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Release status: working

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 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.

The idea is to develop both Mendel and Huxley in parallel, with Huxley being as cut-down and minimal as possible, and Mendel being the machine with all the fancy capabilities. Huxley will be the fastest replicator. Mendel will be the most versatile.


TechZone Huxley Printable Parts TechZone variation of the Huxley These are printable .stl files for the Huxley, the way TechZone did it. --Kimberly Andrus (TechZone) 12:00, Dec 24, 2010 (UTC)
TechZone Huxley Thick Sheet Set TechZone variation of the Huxley This is the Thick Sheet set, the way TechZone did it., --Kimberly Andrus (TechZone) 12:00, Dec 24, 2010 (UTC)
TechZone Huxley Bowden Extruder Gears TechZone variation of the Huxley This is the Gears Used in the TechZone Bowden Extruder., --Kimberly Andrus (TechZone) 12:00, Dec 24, 2010 (UTC)
Your-File-Name SOLID MODEL ASSEMBLY These are CAD files for the Solid Model Assembly, --Example User 12:00, Today's Date 20xx (UTC)
Your-File-Name EVEN MORE FILES These are are even more files., --Example User 12:00, Today's Date 20xx (UTC)|-
Your-File-Name SOLID MODEL ASSEMBLY This is the final finished machine N/A --Example User 12:00, Tomorrow's Date, 20xx (UTC)
Please edit this and click the links to put in your own files! --Sebastien Bailard 08:34, 10 September 2010 (UTC)
Yellow Highligthed areas are examples of how to use this table --Kimberly Andrus 24 Dec 2010

Mini-Mendel Build Instructions - TechZonekit

Information about the TechZone Huxley kit can be found on the TechZone Huxley Page

1) Frame Assembly

2) X Axis Assembly

3) Y Axis Assembly

4) Z Axis Assembly

5) Motors, Belts and Endstops

6) Electronics

7) Bowden Extruder

Mini-Mendel Build Videos*

Pre-Dates Huxley

1) Part 1 Frame Assemblies [1]

2) Frame Integration Part 1 [2]

3) Frame Integration Part 2[3]

4) X- Trolley[4]

5) X Axis Part 1[5]

6) X Axis Part 2 and Integration[6]

*Note: Unofficial


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.

<iframe width='900' height='400' frameborder='0' src=''></iframe>

<iframe width='900' height='400' frameborder='0' src=''></iframe>

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. [7]


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

Frame and Rails Dimensional Variants

Silver Steel Rod (Drill Rod in the US) is a precision ground rod made from steel that has a slightly higher level of chromium in it to resist a small degree of corrosion. Intended as a tool steel for drill blanks, screwdriver shafts and axles, this is widely and inexpensively available in standard lengths of 330mm (13" UK Inches). Given its precise specifications and straightness this makes ideal rails for smaller RepRap builds like Huxley.

The rod can be cut down to work with the current Huxley dimensions or alternatively critical Huxley Frame and Carriage components can be scaled up to minimise reworking this tool steel. As this will result in a slightly larger frame, the bed and by implication build space, can be scaled up if you want. Having measured after framing up using the dimensions below it appears that a build bed of at least 200mm by 200mm is possible. Build space will be something less than that though.

All printed parts remain the same. Belt lengths will have to be increased to suit.

I (aka47) am currently working with a build using these critical modified dimensions for the M6 Allthread components:-

Dimension Mini Dim Huxley SS Dim Huxley SS All-Thread Qty Needed Comment
J1 200mm 270mm 314mm 6 Frame sides, the two equilateral triangles.
J2a 140mm 200mm 245mm 4 Frame bottom cross bars
J2b 140mm 200mm 335mm 2 Frame top cross bars
* * * 292mm 2 Z Axis Lead Screws
* * * 320mm 1 Z Axis Base Plate Rod A
* * * 295mm 1 Z Axis Base Plate Rod B

Mini Dim, is the dimensions as described in the Mini-Mendel Mechanical Construction Notes. Basically the dimensions that Huxley is based on.

Huxley SS Dim, is how much bigger the component was scaled to minimise cutting of the Silver Steel M6 Rails.

Huxley SS All-Thread, is a suggested length of the M6 Threaded Rod for that part including some for components and fixings. This may vary a bit depending on the plastics you are using but the dimensions here worked for me.

Using these critical dimensions the X and Y Silver Steel rails do not need cutting and can be used as is. You may choose to shorten the Z axis rails a little.

All in all the final dimensions look to have worked out so as to give a bed size very similar to those first achieved by Whosawhatsis?


Printed parts

TechZoneCommunications Modified parts

Some Parts which have been modified by TechZoneCommunications are listed below, the files can be downloaded in the Files section above.

    • The Y axis motor mount has been modified to allow Nema17 or Nema14 motors to be mounted, it also has an altered height, in order to work with the modified Leg Vertices (see below)
    • The Y axis idler has an altered height to work with the modified Leg Vertices.
    • The Leg Vertices have been modified to be a little taller, and to have feet (that don't break off under pressure), the two top vertices are not altered, only the four lower vertices
    • The Z drive screw base was inspired by Tim Schmidt's Z Axis
    • The Z Axis motor mount was also inspired by Tim Schmidt's Parts this part is for a nema 17 motor
    • The X axis motor mount has been modified to accept Nema17 or Nema 14 motors
    • The X Axis Carriage has been changed to make it narrow enough for the belt to bypass it (rather than using larger idler bearing space on the X idler bracket and X motor mount) It also uses a bushing on the 360 side
    • The 360 degree side of the X Axis Carriage is now the bushing clamp for the X axis carriage.
    • The 180 degree side of the X Axis Carriage has been altered to allow the belt to pass by without interference.
    • The X Axis belt clamps have been modified to fit the new X Carriage.
    • The bowden extruder is a modified Wades Extruder, it allows for a larger gear, which TechZone cuts from plywood with a laser.
    • The bowden clamps were created from the models done by Erik as published on Thingiverse here.
    • The thick sheet set was modified to make it a little simpler, the print size was increased a tiny bit (file available above in Files section above.
    • The motor end X Bar Clamp was changed to make it a little sturdier (it now looks very much like the Idler end Bar Clamp).

The other TechZone parts used were selected from the various publications of Huxley parts found on Thingiverse. All the parts we modified (except the Bowden clamps) were modified using Google Sketchup. An Stl importer, and exporter was added to Google Sketchup, to allow the stl files to be modified directly - eliminating another cad format. A special thanks to Derrick Huestis, who helped TechZone with the file modifications.



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):

Stepper Driver 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.

Having built a frame using all nyloc nuts I (aka47) would advise caution for anyone else considering going down this road. Nyloc's are great but a real pain when you need to place them a long way along a threaded rod. The main issues were binding and stripping of threads. Next time I build I will be using standard nuts and anti-shake (star) washers.

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 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 Wolschon created a Shelled Mini-Mendel 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 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.
  • Whosawhatsis? has designed an Idler Pulley for Huxley (and Mendel), suggested by Erik, to replace the mudguard washers on the belt idler bearings.
  • aka47? has contributed revised dimensions for M6 frame rods based on using off the shelf lengths of Silver Steel (US Drill Rod) with minimal cutting for axis rails.

Commercial Forks

  • Google Warehouse?