Wednesday, February 03, 2010


Mini Me

Just before he left to Starve in the New Zealand Wilderness Ed did a new RepRap design because he "had to get it out of his head". It was a mini version of Mendel. You can see it on the left in the picture above - a still from
Josef Davies-Coates' short documentary on the Bath RepRap Lab. The machine uses M6 threaded rods and M3 nuts and bolts (as opposed to the M8/M4 used on Mendel) and NEMA 14 steppers. The reprapped parts are about 30% of the volume of those for Mendel, which is to say it could reproduce three times faster.

This is a completely unsupported design for the moment (we haven't got the time...) but we have put the STEP file for it in the RepRap repository at

because it's so neat, and some of you might like to play with it...

Here's a close up rendered by M.BrittCrane:


On reflection, I think that putting the material spool underneath is not a good idea: it tends to jam. Better to have it on a separate reel above (which would make the machine even smaller).


I opened up the STEP and took some screen shots. It looks good:

Mini Mendel would be great for people who don't mind a smaller build size, (~110x140x?). It really would be easier to reproduce than the full sized Mendel. Not only is the total RepRapped parts volume 1/3 that of Mendel, the larger more difficult parts are much smaller and thus easier to print, particularly with ABS. However, I suspect the cost would only be marginally smaller.
I assume it has the print area to reproduce?
Thanks for the pix! Added.

> I assume it has the print area to reproduce?

The build volume looks to be ~110x140x100mm which is certainly large enough to reproduce or to produce a Mendel.

For reference:
MakerBot Cupcake CNC (RepStrap capable of producing a full set of Mendel parts)
Build volume: 100x100x150mm

Mendel build volume: 200x200x140mm
I guess it can reproduce a big mendel? (thinking sell mini-mendels)

I want print it :D !
Here is a render without the bottom base:

The base holds the the material spool and the electronics. Have to find a new place to put the electronics. Would also have to add some simple feet.

Here is a quick-n-dirty solution:

Should be able to re arrange some things to make it more compact and improve rigidity.

What is the toroidal thing underneath?
Oh I see it is a coil of filament!
seeing the different colored model caused me to ask a question.

would the k'nex plastic building toy be able to support the weight/force of the machine?

also does anybody know if those pieces would be able to handle the high temps based on the distance from the extrusion head?
k'nex pieces would be used as the structural beams for the machine instead of the current threaded bars.

sorry left that part out
It would be a great prop to use at lectures if it could be run from a SD card.
Wow! It's really cute!

I'm wondering, would it be less or more stable at when the X-axis makes rapid moves at a high Z-level? Since the Darwin has diagonal ties in all directions, and the Mendel only has triangle frames to make the frame itself stiff. There is no movement that requires the stiffness because the platform moves in this direction, not the printhead, so this is just for robustness of the machine, it seems?

Of course this can easily be tested experimentally: If you print a really tall rod in the machine (e.g. a 10cm piece of makerbeam), it be wider at the base and smaller at the top.
At 1/3 of the build time, this really reduces one of the limiting factors in getting a new Reprap out the door. Given its improved ability to self-replicate, I'd argue that this is more "Reprap" than the full Mendel, and deserves full support!

If people get a MiniMendel and want/need a bigger one, they can print their own parts for a full-size Mendel and even give the mini-frame to the next needy soul! "Village Bike" Reprapping!

Someone wants me to make them Mendel parts. I'm gonna offer Mini-Mendel instead if it gets proper build documentation somewhere and the files get STL'd soon. I'll print one for myself too, and it'll still have only taken 2/3 of the time I'd have had to devote to a full Mendel, and there'll be two new printers in the world.
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mini Mendel simplified

Here is a simplified design of mini Mendel:

The most notable changes are:
- Eliminated complex bottom base with filament spool
- Moved pinch wheel to top of machine & modified pinch wheel block
- Modified vertex brackets to incorporate feet & mounting points for simplified base plate
I went for Building one 1/2 size its strange its almost addictive when you have a vision of what a build is going to look like you cant stop I know exactly how Ed felt.
I figured 1/2 size was enough to do 100x100x70 builds tho.
I guess I must of calculated it wrong

A Stud-frame-end-top 220
B Stud-frame-side 185
C Stud-frame-end 147
D1 Stud-z-base-beam-short 177.5
D2 Stud-z-base-beam-long 209
E Stud-z-lead screw 165
X x-bar 247.5
Y y-bar 203
Z z-bar 165
Thought~ just now of having to go to the Dr's saying "I have a problem I'm addicted to building RepRap machines"

Please help.
Already moved to STL's. lol
All of the STL's should now be in the repository.
Wait, the same STL's, or the originals?
Sorry I should clarify, I put the same ones up, just so everything is in the same place for clarity. If anyone finds any errors, I can get originals out of Solid Edge, if you let me know I'll update as needed.
One other thing that hasn't been mentioned. The mini-mendel hasn't been fully tested. It's just been put together without the extruder and we've all stood back and said something like "awww look how cute it is!", but that being said all the axis seem to run quite nicely.

So it's still to print its first part. I don't think this is going to happen in Bath anytime soon, so the race is on amongst the community so to speak. Oh and thanks to RustySpoon at thingiverse for the STL conversions.
I find issues of scalability very interesting.

mini-mendel is a cool idea to have more parts quickly as a starter kit.

it would be interesting to know if a mini-mendel could print the part for a mendel twice the normal size. probably not...

on the other hand would a 2x larger mendel use more 2x more plastic, or plus? (without a redesign I mean)

has anybody got an idea of the curve the material use would be compared to print area?
MakerBot can print all the reprapped parts for a standard Mendel (we deliberately made Mendel that way), so - if it can print at all :-) - Mini Mendel will definitely be able to make a full Mendel as it has a bigger print volume than MakerBot.
This is now available on the RepRap development catalog at:

If you are making improvements or anything to do with the Mini-Mendel it would be greatly appreciated if you posted or linked-to your work from that page so that it's easily accessible in the future (it's a wiki; you can edit it!).
@Bodgeit, Haven't checked in the repository yet, but there should be an excel file for all the rod lengths needed
@Bodgeit & @eD

I've now added the excel spreadsheet for the rod lengths.
Cheers welshie ;-)

Also, big credit to PADDY for getting his head round the X axis and redesigning it specially for the mini. Couldn't have done it without his german genius.

Love to you all from up south - eD
Does anyone know where to get decent nema14 motors? I'm in the US. I cant seem to find any that aren't ridiculously overpowered and expensive.
I've added suppliers to the Wiki. I think all of the parts can be ordered for under 350 euros, but shipping costs do vary depending on where you are.


The NEMA14 motors are also listed there. If you find more suppliers, please add them to the wiki. I'll include them in the spreadsheet.
I´m currently printing the Shelled Mini-Mendel I created.

Skeinforge ended up with <10h of print-time using just 110g of ABS.

I guess this is the fastest way to print a 3d-printer at the moment. :)
Hi there,
I am a newbie to RepRap, and am very excited about the whole concept.
I want to start by building a Mendle, but all the parts I have come across are .stl which I cant open. Is there any way for me to get .igs or .step or preferably Inventor, because that is the program I work in?
Hi there,
I am a newbie to RepRap and am very excited to get going . I want to build a Huxley, and have got very frustrated trying to download any plans that can be opened. Could anybody point me in the right dirrection please? I do all of my work in Inventor so any file types such as .igs or .step would work. I dont know why it seems so complicated!
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