This design is a derivative of the Paxtruder-0.2: http://www.thingiverse.com/thing:1125 My idler wheel cracked about 2 weeks ago so I though it would be a good time to experiment with the Paxtruder design a bit. I planned on making it a weekend project because I had plenty of acrylic around and I had some 1/2\" thick acetal scrap to make a pusher but, unfortunately, I had to put in an order to McMaster to finish this guy so it didn\'t get completed till now.I wanted a drop in replacement for my extruder hardware for testing that could utilize as much of my current MakerBot components as possible, and this design seems to fit the bill. You can use your existing dino mounts (both MK3 and MK4 designs should work) and extruter head hardware to mount this extruder and you can attach the extuder controller as you did with the idler wheel based design.I\'ve included plenty of pics of assembly so construction should be pretty easy to follow. I cut the pusher from 3/16\" Delrin, as per the original design, on my Epilog 35W with the following settings: Speed: 4% Power: 100% Freq: 500Hz Make sure to use air assist. This probably isn\'t optimal, but it worked fairly well. I also had to file down the pusher a bit to get it to fit nicely with the extruder pulley (see photos).All acrylic parts are cut from 1/4\" acrylic except the topmost layer, which is cut from 1/8\" acrylic. This was done to fit the final extruder body between the dinos. I added an insulator retainer to this design as well (attached with 2 M3x16mm bolts) just because I really wanted to ensure that everything lined up correctly.I haven\'t used this extruder on a build yet, but it seems to work fairly well in basic testing versus the idler wheel design. There are probably a few things to tweak but I\'m looking forward to putting this extruder to work.NOTE: In the picks that have the motor bolted on, I wasn\'t paying attention to the side the wiring was on and eventually had to rotate the motor to get the leads to reach the extruder controller, so be mindful of this when assembling. I did the same thing to the retainer too, so it's on backwards in a shot or two as well :)Update: You can grab a kit of this thing that includes all laser cut parts and hardware listed here from my site: http://www.built-to-spec.com/blog/laser-cutting-services/