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Ring shanks split at the sprue junction


#1

Hi Folks

I having problems with my casting rings, the shanks split at the
sprue junction even if the shank is wide and thick. Thank you in
advance for any help in discover what is happening

Gustavo Suarez


#2

Sounds like insufficient fill due to either flask temp. not high
enough or melt temp of metal not hot enough. Check into either of
those, also check the way you are sprueing the piece. that can make a
big difference also. Casting is like cooking. Lots of trial and error
and lots of variables.

Good luck. Steve


#3

Gustavo: You might be getting a shrink stress in your casting right
at that point. Try making the sprue thicker than the ring shank and
see what happens.

Best,
Phillip Baldwin


#4

Hi Phillip and Gustavo;

at that point. Try making the sprue thicker than the ring shank
and see what happens. 

Phillip is right, in my opinion, that the issue is due to shrinkage
as gold gets pulled towards the cooling ring and likewise the cooling
sprue button, pulling apart the metal in between, at the juncture of
sprue and shank. I’ve seen this happen many times. However, it might
not be necessary to use a thicker sprue but in fact a longer one,
putting the sprue button a greater distance from the ring. What will
happen then is that the ring, and the longer sprue, will freeze in
the mold and the thicker sprue button will have to draw metal from
the sprue further up as it cools and the shrinkage will occur at a
distance from the ring. For instance, when I’m casting a ring of say,
5 grams with a shank of about 3 X 1.5 millimeters, I’ll attach a
sprue wax that’s about 1/8 inch diameter and about 3/8 inch long. My
concern is that if the sprue gets too thick, it too will stay molten
longer and will try to draw metal from the shank which has cooled
already, thereby pulling away from the shank and leaving a porous
area.

David L. Huffman


#5

Thank you FOLKS for the help ORCHID IS GREAT!!! Also I found a very
complete issue about sprueing in the ganoksin page.