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EXPLODED VIEWS
See the
Casting Processes Sections link
Casting Processes to get the complete explanations on
the processes shown in this Section.
1. The Components found in a Mold or
Die.
2. What is Core ?
3. How a Mold or die is " pour
off " ?
4. How does Investment Casting work ?
5. What is Lost Foam Casting, is it
different than Investment Casting (lost wax ) ?
6. A Shell Core Molding drawing.
7. The " V-Process " --
vacuum sealed molding, how it Works.
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1. The Basic Components, found in
Molds / Dies.
see text below diagram ___________
The parts of a Mold / Die are:
Pouring cup - the molten metal is poured in
here. It has a funnel shape to ease pouring accuracy problems.
Runner / sprue - a sprue carries metal from the pouring
cup to the runners. The runners distribute metal to the part.
Gate - a transition from the runner to the cavity of the
part
Riser - a thermal mass where excess metal will remain in
a liquid state while the part cools. As the cooling part shrinks, the
molten metal in the riser will feed or fill in the shrinkage. Risers can
also be used to collect impurities that rise in molten metal.
Mold cavity - this is the final shape of the part, the pattern
would be found here prior to molten material.
Vent - a narrow escape passage for gases that would
otherwise be trapped in the mold.
Parting line
- a line of separation that allows the mold
(made in two pieces) to be put together to make a full cavity. Note that
this line does not have to be a straight line, and is often staggered to
make the mold making easier.
Cope - the upper part of a casting mold
Drag - the lower part of a casting mold
There are important Casting Concepts about patterns,
- Molds are made by compacting sand around the
shape of the pattern.
- Patterns are made of wood, metal and plastics -
the material must be stronger if a large number of molds are to be
made.
- A parting agent
can be used on a pattern to allow easy removal after the mold is made.
- Pattern types include:
a.] one piece patterns (loose or solid
patterns) - low quantity simple shapes
b.] split patterns - for complex shapes made in two patterns for
each half of the part.
c.] match plate - the split patterns are mounted in a single plate.
This allows gating on the drag side to match up with the runners on
the cope.
d.] design of the patterns should include consideration of
shrinkage
e.] a slight taper should be added to the sides all patterns this
will make them easy to remove from the completed mold. i.e. a cone is
easier to remove than a cylinder.
2. What Is a Core ?
Cores are typically used for more complex shapes.
Cores allow features that could not be easily formed into
a sand core.
Cores are made with techniques similar to those for making sand molds.
The cores may need structural support in the mold - these metal
supports are called chaplets.
The cores are added when the cavity are made, and they act as
part of the mold during casting, but
they are rigid enough to allow internal features on parts.
Cores can be made easily in automated settings.
3. How is a pattern or die
poured off
?
4. How does Investment Casting work ?
5. What is Lost Foam Casting ?
Is it different than Investment Casting (lost wax
) ?
Lost foam, is similar to Investment or Lost wax, in that the medium, or
pattern device, is Expendable, they melt or evaporate away, leaving the
cast part.
They both have advantages, for the type of function they were designed.
One Process's advantage, could be the other Process's weak area.
These points are brought up in the text portion of Education Section.
6. Shell Core Molding
7. The " V-Process " -- vacuum sealed
molding, how it Works.
The
V-
Process works like this:
A thin plastic film is heated and place it
over a pattern. A vacuum tightly draws the film around the pattern which is then
surrounded by a flask. Next, the flask is filled with dry, un-bonded, extremely fine sand
and vibrated, so that the sand tightly packs the pattern. A second sheet of film is placed
on the flask, a vacuum draws out the remaining air, and the completed mold is then
stripped from the pattern.
Each half of the mold is made in a like fashion.
Aluminum or the Alloy of choice, is then poured directly from the furnace into the closed halves. As long as the
mold is held under vacuum, it retains its shape. After the mold cools, the vacuum is
released and the sand and completed casting fall free. The "V " Process is
simple in concept but adds a whole new dimension to the Casting Industry. The
plastic film, melts, and diffues into the sand; the sand is left to cool and is
ready to use again.
Examples
of usage would be:
the medical equipment, instrumentation, electronics, machine
tool , aircraft machine tools, musical drivers ( speakers ), church bells, automotive
testing and repair equipment, to mention just a very few applications.
Follow the numbered
steps listed below, to gain a better understanding of this innovative process.
-
set
a pattern on a hollow carrier plate.
-
a heater softens up a thin sheet of plastic film.
-
film is draped over the pattern, and a vacuum
sucks the film down over the pattern.
-
flask is set on the film coated pattern.
-
flask is filled with dry sand, it is vibrated
slightly to settle the sand.
-
the sprue cup is formed, the mold is
leveled…the sprue cup and flask are covered with plastic film.
-
vacuum is applied to flask, and hardens the sand,
containing the pattern.
-
cope and drag are both formed in this manner and assembled.
-
plastic lined cavity is under vacuum.
-
molten metal is poured in, left to cool, part is done, plastic melts
evaporates away into sand.
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