Nerf Rocket Injection Mold

[pyronaught]

One suggestion on your mold: from my previous attempts at mold making, I've found it very handy to model in registration keys with .2mm clearance on the holes. It is super annoying to try to clamp two smooth faces together and keep everything aligned.

I didn't even think about making registration pins until AFTER the print was done. I think it's a pretty simple mold though so not really necessary. The pipe clamps will keep the cylinder halves aligned and the removable pin for making the hollow bore in the middle of the rocket will act as a registration pin too since it locks into a slot on both mold halves.

[pyronaught]

This is what the missiles look like: http://www.hasbro.com/nerf/en_US/shop/d ... BC40:en_US

At $2.67 each that could start to add up if you wanted a stockpile.

What would be cool would be to put a bright LED on the tip for shooting them at night. Tracer rounds

[jsc]

http://www.instructables.com/id/Casting ... hane-Foam/ has some tips on casting foam in 3D printed molds. He links to this foam: http://www.douglasandsturgess.com/mm5/m ... gory_Code=

which is $22 for 5 lbs, although only 10x expansion so likely to be denser than the Smooth-On.

[pyronaught]

http://www.instructables.com/id/Casting ... hane-Foam/ has some tips on casting foam in 3D printed molds. He links to this foam: http://www.douglasandsturgess.com/mm5/m ... gory_Code=

which is $22 for 5 lbs, although only 10x expansion so likely to be denser than the Smooth-On.

Did you see how smooth the printed mold was that guy was using? I asked him about it and he said it was printed using one of those high-end Stratasys Object Connex printers, probably through a print service. Those PolyJet printers are pretty amazing, I wonder how long till an affordable desktop version hits the market? I guess it all depends on how long it takes Stratasys patents to run out, since anything they make themselves will never be affordable.

[pyronaught]

Well, the Great Stuff did not work out too well. It does set up in the mold and the mold does release from it using Turtle Wax, but the problem is that it shrinks when drying and creates a lumpy surface. So it's really only good for creating lumpy organic surfaces like rocks, skulls etc. There are about four versions of Great Stuff, and I used the flexible one for sealing windows. Even with it being flexible the fins still tore off when removing from the mold because it just tears too easily when pulling on it. It's tensile strength is pretty poor. So to get this to work would probably require using the two part foam like what Smooth-on sells. The other option might be to cap the fill hole and let it expand under higher pressure to create a denser foam that might not tear or shrink as bad. The other problem with using Great Stuff is there is no way to measure how much you are squirting in, which you can do with the 2-part kind that is poured in as a liquid.

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[Yodajammies]

Try Foam-it! 5 or Flex Foam-it! 5 from smoothon. Their products are designed for exactly what you're doing. Be careful about breaking your mold though - The 5 series will expand a LOT.