Hello, I dicovered the forum via Youtube movies, which taught me A LOT!! Thanks mr. Coffield!! In the past I casted aluminium in wet sand and sodium silicate bondend sand...both with variable results. At the moment I'm trying to get my head around CNC-routing styrofoam. Yes, I'm aware of the fact that my foam results are looking a bit "fluffy" All my instruments are low budget and home build. On the first couple of projects my furnace was running on butane gas, today I prefer using an diesel burner. Koen.
Hello Koen! Thanks for posting up with the forum. It must be a good feeling to see your parts installed on projects.
Looks like you're doing pretty well to me. Welcome to the forum. What's this pattern? A valve cover? What are the appoximate dimensions? This fail looks like it was caused by a short or interupted pour. Best, Kelly
Hello Kelly. The blue one is a valve cover I made up for a 6 in-line Opel engine....its about 1m long . I designed it having looked at the Bugatti U-type airoplane engine. It should make a simple looking engine look a bit more old.. The first 4 attempts I tried casting it in wet sand but always failed ...then I decided to make it in styrofoam ( not cnc) but still haven't had the courrage to finish and try to cast this one ...
Not a trivial part to pour in lost foam!! I can offer some suggestions if you like but firs sme questions: Can you show the interior features of the pattern? What is the typical wall thickness? Approximatete weight of casting? How much (assuming aluminum) can you melt and pour in a single shot? What kind of flask and vibratory packing equipment do you have? Do you use a pouring cup? If so do you have pictures? Best, Kelly
The project was pre-pandemic so a couple of years ago. It did got on hold because of the size of my oven....It can melt 6 kg of aluminium. I have an old small cement mixer which I'm planning on using for my new bigger melting oven. Maybe even use its pooring system for steady quick poors. The problem in the vale cover was the transition from rather thick (7mm) wall to the thinner (4mm) top part ...it was blocking, obstructing flow....vausing tge alu not getting up the highest point. The piece weighs about 5 kg. The fact that I didn't own a pyrometer, not enough molten alu ( so not really a big pooring reservoir), no pooring cup ... didnt help nether ... All these things I gradually bought or made so the future is bright I made a ceramic pooring cup....it did crack a bit during baking but planning on fix that with heatresistant fire place kit. My crusable is basically a steel 5mm tube. The big vibrating table I made works pretty well, a bit too powerful maybe on small bucket of sand.I havent tried it on bigger stuff but planning on doing the vibrating way before the casting so i can alter if needed. At the moment the air inlet manifold is getting all of my time. I did put an old Mercedes OM 603 diesel engine in a Ford breadvan....not enough place in its new home for an airbox..... Thanks for your interest!! Koen
I considered a tipping/pouring furnace but quickly abandon the idea. It's much more versatile to bring the melt to the mold location in a crucible. You can control the pour much better. I think the bigger problem is the wall thickness is only ~1/8". That is very thin for any sand casting process because a casting that size with that much surface area will lose heat quite rapidly to the cold sand mold. Automotive parts like that are usually made with permanent mold tools that can operate at elevated temperatures. I'd need to see how you gated it but I'd probably thicken the flange on the valve cover the entire length of each side of the part and use it like a combined gate/runner to get hot metal the entire length on each side,.....and pour hot. Increasing the wall thickness would increase the chances of success but you'd need a bigger furnace and crucible. You need a pyrometer.....otherwise you are just guessing and will not be able to troubleshoot failures and control the quality of your successes. I'd like to see that. The problem is almost always not enough power instead of too much power. Here are mine: My New Lost Foam Casting Rig | The Home Foundry Failure due to thermal shock is the problem with most ceramics. They also are very thermally massive and will rob heat from you melt. That's one of the reasons I use the moldable ceramic fiber or ceramic fiber board for my pouring cups. Reuasbale Offset Pouring Basin | Page 3 | The Home Foundry Best, Kelly
Hello Kelly, Thank you very much for your remarks, saved me from another casting disappointment and building the wrong things! I did realize the design of the valve cover had flaws but hadn't thought about overall wall thickness....back to the drawing board! I do own a pyrometer( thermo coupler) now and latest, smaller projects had positive results. I poor at 700°C. Before i made the ceramic pooring cup I did try to make a cup out of mouldable ceramic fibre stuff ...at least i think it was ....it is a combination of a automotive exhaust paste (with fibres in it) and a sort of fireplace kit sealer for small cracks. It became very odd shaped and didn't looked exactely the right thing. A test might bring more conclutions. Sometimes its hard to find the proper products ... Plan is also to test the shaker again too....better be safe then sorry. Thanks again for your feedback!! Keep you posted. Koen
