Holes , small pontic holes , caves into the pontics orinto thick metal supports imake

[Edy]

If you think you are doing everything right and you have been using this metal for a long time with no problems till now than I would switch metal.

Could be a manufacturing problem they aren't telling you about. Maybe they lost one of their suppliers or have a bad batch.

They don't recall products they just let us think we are crazy. Sometimes its not our fault. We can go along for years with no problems then all the sudden problems for a month then they go away.

Maybe the material is great 99% of the time but dosent work 1% like large pontics.

I always used Rex 3 for NP for 20+ years and never saw porosity. Very forgiving except when I waxed under .3 thickness. It was so easy and very forgiving for technique inconsistencies.
Pd based Noble alloy on the other hand is sensitive to sprueing technique for suck backs and porosity and taking in gasses from casting.

Who knows Al , he did attract me to buy this brand with a very nice discount , i will try to do all the above , my main problem may be that i stay too much with flame and overheat my alloy , my thinking is if the alloy will be more liquid will flow better , this can be my mistake.

 

[Edy]

Al, I dont know if you read correctly; but he has his own technique, he's already making them hollow.

, only problem its not so accurate how i wanted it to be , sometimes i get the hallow effect inside the connectors and not the pontics , there i start the facepalms hhhh

 

[dmonwaxa]

, only problem its not so accurate how i wanted it to be , sometimes i get the hallow effect inside the connectors and not the pontics , there i start the facepalms hhhh

Edy, we got the hollow pontic technique down, can you share how you do your hollow sprues and runner bars? I'm sure I'm not alone here, but mine gets filled every time, must be my technique.

JK. Hope you vget it sorted out soon.

 

[Edy]

well actually the sprues and runners bars is a secret technique , if i share it alloy companies will get mad at me i share stuff which help technicians save precious amounts of metal ^_^ , i hope too to sort this out because its getting costly.

 

[Bumfrey]

I get this problem occasionally on pontics only. My apprentice got it a lot until she used the thickest sprue wire we got. She never gets it now.
I am stubborn and hate using thick sprue wire so i guess its why i still get the odd one.

 

[Al.]

Who knows Al , he did attract me to buy this brand with a very nice discount , i will try to do all the above , my main problem may be that i stay too much with flame and overheat my alloy , my thinking is if the alloy will be more liquid will flow better , this can be my mistake.

Ok my guess is you are over heating it. Like Dmonwaxa said it slumps only, dosent get liquid like N. He recommended jiggling the crucible what I do is jiggle my flame to see slight movement in the metal then I sling
it. With multiple ingots they will not become one but when the edges connect is when I cast.

 

[Al.]

Also NP is lighter so if in doubt add another ingot, you need a nice button or more weight to help push all the metal in, and do NOT reuse the buttons, throw them away, always use 100% new metal for NP or you will eventually have problem like gassing in your porc or bonding issues.

All the NP I have used leaves a skin of metal in the crucible. It should come off with a simple flick with a instrument or even turning it up side down and tapping it. If the skin is stuck to the crucible than the metal was overheated. If there is no skin it was over heated. That is the way it is with Rex 3 or nickel based NP.

 

[dmonwaxa]

Also NP is lighter so if in doubt add another ingot, you need a nice button or more weight to help push all the metal in, and do NOT reuse the buttons, throw them away, always use 100% new metal for NP or you will eventually have problem like gassing in your porc or bonding issues.

All the NP I have used leaves a skin of metal in the crucible. It should come off with a simple flick with a instrument or even turning it up side down and tapping it. If the skin is stuck to the crucible than the metal was overheated. If there is no skin it was over heated. That is the way it is with Rex 3 or nickel based NP.

Great points made wiith the last two posts Al. Also I meant cradle not crucible. Your technique is different but accomplishes the same thing. Shows there's more than one way to skin a cat.

 

[Edy]

Al , the way the metal skin remains on my crucible is that i always scrap it from the crucible and even it penetrates inside it and parts of the skin stay glued to the crucible , so... i am overheating it , i was always thinking that if i melt the metal a bit more it will flow smoother , now in 1 hour i have 2 big rings of casting , i will try not letting the alloys become too liquid , but that scares me that the alloys wont pass the small hole of the crucible lol , with my previous metal "ugirex III" the alloy will show small red bubbles inside the heated alloy which let me know when to release the centrifuge , this new one has nothing to let me know when to release , but will give it a try

 

[dmonwaxa]

Edy

One of the things to consider also is the number of turns on the cenrifuge, if your'e doing 3 for N, HN and Au, then you'll need to increase it to 3 1/2 to 4 for NP because the alloy is lighter. Also by shaking the cradle up and down you'lll be able to see the slump in the ingots. PM me if you have further questions.

 

[Tayebdental]

I agree with all the above. Sounds like porosity issues which is usually a spruing and reservoir problem.

I recently started (2 months) casting everything with the Neo Super Cascom, it uses electric, vacuum, argon and compressed air.
Im getting really beautiful dense porous free castings. An amazing difference from the centrifugal and torch castings.

Al,
Do you recommend this casting machine? I know it is big $$$

 

[Edy]

I am so happy i solved this issue , all goes into the extra 10-20 seconds of overheating the alloy ingots , i was trying to bring them into a liquid pool for a better cast , i was wrong , now i just released my centrifuge when the ingots lost their original shape , 5-6 seconds until i put my ring from furnace on the cardle (ehe ) , then released , not even one single damn hole in the alloy , {my wax work look bad and not smooth because i was in a hurry to redo this work which i had the holes with it earlier},And Al what u said about the metal skin , this time i just turned it around and it fall on ground , just lovely !


Uploaded with ImageShack.us

 

[Al.]

Al,
Do you recommend this casting machine? I know it is big $$$

Tayeb I have some pics of some castings I will post later.

 

[Al.]

Al , the way the metal skin remains on my crucible is that i always scrap it from the crucible and even it penetrates inside it and parts of the skin stay glued to the crucible , so... i am overheating it , i was always thinking that if i melt the metal a bit more it will flow smoother , now in 1 hour i have 2 big rings of casting , i will try not letting the alloys become too liquid , but that scares me that the alloys wont pass the small hole of the crucible lol , with my previous metal "ugirex III" the alloy will show small red bubbles inside the heated alloy which let me know when to release the centrifuge , this new one has nothing to let me know when to release , but will give it a try

Yeah that is what I always look for, how easy the skin comes off.
Like Dmonwaxa said I give NP one half extra turn on the casting machine.

 

[Tayebdental]

Congratulations edy, shalom.

What a great community!! Lets share the joy with some dunots with holes and caves.

 

[dmonwaxa]

Congratulations edy, shalom.

What a great community!! Lets share the joy with some dunots with holes and caves.

Are these the holie pontics he was talking about? Now I got it, a picture is worth a thousand words. He never mentioned they were sugar coated. Bet it happens when the heat from the torch hits the sugar....starts bubbling. Patients might like it though, they'll probly return to get more bridge work done.....

Let us know how it turns out Edy.

 

[Edy]

Everything turned out just lovely . . no more donuts holes at all , with this other bridge i heated the metal correctly but because i had like 11 ingots 3-4 ingots were overheated a bit again while i was trying to worm them all at the same time .. but still not even one hole in the pontics areas or in the sprue leading bars like i had in the last 3-4 months , just beautiful , i got a little tiny hole in the bucal of central maybe because i waxed it too thin 0.3-0.4 , next time i will do it .5 to be sure , or maybe it is because those 3-4 ingots which were overheated the hole appeared .. but this turned out 180 degrees from my other castings , thanks again for support guys , love you a lot !



Uploaded with ImageShack.us

 

[marekt]

hi guys,
could anyone tell me how much mm (diameter) is 6, 8 and 10ga?

 

[Tayebdental]

hi guys,
could anyone tell me how much mm (diameter) is 6, 8 and 10ga?

I hope this will help!!

 

[marekt]

Thaks Tayebdental you are GREAT!