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Release status: experimental

CAD Models
External Link



RepRap Version III "Huxley" is being developed on this and associated pages. It is based on Ed's original Mini-Mendel design, together with a lot of work already put in by others (ErikDeBruijn and others). Huxley is named, like all RepRaps, after a biologist: Thomas Henry Huxley.

To clarify, Huxley will be Mini-Mendel with some re-designed parts plus more documentation, defined integrated electronics (with alternatives, of course), and a selection of alternative firmware and host software configured to drive it. We will be integrating as much as possible of the work such as Brutis already done on Mini-Mendel.

The machine uses M6 threaded rods and M3 nuts and bolts (as opposed to the M8/M4 used on Mendel) and NEMA 14 Stepper Motors. The reprapped parts are about 30% of the volume of those for Mendel, which is to say it could reproduce three times faster.

Mendel can print itself, and so will Huxley. In addition, Mendel will be able to print Huxley, and Huxley will be able to print Mendel. We will continue Mendel development to turn it into a multi-material machine. Huxely will be a one-material machine, though we will probably also add a Pen Plotter so we can write etch-resist on PCBs and use an Oil Pen to facilitate separation of Support Material for overhangs.

Things to do

Add to this list...

  1. CAD Files
    1. Put them in which !*$!! format?... (Potential CAD program beauty contest.) --Sebastien Bailard 01:27, 5 September 2010 (UTC)
    2. OpenSCAD versions would allow the entire machine to be parametric.
    3. Upload .stl and OpenSCAD files to wiki.
    4. Put files in Git Repository
  2. Get rid of filament storage underneath
    1. This is a neat idea in principle, but should not be integral. How about a filament cartridge with the geared extruder drive built in, and a PTFE Bowden tube with the filament coming out to a snap connector onto the extruder? Huxley could clip onto the top of the cartridge, or it could be placed elsewhere.
  3. Get rid of under-dents on Huxley X Motor Bracket
  4. Redesign Huxley X Motor Bracket and/or Huxley X carriage so belt does not go back on itself
    1. A basic version of this has been posted on Thingiverse here and here.
  5. Nema 14 Geared Extruder
    1. Roman Gears?
    2. Mount by Y idler?
    3. Polymer transport path?
  6. Add Mendel/huxley buttons to host software and make them do something sensible
  7. Huxley Pinch-Block Y-Bar Clamps[1]
  8. Huxley 4 Vertex Feet[2]
  9. Slider bearings (or bushings) rather than ball bearings?
  10. Huxley Printable Frog
  11. Get rid of Y axis and replace it with a belt for continuous production like Ed's initial idea?
  12. Bed with only 3 sprung support points - no redundancy.
    1. This will also prevent the bed from wobbling because the screws are not all at the same height.
    2. This could be done by attaching the screws to the froglet rather than to the bearing parts. This would make the bed sit lower (increasing build height) and would prevent the screws from transferring heat from a heated bed to the bearing parts.
  13. Huxley Heated bed
  14. Huxley XLR bracket on frame
  15. Huxley Electronics Box? (For which electronics? Unless the box integrates with the frame, best to leave this with the electronics development.)
  16. Huxley Opto Stops
  17. Add PCB-pen/oil-separator-pen holder
  18. Redesign motor brackets to allow for Nema 17's
  19. Redesign Huxley Z-Base pieces to work like Vik's simplified Z-axis (or like Nicholas C Lewis'
  20. Captive nut Z-axis pulleys like [3]
    1. Perhaps attached to a 623 bearing instead of putting the rod thought a 626, so that only one type of bearing is required?


  1. Z gears incorporate 1 flange [done - in SVN]
  2. Nophead's Pulleys [done - in SVN]


I've (Erik) found suppliers for all of the parts, and the estimated cost of the Mini-mendel would be under 350 euros (in Europe). Note that because the design is not yet stable, you may need to order more to get everything working satisfactory.

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You can ask ErikDeBruijn for edit permissions to this Google Docs sheet.

Deep link to both of the Google spreadsheet (combined), in case reading them while embedded is difficult. [4]


Apart from the sources listed here, also check out the forSale-subforum in the RepRap-forum.

Printed parts


The primary electronics design will probably be the Pololu Electronics, as we are very close to being able to make the PCBs for these in Mendel. Huxley will also be able to make them.

Identical to Mendel or you can use the BitsFromBytes -electronics that allow standalone operation from SD-card. When using the BitsFromBytes electronics, be advised that this requires a proprietary tool chain to build new firmware that works with the mini-mendel. Also, the latest versions of the source code for their electronics are frequently not publicly available.




Bowden cable



Standard 3xNEMA14 and 1xNEMA17(extruder) steppers. Smaller and less expensive than on the full sized Mendel.

Sources (steppers):

Sources (Allegro A4983 based stepper-drivers):

(or use the BitsFromBytes-electronic that include stepper-drivers)


The MiniMendel uses a bowden-extruder that has less moving mass and thus higher speed due to the stepper not being on the print-head.

Sources for parts:

Timing belt

The MiniMendel uses the same 5mm pitch Synchroflex timing belt as is used on the Mendel.
"Synchroflex(R) timing belt,800Lx10Wmm" and
"Synchroflex(R) timing belt,550Lx10Wmm"



Nuts and bolts

All metric and obtainable from mcmaster in the US, and in every home-improvement-store in the rest of the world.

Thick sheets

These 2 sheets can be cut from plexiglass or wood with simple tools.

Success stories

  • Whosawhatsis?
    Whosawhatsis's oversized Huxley
    • I've built an Oversized Huxley[8] by cutting the rods and belts longer to make it almost as big as Mendel. The build platform is 8"x8" (about 195x195mm usable), but the outside is only 15"x14"x13".
    • I've had a lot of trouble getting reliable extrusion, and I've taken the bowden cable out of the equation (at least temporarily) and have been working with carriage-mounted extruders. This seems to work fine with the NEMA 14 motors I bought, which meet the 13.7 N-cm torque requirement for Mendel.

Ongoing development

  • Marcus created a Shelled Mini-Mendel[9] that only required 110g of ABS and less then 10h to print. (It may be filled with epoxy after printing but that is not required in all cases.)
  • The Mini-Mendel is the first step in optimizing replication time; further steps in that direction are discussed at RepRap Breeder.
  • Whosawhatsis? has Redesigned Y-Bar Clamps[10] for Huxley (and Mendel) to print in one piece and require no screws. Instead, the nuts on the threaded rod are tightened-down on piece to clamp the smooth rod.

Commercial Forks

  • [14]
  • Google Warehouse?