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CosmoWenman

Metal Casting

by CosmoWenman Jul 9, 2012
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file:///C:/Users/clutc/OneDrive/Desktop/Low%20Melt_Fusible%20Alloys%20-%20RotoMetals.html

www.rotometals.com/lead-free-fishing-tackle-weight-bismuth-tin-alloy-281/

How do you make the mold from the object?

"For all I know it gives off gamma rays too." ...Always a good assumption.

Wow, I am amazed by this! I did not know you could do this using a 3d printed mold.

great stuff! I love it

HIPS has similar melting point to ABS I think.
http://www.makergeeks.com/hiimpohfi3.htmlhttp://www.makergeeks.com/hiim...

it dissolves easily in Limonene.

Awesome. Low temp melting metals directly in ABS molds. Did you print the ABS with a heated print bed? I have lots of ABS left, but I experience cracks between the layers because of the warping? I do not have a heated bed to print on. Any hints? Or just by a heated print bed?

I was thinking about printing PLA model (with support if necessary and clean up the model). Make a mold of Ca2SO4 (gypses?) Dissolve the PLA (with NaOH?), or heat melt it away? And pour the metal in the gypses mold. And destroy the mold afterwards to release the object. Too bad that both the print
ed object as well as the mold will be destroyed in the process.

  • Yes, I used a heated print bed, 115F

  • I get cracks in ABS on medium to large objects. Small objects, like in this demo, seem to print OK.

  • In my opinion, the heated print bed only solves adhesion problems. I can't see how it makes any difference on the cracking issue, which seems to be related to various mass/surface area/uneven c
    ooling rate ratios, regardless of the temperature of the bottom few layers.

  • I haven't tried PLA yet, but I intend to, for larger prints. I don't know what will dissolve PLA yet.

  • I've only done a few tests with plaster of Paris; see the photo of the bull creature in white: that is plaster of Pa
    ris cast into an ABS mold. (A simple break away mold; no dissolving) I don't see why you couldn't make a mold out of it too.

Hey Cos' here's a question. Could you make this process work for a multi part print such as a simple chain or mechanical something or other? Print, cast, dissolve= moving connected parts? I guess the main consideration is metal flow but if it moves through tiny holes or separate pour sites, it should work. Hmm, perhaps I will explore this further.

I'm pretty sure, topology-wise, that if the positive parts can be printed nested or interlocking, their negatives can be too.

Make sure to have a thick enough wall between the parts, or the metal may leak out between them and fuse them.

Each hollow to be filled will need separate pour inlets, and consider adding air vents if you've got internal high points that will trap air. At some scale, or level of complexity and de
tail, I imagine surface tensions and air pockets and flow will start playing a bigger role than I encountered on my tests, and it will start making sense to route the metal to the hollows' low points first, so that it rises smoothly upwards within the hollow, rather than tumbling down through air as
it is poured from the top, like it was on mine. In my experiments, once the mold was filled, I was able to just tap it to jostle the air out of any small pockets.

If you print the positive first you can get a preview: any problematic overhangs on the positive will translate into the same spots on
the negative where you will have air-trapping high points while casting. If you imagine where you'd put break-away support struts on the positive, that's where you'd want to put vents too for the mold.

The metal is fairly soft, so I don't think it will make for a very durable working part, and if y
ou're going to be machining it, or if the working part will wear, you should consider the same safety precautions with the dust as you would with its vapors when melting it.

See updates on toxicty, and "Field's Metal"

See updates on toxicty, and "Field's Metal"

You might want to be careful about where you are melting the 155. Based on what I see the only bismuth allows that don't contain lead are low 144, low 281, and low 281-338. These are fairly standard alloys with different brand name. Cerrosafe definately contains lead. Cerrobend may not but its melting point may be too low for some casting purposes.

The best no lead option I see for this type of casting is the low 281. It's a bit warm for ABS casting but would probably work without destroying the mold.

Very cool post.. thanks for sharing so much information, I've been looking for something like this for a while now.

Thanks - I double checked too. The Bismuth alloys I've been using from McMaster have lots of lead, and cadmium too. Definitely wear a ventilator. I'll put an update in my notes above.

I am looking to do some castings using prints,

direct low tem metal was not one i had seriously considered until now.

Your rockets would look cool in metal, and based on their shapes they look like they would cast very well. Also, because they don't have many trapped details, you might be able to make very close-fitted molds, and simply tear them away instead of dissolving them (which is what I was able to do with that winged bull piece in the video).

I'm scanning one we made in clay right now. It has a lot of detail, but maybe I can do a Boolean subtract using the model to create a mold if I can't get it to work with this.

See updates on toxicty, and "Field's Metal"

Nice! I've been wanting to do some field's metal casting for a while...

This sounds like a very cool process. After "I'm totally high on molten bismuth fumes at the moment" set the tone for your write-up, "But I've been breathing the stuff for weeks and I feel fiej." had me rolling on the floor. I think I'll give this a go, but will opt for the respirator.

Thanks!

See updates on toxicty, and "Field's Metal"