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.
Huxley Build Instructions
Information about building the TechZone Huxley kit can be found on the TechZone Huxley Page.
Information about building the eMaker Huxley kit can be found on the eMaker Huxley page.
Mini-Mendel Build Videos*
1) Part 1 Frame Assemblies 
2) Frame Integration Part 1 
3) Frame Integration Part 2
4) X- Trolley
5) X Axis Part 1
6) X Axis Part 2 and Integration
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. 
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?
- Check Mini-Mendel Variation for updates and improvements.
- You can easily print these Huxley Production Files in 10 Makerbot-sized plates.
- You may print an (experimental!!!) Shelled MiniMendel using less material and time
- Individual parts can of course be printed too
Different variants of the Huxley have been sold with different electronics; the eMaker Huxley page came with Sanguinololu and the RepRapPro Huxley is provided with the Melzi, a surface mount version of the Sanguinololu that incorporates an SD card.
If you are looking to build your own Huxley and are wondering which electronics are the best, any of the established electronics that work will with the Prusa will work well with the Huxley. The common ones are RAMPS, Sanguinololu, Gen6, Gen7, Gen3. Other Mendel compatible electronics may also work.
- Ultimachine (Arduino Mega/Pololu electronics)
- Makerbot (Gen 3 electronics)
- Techzone (Gen 3 electronics on smaller boards)
Standard 3xNEMA14 and 1xNEMA17(extruder) steppers. Smaller and less expensive than on the full sized Mendel.
Stepper Driver Sources (Allegro based stepper-drivers):
- Pololu stepper driver board - see links
(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:
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.
These 2 sheets can be cut from plexiglass or wood with simple tools.
- 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.
- I purchased the kit from Techzonecom.com and documented my build on My blog. So far I have one good print and I have to adjust the Z axis so ooze does not occur when the Zaxis is raised.
- Main development seems to be going on in the RepRap-forum and on Thingiverse.
- 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 Pulley Extenders to fix the x-belt alignment so that it no longer rubs against the carriage. There are also replacements for x-blunt-plate_1off.stl and x-motor-end-clamp_1off.stl that have these extenders integrated. Note that these are not symmetric, and the L-shaped portion is designed to align with the belt clamps on the carriage. The carriage is backwards in Erik's picture above.
- Erik has designed a Belt Extension Clip so that the pulley extenders can be used without a longer belt.
- 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.
- nophead has contributed improved drive pulleys for the Mendel. As Huxley uses the same belts these are also a good idea for huxley.
- RustySpoon has contributed a pair of Bowden nut couplers so that Wades Extruder can be used together with the Mini-Mendel as the Feed for the Bowden assembly. Again these parts are use-able for a Huxley build
- nophead has contributed an improved drive gear and beefed up idler plate for the Wade Extruder. If this extruder mechanism is being used to feed the Huxley Bowden assembly then these parts are recommended.
- Google Warehouse?