The Makibox "Zen" extruder is remarkable for its simplicity and low-profile design. However, in its first shipping version, it has some issues, notable that the idler tension is not adjustable and the idler wheel spokes often break, leaving one with an extruder that doesn't work reliably. This my design for a replacement extruder that addresses those issues. Primary design criteria were: 1) Must fit in the existing Makibox extruder location. 2) Must utilize the Makibox standard stepper and (non-removable) extruder gear. 3) Must be 3D-printable. 4) Must use a minimum of easy-to-source parts (for non-printable components). Initial tests are quite positive. Huge thanks to the Airtripper and T2 extruder designs for inspiration. Feb. 19, 2014: 2nd main body version uploaded (look for "Chopped" in the file name); this eliminates a couple of overhangs that may be harder to print. The original version is preferred and is aesthetically better but if you're having trouble printing this, try the "Chopped" version. I have printed and assembled one of these, and results so far are very good - I've printed 5 very nice items without any of the slipping that the stock extruder exhibits (my stock extruder had broken idler wheel spokes, so I had to manually keep pressure on the filament to keep it feeding through the old extruder in order to print my FroZen extruder). I have made a few minor tweaks to the design (hence the v1.1 moniker) based upon assembling my prototype; those are reflected in the provided files. Feb. 19, 2014: 2nd main body version uploaded (look for "Chopped" in the file name); this eliminates a couple of overhangs that may be harder to print. The original version is preferred and is aesthetically better but if you're having trouble printing this, try the "Chopped" version. I had better luck with Cura than Slic3r for this set of prints. I used .15mm layer height, 60% infill, 3 perimeters and the parts are very stout. I printed this in ABS, which I think is a good material for this application. I suspect PLA would work as well. There are a few small overhangs; I printed this without support. As long as your machine is tuned up to print reasonably well, it should come out acceptably. The overhangs that are most likely to droop a bit are in dimensionally non-critical areas and any excess plastic can be trimmed off after printing. Parts required: Printed Extruder Body Printed Idler Arm 1 Printed Idler Arm 2 Printed Backplate 608 bearing (8mm ID, 22mm OD, 7mm width) 5 x 25mm M3 screw 1 x M3 nut Assembly should be obvious from the exploded diagrams: 1) Print the parts and clean up any imperfect bits; test fit idler arm parts together and make sure both shafts can enter their mating holes and that the overlapping flanges at the bottom of the arms mate cleanly. Do not press the arms together completely when testing fit, or you may not be able to get them apart. Drill 4 x M3 mounting holes to clean up hole size if desired. Drill M3 tensioning holes in idler arms and extruder body to clean up hole size, and move drill bit around a bit to create space for the tensioning screw to move when adjusting the idler arm tension. 2) Place bearing on large shaft of idler arm and press other half of idler arm on to fix it in place. The fit should be tight enough that they stay together and there is no play in the bearing. The bearing should still spin freely. 3) Test fit the body and the assembled idler arm on your Makibox extruder stepper with extruder gear. Feed a piece of filament through to confirm that the gear teeth, body holes that the filament passes through and the bearing surface are in proper alignment (it should be perfect if your prints are accurate and the idler arms are fully pressed into each other). Remove the extruder body and arm from the stepper. 4) Feed your Bowden tube through the hole in the acrylic top of the Makibox (the same place it goes for the stock extruder) and press the nut of the Bowden tube into the receptacle of the extruder body. It is a tight fit, and you may need to use a small file or Dremel tool to get it to fit - make sure you keep it tight though. Once you have the Bowden tube installed, push another piece of filament through the extruder assembly to make sure the Bowden tube fitting is aligned with the feed hole of the extruder body. 5) Put the hot end wiring through the channel in the extruder body (just like the stock extruder). 6) Place the extruder body and idler arm assembly into the mounting location on the Makibox - it's exactly the same place the stock assembly goes, but the bosses on the acrylic go into recesses on the FroZen body such that the assembly mounts flush with the acrylic. Make sure to get the top part of the Bowden mount through the hole in the acrylic top plate. 7) Place the "backplate" on the print bed side of the acrylic that the extruder mounts to (inside the print envelope, near the hot end and the Y-axis carriage). This is critical, as it provides additional structure for the assembly and makes sure your 25mm M3 screws do not hit the screws that hold the stepper together. 8) Optional but HIGHLY recommended: drill a 4th hole in the Makibox acrylic to allow you to use all 4 mounting screws. The stock extruder assembly only uses 3. 9) Put 4 x 25mm M3 screws through the printed "backplate" holes, through the mounting holes in the acrylic, through the extruder body and/or the idler arm pivot, and into the stepper. Tighten them down fairly tight (obviously not so tight you break the plastic or acrylic, but you want it pretty firmly mounted in order to firmly fix the relationship between the stepper/extruder gear and the bearing that is supported on the idler arm shaft). 10) Place your last M3 screw up through the hole in the bottom of the extruder body, through the lower part of the idler arm, and out the top of it. Thread an M3 nut on to the top. If you want to add a spring to provide more variable tension, you can do that here but I had the best results with no spring. 11) You're done! Adjust the tension of the idler arm until you get very firm filament hold against the extruder gear, cross your fingers, and start printing! Enjoy.