Tried out foam for the first time on some freezing block for an old GE monitor top refrigerator. Turned out better than expected. Some porosity which I'm assuming is pouring too hot but otherwise I'm happy. Thank you Kelly for all the posted guidance. Foam blanks ready for casting. I experimented with a laser etched logo on hardboard dipped in acetone and then pushed into the foam. It worked ok given the method. Laser cut profiles for the foam cutter. I used the instructions at: http://www.rcsoaring.com/rcsd/RCSD-2008-11.pdf to build my hot wire cutter (page 101).
Nice job Mach. Very interesting method you developed for applying the logo. Hopefully it is the first of many more successes yet to come. Best, Kelly
I'll second my thanks to Kelly for his well written guidance. I've had better experience with lost foam than I ever dreamed and use it as a regular tool. What material did you use and what did you heat it with? It is a lot of porosity.
I used wheelium purchased from Art over at AA. It was heated with natural gas but I was screwing around with different blowers. I've got a problem with the flame burning back into the tuyere and was trying to upsize the blower while it was melting so several starts and stops.
Regarding porosity, higher pour temps, extended melt times, rich furnace atmosphere will contribute to porosity. Same goes for the more times metal is re-melted, especially without de-gassing. Sprues and heavy sections are the most likely areas for porosity to reveal itself. The surface of the part looks pretty much like the pattern. I presume it was coated with something like drywall mud....yes? For me, it depends on what the part is as to whether I degas. For decorative or ornamental parts, no, unless it is going to get polished. Best, Kelly
Raced the rain to get a few more castings. Experimented with sprueing using aluminum flashing. It worked but looks like I got lucky. I didn't thinking the one of the right was going to turn out when the flashing melted but it held together. I went thin on the drywall mud an it look like I've got some grains of sand stuck on in places. Still amazed that this works. These fit in the freezer section of a '20s refrigerator so ice trays sit flat.
Nice work Mach. Heck, two years on I still feel that way LoL What was used as refrigerant in those days? Ammonia? Best, Kelly
Sulfur dioxide is used in most of those. Some earlier ones used methyl formate. Sulfur dioxide was phased out in the 40's in favor of freon due to safety concerns.
SO the EPA has been screwing us since at the least the 1940's. A company comes out with a new refrigerant and pays the clown at the EPA to declare it "baaaadddd" Just wait until 2020 hits and R22 production goes dry! 2 years ago it was 200bucks for 30lbs, today it's approaching a grand.
It wasn't the EPA on sulphur dioxide. Repairs meant the fridge had to be shipped back the factory when leaks occured. Turns out moisture in ans SO2 system leads to sulfuric acid. Repairs were just too expensive. That and SO2 killed a number of sleeping people when they tried to defrost with an ice pick before bed time. The reason these fridges have lasted this long is they're overbuilt using stainless steel. Even then, a homeowner with an icepick can undo all the over-engineering in the world. Interesting story, Einstein designed an alcohol fridge after a Berlin family died from a sulfur dioxide fridge leak.
The plant I'm working in at the moment uses over 3 tonnes of ammonia as refridgerant, but then it is a 60 foot tall, 200,0000 square foot fridge! We have an evacuation plan if there's a rapid leak. Edit, i may have missed a nought of that amonia figure. More on topic, CNC router with the sole intention of foam patterns makes for some interesting compromise in rigidity and speeds, has me thinking...
Run to the muster point 3 miles upwind? Oh I've been more than thinking about a cnc router just need time to assemble it. The project queu is too long.
