Screw/ Worm drive filament extruder Bowden

A 3D printer filament driver for a bowden setup utilizing a wood screw and geared stepper motor. This drive unit is capable of provding significantly higher forces than a traditional filament extruder because of the increased number of engaged teeth and the mechanical advantage of the worm gear/ wood screw. The wood screw is designed to be easily replaceable by unscrewing the tensioner bolt and poping out the screw, then putting the spring on the new screw, compressing the spring and inserting into the slot. The spring pressure on the screw holds the driver securely into the screws head to prevent slop.
The filament enters the top of the assembly through a filleted hole, passes in-between the spring loaded hinge and a wood screw, forcing the filament to travel the length of the wood screw and out the push to connect fitting. The wood screw is held in position by a compression spring and is supported by two 1/8'' rods.

note* some images are slightly* outdated.

This is an experimental filament driver based on Werner Berry's concept described here:
http://www.youtube.com/watch?v=rWKe1mUl8bw&noredirect=1

Bill of Materials:
1x 5'' long, 1/8'' diameter steel or stainless steel rod for hinge
2x 1.12'' long 1/8'' diameter steel or stainless steel rod for screw support
1x compression spring. McMaser 1986K930 for hinge pressure
1x Compression spring McMaster 1986K710 for securing screw
1x 2in wood screw (sharper threads the better).
1x Matching 1/4'' hex driver for chosen wood screw
shaft coupler for motor to hex screw driver
1x McMaster 91251A875 Tensioner Bolt for hinge
1x washer for tensioner bolt and spring
2x thin profile nylock 1/4-20 nuts for lever arm and tensioner bolt McMaster 90101A007
1x push to connect tube adapter (filament exit) McMaster 5779K117
1x shoulder screw for lever axle. McMaster 91273A301
4x. your choice thread tapered head mounting screws for assembly
4x M3 stepper motor tapered thread screws.
1x geared stepper motor. I chose the Kysan 1040212 Geared Stepper Motor. 26.4Kg-cm. NEma 17. for $45 at http://www.kysanelectronics.com/Products/Detail.php?recordID=5180

Warning: Due to the relatively small bend radius the filament needs to follow, there is a chance of PLA filament breaking. If this happens, please let me know and I'll increase the bend radius in a bug fix.

Bug Fixes:
180 degree filament curve added to help prevent filament twist.