V9 Extruder Upgrade for MK7 Drive Gear

by Tunako, published

V9 Extruder Upgrade for MK7 Drive Gear by Tunako May 21, 2012
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The http://mendel-parts.com V9 1,75mm Hotend/Extruder works reliable as it is, but it has some downsides.

It uses a brass drive gear which is not very reliable. If the filaments runs out or snaps the teeth of the brass drive gear touch the hardened steel surface of the bearing and become dull.

Also filament change is complicated and time consuming. It is often necessary to disassemble the screws that hold the springs if you don't have 3 hands. ;-)

The MK7 Drive Gear is a useful upgrade. It has a better grip on the filament, is made from stainless steel and makes filament change easy.

The enhanced driveholder guides the filament more reliable and can be fixed down to the lower aluminum plate to increase stability.

To fit the MK7 Drive Gear on an V9 Extruder some modifications are necessary:


  1. Print extruder_corner_small.stl and driverholder_enhanced.stl, the other parts are optional, V9_extruder_filament_guide_MK7_2.stl is usefull if you plan to print with 1.75mm ABS (see http://www.thingiverse.com/thing:16319 for instructions)
  2. Drill out holes if necessary. It is important the the screws which hold the springs can move freely.
  3. Remove old driverholder, the left extruder corner and the brass insert.
  4. Attach the MK7 Drive Gear to the motor shaft.
  5. Readjust the motor position, so that the groove in the drive gear lines up with the hotend entrance.
  6. Attach the smaller extruder corner.
  7. Attach the new driverholder.
    7a. Optional: Drill a 4mm hole through the aluminum plate, to fix down the driverholder with an additional screw.
  8. Attach the idler with the 4 springs an screws.


  1. See http://www.thingiverse.com/thing:16319 for the optional filament guide which is useful for printing with 1.75mm ABS.

  2. Print out the extruder_wheel.stl and press in the old brass insert. The wheel can be attached to the back of the motor shaft and is useful for changing filament.

You can now insert the filament by slightly pushing it in and turning the wheel. It isn't necessary to press against the springs anymore.

Comments/suggestions are appreciated.

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The first 1-1/2 year I printed over 1200m of PLA with my V9 extruder with brass insert, no problem.
Last summer I got the problem that my PLA was cut in two by the insert because it was warn out and became sharp edged.
I filed down the sharp edges and now it is printing flowless again.
Printing with homemade Stainless steel mendel+Slic3r+Repetier host


can you elaborate more on disadvantage of brass insert. and if i use what precaution should i take.