aluminum casting furnace first run dudes

[Brian Thomas]

Hi Dave
Great work .
We did castings in metal shop in high school .
We melted down old Briggs motors over a gas furnace . We added flux then we skimmed off the slim.
We used a sand cast that was a upper and lower frame with the parts to be cast put in the middle adding moist casting sand below and above, using a tube to cut vent and fill holes, then we used a piano wire to slice the halves apart and then touch up as necessary as close to the mother part as possible.
How does this compare to how you are doing it ?
Brian

[david a luciani]

very much the same.
the frames you refer to are flasks with the bottom being the drag and the top being the cope, or maybe vise versa.
my method is yours since sand casting hasn't changed much in thousands of years.
i put a board under the drag ,dust the part and the drag with plumbago or some kind of parting dust.
sift sand onto the model and ram the sand tight around everything.
after ramming the mold you turn it over add the second 1/2 of the flask (cope) dust model and sift sand onto the model again ramming mold.
you then cut your gates and risers in and add a sprue hole.

the tricky part is positioning the gate, risers ,sprues and vents in an effective manner.
MANY TIMES IT'S JUST TRIAL AND ERROR UNTIL YOU GET THE RIGHT COMBO.
@#$% caps lock.

the the sprue is the hole going to the model that molten metal is poured into.
the gate allows metal into the mold area at given points.
the risers put molten metal at point where the model will need extra as it cools because the metal shrinks when it cools.not enough riser area gives you shrink issues.
the vents let excess gas out of the mold that are created when the molten metal vaporizes everything in it's path.
sand castings naturally vent but in thick thin pieces you need to add venting with a wire or thin rod.

on my first casting i was playing with my sand to see if it was well tempered.
on a spur of the moment thing i decided to cast the mold.
of course i kinda forgot to vent it at all , the sand was a bit wet ect., ect.
i realized my mistake when the metal that was running clean into the mold started coming back up.

that's a strong indicator of steam build up and explosions often occur next.
i suppose years from now i'll see it as a funny time but right then i was running away with a 1400 degree pot of molten aluminum.
i was busy remembering some of the various casting explosion horror stories i'd heard.
anyway i got lucky and only the mold was wrecked , i determined the sand was to wet and i'd over rammed the mold and left out the vents.the over ramming actually saved me since the sand was too tight to burst.

the second mold i made after thanksgiving dinner as a way to distract my various nieces and nephews from destroying the house.
i used the newly tempered sand this time being careful to vent the cope.
again on a flyer i decided to cast , everything went well no excitement but when i poured i had too much metal left over.
i figured that something fell in the gate it was dark outside and i couldn't really see the mold well with the kids running in and out of my light.
as it turned out i hadn't remembered to vent the drag so the bottom half couldn't vent fast enough.
otherwise i might have gotten a couple of very nice stuffers.

right now there's technical problems i need to fix.
1. the crucible walls are to thick so the metal takes about 1 hour to melt instead of twenty minutes.
2. the sand temper is off a bit.
3. i need to be alone and focused not just playing around after work or what ever.
over all i expect to have the rig running smoothly by spring maybe sooner if work gets slow and my bills disappear!!!

i'm in no real hurry since this is a hobby , but i do hope to have clean runs soon .
dave