Lost Foam Casting Aluminum

Lost Foam casting starts with a piece of polystyrene foam cut and shaped into the desired part. It is sometimes then coated with "investment" such as sheetrock mud or just place directly into sand. When the aluminum is poured into the feeder it burns the foam away leaving aluminum in it's place.

Category:

Education

Tags:

• Aluminum Casting
• Lost Foam Casting
• Molten Aluminum
• Investment Casting

[steveBB30]

Can't see sheetrock mud being gypsum/plaster based as when hydrated gypsum is heated above 150 deg C it'll decompose producing lots of steam-I once tried a lost wax alu casting in a plaster of Paris mould but found the molten alu reacted quite violently to the plaster. Loads of blow holes throughout the solidified alu.and loss of detail where mould material had turned back to powdered gypsum

[submarineboat]

@steveBB30 The mud I've used: See wikipedia "Joint compound" turn becomes like porcelain when it's fired to about 700C. I tried the wax and plaster too, I think it absorbed some of the wax when I melted it out. It was bad about cracking too so I didn't use much heat. And it did exactly as you described. ALpHASET is said to be great stuff because it vents through the surface unlike sheet rock mud.

[steveBB30]

Any help for what sheetrock mud contains?Have dry wall in UK but can't find "mud" in conduction with it anywhere, maybe called something different? Any chance it's cement render?

[submarineboat]

@steveBB30 According to wikipedia : "Ready-mix lightweight joint compound is a pre-made form of joint compound designed for fast application and easy maintenance. The compound is a complex combination of water, limestone, expanded perlite, ethylene-vinyl acetate polymer and attapulgite."

[KEF791]

Hey, was wondering about what size is the bore going to be for the stern tube and the length of the tube, was rounding up some of my props for a video and the question came to mind...Keith

[submarineboat]

@KEF791 Hmm... well, let me measure the shaft tomorrow and get back with you on that. I know the shaft is about 12 ft long and off hand I'd guess it's about 2.75" OD. And I really appreciate your assistance on this. Paul , with the 65 footer up on Vancouver Island might be interested doing this on his boat too. I think he's got a 1.5" shaft in a stainless log that is about 3".

[steveBB30]

@submarineboat Thanks. . Will see if I can find a small amount for next time I fire up my tiny gingerly foundry. Kicking myself for not checking on wikipedia. Can be problems with wax absorption with lost wax, commercially they vaporise/bake it out. Domestic oven , or heat treating furnace should work. Dusting powdered clay cat litter[bentonite clay ] misting with water, and then setting in dry sand/leaving to dry completely may work as investment for lost foam.

[submarineboat]

@KEF791 It's just some old video that I'd been hosting on my ISP so I moved it to YouTube. But we picked up about 60 pounds of NiBrAl for casting prop blades today. But I may need to build a new furnace first. And I still have to finish the pattern.

[KEF791]

Sure! give us a cliff hanger...LOL... Keith