Sand casting

GMtb42 · Sep 24, 2013

Has anyone here done any sand casting? I am trying to cast a part from aluminum and want to learn how to sand cast, I have watched Youtube videos of it and it seems rather easily done.
I have the sand mixed with the Bentonite clay (green sand), boxes made for the sand mold, just wondering if there are any tips of the trade and pitfalls to watch for.

charlz · Sep 24, 2013

Haven't done it myself but am interested in it and also have watched a ton of youtube videos. Using scrap cast as your material (versus extruded etc), fluxing and degassing seem to be key items. Mostly I like MyfordBoy's casting videos, he has a lot of them and always seems to have a successful pour. What type of furnace have you built/bought?

SPIKER · Sep 24, 2013

Having the sand rammed tight, and controlled moisture content when pour begins too much moisture and it can blow up the cask from steam explosion and shoot metal out the funnel!. Also vibrator shaker to help settle it as well helps then ram and re-fill & plate compress. I worked maintenance at place where brass fixtures were made so lots of hollow cores made and set in between two part casts and the brass poured around them. after cooling shaker knocked loose most of the extra sand and then cut apart into individual bits then cleaned of the sand cores. cut to size and then machines after inspection... lots of work to make a spigot !

Mark

forgeblast · Sep 25, 2013

What spiker said about the moisture.
We would make forms out of styrofoam, and then add a spru (piece you are pouring into). Then we would pour the aluminum right on top of the styrofoam (which was packed in sand) and the stryofoam would vaporize and the aluminum would fill the void.

mikehaugen · Sep 25, 2013

forgeblast said:
What spiker said about the moisture.
We would make forms out of styrofoam, and then add a spru (piece you are pouring into). Then we would pour the aluminum right on top of the styrofoam (which was packed in sand) and the stryofoam would vaporize and the aluminum would fill the void.

That sounds like a good idea!

The vaporizing Styrofoam doesn't cause any issues?

forgeblast · Sep 25, 2013

Only if you breath it in....do it outside and your fine. One thing I noticed was that if you sand the form a bit it will have a better finish.

RoyJackson · Sep 25, 2013

Degassing the molten metal is very important...reduces porosity.
Your ingot should be one alloy...don't just throw any aluminum in the pot.
Watch your pouring speed...too fast, you'll get turbulence (results in porosity), too slow and the metal might freeze before the mold is filled which results in shrinkage and a weak casting.
Don't get discouraged if your first attempt doesn't work out....casting is an art as much as it is a science.

mikehaugen · Sep 25, 2013

This is an interesting thread. I have never considered trying this, I guess I just assumed it was one of those things that was out of the realm of home projects... and I am usually one of the last to think like that!

namyessam · Sep 25, 2013

Did this back in the middle to late 60's with my dad. I was a little squirt then, but remember laying out the pattern so there weren't any undercuts. then packing sand in the bottom of the form. I believe the proper terms are the top is the cope and the bottom is the drag. after you have properly pack the sand level, you turned over and removed the sand to create a parting line half way down. You then sprinkled a very fine sand on the surface you created. Then put the top half of the form on and packed it with sand with the sprue plug in place. We found that if you put another plug at the far end of the pour, this would allow the gas to vent and help to completely fill the void. Once that was done, you lift off the top half and hope the pattern is still in the bottom half. you then remove the pattern and cut a runner to the sprue and vent. assemble the mold carefully and you were ready to pour. I have not watched any u-tube videos of this process and am going completely by memory from almost 50 years ago. angled sides of the pattern and additional stock added to the pattern to allow for machine stock has to be taken into consideration. Brings back good memories of the things Dad taught me over the years. Thanks for bringing this up.