Casting my own Bricks! Any suggestions?

[derpybricks]

So I've recently acquired some ABS pellets and I am thinking of trying to melt some down, and making my own rendition of a brick. How would I go about getting the molten plastic in the mould? I obviously don't have an injection machine so I guess my only option is pouring it in gently?

I'm getting a bit ahead of myself anyway. To melt it down, I'm thinking of fashioning a crucible from a tin can (because it's actually steel) and chucking it in the oven. ABS plastic has a melting point of 105 degrees celcius so that shouldn't be too hard, but is this safe?

Has anyone tried to cast their own bricks, or those who have cast weapons/accessories may be able to give some suggestions. I'm not doing this to sell them, I'd just love to experiment with it.

[OpusMcN]

Molten ABS is still quite a thick liquid, you'll have great trouble pouring it into any mould, and not have it solidify before it gets to the far corners. ABS starts to soften at 105C, but doesn't really melt until 230C or above (depending on the actual plastic) I've done bit of casting of white metal figures (which does melt to a very pourable consistency) and it's still a major pain. You _must_ heat the mould to above the melting point, and leave channels for the air to escape while the metal/plastic goes in. There's a bunch of videos/etc on the interwebs about casting metal. There's been a bit of discussion in the 3D printer community about using 3D printer extruders to push molten plastic into moulds. That might work if you could seal the extruder onto the entry of the mould. You'd still have to heat the mould, and I don't know what material would be best for it. I used plaster for metal casting (which is easy to heat) that that would be a nightmare getting out of the intricacies of a lego brick, and would probably only last a single brick.

Melting ABS does give off some nasty fumes, so be well ventilated if you try anything. You could also try PLA plastic, it's not what Lego uses, but it melts at much lower temperatures and is much safer and more pleasant to deal with (I've got a couple of 3D printers, and use PLA whenever possible, it smells like caramel as it melts :)

If you try anything, let us know!

[derpybricks]

Haha, nawww. Sounds like I was having another pipe dream. I suppose I just wanted to see what it would look like. My goal was actually to create a marbled brick since I have red, yellow and blue, so I guess I could just melt down a bunch of pellets into a flat sheet full of swirls. Idk, I'll see what I can work with.

[MAB]

For weapons and so on you can just about get away with dissolving ABS in minimal acetone (and I mean minimal, allow it to slowly dissolve adding a drop at a time) and casting with that. For bricks it doesn't really work as the castings will shrink a little as the acetone evaporates plus they can deform as well if one part dries quicker than another. And they tend to be rather flexible afterwards too, much more than normal lego. Warnings similar to above about ventilation apply.

[GallardoLU]

another thing to consider is the force on the mold. I work in the plastics molding industry (we make the machines) and injection machines are listed by their clamp power, virtually all of which have a clamp force over 100 tons, which is present during the injection. the clamping force is required so that during inject the molten plastic cant force the clamp open, it then holds under pressure, while the part cools low enough to prevent deformation. Granted Industrial settings are far more unforgiving than personal ones, and clamp force can be much lower depending on size of part and injection pressures.