NOTE: LICENSE IS GPLv3+. YOUMAGINE ONLY ALLOWS SELECTION OF GPLv3 IN THE DROPDOWN HOWEVER THIS DESIGN IS *SPECIFICALLY* RELEASED UNDER THE GPLv3+. THIS IS IMPORTANT, FOR YOUR FREEDOM AND RIGHTS, AS THE GPLv3+ GRANTS *YOU* THE RIGHT TO RELEASE MODIFICATIONS UNDER A LATER VERSION OF THE GPL AT YOUR OWN DISCRETION, WITHOUT HAVING TO REQUEST MY PERMISSION AS IT HAS ALREADY BEEN GRANTED.This is an adaptable and compact Geared Bowden extruder design, which had to be made as it is unusual. In its default form it suits 3mm filament, and takes a MK8 Drive Gear at the centre.At only around 5-10 minutes assembly time it is quite a simple and quick build. Also with a 4.07:1 (53:13) gear ratio it produces considerable pressure, especially when used with a MK8 Drive Gear, in a small space (approx 55mm diameter and 35mm height).The drive gear attachment is a separate part that fits into the main gear's hub and is locked down with four M2.5 self-tapping screws, and the filament exit likewise may be replaced without requiring a reprint of large amounts of plastic. Thus with only two simple-to-make replacement parts, this design may be changed to suit any filament diameter, any bowden adapter type or size, and any drive gear including hobbed bolts.The main 5mm driveshaft does not require a nut to keep it in place: there is sufficient friction against the plastic of the large gear to hold it in place. The tricky part is getting the MK8 Drive Gear into the holder. Without access to a vise, this is best done by putting an M5 bolt through the holder and the MK8 Drive Gear, then using a wing-nut to slowly clamp the Drive Gear down until it is fully in place: it takes a lot of force. If the MK8 Drive Gear ends up off-axis, no problem: just reprint another holder (about 10mins) instead of wasting an entire (large) gear.Assembly is fairly self-explanatory: leave the M5 Bolt until last (drop it into the centre and screw it down). Only tighten up the spring-press once all nuts and bolts are in place. The only other piece of advice is, do not tighten up the nut(s) on the M3x40 bolt for the extruder arm: if it is overly tight it will stop the arm from moving.Plastic parts may be obtained by following the links and instructions here:http://hands.com/~lkcl//foldable3dsandwich200/A detailed build manual including photos and a commissioning video may be found here:http://hands.com/~lkcl//foldable3dsandwich200/extruder.html