This is a filament feeder that assists by powering the filament off the spool to reduce the extra drag seen by the actual printer extruder motor system. With Sailfish firmware and P-Stop enabled. this can also trigger a pause in printing when the system is unable to feed filament due to the all too common spool tangle that can happen. Most of thee parts for the stepper pulse generator can be purchased at Radioshack, and others have committed to improving on the design. BTW, a HUGE thanks goes out to Dan and Jetty of the Sailfish team for implementing the function in the firmware and also to James Armstrong who did the amazing CAD work to make this come to life.Note, new V2 version can use either a compression spring or a tension spring on the back side (motor side). Shuttle is best printed as oriented because the cone entrance offers minimal contact to the build surface. The part will print fine, the overhangs on the flags were designed for easy printing by most printers. The point behind moving to a tension spring was to remove the spring inside the filament path thus making loading easier. Also, it is now easier since all the screws can be the same size M3 x25mm long. Thanks to James for basically designing the CAD to my idea. Obtain the parts: Stepper motor, NEMA17 and preferably a 5mm shaft. This should be a low cost motor, we don't need 1.5A 5.5kg/cm torque monster. Preferably any of the 12V 0.4A ones around from Sparkfun, Adafruit, and others. I chose the Easy Driver at Sparkfun because it had a built in 5 Volt regulator. You can use the more common Pololu or compatible A4988 or A4983, or those other new chips. We need the 5 volts to also run the optical interrupter style limit switch and the 555 timer. None of them draw much power but we have to get it from somewhere. I had a couple of MK7 pinchwheels for 5mm shaft.. You need to print the parts and obtain any opto switch out there. So print this http://www.thingiverse.com/thing:35810 And then the parts attached. You need to use black or some other dark plastic as white and some translucent plastics transmit IR and a will not trip the opto switches!!! I'll try to add more detail in the next few days, in the meantime a lot of discussion and notes over here https://groups.google.com/forum/#!topic/jetty-firmware/BSnIX3vWUHE BTW, this works with ANY printer that runs Sailfish. So T-O-Ms, Cupcakes, U-T-O-M, and the new Replicator series all can use this. Hoping to have some nice boards for the electronics made up, maybe even some kits. Also, this is going to be made into a standalone spool system for 5 and 10 LB spools and just connect into the bot via the endstop cable. It's that easy and universal. Also, put this before the feeder and between the spool and the feeder and wire this http://www.thingiverse.com/thing:83274 in parallel with the P-Stop to trigger out of filament detection as well. The ultimate protection besides an UPS for those long prints!!!