by kludgineer, published

MendelMax by kludgineer Oct 17, 2011


UPDATE: A New updated version of MendelMax is available at thingiverse.com/thing:20355. It is recommended for all new builds.

MendelMax is a new RepRap 3d printer designed by Maxbots. It is a true reprap, using printed brackets, but instead of using threaded rod for the structural elements it uses inexpensive aluminum extrusions. This gives a huge increase in rigidity for a minimal extra cost (Self sourcing will cost about $50 more than a standard Prusa when purchased from the recommended suppliers). The required extrusions are available world wide from a variety of suppliers.

In addition to greatly increased rigidity, this design is faster to assemble (probably 4 hours for most users), easier to print, has a larger build volume (~215x235x190 if built at the standard dimensions), and is easier to hack on.

Update 2/7/2012: MendelMax full kits and hardware only kits are now available from Maxbots (aka Kludgineer on Thingiverse) @ store.mendelmax.com!

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Ok, thanks. That's a pity:-( The extrusion is relatively cheap, but in my case very expensive because it has to be orderered especially. The nuts, bolts, wingnuts and T-bolts are the biggest cost and these I have in large quantity's on hand......for the 30x30.

I'll have to think some more about the redrawingtime against the expenses....

You'll hear from me.

I do not recommend you try to use 30mm extrusions. You will need to completely redesign everything if you do, all the hole spacings are designed for 20mm extrusions. That is true for both the 1.0 and 1.5.

kludgineer tnxx for all the good work, it looks realy nice and I'll start tomorrow at a fablab in The Netherlands to reproduce some of the parts. So far so good...but I have a lot of Bosch/Rexroth materials based on 30 and 45mm extrusions. The 30mm type is what I want to use for the project. For that reason, I'll need to resize some of the parts. From this point, the question:

In your opinion, which parts will give me the most difficulty? I'll use M6 bolts and wingnuts. Tnxx.

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MendelMax by kludgineer is licensed under the GNU - GPL license.

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For full assembly instructions and parts lists, see mendelmax.com.

The X & Y axes are standard Prusa parts, so any design can be used.

UPDATE I finally got an STP file uploaded. Please let me know if you have any issues with that file.

Update: The SCAD conversion is mostly complete and available at github.com/maxbots/MendelMax

To learn how to execute scripts in FreeCAD, read the tutorial at: mendelmax.com/tikiwiki/tiki-index.php?page=Getting+Started+with+FreeCAD+scripting

Note there may be minor incompatibilities between SCAD generated parts and the parts here on Thingiverse. It should not be an issue intermixing to some extent, but parts that directly connect to another (for example the Y & Z rod mounts & clasps) should always come from the same source.

Also note that the SCAD parts are untested at this point so I recommend only using them if you already have a working printer to reprint any parts that may need tweaking.

Update 1/15/2012: Y motor mount & Y Idler mount replaced with much more robust designs. These should fix any flexing issues you might have.

The part "Lower Vertex Cupcake" is a replacement for the standard Lower Vertex, but is reduced in height slightly to allow printing on the Cupcake and other small-format printers. Either part will work, but you only need to print one or the other, don't print both.

Update 2/7/2012: New, improved Lower Vertex pieces uploaded. These parts should be easier to print, easier to assemble, and better looking, though that comes at the expense of being somewhat slower to print.

The new parts need to be printed in mirrored pairs, so the the included STLs include one of each part. Print two copies of each of the parts (lower vertex lower and lower vertex upper). You will end up with 8 parts total. If you prefer, you can get the individual STLs for each of the four different parts in the individual lower vertex zip file.

One important not about these new parts: WHile they are just as rigid as the old parts, they are not as storng as the old ones. They are amply strong to use the MendelMax as a printer, but DO NOT STAND ON IT!

The original parts are still here if you prefer them.

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12much on Dec 12, 2012 said:

kludgineer tnxx for all the good work, it looks realy nice and I'll start tomorrow at a fablab in The Netherlands to reproduce some of the parts. So far so good...but I have a lot of Bosch/Rexroth materials based on 30 and 45mm extrusions. The 30mm type is what I want to use for the project. For that reason, I'll need to resize some of the parts. From this point, the question:

In your opinion, which parts will give me the most difficulty? I'll use M6 bolts and wingnuts. Tnxx.

kludgineer on Dec 13, 2012 said:

I do not recommend you try to use 30mm extrusions. You will need to completely redesign everything if you do, all the hole spacings are designed for 20mm extrusions. That is true for both the 1.0 and 1.5.

vladimir07 on Dec 6, 2012 said:

Can someone tell me what settings to use in replicatorG when converting the STL to gcode and printing with a Makerbot Replicator.  For example what infill  % should I use?  Should use a raft?

kludgineer on Dec 6, 2012 said:

I typically print at a 35% fill, and that should be fine for most parts. A bit more is fine. You should not need a raft, but that is entirely dependent on the printer, so you may need one on the Replicator.

BHHSStudent on Mar 17, 2012 said:

Hi i was wondering if you still had your original solidworks part files. I need to split the parts up because of the size makerbot we have.

kludgineer on Mar 17, 2012 said:

The model was not designed in Solidworks, so I don't have Solidworks files. In the comments below someone links to a SW port of the design, though.

kludgineer on Feb 29, 2012 said:

Very nice! Can I suggest that you upload it here as a derivative?

Anonymous on Mar 3, 2012 said:

If I knew how I would. I just converted this for whoever needs or wants it.


erguezga on Feb 23, 2012 said:

Hi, I am trying to open the step file (MendelMax.stp) with SolidWorks but I can't :'(

Could anyone post the MendelMax in SolidWorks format? Thank you.

Brojt on Feb 27, 2012 said:

You can go to http://www.techdesignandcad.co... to download in SolidWorks format.

Only what is seen here on Thingiverse is included and the files are converted from the stp file that is available.

Have Fun

kludgineer on Feb 24, 2012 said:

Sorry, it was designed in Alibre, and it is not that easy to go from one CAD program to another. I know the latest solidworks with all updates can open the STP file.

NewPerfection on Feb 19, 2012 said:

I'm not seeing the SCAD conversion on your github.

BTW, I've ordered everything I need except for the aluminum extrusion, aluminum plates, and power supply. Should have this up and running soon!

kludgineer on Feb 24, 2012 said:

Sorry, I should have been more specific. It was converted to FreeCAD, not OpenSCAD. Both are Scripted CAD, but I personally think FreeCAD is a nicer language (though it is not quite as simple to use in a purely scripted manner).

DarkerMark on Feb 12, 2012 said:

Looking at pictures an the parts I printed I can't seem to figure out what the 70mm Jig is used for, was it meant for one of the old versions of the parts?

kludgineer on Feb 12, 2012 said:

The two 420mm have holes drilled 70mm from each end that are used to create a blind joint with the diagonal uprights. That jog is used to make it super easy to position the hole when you drill them.

timdriedger on Feb 3, 2012 said:

Has anyone tried building a MendelMax using printed beams like this http://www.thingiverse.com/thi...

on Jan 31, 2012 said:

I'm about to build a MendelMax, since nophead doesn't seem to be releasing the files for his Mendel90 anytime soon.

I have a question about the MendelMax's frame design, though: does the extruder collide with the frame triangle like it does on the Sells or Prusa Mendel? On my Prusa, i simply built X 150mm longer and added a large heatbed, will i need to oversize the Max as well?

kludgineer on Jan 31, 2012 said:

It depends on how you mount it. If you rotate the extruder 90 degrees, then yes, at extreme Z heights it limits your movement a bit, but not until you are greater than ~100mm above the table. Even then the build volume is bigger than a Prusa.

granz on Jan 15, 2012 said:

Awesome design! I have a working Prusa and was planning to build a larger bot and the rigidity of the extruded aluminum used for the MendelMax makes this possible. You instructions recommend the GT2 belts (T5/XL is definitely the worst choice for linear motion.) I just thought I'd let you know about this synchromesh cable as another possibility:


It works great on my standard-sized Prusa so I plan on using it for my double-size MendelMax. Also, I'm currently modifying your parts to use 12mm rods instead of 8mm for building scaled up versions (I will post the modified parts once I've got everything w
orking)--I only have the frame built currently, but it's very study even with all dimensions doubled!


kludgineer on Jan 16, 2012 said:

Technically, Synchromesh does not appear to be an anti-backlash design. At least there is no mention of the benefit on the Synchromesh product page at:


That said, it will almost certainly have a lower backlash amount then T* belts. The big benefit of Snychromesh is that it can be used in multiple planes, since the "teeth" wrap all the way around the cable. That allows you to use a single belt to drive pulleys that can be mounted at odd angles to
one another easily, somthing that would be difficult or impossible with a traditional belt.

I recommend 2mm GT2 because it is the most cost effective anti-backlash design that I have found. There are several other suitable design, such at HTD, AT* and more, but they are typically more expensive.

IanEagland on Jan 12, 2012 said:


Just to let you know that after applying the latest service pack Inventor 2012 Imported the stp files perfectly

kludgineer on Jan 13, 2012 said:

Great, glad to hear you were able to resolve your problem.

kludgineer on Jan 3, 2012 said:

Umm... Wrong angles relative to what?

As to your second question, some lengths can be adjusted a bit, others cannot. This is both a feature and a bug, depending on how you look at it.

When I designed the MendelMax, it was deisgned to take advantage of Misumi's extremely accurate cutting. Their standard cuts are +/- .5mm, but in prac
tice they are almost alwatys dead on. Their cuts are plenty accurate for our needs. As I note in the FAQ, I do not recommend you cut these parts yourself because of the high level of accuracy that is required.

That required accuracy, though, has a big benefit. Because I am relying on the accuracy
of the parts, the assembly process is relatively trivial, and almost all of the fiddling that a Prusa requires to square everything up is eliminated.

All that said, the required lengths are actually quite forgiving. It does not matter so much if your extrusions are a mm or two longer or shorter th
an the specified lengths, all that matters is that they are consistent within the length... So it is ok if your 300mm extrusions are really 302mm, and your 340mm are only 338mm, so long as each length is the same length. The only exception to that is that two of your 420mm extrusions need to be th
e same over/under as the 300mm (I am open to hearing suggestions to fix this). In practice, this is not an issue if you get your extrusions from the recommended source or another source with accurate cutting capabilities.

laszlo on Jan 3, 2012 said:

gt; (I am open to hearing suggestions to fix this)

Drop the triangular shape, and stick to the boxy form.
The extrusion profiles are designed to squares for a reason.

At least this is my conclusion after a week debugging.


laszlo on Jan 3, 2012 said:

gt; Umm... Wrong angles relative to what?



In that triangle there is no play allowed at all.

So if the extrusion is 338mm instead of 340mm (lets assume the models are not wrong), then the angles of both z_motor_m
ount and lower_vertex_middle and top_vertex_y needs to be adjusted. To be *accurate*.

At least if you care, the machine is flat at the bottom, or on a table it waggles.

I was quite surprised, that when I put everything in CAD, the two leg of the triangle is almost touching each other at the top (5
mm gap between them).
(I was also equally surprised that when I fastened the bolts, the machines started waggle on a table)


ProtoParadigm on Dec 15, 2011 said:

I'll just leave this here...

20mm Plastic T-Slot http://www.thingiverse.com/thi...

cyborg527 on Dec 27, 2011 said:

I was just about to drop that here after I saw someone made it. :-P

justin_treon on Dec 8, 2011 said:

To reduce the parts list why not run rollers on the extruded aluminum for they Y-axis? I know this will not be as effective as the Makerslide, but for a scaled up version it should be better than 8mm rods.

kludgineer on Jan 3, 2012 said:

My first bot did exactly that. Trust me, it increases the part count, not decreases it.


A group of us built MendelMax' using Makerslide, and honestly for our purposes it was not a good choice. It is more expensive, more complicated, and higher maintenance than linear rods,
and there is nothing really gained to justify it. For a laser cutter or other projects with a long moving axis it is beneficial, but for a printer you are better off sticking with linear rods.

nhand42 on Dec 5, 2011 said:

For anybody who is having trouble printing the Y Rod Mount on a ToM or Cupcake due to its immense size, kludgineer has pointed me towards a ToM/Cupcake friendly version.


This smaller Y Rod Mount printed perfectly on my ToM. Thanks kludgineer!

nhand42 on Dec 5, 2011 said:

I see kludgineer already gave this link in an earlier comment. Doh.

justin_treon on Nov 30, 2011 said:

I would love to see a scaled up parts list

kludgineer on Nov 30, 2011 said:

Other than the extrusions, the parts are the same if you scale it up, and the extrusions lengths are documented in the scaling document at http://mendelmax.com/tikiwiki/... so basically there already is a "scaled up parts list".

Note, large scale printers are not recommended for beginners, and are not really supported. Unless you know what you are doing, I would not recommend you make a printer much larger than the stock size.

owais on Nov 27, 2011 said:

What the total cost of parts come out to? Assuming you are using all the distributors on the mendelmax.com website.

kludgineer on Nov 28, 2011 said:

The BoM online gives you a good idea, but you should understand that it is for a fairly premium build, with careful shopping and cutting some reasonable corners (printed bushings instead of commercial ones, Sanguinololu instead of RAMPS, etc) you should be able to make a MM for at least $100 less than the total posted there.

danielpublic on Nov 27, 2011 said:

It's mostly those T-slot Nuts that cost a fortune. But thankfully there are alternatives: http://www.thingiverse.com/thi...


Have look at the BoM and its suppliers list: http://reprap.org/wiki/MendelM...
Add if anything is missing! Thanks.

bsg on Nov 9, 2011 said:

How does Mendelmax's greater rigidity translate to vibration? Does vibration propagate from the extruder moving around to the frame?

kludgineer on Nov 9, 2011 said:

The frame itself does not seem to conduct vibrations badly. Since the extrusions are connected together by plastic, the vibrations tend to be deadened, and the extruder is mounted on the same rods and X ends as on the Prusa, so not a lot of vibration is transmitted to the frame itself.

The one area where I am currently having noise issues is on my table. Currently I am using a sheet of 1/8" aluminum with blue tape, and that acts as a speaker and amplifies the sound of the vibratiions. That should be solved once I install the silicone heat bed and the fiberglass insulation which
together should dampen much of the vibration.

msmollin on Oct 31, 2011 said:

Brilliant design again. Just looking at it the printable pieces.... are they printable on a Cupcake?

kludgineer on Dec 5, 2011 said:

A cupcake-printable Y Rod Mount is now available in out GitHib repository at https://github.com/maxbots/Men...

I am no longer recommending the Y Top Vertex for normal use because the printer is plenty rigid without it, so it seems to be superfluous. Because of that I will not be releasing a Cupcake-printable version of that part, if you really want one, you can always print it after you get your MendelMax

kludgineer on Nov 1, 2011 said:

Most pieces are easily printable on a Cupcake, but a few are not. Currently the Top_Vertex_X and Y_Rod_Mount parts are larger than the build area of the Cupcake. You could probably get by without the Top_Vertex piece long enough to print them on the MendelMax (the motor mounts serve the same purpose, these just add rigidity). It would be easy enough to make a smaller version of the Y Rod Mounts that could be printed on the Cupcake, but that would make the rods closer together, so you would lose some rigidity, but again, this should work fine long enough to print the correct part on the MendelMax. I will try to put up a Cupcake printable version of that part sometime in the next few days.

Anonymous on Oct 30, 2011 said:

How does this printer compare to the Thing-O-Matic?

kludgineer on Oct 30, 2011 said:

MendelMax will cost about 1/2 as much for a fully loaded system when self-sourced (see MendelMax.com for a full BoM), is faster to assemble, gives you about 4x the printable volume, will print faster, and will be more easy to hack on if you are so inclined. I'm sure ToM is better in some way, but I can't think of any.

I guess strictly speaking, ToM has a larger installed base, but since MendelMax is basically just a Prusa Mendel on Steroids, that benefit doesn't really get you much.

4ndy on Oct 30, 2011 said:

To make this worthwhile, it could do with a further redesign to replace the M8 smooth rods with those same extruded beams in all axes.

Specialised X/Y carriages would then be needed, probably using skate bearings instead of linear bearings, but without that you're not really gaining rigidity where it counts most, and so can't scale the machine up by a significant amount.

After that, +1 for the first maker to replace their T5 belts with bicycle chains. 8-)

kludgineer on Oct 30, 2011 said:

Oh, and regarding scaling, I already address your concerns about scalability here: http://mendelmax.com/tikiwiki/...

kludgineer on Oct 30, 2011 said:

Trust me, it is quite worthwhile as is. ;-)

As noted on MendelMax.com, I plan on releasing an X
amp; Y deisgn using Makerslide as soon as it starts shipping to the general public (http://makerslide.com/).

My first RepStrap design used the aluminum extrusions as the linear rods, and while it worked very well, the parts required to properly constrain the carriages were considerably more complicated. It is much simpler to stick with the current designs and use linear bearings (or better yet, linear bu
shings) until a proper linear motion system such as Makerslide is available.

Bike chain would work, but would have the same problem that T5 does only much worse-- they are designed for rotary motion, not linear motion, so they make no attempt to eliminate backlash. I suspect you would have backlas
h of 1-2mm or possibly much more with bike chain. To get the best quality prints, you really need to switch to a belt design that is intended for linear motion, such as GT2. See my Choosing Pulleys FAQ for more information: http://mendelmax.com/tikiwiki/...

owais on Oct 29, 2011 said:

So whose going to be the first who will test this?

kludgineer on Oct 30, 2011 said:

At least a few people have parts on order, I expect you will see a few copies soon.

My prototype is actually working now, here is a print of it printing at 150mm/sec:


It is currently only working ok at those speeds, but the problems are software ones, not hardware. I also need to rebuild my Y axis to make it more rigid, but that is an
assembly problem, not a design one. I should have that done before the end of the weekend time allowing, and I will post an updated video then.

RichRap on Oct 25, 2011 said:

Outstanding! What a mean and cool looking machine. I want one! 8-)

Auzze on Oct 20, 2011 said:

Outstanding work...

I will have to add this to my to-do-list.
8-) 8-) 8-) 8-) 8-)

lusimon on Oct 19, 2011 said:

Looks great! Can you please post videos of it printing as well as detailed pictures of non-trivial objects printed by it, so that we can get an idea as to the print quality?

kludgineer on Oct 19, 2011 said:

It's not printing yet, but I will certainly post pics once it is. Print quality should be at least as good as a Prusa since it is a Prusa, just with a stronger frame.

elk on Oct 18, 2011 said:

Really nice Idea. The only thing I would change is the Z axis - i would go for a belt / one motor design. But this is just my opinion... ;)

kludgineer on Oct 18, 2011 said:

A single motor/belt design would add complication with little savings. The extra motor costs $20, two pulleys and a belt would cost near that much, quite possibly more (unless you print your pulleys, which I do not recommend for best print quality).

A single motor design would also increase both the printed part count and the vitamin count since you would need to design a tensioner mechanism.

Personally I prefer the current design, but since the design is (or at least will be) Open Source, I look forward to seeing the new ideas other people
put forward. I fully intend this design to change rapidly as other people submit designs.

ChrisGray on Oct 18, 2011 said:

Forgot to ask, what software did you use to design the bot?

kludgineer on Oct 18, 2011 said:

It is currently designed in Alibre. I will be porting the design to FreeCAD in the near future.

ChrisGray on Oct 18, 2011 said:

Thanks for bringing this to the Seattle Makerbot night at StudentRND! Awesome work!

brnrd on Oct 18, 2011 said:

Why not give more vertical clearance for the extruder by moving the vertical frame all the way to the outside and making the bottom horizontal frame sections the same length as the top ones? This is a problem with the Mendel frames that limits the vertical build height to well below the 140 mm spec unless you use the original extruder and hot end design.

kludgineer on Oct 18, 2011 said:

I am not 100% certain exactly what you mean, but this design nearly doubles the usable Z axis to about 200mm including the extruder (compared to ~100mm including the extruder on a Prusa, final usable clearance TBD).

Making the bottom cross-wise (X axis) extrusions longer would not give you any additional build area in any axis. The limiting factor is the ends of your X carriage. By moving them outside of the main frame you lower the build cost slightly, and reduce the overall footprint of the machine.

jmil on Oct 18, 2011 said:


Anonymous on Oct 18, 2011 said:

Is this a Mendel made with Makerbeams? That's awesome

kludgineer on Oct 18, 2011 said:

No, Makerbeams are a 10mm profile, which would not really be rigid enough for a full sized Mendel (though at least one person has already told me of plans to take my design and build a Huxley scale bot with Makerbeam).

This design uses Misumi or any other 20mm profile aluminum extrusion. 20mm Profile extrusions are available from a number of global suppliers and are very in expensive ($5.20/meter from Misumi).