Recently, I made a copy of the Planetary gear calling card by phooky from (thingiverse) with a more permanent material. My version is made from 1/8in (3mm) fiber board that is very inexpensive, a 4ft by 8ft sheet is only $9.50 at Home Depot. This cut only costs about 7 cents in material.
What is this wondrous and mysterious material? It's cheep imitation wood-grain wood paneling. Normally this is used to nail to the back of inexpensive bookshelves, or for fake wood wall paneling. The type I found is smooth on both sides, there is also a version that has a rough finish on the backside, which is not quite ideal.
Update: I got this paneling at Home Depot in Oregon, but it may not be everywhere. If they do carry it, you can find it shelved in the "Molding" section, and the product label reads:
Sparta Oak 4x8 Panel
BLUELINX PANELING
739522 - A 520-934
I am very impressed with the durability of this material, even the thin outer ring of the planetary gear set is sturdy and I have no fear of breaking it accidentally. The gear teeth and edges of the card were cut cleanly, the edges were blackened but the cuts are crisp and the material does not flake apart easily.
As for strength, I estimate a fiberboard of the same size can take about as much force as 0.08in (2mm) Plexiglas and costs about 1/20th of the price.
The bulk of the material takes this project out of the range of a calling card and more towards a desktop nick-nack. I think it's substantial enough for people to hang on to for novelty, but still inexpensive enough to hand out for promotional reasons.
I'm also linking the high-resolution symmetrical circuit design that my version of the card is engraved with, it looks pretty good engraved in wood.
