I wanted a rotary for the ULS since I got it, didn't really want to pay big bucks for one though. I had a 5C indexer laying around so I modified it and fit up a stepper and manage to make my own indexer. Been done for a while, just hadn't gotten round to testing it out other than burning "Test" into a wood dowel. Picked up some 20oz Tumblers the other day and decided to give it a go. Results are as good as I could have hoped for.
Cup sitting on the jig
IMG_2502.jpg
Mandrel I made to fit the cups, needed a piece of tape to make the cup snug on there
IMG_2503.jpg
Results of one logo (for my local home machine shop club)
IMG_2506.jpg
And the logo I use
IMG_2509.jpg
And if you are really bored, a youtube of the engraving.... I know watching a rotary engrave is about as fun as watching paint dry...
http://www.youtube.com/watch?v=P01EfGshaPw