FOUNDRY FACTS-LEARNING LINKS

Wikifoundry link
Wiki-Casting

SAND   SAND    SAND
Greensand recipe:
100 lbs sand
Silica or Olivine
 12 lbs powdered bentonite
 7 lbs water (1 gallon)


1.Mix sand and water thoroughly,

 
2. Gradually add bentonite and mix well. Bentonite is a fine clay

3. Stomp with feet until flat and mix (fluff up) with shovel.
Repeat this step at least 3 times, this is called "mulling".
Mulling is very important to coat each sand grain with clay.
 

4. Keep covered to retain moisture.
Moisture evaporates quickly from greensand.

If your sand dries out, add water and "re-mull".

 


 This greensand mix will give very fine detail every time.120 grit silica (or olivine) sand is ....fine, almost like dust.  70 grit or less will give you a rough or pebbly texture. Grit size is determined just like sandpaper.

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
with your zip code for location nearest you.

Shipping sand is very expensive, mix your own and save!

Note: Do not use Fireclay for molding sand.
Sand mixture for iron and steel casting is LESS than 5% bentonite and 70 grit. Sea coal is also added to prevent burn -in.

Sand sand sand sand sand sand sand sand sand sand sand sand sand sand sand

 

 

 

 

 

 

Aluminum is the most abundant metal on the earth's crust.
It is also one of the most reflective metals. The shiny part of  CD's and DVD's is aluminum. Aluminum was once considered a precious metal, more valuable than gold. Aluminum has been produced in commercial quantities for just over 100 years. The Washington Monument was completed, with the 100 ounce (2.8 kg) aluminum capstone being put in place on December 6, 1884, in an elaborate dedication ceremony. It was the largest single piece of aluminum cast at the time. At that time, aluminum was as expensive as silver.........Wikipedia.

 

 

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.
Greensand is soft & breakable, core sand uses a binder that is much stronger allowing you to pickup and hold the cores. You can buy core binder from budget casting supply.
 


Ingot pattern made from wood then shellaced and sanded.
Ingot Video


How does sand casting work?   
 
Click on photo!

HOBO CASTING
Free furnace plans and melting aluminum in a coffee can on the barbecue, who needs a furnace?

Crucibles Silicon-carbide, Fireclay and Steel

 

 Step by step molding and melting instructions.

Gold and Silver can easily be melted with a crucible furnace,  you will need a Fire clay crucible, silicon carbide, clay graphite or ceramic crucible.  Boric acid is used as a flux to keep molten gold from contact with air (atmosphere). A pinch when starting to melt, another after it turns molten.

Lost Foam  Create complex parts the easy way.


Flux and degassing: 
1. As soon as aluminum turns molten, it starts absorbing gas. Melting aluminum does not require de-gassing or flux, if you pour it right away before it has a chance to absorb any. Pour aluminum 3 minutes after the last piece turns molten.
2.Bronze and brass do not need to be degassed. B & B can be fluxed to clean the melt, but is not required.
3. When melting iron in a crucible furnace, use a small handful of crushed limestone as a flux or cover.

Bronze and Brass Scrap

 

 

Shrinkage, two types.
Vertical: Castings should only be 1/4 to 1 inch thick. Castings thicker than 1" will shrink or dip in at the thick spots. If we cast a hockey puck flat, it would not shrink. If we had the puck standing up vertical when we cast, it would shrink at the top because it is almost 4" thick. To counter the shrinking effect we can place a riser over the area that will shrink.

 

 

 

 

 


Riser over thick area of casting feeds shrink area.

Horizontal: Aluminum shrinks horizontally at a rate of 1/8" per foot. Example- An aluminum casting 24" will need a pattern 24 1/4".

Art Foundry Links

Glossary
Bentonite-Powdered form of clay, holds mold together.
Casting-Object made by pouring molten metal into a mold.
Crucible-Molten metal receptacle. A steel pot, silicon carbide or clay graphite.
Cope-Top section of mold.
Drag- Bottom section of mold.
Dross- Layer of gas filled aluminum on top of molten aluminum.
Ingot/Pig- Extra metal is poured into open, cup shaped mold.
Flask- Wood or metal box that sand is packed into, also called mold.
Flux- Covers top of molten metal in a crucible to prevent absorbing gas,
only used in commercial foundries when metal is molten for long periods.
Gate-Area between casting and runner bar.
Greensand- Mixture of sand, clay and water.
Pop-up-Vent on the runner bar that relieves pressure when the mold is full.
Riser- Reservoir of molten metal that feeds a thick area of a casting.
Runner Bar
-
Metal flows from the sprue, through the "runner bar", to the gate.
Skimmer-Removes dross prior to pouring, a slotted steel spoon.
Sprue-Metal enters the mold through the cope and to the runner.

Safety

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.
Place on level ground tilted slightly toward the drain hole. On concrete floor, loose dirt or sand.

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
dangerous
results from trapped moisture in the concrete.

Do not operate near anything flammable.
During use, never introduce anything to the melt (liquid metal)
 that has not been preheated first. Pre-heat items in the exhaust flame on the lid.

A cold item placed into the molten metal will cause splattering and dangerous
splashing of molten metal!
 

Personal Protection-

Safety glasses- Always wear proper eye protection.
Leather gloves assume everything is hot! Always wear gloves.
 Shoes- shoes with laces are dangerous, cover-laced area.

 

Molten Facts

How hot? Barely Hot Hot Very Hot Too Hot
Temp Below 1000F 1000F-1500F 1500F-2250F 2250F or Higher
Metal Tin, Lead, Zinc, Linotype, Pewter or Pot metal Aluminum
1220F
Brass, Bronze, Gold, Silver or Copper Iron, Steel,
Tools These alloys can be melted on the stove in a soup can.  Caution: Most low-melting alloys are TOXIC, vent well and use a respirator. Aluminum can be melted in a coffee can on the BBQ, use propane, wood or charcoal for fuel. A gas or electric crucible furnace is typical. Electric Induction furnaces are used for large commercial foundries. Cupola furnaces use coke (refined coal) for smaller batches.
Safety needs Safety Glasses Leather Gloves, Glasses or face shield Thick shirt and pants or Apron, glasses or face shield & leather gloves. "Going into a volcano" suit.

 

Can I convert my furnace to natural gas?
Yes, but need to add a blower.
  
Propane comes out of the tank at 40+ PSI.
 Natural gas pressure is less than 5 PSI and needs a boost!

 


Molding Links

Mix molding sand

Make a Rammer

 Make a Flask

Sand Reclamation

What molding tools do I need?

How do you make a core box?


Casting Problems?


 Is your sand too wet? Torch the casting area until it turns orange, this will dry out excess moisture. This small mold was torched less than a minute, sand will blacken.


Remove pattern carefully!

TIPS:
1. Gating system must be smooth and slick to prevent erosion. Small holes in the bottom of a casting are from loose sand washed into the casting, not gas. Absorbed gas is inside the casting and only seen if the casting is cut, polished or machined.

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.

 

Oil-based sand

Oil-based sand is only used as a facing sand, only to cover the pattern. Should only be used with coarse greensand in a mold to get a smooth surface.
 

 

 

What does the sand look like the first time it is used?


Melting Links
See Tips: Below

What is a Crucible?

What melting tools do I need?

What does it look like during pouring?

Aluminum Alloys

 Bronze and Brass

Homemade Pyrometer
 

Bronze Pouring Tools

When melting with a silicon carbide or clay graphite crucible, you will need lifting tongs and a pouring shank. Fabricate your own for about $50. Post-hole diggers can be used for lifting tongs with smaller crucibles. The pouring shank is just a steel circle slightly smaller than the crucible diameter, with a handle or two welded on.

Tips:
1. Do not overheat aluminum (brass and bronze also), a major  cause of casting defects. If you do not have a pyrometer, metal will be at pouring temp 3 minutes after the last piece has turned to liquid. With brass and bronze, 5 minutes after last chunk has turned molten.

2. PIGS
Thin pieces of aluminum should be melted into pigs before pouring into molds to prevent gas. When the pigs (ingots) are remelted, the gas is gone. More surface area on your melting aluminum.......means more gas absorbed into the melt.

DO NOT pig brass or bronze! Each time the alloy is melted certain elements (zinc, lead) are released in the smoke that give the alloy it's fluidity. Also, melting brass and bronze wear out the crucible faster if you do it twice as much.  These alloys do not pick up gas during melting like aluminum does.

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.

 

 

CamchoyironFoundry
Melting iron with a cupola furnace. A cupola furnace is a vertical firebrick lined tube, with blowers at the bottom. Fuel (coal or coke) and iron are loaded at the top. Combustion takes place at the bottom of the tube. A molten bath forms at the bottom. A hole 6" below the blower allow slag to exit the bath, when iron starts to exit, it is full! Then the iron is tapped. Check out the very cool furnace on this link!

 

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.

 

http://www.atlasmetal.com

 

HOME
 

Gating.....why 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!