spruing FGC techniques

[kimba]

Thanks once again to all. The suggestons ranged from what I was doing, what I knew I should have been doing but not thinking it would make too much difference and things I had not thought of.

I think round table discussions like this are invaluable in our profession. with all the variables we face daily in takes only 1 small piece of info to make a huge difference.

 

[2oothguy]

I use a indirect sprue bar always and never have any issues. Casting at 1250f. Some things I have notice over the years is to make sure I don't leave it in the furnace to long after its ready to cast. Also make sure your gas is at 2lb and your air is no higher than 6lb. Weighing the wax up is good to if you can't figure out how much metal you need to throw. I used to do it but cast so many now I kinda know how much I need. Also don't try to put to many FCC in one ring. Sprue on the lingual of your crown and keep your sprue 1/4 no more at the runner bar. Make sure to blow off any excess debubblelizer if you use any. Also keep crown aprox 1/2 inch from top of your ring. Hope this helps.

 

[Hary]

No the porosity is localized, not all through. I dont think I we are overheating the metal, but I will duoble check over the next few weeks. I am thinking more and more it is positioning and reservoir size. Thanks for input

Less heat, we are all used to casting palladium alloys or non precious alloys, control your gas and oxygen and all of the above you'l be ok.

 

[zero_zero]

We used to have porosity issues with high noble full gold ( also high Ag content ),while the HN and Pd based porcelain alloy castings were perfect. A pinch of flux solved the problem...

 

[2oothguy]

Here is they way i do it works every time. That is if i can load these pics

http://i1327.photobucket.com/albums/u680/2oothguy/IMG_1365_zps83ae2b05.jpg
http://i1327.photobucket.com/albums/u680/2oothguy/IMG_1366_zpsb1e2d780.jpg

 

[kimba]

Thanks again everyone for continued recomenndations,

I think our problems where little changes due to complacancy that overtime finally have reached critical point. we seem to have solved the problem by going back to basics that we knew and were reminded of by all out there in DNL.

its always interesting to see how people do things slighly differently but similar to you