The Lost Art of "The Lost Foam" Technique

mrrsm

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Oct 22, 2015
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Nope... NOT Root Beer Foam... But since every once in while we discuss the strange idea that the Aluminum Engine Block and Head for the GM Atlas 4.2L and the smaller flavors of Atlas Engines all get manufactured using what is called "The Lost Foam" Technique of Casting Aluminum... I thought it might be nice to see an analog of how they do it. Essentially... Fully Formed Molded Styrofoam Planks in the shape of the Engine Block and Head are glued together and then covered or buried inside of a lot of high quality sand. Some vents for out-gassing are essential and these are made by leaving some pieces attached foam sticking out that will form the Pour Holes and Gas Escape Ports necessary for a complete formation of a homogeneous, solid piece of Cast Aluminum.

This procedure will faithfully recreate practically all of the Internal and External Features desired and become damned near ready to go after post-prepping is done and the metal is cool enough to be picked up with a bare hand. THIS Technique is a great way to rescue long dead cast car parts from disappearing forever into the 'sands' of time. And speaking of Sand... this technique as used by GM allows them to recycle almost all of the Waste Sand that usually winds up being left behind as mountains of useless, contaminated dirt as is the case when molding Cast Iron and Steel components.

The critical thing to watch is that the Foam Planks get rapidly vaporized as the Liquid Aluminum gets poured into a reasonable number of "Sand Volcanoes" shaped to accommodate a steady amount of liquid metal reaching from the bottom to the top of the mold rapidly enough to remain a liquid and not cool prematurely anywhere inside and allow gas pockets or any casting defects to form. You can tell when "The Lost Foam" Technique has been used if you can see what looks like a surface covered and texture impressed into the Aluminum that is identical in appearance with that of a "Styrofoam Cup".

The vapors belching out of the VOP's Kiln are, of course... Ridiculously Toxic... so this activity is best restricted to being done out of doors in the open air and not in the Garage or out on the Covered Back Porch. So if you Smelt your own Scrap Aluminum, etc... beware this extra concern for your safety and take the right precautions so you don't wind up dead from trying to re-create your own replica of that NATO FN-FAL Combat Rifle you always wanted to have hanging over the Fireplace:

 
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