Lost Foam Aluminum Casting

[sourcecharge]

Don't forget that dealing with little guys means a lot of overhead for a given amount and generally a lot of pain dealing with people. I know a fair few companies that don't do it for that reason. It's just too much of a hassle for what you earn.

they might actually give him a raise and a promotion if this idea works!

The "make a master, make a flexible  mold, make a wax  investment"  is how jewelers make multiples of the same design.  Any of the jewelry supply houses can supply the materials.

Casting large kirksite (a zinc-tin alloy) in plaster molds was used extensively during WW II to make dies for aircraft fuel tanks.  The dies will last for about 10,000 pieces if well designed, which is a lot more than the number of aircraft of a design that were built in many cases. 

The example  in one of my books was a 2000 lb die set.

As I noted, you *do* have to dry the mold before pouring hot metal into it.  For the 2000 lb die it probably took a couple of days to dry.  Though if the plaster is just the facing of a stout wooden mold it would dry more quickly.

I think most people use a ceramic kiln for wax  burnout of investment castings.  For small work a large junk electric stove burner in a suitable refractory housing should make short work of burnout of the 3D printer wax for a one off.

I don't see why I can't use EPS, it really shouldn't be this hard.  Someone has to sell expandable polystyrene beads for consumer use.  I can't believe I'm the only one that can see the potential consumer use of such a process.  The time to make the required part would be 1 hour compared to 2 to 3 days.  And that's only if you have one 3d printed negative mold.

Powered aluminum and plaster will not make what you are thinking.  It requires rust.  That is why I used a wire wheel on the inside of the crucible before I started melting anything.  Now the aluminum is coating it and I don't think too much rust will accumulate.

A thermite reaction requires a metal and an oxide to react.  It does not have to be aluminum and iron oxide.   Magnesium / copper oxide produces more heat than AL/iron oxide and is particularly energetic.   Not sure if AL/plaster is a true thermite reaction, but it works the same.   The solid plaster / AL mold may not cause problems since the materials are not well mixed.
 

ya, I was very cautious about the rust, didn't want molten aluminum going through the bottom of it.  I've heard that a 1 to 2 day drying time is optimal if you are going to use plaster, but I'm hoping to not even have to use plaster, just sand and a positive EPS object from a 3d printing negative mold.

[sourcecharge]

Gone fishing!

 

[jmelson]

ya, I was very cautious about the rust, didn't want molten aluminum going through the bottom of it.  I've heard that a 1 to 2 day drying time is optimal if you are going to use plaster, but I'm hoping to not even have to use plaster, just sand and a positive EPS object from a 3d printing negative mold.

Unless you need extreme detail on the part, like a display plaque , you do not need the investment.  I've seen lost foam casting done with simple sand molds, and it worked very well for mechanical parts.  This was done with styrofoam insulation board machined on a CNC router.  You put the foam master in the casting sand and pack more sand around it.  Make a few holes for risers and vents, and pour the molten aluminum or other metal into the mold.  the styrofoam immediately flames up and is gone in several seconds.  The smoke from that DOES look pretty nasty, though.

The casting sand is mixed with some form of motor oil and additives to make it sticky.

Jon

[sourcecharge]

Gone fishing!

 

https://www.ebay.com/itm/Expandable-Polystyrene-EPS-Beads-High-Impact-Foam-For-Floating-Fishing-Lures/263681639645?hash=item3d64a684dd%3Ag%3AJz4AAOSwlSda9whP&_sacat=0&_nkw=expandable+eps&_from=R40&rt=nc&_trksid=m570.l1313

 

[CopperCone]

My recommendation for anyone that wants to get into casting is to go to home depot and buy a bunch of roofing lead first, then experiment with casting lead.

It is alot safer then aluminum in terms of heat hazard so you can get used to handling molten metal, making molds, using crucibles, pouring metal..

when you get a hang of that then go for aluminum.

I recommend doing open face molds for a while before going to covered molds. My choice is to set sand with sodium silicate and CO2.

Casting is one of those things that seems really easy but if you miss a step or detail you can get injured pretty bad.. for instance if you are casting a closed mold that has moisture in it, you can get aluminum/steam shooting out at you, steam explosions, all sorts of bad shit. Take it slow and actually observe the properties of the stuff you are working with.. I really get a sense here that people are getting too complicated too quickly in this thread for a newbie. Someone just melting a kilogram of aluminum and pouring a complex mold for the first time in their life is asking for trouble.

Watching all of MrPete222's videos about casting is a good primer I think:
https://www.youtube.com/channel/UCKLIIdKEpjAnn8E76KP7sQg (just search his channel for casting).

But seriously start with lead. I studied it alot before I started doing small castings but it was still different because you just feel different when you are pouring a buncha liquid metal, wearing all the safety equipment, feel the heat, etc.

[rhb]

Be *very* careful about working practices shown on YouTube.  There are people who pour aluminum in their kitchen and others who pour iron on their concrete shop floor.  Amazingly some of them seem to have gotten away with such dangerous practices for a long time.

Steve Chastain has some very good books on metal casting which I highly recommend:

http://stephenchastain.com/store/

Lindsay Books reprinted a lot of good books, but alas, he retired and closed the business.

David Gingery also wrote some good books:

http://gingerybooks.com/