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Lost Foam Casting: a Crankcase in Zinc Alloy

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Fergus OMore:

Somewhat rudely- possibility of creating phosgene.

vtsteam:
Doesn't seem rude at all Fergus -- an attempt to be helpful, I'd call it,  but can you give the specific reaction that will in this case do that?

ps. I mean from straight polystyrene, not if a thinner (like acetone) was used.

The only reference I remember several years ago to dangerous phosgene-like byproducts inhaled was in conjunction with an accident using an unspecified synthetic brake cleaner solvent and gas welding. I've actually referenced that link for others in the past.

I use an activated charcoal mask when doing lost foam casting, btw. I also work outside and hold my breath for the few seconds the tiny amount of foam smokes away. I stand back from the mold as soon as poured and let it cool by itself for a half hour before breaking out.  All these are I think common sense precautions.

vtsteam:
Oz, I can't take credit for this specific way of doing it -- Dave Kush worked out the details for himself many years ago where I first read about it on his website, www.buildyouridea.com.

I was incidentally casting in the above photos "my own idea" of his original linear bearing design to try to do it with less material usage.

Pete W.:
Hi there, Steve,

I look forward to seeing pictures of the castings.

Do I remember you mentioning a numerically controlled hot wire foam cutter in some earlier post? 

vtsteam:
Thanks Oz, Pete.  :beer:

Pete I do have a cnc hot wire foam cutter I built several years ago for cutting model plane wings.

The casting was a disappointment. It looks as if the polystyrene melted but didn't burn off, so there are plenty of flaws in the casting. The metal didn't have enough heat to do the job, as I suspected it might not. I'll post some pics later.

I have another foam pattern ready to go and will probably try aluminum tomorrow.

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