Hello,i fit the models to the tree in a 45�angle.is this
correct? which is the best angle for sprueing?i have incomplete
castings,i think that the correct angles is the solution for my incomplete
castings.thanks for all
While sprueing at 45 angle is what we commonly do, this is most
likely not the problem to incomplete fill. We vary the angle based on
the type of pieces we are casting. Sometimes for high dome pieces, in
order not to trap air, we sprue them at a 45 degree downward angle. I
would suspect flask temperature as the main culprit.
Hello Nardon; I would suspect other reasons for your incomplete
castings other than the spruing, Main cause for incomplete castings
is the metal is too cool , It may seem mike it is melted but to
properly the metal must be Liquidous and that means just a wee bit
thicker than water, If you ar3 stirring it with a carbon rod and
flame melting then you should feel very little drag on the rod, it
should feel like your are stirring water, If you are using an
electromelt then turn it up a bit, remember there are 4 stages to
metal Solidus Melted and Liquidous the Gaseous. The 45 degree is good
but many times it takes up more room in a flask than necessary , Also
you didn’t tell whether you were doing Centrifugal or Vacuum casting,
If your doing Vacuum or Vacuum assist then you may be pouring your
metal too slowly and still the result is the same the metal is too
cold by the time it gets to the pieces, you really have to consider
the flow dynamics of the molten metal, in truth gating /spruing can
be at near 90 degrees to the main sprue and still work especially
with centrifugal casting, I tend to add a bit more angle though when
using my Vacuum set up. Also make sure that you flask temp is near
950 if your doing the work by your self remember those suckers cool
faster than you think and make sure that the metal is not just melted
but is Liquidous (really really HOT) Ken Ferrell www.shadras.com
I would recommend you get a copy of the 8/03 issue of AJM and read
Tyler Teague’s article on Casting Calculations. He discusses various
casting myths from a financial perspective and covers a lot of
technical issues. His recommendation is typically an 80-90 degree
angle. But you will find many other interesting ideas to help with
your castings in that article. Good Luck! Rachel Silber www.SILBERS.com
80-90 degrees is the best range of angles for spruing. As you have
found out 45 degrees will often lead to incomplete fills caused by
the initial drops of metal entering the main sprue splashing into
the downward angled feeds and freezing before the main flow of metal
reaches the feed sprue.
Jim
...i have incomplete castings,i think that the correct angles is the solution...
Tyler Teague’s article for AJM (August 03) was very interesting. It
made a case for using a more horizontal (80-90 degree) attachment in
the interest of having fewer failures. In practice, 45 degrees
should work ok for most parts most of the time. Test your parts.
Put a few pieces on with a 45 angle and a few pieces on with a 90
angle, at the same height on the tree.
Others have mentioned temperatures. If those are in the right
range, check your sprues. You might need to feed more metal into the
piece or into the area that isn’t filling.
Dana Carlson
Ok I have to chime in on this one because casting precious metals
has been the story of my miserable life for the last 15 years. What
you really have to look at is the location and shape of the gate on
your piece. I see pieces gated for every reason under the sun EXCEPT
for the purpose of getting a good casting. We gate for ease of
cleaning, we gate for ease of mold cutting, we gate to make it look
nice ( the gate that is, I’m not kidding). The last thing on anyone’s
mind is getting a solid casting. Make the gates round!!! Don’t pinch
the ends!!! Fillet the joints!!! Gate to the thickest part of the
Piece!!! Use multiple gates if you have to. Better to make a good
casting that hard to finish then a bad casting that’s easy to finish.
I’ve been fighting this mind set for years. Do all the above and you
can cast with the mold at room temperature and get fill. I’ve done
it. Hey, there’s a reason why the water pipes in our houses are
round and not square or flat! Ok, off the soap box.
Tino Volpe
Metallurgist, Technical Manager
Tiffany & Co.
300 Maple Ridge Drive
Cumberland, RI 02864-8707
401-288-0124
Hi Tino; I agree completely! But I think there’s even more to it.
When I design a piece of jewelry, I know that not only am I going to
carve the model, or fabricate it, I am going to be casting it, making
a rubber mold, if called for, setting the stones, and polishing it.
It may get damaged, and I’ll be the one fixing it. After 30 plus
years of doing this, one comes to appreciate what has been lost in
the specialization thats taken place in our industry. Everything has
to be anticipated, and this take experience. The answer to this
problem, in production situations, is good shop management. You need
someone, at least, to oversee the entire process, from design to
packaging, to get the best product possible and to fight off the
bean-counters who insist it can’t be done right. Keep up the good
fight.