Summary

A proof of concept working momentary switch. It can be made using either a single or dual extruder. It incorporates brass contacts that are added to the print at specific times using the "pause" command.

Instructions

THE METAL PARTS:
Before you print the switch, you'll need to make two brass contacts. The first image shows the steps:

The contacts are made with .030 1/4" wide brass strips, available at most hobby shops in 6" lengths.
You'll only need 2" for this switch. Cut two, 1" pieces.
If you stack the pieces, or cut a single piece 3" long and bend it in half, the job will go quicker. Drill holes for the leads and file for the notches. Make the notches slightly oversize to fit.
Round off the edges. If you used a single 3" piece, now's the time to cut it into two 1" long parts. Finish the cut ends.
Using a 1/4" chisel or screw driver, raise a .010" ridge by tapping the back side. This job can be made easier by grinding a small slot into a scrap piece of metal and using that as a mould. Make sure the protrusion doesn't exceed .010". It will be much better to err on the small side here. This step may not even be necessary. Experiment.

THE PRINTED PARTS:
This is designed to be printed at .27mm. As the print is progressing, watch the small squares next to the housing. When you see the number "1" being printed, pause the machine and set the first contact into the slot on the housing. Un-pause the print and watch the other square. When the number "2" is printed, pause the machine again and set the second contact in place.

Un-pause the machine once more and let the print finish.

I've added a file called "Print This-Single Extruder" with both parts in place. If you want it in one color and don't want to mess around trying to align the parts in MakerWare, this is the one to use.

MAKING IT WORK:
At the moment, my machine is down, so I'm unable to print this myself. I've printed moving parts and added secondary components to prints before, but never at the same time.

Theoretically, this concept is valid, but there'll be a bit of difficulty in getting the button to move at first. The plastic around the gaps between the parts will stick them together. PLA might be easier to break free, but there's no reason why ABS can't be used. LIGHTLY tapping the button with a phenolic hammer might shock the button enough to break it free. Not very hard though... You wouldn't want to permanently bend the upper contact and short the connection.

The operational movement of the button is very small (.010 designed). There's more movement of the button available (upward) and space beneath it in the print to allow the second contact to be added. There'll be a bit of loose, low density material between the button and upper contact that might allow the button to move further and help with the break.

You might also want to reduce the thickness of the brass. .030 is pretty hefty and it will take some pressure to make contact. As I said, this is proof-of-concept and I don't have a working machine. Hopefully, this will change as soon as MakerBot answers my request for help. :)

As previously stated, I'm already confident about the ability to produce each of these unique additions (moving parts and embedding non-printed components), but not at the same time.

If you attempt this, I hope it works. As soon as my machine is back up and running, I'll be trying it as well, and when I do, I'll update this thing with my results.

I've added an stl file named "Do Not Print This" showing all of the parts, including the metal ones. I thought this would show better than my sketch until I get my printer back:)

Enjoy

4/22/13 Update:
I've added a Go-No-Go gauge so you can check to see if your contacts will fit the print when its time to add them. Print this part out first, before you make your contacts. if they fit the gauge, they'll fit the print.

4/30/13 Update
This is still only a concept as there are too many other things on my plate at the moment, but I have been experimenting with PLA hinges and have discovered the .020 gap that is good for ABS isn't going to work with the lower melt temperature of PLA. For PLA hinges, a .030 gap seems to work very well. I recommend if you make this switch in PLA that you reduce the size of the button by 10%.

Working Electric Switch-Single Print-No Support Needed