Bronzebullion Posted July 31, 2017 Share Posted July 31, 2017 okay, so I have been melting and casting metal for about a year now, I use a metal trash can, with a plaster of Paris sand mix lining, I use charcoal to power it. I mostly melt bronze and make swords. My friend from school asked if I could cast him a very immature joke object as a gift. I had him 3D print a plastic model of it to make a mold. problem being the object in question is very oddly shaped. I tried to to use green sand, which failed. I then encased the object in plaster of Paris and tried to pour.. which failed. my new hope to make the object would be to use some sort of foam sacrifice method. I would like to make a mold using silicon and fill that mold with a foam like material, in order to then bury it in sand and pour into it. Down to my question, will this new method work? And does anybody know a material that Will work like foam but is able to be poured into a mold? Quote Link to comment Share on other sites More sharing options...
Lou L Posted July 31, 2017 Share Posted July 31, 2017 I had to Google it. I can't take this seriously. Fortunately for you I had no good advice beside "try casting it in two halves" but I just can't...I can't... BTW, you may want to edit this post if you can because I don't think that word will pass muster considering the family-safe rules of this forum. On top of that, I would completely enjoy watching you try to use wordplay to describe this project without being inappropriate! Thanks for chuckle. Tell your friend to seek help... Lou Quote Link to comment Share on other sites More sharing options...
Bronzebullion Posted July 31, 2017 Author Share Posted July 31, 2017 Thanks for taking the time to reply, as well as for the advice. Although it's a very stupid object to cast, it just goes to show the dumb things people will ask for, when they find out you cast metal. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted July 31, 2017 Share Posted July 31, 2017 Silicon caulk type stuff is a LOW TEMP casting material. Pewter is about it's top and you may have problems then with large cross sections. You didn't mention what metal you were trying to cast this in. You may want to look at lost wax casting and use a PROPER INVESTMENT to cast with suited to the metal you will be casting. Using poor techniques or improper materials can be a LIFE CHANGING experience in the worst possible way! Have you looked over at the alloyavenue.com where the backyard metalcasting forums moved to? Is this part of a person's wedding tackle? Quote Link to comment Share on other sites More sharing options...
Lou L Posted July 31, 2017 Share Posted July 31, 2017 9 hours ago, Bronzebullion said: Thanks for taking the time to reply, as well as for the advice. Although it's a very stupid object to cast, it just goes to show the dumb things people will ask for, when they find out you cast metal. Aww...you changed it in a way that avoids hilariously awkward wording! Suffice it it to say, Thomas, that the piece is stout and beefy and is an amalgam of various inappropriate body parts fused into a cartoon character. I sure hope it isn't wedding tackle... There are plenty of people here with casting experience but the backyard metal casting people are experts. You may as well have a go asking in both places and work out the best ideas. Good luck and be safe. Lou Quote Link to comment Share on other sites More sharing options...
JNewman Posted July 31, 2017 Share Posted July 31, 2017 I have heard that PLA can be used like lost foam but have no actual experience with it. 3D printing he can make the print with minimal plastic internally with a honeycomb internal structure so there is less to burn away. If you have any core sand like a SO2 you can take the time and mould just about any shape with time and lots of parting dust. The traditional moulder journeyman test was to mould a teacup sitting on a saucer with a teaspoon and sugar cube in the cup. I had a customer who had 2 castings of this test sitting on his boardroom table who asked me if I knew what they were. I am a patternmaker not a moulder but I think I could pull it off in airset sand but not in green sand. . Quote Link to comment Share on other sites More sharing options...
Smoggy Posted July 31, 2017 Share Posted July 31, 2017 It is not difficult to fashion most shapes in polystyrene for lost foam casting (individual parts can be glued together with hot glue), Lost wax is a superiour process in many ways. Coat in slip (clay is preferable to PoP for anything other than pewter or similar) and set it in greensand. Gating and venting all depend on the shape, of which I have no idea, so cannot comment on. Is it do-able almost certainly, Is great care required....absolutley. Note: if using Polystyrene foam, additional caution is needed as regards casting area ventilation when pouring, nasty stuff burning polystyrene, you don't want to be breathing any in. I also agree with the recomendation to visit the backyard metal casting/alloy avenue site for more information. Quote Link to comment Share on other sites More sharing options...
Frosty Posted July 31, 2017 Share Posted July 31, 2017 Welcome aboard, glad to have you. Have you taken any casting lessons? This really is jr. highschool metal shop 1 level casting project. Not the bronze casting but the pattern and mold are really simple if you're using the right materials and methods. First, how about using a proper refractory in your melter? Plaster of Paris, (POP) is a Youtube "expert's" standby but a BAD excuse for a refractory. Even if you don't need high end refractories like you're melting iron lining it correctly will not only last longer and save you money in fuel, it's much MUCH safer. Seriously, fire clay is cheap, 1pt. fire clay, 2pts. sand, 1 pt. saw dust by volume and a cap of Elmer's glue in the water is the recipe. Leave out the saw dust for hard brick or liner. ONLY add just enough moisture the mix will clump in your fist with a hard squeeze. It should break cleanly, if it crumbles add a LITTLE more moisture. If it leaves your hand dirty add a LITTLE more mix, it's too moist. No, dusty doesn't count. When you add the moisture put it in a sealed container and give it a day for the moisture to equalize through the mix. So the same if you have to adjust the moisture. Once mixed and tempered ram it in the mold, brick mold, liner sections, the liner, etc. Let it dry thoroughly before firing it for a few minutes. let it cool and fire it for 15 to 30 minutes, keep it below red heat. let it cool. Fire to red heat and hold it there for an hour or so. Let it cool and it's ready to go to work. Or you can do it old school and fill it with charcoal briquettes and let it burn to ash. Briquettes don't cause heat checking in un-fired fire clay like lump can. Same story for your mold investment. Aluminum is too hot to safely cast in POP investment. Just buy the right stuff, safer and better. Have your customer make the pattern. Charge a LOT if he wants himself modeled live! If you want to be mean don't tell him to shave and lube up with Vaseline, etc. before making the mold. If I were asked to do this I'd just decline, it solves sooooo many problems I don't want to touch. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
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