Nicodemus:
A 3d printer costs lots of ££££$$$!
we common people wont afford it :(
warh
Printer prices alone are insane, not to mention materials costs. You'll also need some special training. That being said zobo1942 has the right idea, if you can supply a 3D model they can print it (usually after consulting with you about potential problem areas with the design). That being said lots of designs that won't work with conventional molds can work just fine on a 3D printer.
We get stuff printed pretty regularly for work (reciprocal mouse, anyone?!?). The cost is pretty good, so if you can make good 3D designs on a computer then the price of a 3D printed master isn't too bad. Particularly if you consider getting 10+ printed usually isn't too much more expensive than getting one printed (setup and consulting fees etc are a big part of the total) then you can keep one master in storage and start modifying the others with GS or what ever else. Once you have a design you like it's relatively easy to slice parts off for conventional casting.
Consult with the company about plastic choices, particularly if you're planning to use them as-is from the printer as there are a few things to be aware of:
1) unless the company does it for you there will be lots of cleaning up of the printed model, much more than with conventional casting from a 2-part mold.
2) choices of plastic types for these printers vary considerably, which is a good thing, but it may also mean that the plastic will be fairly soft or will be too brittle to stand up to much handling.
These will be a problem if you're going to clean off all the gunk from the surrounding matrix and then prime and paint them. With most materials I've tried the plastic is very soft when it's new (or if you store it uncleaned, i.e. with all the matrix gubbins, in an air-tight container). It's usually soft enough (in my experience) that it will warp if you're not careful, and then it'll set like that and over time will harden and become brittle. In any event, while it's still new wash with water and as a final rinse wash with a little ethanol and then with water again, then pat is down dry as much as possible and leave it to air dry, or better still set it in front of a fan to dry. With most of the plastics I've used the small thin areas and fine detail will warp and distort if left wet.
Best choice would be to 3D print, treat the printed piece as a precious master and use it to make further moulds from.
The big caveat with all of the above is that if you can find a vendor who can assure you that the plastics they are using stand up well to handling with minimal shrinkage/warping/etc and understand what you're making you should be set. I have had some batches of plastics that have held up remarkably well and are rock solid, not brittle and durable as all heck.
Most university engineering depts these days have such printers and most provide fee-for-service so that they can remain financially viable as they are usually producing stuff at cost to their affiliated department(s).
~N
