Finally
the flask has been constructed, the sand is mixed,
and we are ready to send some stinking hot metal into
these moulds!
The only
thing I had missing were some objects to actually
make a casting out of! So I grabbed the first thing
I saw - it just so happened to be one of those decorations
that are meant to be put on bed posts or something.
Anyway,
so be it. Here is the sand all rammed up, cope lifted
off the drag, gate cut, and ready to be closed up
and to receive some metal.
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A completed "bed
post decoration" mould
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The
mould ready to be poured into
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Here the cope is lowered
back onto the drag, and ready for casting.
The large hole is the sprue
hole, and is where aluminium will be poured into.
The smaller holes are vent holes, which allow any
water vapour to quickly escape before bubbling back
into the molten metal. Had these not been constructed,
the gas inside would form large voids inside the metal
and rendering the casting pretty much useless.
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Aha, this
time I did bother using the self timer function, and
glad I did so, for this shot totally sums up the process
of pouring metal. Well not really, but the most interesting
bit anyway.
I was suprised
at how fast the mould filled up with aluminium, since
I was expecting it to hold quite a large amount of
metal.
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Pouring of the mould
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Original vs. casting...
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The casting turned out
very nicely. In this picture the sprue and gate have
already been cut off the finished casting, and a little
sanding has been done to brush up the surface a bit.
You might notice that the
lower skinniest part of the casting turned out thicker
than the original part. The reason for this is that
I used glad wrap as the parting compound (used to
separate the cope and drag). Evidently the glad wrap
was wrapped a bit too tightly, resulting in some "stretchy"
bonds.
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Well I
have to say I was quite happy with that last casting,
so just for kicks, I decided to turn an old mobile
phone into a solid aluminium one. I mean, why not?
This is
a seriously old Motorola phone, but I think it would
be more representative of a phone because of the visible
antenna and large pop out buttons.
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An "old school"
mobile phone mould
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Freshly opened mould
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Tada! Another successful
pour yields a beautiful new shining fully functional
solid aluminium Motorola mobile phone. Hmm, perhaps
skip the "fully functional" bit.
Sand in the immediate area
around the casting loses its moisture content and
forms a hard brittle composite much like hardened
clay. The sand can be reused by thoroughly crushing
it up and adding more water to bring the moisture
level back up to the workable level.
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Heres a
comparison between the original and the aluminium
clone. The level of detail in the casting is not bad
considering I didn't bother to sieve the sand beforehand.
All the buttons are very evident, and even the speaker
holes turned out quite well.
A faint
outline of the screen area can also be seen.
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The phone casting weighs
in at 284g
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The Motorola logo is
not visible in the casting
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Here
are the undersides of both phones. It is here where
the lack of minute detail is clearly demonstrated -
the engraved Motorola logo does not show up on the casting.
Perhaps next time I will attempt this again with some
finer sand. |
Next,
a demonstration of how useful having a backyard foundry
can really be. For some while now, the wood plane
in the shed has been gathering dust due to this broken
piece. Prior to metal casting, I had not ever imagined
it be possible to repair this AND stop it from ever
snapping again!
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A broken segment of
a wood plane
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The new prototype segment
ready for moulding
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Here
I have cut small foam strips and taped them in place
of the missing wood. I have found that foam is sometimes
too soft a material to be rammed in sand (it can shrink),
but wrapping it in electrical tape increases its strength. |
The mould
is prepared for the new replacement part and a nice
smooth pour results in a beautiful metal version of
the wood + foam prototype.
I haven't
yet figured out how to remove the casting without
disturbing the mould so that a second casting can
be poured immediately... perhaps next time I will
try pouring the metal only half way up the sprue so
that there is no "cone" to disturb the soil
as the casting is pulled off the cope.
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The freshly repaired
and cast segment
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Rough edges and flash
are visible prior to "cleaning up"
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Here is what a casting
looks fresh from a mould, with both sprue and gate
still attached. Notice the shrinkage on the top of
the sprue - this is caused by the metal on the mould
shrinking as it cools and thus sucking down more liquid
metal from the sprue. Preventing shrinkage is in fact
one of the most important functions of the sprue.
There are also jagged edges
around the casting where the cope met the drag - this
is known as flash and is quite normal in a greensand
casting. It is, however, easily removed. A good sanding
and a bit of polishing will make this piece look good
as new!
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I decided
to make an aluminium plaque of some sort. After a
bit of thought on what text should go on the plaque,
it was without doubt that "Penguin's Lab"
would be the most appropriate!
I have
heard of others getting their patterns laser cut so
that the words are nice and flash, but I wasn't too
fussed. First, a nice block of pine is cut to size
to use as a base and the text pencilled in.
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Then 10 gauge enamel coated
copper wire is cut and bent into the shape of the
letters. For complex letters (pretty much anything
other than "U"), I used two or more lengths
of copper wire. The copper wire is then super-glued
on to the base.
Its a lot of work, but
with a bit of practise its not too time consuming.
Besides, this is probably the cheapest way!
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After
the superglue has dried, the gaps in between and around
the lengths of copper wire are filled in with PVA wood
glue. This is so that there will be no undercutting
(wedges where sand will lodge, and thereby destroying
that part of the mould when the pattern is removed)
underneath the copper wire. Copper wire, being cylindrical,
is not the ideal material I suppose. |
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Once
the pattern was dry, a mould was made and the furnace
fired up! Due to time constraints, I had to fire up
at night. But the amazing photos are definitely worth
it. Here the furnace is just being lit, and the flames
are the ones coming off the firelighters. |
Well, unfortunately
the pour didn't go so well. The charcoal underneath
the crucible was not lit, and thus the bottom half
of the aluminium load was still solid. Ignorant of
this fact, I skimmed and started to pour and only
then realised there wasn't going to be enough. The
good news is, the text still turned out pretty well
and the corners are nice and round since the aluminium
didn't have enough pressure to ram right in. Perhaps
its better this way...
Now onto
the more serious furnace that uses alternative, cheaper
sources of fuels...
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