Add a reliable stepper extruder to your original MakerBot Cupcake using this little board.
This board adds a fourth stepper channel to the original RepRap Gen3 electronics by repurposing one endstop pin from each axis. It's software-compatible with Tinkerings' original 3G 5D Shield, so it works with firmware available through RepG. No hacks required.
Unlike the original, the Mini doesn't break out separate endstop connectors, or provide ANDing of endstops. But fear not! Endstops still work using the old-school connectors on the Gen3 Stepper Drivers -- use one per axis without changing a thing, or convert them to open-collector to use two.
For more information and current revisions of the files, visit: http://cliffle.com/project/3g5d-mini
Update 2012-02-20: Shrunk the board by another 300 mils vertically and a bit horizontally. Now measures 3.775 x 0.65 inches, giving improved clearance for the all-important reset button.
Update 2012-03-05: Boards are back from the fab and they work great. Added pictures of the finished product.
Populate the top headers with shrouded male connectors, such as Digikey S9185-ND.
Populate the bottom headers with unshrouded female connectors, such as Digikey 3M9574CT-ND. Alignment is important. I used the motherboard as an alignment guide: plug the female connectors into the motherboard's stepper ports, clamp the shield on top, and solder as many pins as you can reach to hold the connectors in place. Gently pry it loose and solder the rest.
Unplug your stepper drivers and plug this board into all three axis connectors. (Make sure it's oriented correctly!)
Plug the stepper drivers back into the X, Y, and Z ports.
Reflash with Tinkering's 3G 5D Shield firmware and attach a stepper-driven extruder.