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Plastic for Mold Patterns


#1

Hello Everyone - I just completed an unsuccessful casting. I
was using plastic as my model and allowed for an extra 1.5 hours
in the burnout cycle. The casting was incomplete and the silver
did not enter all the areas of the cavity. Many of the portions
that did fill appear to be pitted (ash residue?) and some of the
cannels look to partially blocked. The design was "filigree like"
with many fine lines, round and about the size of a quarter.

I was using a hand held “Castex” Steam caster. I used three 14
guage wax wires for the sprues leading to the single main sprue
that fed the casting. It looked rather like a pitch fork. I did
not attempt to blow out any ash as was suggested in an earier
dicussion.

Does anyone out there have any ideas as to what I could do
differently next time?

Thanks - Steve Wiser

Steve Wiser
PO Box 938
Santa Margarita, CA 93453
(805) 438-5232


#2

14g sounds way too thin for sprues, Steve- I would reccomend at
least 8 guage. The sprues probably solidified before hitting the
cavity.

Rick Hamilton
Richard D Hamilton, Jr.
@rick_hamilton


#3

Hello Everyone - I just completed an unsuccessful casting. I
was using plastic as my model and allowed for an extra 1.5 hours
in the burnout cycle. The casting was incomplete and the silver
did not enter all the areas of the cavity. Many of the portions
that did fill appear to be pitted (ash residue?) and some of the
cannels look to partially blocked. The design was "filigree like"
with many fine lines, round and about the size of a quarter.

I was using a hand held “Castex” Steam caster. I used three 14
guage wax wires for the sprues leading to the single main sprue
that fed the casting. It looked rather like a pitch fork. I did
not attempt to blow out any ash as was suggested in an earier
dicussion.

Does anyone out there have any ideas as to what I could do
differently next time?

Blow out the ashes!!!

As to the sprues… did you get a good flow through them or did
they cold shut? If they are are all solid and filled the entire
length, no need to change them but if they did not all flow and
fill, they are too small. If you really had a problem with
porosity I really think that you had ash in the cavity. Many
plastics have fillers in them (read clay or other mineral
materials) and this may very well have been your problem.

Good luck in the next casting.

John Dach and Cynthia Thomas
Maiden Metals
a div. of The relative weight of difficulties
MidLife Crisis Enterprises is largely a function of our own perceptions!

PO BX 44
Philo, CA 95466
707-895-2635(phone/fax)
@John_Cynthia_MidLife