The trickiest part of this project, as is often the case, was the design stage. I started with an idea in my mind of a business card that involved gears and that could move in an interesting way, but very little beyond that. I knew that it had to meet the following specifications:
Must be able to fit on a 3.5" by 2" business card
Must not be unreasonably thick
Must have room on which to print an email address and a logo
Must have one simple lever or slider by which to control the mechanism
At first, I expected Number 1 on this list to cause the biggest problems, as 7 square inches really didn't sound like much space for a set of working gears. After a bit of playing with the laser cutter and some scrap card, however, I found I was able to cut effective gears which were incredibly small. I'm fairly sure that it would be possible to make this card half its current size without any functional problems. To design the gears, I used a wonderful piece of software made by Matthias Wendel
, called Gear Template Generator
. I highly recommend this to anyone interested in cutting their own gears, whatever the size and material.
Another factor that helped with this size constraint was the realisation that, while the mechanism had to fit within a business card when inactive, there was nothing stopping it from overreaching the card's boundaries once the mechanism was deployed.
Number 2 on the list then became the most limiting, as I soon realised that all my gears and levers would have to fit onto a single plane to prevent the card becoming a brick. I played around with different types of card and decided that the best way to build this card would be to use three layers: a thin base layer, a thick, rigid inner layer containing the mechanism, and a thin surface layer.
One morning, while I was sketching ideas for this project, someone showed me a video of a 3D printed grabber mechanism
and the rest of the idea just fell into place.