Metal cast problem

[DonSinke Lab]

Does anybody know answer

 

[DonSinke Lab]

I've been having problems with open flame broken arm casting and not shure on approx 20 casts -1 miscast full of holes .Does anybody knows possible reason?

 

[rkm rdt]

Just tell us what happened.

Could be dirty wax
Thin areas
improper spruing
contaminated metal

 

[Marcusthegladiator CDT]

Lets see a pic of the button and copings... then well know...

 

[MasterCeramist]

When you say holes do you mean porosity or do you mean incomplete castings. If porosity then it could be sprue size, sprue location , overheating of the alloy, too high of a burnout temp. In the case of a miscast if the edges around the void are somewhat rounded then it sounds like under heating of the alloy or too low of a burn out temp. It is more than a two choice answer though.

 

[charles007]

Need pictures of button, crowns, type of metal, oven temp and burnout time, sprue size and length... oxy and propane settings ...
Can't help without ALL the information !!!

This week I had a run on pfms which I haven't casts in many months.. buccal was a beautiful .3 and a touch less and cast 2 attachment bridges using Stern tube locks without any porosity,, molar abutment and molar pontic were full contour metal to ridge.. fyi used 2 large reservoir sprues on pontic and abutments... 8g on all singles pd/ag alloy 1550 F 4 turns on Kerr casting machine, 45 minute hold. Zubler investment and patterns were out of thermal zone like you do with emax.. Tilt patterns to outside wall.. Been using this technique since the early 80's with very little metal finishing which I hate....
I've cast singles, abutment on buccal, facial, lingual at .3 for over 25 years using this same technique using Argelite 61, and Superior alloys: 60% Pd/ 25 to 28% Ag .. and easily cast NP at .2 and less using same technique with extra turn on casting machine..

 

[DonSinke Lab]

ok ,I guess I need to explain closely, Alloy I use is Argeloy np,as I said I have broken arm open flame, Oxy + Prop.and I am casting at 920 C temp in furnace.Spruing is 2,5 mm, as well as 'pontic' reserv.sprue to feed cast if need .It is not porosity, its well rounded holes on the crown and sprues and keep happening approx.every 20th cast.
thanx

 

[zero_zero]

Thicken up them copings a bit, if you got short cast on sprues as well that means cold casting...heat it a bit more and wind the arm one extra turn...

 

[aidihra]

Maybe try casting at a slightly higher temperature or raising the temperature in the burnout oven. I think this is related to not having enough heat.

 

[DonSinke Lab]

Yap, I,ll post a picture so you guys can get a better view of problem,so I just have to figure out how to post a picture

 

[charles007]

ok ,I guess I need to explain closely, Alloy I use is Argeloy np,as I said I have broken arm open flame, Oxy + Prop.and I am casting at 920 C temp in furnace.Spruing is 2,5 mm, as well as 'pontic' reserv.sprue to feed cast if need .It is not porosity, its well rounded holes on the crown and sprues and keep happening approx.every 20th cast.
thanx

Smooth and rounded probably relates to something on the cold side.. torch setting would be my first guess without knowing more.. hot hissing tip, (what is your oxy and propane setting )? alloy slumps and cast fast. Measure wax patterns to make sure its .3 If you can't cast at .3 you will probably have miscasts at .4

 

[Marcusthegladiator CDT]

ok ,I guess I need to explain closely, Alloy I use is Argeloy np,as I said I have broken arm open flame, Oxy + Prop.and I am casting at 920 C temp in furnace.Spruing is 2,5 mm, as well as 'pontic' reserv.sprue to feed cast if need .It is not porosity, its well rounded holes on the crown and sprues and keep happening approx.every 20th cast.
thanx

Take every 20th cast, and just redo it. Or take a pic of the situation and post it for best results.

 

[DonSinke Lab]

Take every 20th cast, and just redo it. Or take a pic of the situation and post it for best results.

 

[DonSinke Lab]

At least you make me smile with 20 th ring redo stuff.as I said Ill post a picture and would be easier to give a thought.

 

[MasterCeramist]

With non precious you can also get large voids in pontics if it is overheated. There was a thread not too long ago on the subject. Will be able to tell more when pictures are up.

 

[dmonwaxa]

Cold ring? Not heat soaked enough. ie hold time at temp. Since I see you're casting in your furnace at 920*C ... that might be the problem

 

[TheLabGuy]

no pic, no comment

 

[dmonwaxa]

C'mon Rob just play along!

 

[TheLabGuy]

C'mon Rob just play along!

I'm old, foreplay is overrated

 

[DonSinke Lab]

been having problems uploading pict. of my miscast????