coryatjohn
11-26-2019, 04:58 PM
I've been using store bought pink foam for projects and have been disappointed by the cutting characteristics of that material. For my latest project, I used liquid urethane foam. What a difference!
Liquid urethane foam comes in two parts that are mixed equally, stirred for a short time, poured into a mold, or whatever, then allowed to rise to completion. From the start of the process to when the foam can be machined is about 20 minutes, a bit more for very thick pours. Multiple pours can be combined for really thick or complex parts. No prep is required to pour another layer.
This foam is incredibly easy to machine. No tear out, very stiff, strong in compression and pretty good in tension. The waste turned out by machining is more like little bits than dust. It doesn't stick to everything like the pink stuff does and since it's heavier, tends to settle and not be airborne.
This material comes in various densities from 1/2 lb. per cubic foot to 16 lbs. per cubic foot. The 1/2 lb. foam isn't that durable and is less useful for machining. From my experience, 4 lb. foam is the lower limit and machines beautifully. For thinner pieces or more detailed work, up that to 8 lb. foam. That stuff is incredibly strong and will take detail beautifully.
To finish, coat with epoxy (urethane resins will melt this foam) and fiberglass to turn it into an indestructible piece.
I'd include pictures but the project I'm working on is NDA.
Liquid urethane foam comes in two parts that are mixed equally, stirred for a short time, poured into a mold, or whatever, then allowed to rise to completion. From the start of the process to when the foam can be machined is about 20 minutes, a bit more for very thick pours. Multiple pours can be combined for really thick or complex parts. No prep is required to pour another layer.
This foam is incredibly easy to machine. No tear out, very stiff, strong in compression and pretty good in tension. The waste turned out by machining is more like little bits than dust. It doesn't stick to everything like the pink stuff does and since it's heavier, tends to settle and not be airborne.
This material comes in various densities from 1/2 lb. per cubic foot to 16 lbs. per cubic foot. The 1/2 lb. foam isn't that durable and is less useful for machining. From my experience, 4 lb. foam is the lower limit and machines beautifully. For thinner pieces or more detailed work, up that to 8 lb. foam. That stuff is incredibly strong and will take detail beautifully.
To finish, coat with epoxy (urethane resins will melt this foam) and fiberglass to turn it into an indestructible piece.
I'd include pictures but the project I'm working on is NDA.