hard coating

Has anyone tried printing the filament drive gear and dipping or coating the ABS/PLA/nylon/whatever in something that dries to become harder than the plastic? If the drive gear and/or hobbed bolt could be printed, and then made hard enough to drive filament with some kind of coating, that would be cool. Just wanted to check and see if it had already been done and I missed it.

As far as I know, HardCoating is usually a very very thin layer. It is used to protect polished surfaces against scratch and dents. This process is often used in plastic injection molding.
The printed pastic is too soft and the hardcoat would chip with a very small deformation generated by filament pressure.
Also the costs are very high for this process.

A standard 4$ driver gear is more economic.

I can't find anything that's already used to add a relatively thick, harder outer layer to a softer part. And you make a good point that the coating would have to be pretty thick to support itself, otherwise the soft middle would deform and let the surface crack. Like a hard boiled egg.

But there are plastics that are harder than the extremely common ABS/PLA. For example, nylon might be a little harder and acrylics are significantly harder [www.machinist-materials.com]

Taulman has an acrylic filament
[diyzilla.com]
[taulman3d.com]

There are also hobbyists and artists who use acrylic resin in molds
[fun.familyeducation.com]

In this thread it seems the off-the-shelf acrylic resins are hard to work with [forums.reprap.org]

Taulman's T-Glase filament isn't acrylic. It's PET, which also is rather hard (and brittle in the case of the filament I bought from plastic2print). There was a thread in the German subforum where someone used snap-off blade segments embedded in a printed receptacle as a drive gear. Sort of closest I can think of to what you envision.

Edited 1 time(s). Last edit at 12/06/2013 09:18AM by uGen.

Epoxy coat the gear, add graphite to the epoxy to reduce the friction.
Straight epoxy would have too much friction.
Ideally you want the contact surface to be mostly graphite.

Use West System G/Flex epoxy, as it flows very well, it should give you a thin coating.
But adding graphite will thicken it up, so you'll have to experiment.
You might try dusting the graphite onto a coating of G/Flex epoxy.
[www.westsystem.com]

WEST SYSTEM
#423 Graphite Powder - 12 OZ
423 Graphite Powder is a fine black powder that can be mixed with WEST SYSTEM epoxy to
produce a low-friction exterior coating with increased scuff resistance and durability.
Epoxy/graphite is commonly used as a bearing surface,...
[www.westmarine.com]