Hi all, I am looking for on delft clay casting. ...
when I tried to do it all I get is half a ring, it wont cast the
whole way around...
For an incomlete casting I’d suspect one or all of:
- insufficient venting
- too cool pour temp
- too narrow feeder sprue
- too sharp an angle where the sprue meets the ring cavity
Insufficient venting. Delft need venting, not like cuttlefish where
you might get away with no venting because the material is porose
(sp?) or the join is not 100%. Delft needs a good 2mm vent at the
bottom of the object, and the vent is to exit at rhe top of the mold
away from the feeder sprue and button.
Too cool pour temp. The sand is cold. Not like investment casting
where the mold is 500C. It may be that the metal cooled down and froze
halfway through the mold.
Too narrow feeder sprue. The metal has to get into the mold quickly,
so provide a sprus as thick as the part you’re joining to, and attach
in to the thickest part! At least (guesses) 3mm thick.
Too sharp an angle where the sprue meets the ring cavity. Think of
hotrod exhaust systems where the flow frim the engine is given smooth
curves. No sudden turns or performance in reduced. They restrict
metal flow and are vulnerable to coming away from the mold. Maybe the
metal took a little bit (or a big chunk) of sand with it.
Does any of this seem likely? Tell us about your casting conditions.
That’s all I can think of at 7:30am.
B r i a n ? A d a m a n d R u t h B a i r d
Auckland NEW ZEALAND
ph/fx +64 9 817 6816