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Originally Posted by Ez2cDave
That's a very interesting idea . . . The idea of molding nose cones caught my attention.
With a 3-D printed mold ( I don't have a 3-D printer, but I have a friend that does ), it might be possible to "injection mold" nose cones, using epoxy in a syringe.
The two halves of the mold would be clamped together and the syringe attached to a threaded nipple on the mold . . . Of course, there would have to be a small hole to allow air to escape and the resin to completely fill the mold . . . . Once cured, the mold is unclamped and the sides are separated . . . Presto !
Thoughts ?
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Yes, that works just fine. Spray-on (in aerosol cans), wax-based mold release prevents the polyurethane casting resin from bonding to the 3D printed plastic mold. (Some resin casters even use molds made out of the same resin--such as, say, Alumilite--that's used to cast the parts themselves! As long as the mold cavity [and any places where the mold halves fit together] is sprayed with wax-based mold release, the cast part [and any excess resin] doesn't glue itself to the mold.) In addition:
Epoxy casting resins are also available, but they're more expensive than polyurethane (they do produce slightly more dimensionally accurate cast parts than polyurethane casting resin, but the difference is very small, and the mold cavity size can--if desired--be very slightly "nudged" in order to compensate for that). But even at the very worst, a cast resin duplicate part is just a tiny bit looser in the body tube than an original injection-molded or blow-molded styrene or ABS plastic part (or a properly sanded, sealed, and painted balsa nose cone that's used as the mold master part). Also:
Another method, which I used, is to create an RTV--Room Temperature-Vulcanizing--rubber mold (the platinum-cure rubber molds last longer and produce more dimensionally accurate parts, but I've used the cheaper tin-cure rubber with entirely satisfactory results), and produce solid-cast nose cones in it, and:
The rubber molds can also be made in two halves, and single-piece molds--which I used--also work fine. The nose cones can be lightened if desired (although small, solid resin BT-5 and T15 nose cones aren't too massive) by mixing microballoons (micro-bulb filler) into the resin, to lower the density of the cast part. Such single-cavity RTV rubber molds can also produce hollow nose cones, transitions, and tailcones by rotating the mold, even by hand (although roto-casting tables can be bought or built for casting such parts in quantity. This (see:
http://www.ninfinger.org/models/rms...resin_cast.html ) article that I wrote, "Resin Casting for Rocketeers," covers the various resin casting methods.