Build the wax piece around the WSW so it is completely
surrounded by the regular wax.
Leave a hole somewhere, and the put the piece in water until
the inside wax dissolves and runs out. We now have a hollow piece.
Not quite. You have a hollow piece with a hole to the interior.
two or three would be better, unless it’s fairly large.
3. Send it to caster and poof--it all caves in when the
pressure of the hot metal hits the hollow wax
Hot metal never hits any wax, water soluble or not… The wax is
gone by then. In the investing process, because of the same hole
though which you dissolved the WSW, investment fills the hollow
center of the piece. The investment mold thus has a solid investment
core, connected by a bridge the size of that hole, to the investment
surrounding the wax. After the wax is burned out, the mold cavity is
also the thin hollow shape of the wax, surrounding that center core,
which needs to be held in position by that bridge. If the hole was
large enough, so the bridge securing the inside core to the rest of
the mold is strong enough to withstand the casting process, then your
casting is also a hollow metal shape, from which you’ll have to then
clean out the investment. This is why two or more holes are better,
since it better secures the center core, and makes cleaning easier
too. If you don’t want holes, other than the at least one through
which investment can fill the original wax during investing, you can
also poke metal pins through the wax model, so they extend from
outside the model to inside the model. If they are sufficiently
strong, and high enough in melting point to survive contact with the
molten metal in casting, then they can help hold the interior core in
place, since after burnout, they will extend from being imbedded at
one end in the core, through the mold cavity, to be imbedded at the
other end in the outer mold surface. After casting, they can be
just cut flush on the outside. If the wires are thick enough, they
usually can be the same metal being cast. And if the original hole
in the wax is too small, and you don’t use pins, then the center
investment core will break away from that bridge, and fall to the
bottom of the mold cavity, giving you a defective casting, since then
there will be a new, probably destructive, hole where the core now
touches the molds outer cavity. If it doesn’t touch, and the metal
completely covers, then the core is floating in an unpredictable
position inside the casting, and can’t be removed without drilling a
hole somewhere. When that’s done, probably it will be found that the
wall thickness of the hollow casting is way too thin somewhere, where
the core came nearest.
- Follow 1 as above.
- Do not melt out the WSW wax
- Send it to casting person–then what happens?
If the WSW is left in place when sent for casting, it then makes no
difference that it happens to be a different type of wax. you’ve
sent the caster a solid wax object, not a hollow one, so you’ll get
back a solid casting. All the wax, whether water soluble or not, is
removed during burnout. The WSW only becomes significant if you
dissolve it prior to investing the model. If you don’t then it
serves no purpose that’s any different from any regular wax…
I know I am missing something. Can someone take me through the
completely solid surfaced hollow castings can be done this way. You
need some sort of entrance into the model for investment to get in,
and for it then to be cleaned out. An alternative to this is to carve
the core of investment itself, using just pins extending through the
wax, to support it’s position. then you probably need less of a
hole, or can, if the pins are something like steel, pull them out of
the casting after, to get cleaning holes, filling them later.
Most commonly, water soluble wax is used to build cores for things
that are not completely enclosing a form, such as a filigree surface.
or wire frame sort of surface. Then the WSW is used just as a
support on which to build the rest of the model, and after dissolving
the WSW, you have a form with a hollow interior, but plenty of access
to that interior both for the WSW to be dissolved out, and investment
to then flow in.
did that help?