FOUNDRY FACTS-LEARNING LINKS
SAND SAND SAND
Mulling: Stomp with feet until flat and mix (fluff
up) with shovel.
4. Keep covered to retain
If your sand dries out, add water and "re-mull".
If you add too much water....it will not blow-up! Only pouring iron and steel into moist sand will cause blow-outs. If you look at greensand through a microscope it is like a sponge, allowing steam to easily escape out of the pores. Pouring aluminum, brass, bronze or any other low-melting alloy into greensand is very safe!
You can use the coarse sand from Lowes or Home Depot and mix your own. When you make a mold, only the sand that touches the pattern matters! Use a handful of our fine sand through the wriddle (sieve), only enough to cover the pattern. Then fill the rest of the mold with the coarse sand mix. The sand that touches the pattern is called "facing sand", it mixes in with the rest when you shake out the mold.
Powdered Bentonite: call 1-800-735-6075 Ask for
Shipping sand is very expensive, mix your own and save!
Note: Do not use Fireclay for molding sand.
Aluminum is the most
abundant metal on the earth's crust.
Bronze and brass are copper-based alloys. Copper, as native copper, is one of the few metals to occur naturally as an un compounded mineral. Copper was known to some of the oldest civilizations on record, and has a history of use that is at least 10,000 years old. Copper metal can be used as an anti-germ surface that can add to the anti-bacterial and antimicrobial features of buildings such as hospitals..........Wikipedia.
Building a Ferrari V12
Casting a engine block using core sand.
All castings have a gating system attached.
1. Metal is dumped into the "sprue".
2. Metal travels down the "runner".
3. Sideways through the "gate" and into the casting.
4. There is a "pop-up" in the center of the runner.
The pop-up is 1/4" and will release pressure once the mold is full.
Gating is removed after casting and re-melted.
Why do I need gating??
When you pour molten metal there is always dross, floating on top.
Dross is like the foam on beer, caused by exposure to the air and turbulence. During pouring, the dross goes to the end of the "runner" and sticks. Metal is skimmed as it travels through the gate.
Silicon-carbide, Fireclay and Steel
Step by step molding and
Create complex parts the easy way.
Shrinkage, two types.
Horizontal: Aluminum shrinks horizontally at a rate of 1/8" per foot. Example- An aluminum casting 24" will need a pattern 24 1/4".
DO NOT touch anything that is hot, wear leather gloves when doing foundry work.
For outdoor use only. Not For use
by minors or individuals under the influence of alcohol or drugs.
Never leave furnace unattended for any reason during operation. Turn furnace off.
Always pour molten metal on sand or dirt
floor. Molten metal spills on concrete floor causes
Do not operate near anything flammable.
A cold item placed into the molten metal
will cause splattering and dangerous
Safety glasses- Always wear proper eye protection.
Can I convert my furnace to natural gas?
2. If the sand is too wet, it will bubble in the pouring cup, it will not blow up (only iron and steel have an explosive reaction). If the sand is too wet, let the mold sit overnight or torch it with a flame prior to pouring. It should hold it's shape when squeezed into a ball and slightly stick to your fingers.
3. Castings should be at least 3/16" thick, when larger than 4"x4". Smaller castings of 1/8" or less can be no larger than 4"x 4".
4. Runner bar should be at least 3/4" deep and 3/4" wide. The thick runner will keep the metal molten longer to reach the casting HOT.
What does the sand look like the first time it is used?
Bronze Pouring Tools
3. Do not stir molten metal, this causes gas to be absorbed. Stirring rods are for poking at anything on top of the melt to see if it is molten. Try not to break the surface, as this will introduce gas to the melt.
4. DO NOT OVERHEAT CRUCIBLES! See tip #1. Crucibles wear out very quickly if you overheat them.
5. Clamp or put weights on your bronze or brass molds. Also aluminum molds with a lot surface area.
When sand is first used it is white. After a few hundred uses it turns light brown. After a thousand uses it turns black. In a commercial foundry it is always black from continuous use.
The sand on the left is new, the right side has been used a few hundred times.
can't you pour directly into the casting?
Molten aluminum absorbs oxygen when exposed to the air. A layer forms at the top called dross, like the foam in beer. Dross has too much gas to make a good casting, it is scooped off prior to pouring (center photo below). Turbulence and exposure to air cause dross, molten metal gets both on the way from the crucible to the casting cavity. When pouring, the sprue base captures and holds dross, it also cushions the incoming metal. Metal flowing into the runner bar flows past the casting trapping the dross in the "runner bar extension". The gating system skims the dross off the metal as the casting fills.
Copyright 2011-Lost & Foundry of Spokane!