temps. Have you changed your mix time or RPMs?
 
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Ask yourself what has changed ? If you change procedure , only change one thing at a time other wise you won`t find the cause !
 
EJADA

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My understanding with theses types of investments is you can go as much as 50% water. Keep it moving until you see a difference. If it is a new box of investment and you can't get it to work get a new box overnighted to you. Just make sure the lot # is different.
 
amadent

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I have always seemed to have loose castings. can burnout temps make a difference. My np calls for 1700, should I try and lower that, to say 1600?
 
jackjabbour

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this happened to me once and I had to DRASTICALLY change the ratios. I never would of believed that the ratios im using now would of worked but they do, even tho its so different than what i was using before......dont ask me but its working now.
 
aidihra

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Try adding more water to make the investment more liquidy. If you're instructed to put 10ml, try adding 1ml or 2ml extra.
 
ps2thtec

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Check out page 4 of this document on fits. Have you tried cooling your liquid?
http://whipmix.com/wp-content/uploa...hooting Phosphate Bonded Investments_0611.pdf

I was always skeptical when a product is new and improved, usually not for the better. But WMix did that late last year on Formula 1 and have to say its definitely better. Creamier mix, harder, and castings a super clean. Easy to adjust fits changing your ratios. My two cents.
 
amadent

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ill try changing the ratio even further. let you know later on in the week
 
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I have always seemed to have loose castings. can burnout temps make a difference. My np calls for 1700, should I try and lower that, to say 1600?

It makes a huge difference. Im at 1585.
 
amadent

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I used 8 water and 15 liquid for my np (tilite p) they were actually a little snug. thanks for suggesting that I change the ratio drastically. 8/15 was a great ratio for my noble metal. Are you burning out at 1585 for your np? what temp do they reccommend?
 
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I used 8 water and 15 liquid for my np (tilite p) they were actually a little snug. thanks for suggesting that I change the ratio drastically. 8/15 was a great ratio for my noble metal. Are you burning out at 1585 for your np? what temp do they reccommend?

I use microstar and zubler 144 investments. They recommend 1600 for burnout. I just like the results Im getting at 1585. for NP (RexIII) Im using 21 liquid and 4 water. 1 hour in the oven.
 
Bob Smith

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1585 for me also. Great fits. Good luck.
 
hammerhead

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Amadent --Always start with a known

Put both water and liquid in fridge

Investment in a cool place.

never ever deviate . You will see consistant results always unless manufacturer changes

Lastly make test casts to find right mix. Good luck
 
Tayebdental

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I use the Bego bellaStar XL investment, I could control the casting fit easily by adding more or less distilled water as mentioned before, I have found, in order to have a consistent result to measure the thickness of wax coping befor investing (wax caliper) and invest the thin wall coping in separate ring(plastic ring)and the thick coping in another ring (plastic ring)to control the expansion separately, when I invest thin and thick wax coping togother in one ring the result is the thin wall metal coping fits good while the thick metal coping is tight and vise visa. I do not know if it makes sense with my fellow technicians, but it works for me, another thing you have to keep in mind is the setting expansion and the thermal expansion of the investment, I think there is a defference in the fit of the casting results between metal or plastic rings being used for investing ( expansion ) my investment high temp for ceramic alloys if 1560f, hoping this will help and I am open for any suggestion, thanks
 
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jackjabbour

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Good stuff Tayeb!!


I use the Bego bellaStar XL investment, I could control the casting fit easily by adding more or less distilled water as mentioned before, I have found, in order to have a consistent result to measure the thickness of wax coping befor investing (wax caliper) and invest the thin wall coping in separate ring(plastic ring)and the thick coping in another ring (plastic ring)to control the expansion separately, when I invest thin and thick wax coping togother in one ring the result is the thin wall metal coping fits good while the thick metal coping is tight and vise visa. I do not know if it makes sense with my fellow technicians, but it works for me, another thing you have to keep in mind is the setting expansion and the thermal expansion of the investment, I think there is a defference in the fit of the casting results between metal or plastic rings being used for investing ( expansion ) my investment high temp for ceramic alloys if 1560f, hoping this will help and I am open for any suggestion, thanks
 
Tayebdental

Tayebdental

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Thanks a lot Jack, it was good talking to you and your brother, I've learned a lot, I am getting the system soon.
 
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Well there are few reason why this happens, I know cos I manufacture investments:
1. More percentage of Cristoballite in investment that gives more expansion on elevated temperatures. Expansion start from 550 deg C to 850 deg C. Eventually you cannot reduce cristoballite percentages in investment.

2. The temperature of the liquid is high then recommended. It should be stored between 5-20 deg C. The more the temperature of liquid the more the expansion.

3. Also there are liquid's available in different composition matching the investment. Try using another company liquid and should resolve your problem.

4. 30% sol is best suitable for your problem

5. Try reducing the burnout temperature to 800 deg C. Do not provide more temperature to investment to undergo expansion process

6. All the best.
 
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Make sure you're using the same measure all the time. They can vary. I use the same procedure every day. I've also noticed if I wax a coping and let it sit over night then it doesn't fit as good. So I invest my copings the same morning I wax them. We recently changed to formula one and I've had to tinker with the liquid ratios to get the fit I want. Getting very close. Had to lower the liquid down 1.5ml across the board. Did two FC NP crowns Thursday and they were spot on.


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