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Mendel90

by nophead, published

Mendel90 by nophead Feb 19, 2012

Description

RepRap Mendel variant using two sheets at right angles for the frame.

Recent Comments

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Nop,
As always, your skills at designing amaze me.
If the rod is bent and you constrain the top then for the carriage not to be displaced the coupling at the bottom would need to be able to displace radially rather than just bend. If the top end is free to wobble it has no effect on the carriage so preventing it from wobbling is detrimental not beneficial.
Your design is very good, but I am looking for solution wich is more simple regarding assembly process and have less dependencies (motor, coupler with flexible insert). In case of hanging Z, you have only put bearings and connect any flexible coupler - commertial one made of alloy, printed or just made from flexible tube.

All true with assumption that you have quite solid coupler at the bottom. My concept is base on "floating" threaded rod - as flexible coupler as possible, rood with some clearance between the ball bearing internal hole. At the end you have no wobbling, and adventages I have mentioned before.

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License

GNU - GPL
Mendel90 by nophead is licensed under the GNU - GPL license.

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Instructions

See hydraraptor.blogspot.com/2011/12/mendel90.html

This is the 8mm rod version with NEMA17 motors, T5 belts
and an acrylic frame.

The source files and STLs for other sizes are on Github here: github.com/nophead/Mendel90. There are also bills of materials for each sub assembly, so you can see which parts go where.

Detailed instructions will be on the RepRap wiki soon.

I have built this version, but not run it yet. The "Sturdy" version has been running for three Months.

The base sheet is designed to be 10mm acrylic and the rest of the frame 6mm.

Print:

10 fixing-block.stl
2 z-screw_pointer.stl
4 z-coupling.stl
2 pulley.stl

and one of all the other STL files.

Vitamins.txt lists all the other mechanical parts.

File Name

Downloads

Size

Nop,
As always, your skills at designing amaze me.
I'm planning on building the Sturdy over the next few months. Do you know of a good source for a vitamins complete package? I live in a rural area in Canada and it's difficult to source here. Thanks!
Hi nophead,

I am looking on latest x_idler_bracket and x_motor_bracket from Github and wonder why nut hole is much biger than M8 nut. How you would like to mount NUT for Z axis ?
Thanks, now I see :).

BTW

I have redesign Z axis little bit. I have roods hanging on ball berings, to achieve a few advantages:

- minimize floating of Z,

- reduce the impact in case when printing head meet the bed :)

- reduce temperature impact on Z axis - z rod lying on motor shaft is not so stable (shafts in motors I have have ability to move a few milimeters under presure)

Take a look:
http://www.thingiverse.com/thing:167396
Yes I have seen that. The kits I sell have a stable Z axis with the existing design. It probably depends on the make of the motor. The screws need to be free at the top otherwise the axis is over constrained and any wobble in the rod will disturb the X axis.
Your design is very good, but I am looking for solution wich is more simple regarding assembly process and have less dependencies (motor, coupler with flexible insert). In case of hanging Z, you have only put bearings and connect any flexible coupler - commertial one made of alloy, printed or just made from flexible tube.

All true with assumption that you have quite solid coupler at the bottom. My concept is base on "floating" threaded rod - as flexible coupler as possible, rood with some clearance between the ball bearing internal hole. At the end you have no wobbling, and adventages I have mentioned before.
If the rod is bent and you constrain the top then for the carriage not to be displaced the coupling at the bottom would need to be able to displace radially rather than just bend. If the top end is free to wobble it has no effect on the carriage so preventing it from wobbling is detrimental not beneficial.
Had anybody problems with z axis stability ?

If yes, I have made and tested "hanging" screws there thingiverse.com/thing:167396
BTW you can use motocycle lamp 6v 50W as PSU 5v load. It will be light source too.
or just some 12v Leds :)
I only use a top limit switch. The bottom one can be turned on by changing the config file.
I see z-limit-switch disappeared from latest git ?
What is the difference between the versions? Especially sturdy and mendel. (Looking at the ones on github)
Mendel90 is acrylic with 8mm rods, so pretty much equivalent to a Mendel. The sturdy version uses 12mm MDF and 10mm rods and has a slightly bigger build area.
Hey nophead,
i want build the MDF 10mm Rod version.
Can you tell me the size of the MDF and the rods with 250x250x200mm build.

Thanks and happy christmas.
Hi,

I have made Mendel90 with bed size 250x250, would you like to have dimentions ?
How much amps you would like to have to heat the bed ?
What spped is expected ?

Some photos are here printerzero.blogspot.com/
The latest design (200x200x200) is on Github and the bom is here github.com/nophead/Mendel90/blob/master/sturdy/bom/bom.txt.

The best way to get the dimensions of a bigger machine is to download all the files, change the configuration and run make_machine.

Adding 50mm to X will make the X rods 50mm longer, the base, gantry and bed 50mm wider.

Adding 50mm to Y will make the bed 50mm deeper but the rods and base 100mm deeper.
fan mount for mendel90 thingiverse.com/thing:29567 thanks for richgain
Hi nophead, could you recommend anywhere we can buy the electronics required to build this? (UK)
Think3dPrint3d sell Sanguinololus: emakershop.com/browse/listing?l=174

but it will work with any reprap electronics.
have anyone add fan mount to the x-carriage? )
fest - in reply to Telemah
I tried, but I failed :-[

Here's my attempt lh3.googleusercontent.com/-EZnxQsUj2_w/T_nrR9PKKeI/AAAAAAAABsk/JX_LSibBko8/s1024/IMG_3298.JPG

(the side of fan duct closer to carriage is actually vertical, picture is shot from weird angle).

The problem with this design is that airflow is too low/exit is too far from nozzle. I get better results with 120mm fan blowing across the whole heated bed. Attached to carriage is 60mm fan.
I'm now building one from my previous Prusa Mendel's parts. I got fed up with bed leveling issues and difficulties getting axes perpendicular. I also had a verusion with PLA bushings and was unable to tension X axis belt properly- because when tensioned enough, PLA bushings popped out of Z bars.

I do have a couple of comments regarding Mendel90:
* I do not find X axis belt tensioner (plastic half-circle) strong enough to tension belt- it split open for me. I replaced it with nyloc nut and it seems to work better.
* I have dual shaft steppers, and the second shaft is in the way of ribbon c
able for X axis. The only option for dual shaft motors is to mount X axis ribbon cable perpendicular to gantry frame, to the side of motor. I will probably try to do it once I get the printer working. Back to wiring :)
Odd the tensioner split, I have no problems with 3 I printed in ABS and PLA should be harder if anything. Did it de-laminate? If so perhaps the hole was a bit tight. It could also be printed lying down which would make it stronger.

I started with just a nyloc but the belt stopped it turning so the screw went through it and cut into the belt.

Yes I can see duel shaft could be a problem. Maybe the gantry should move back a bit.
I think I got the reason why it split- it was printed with a low infill of 0.4. The tensioner de-laminated because the screw threaded into tensioner and de-laminated layers.

I also thought of moving gantry back 8-10mm (length of shaft sticking out) but I think the shaft will eventutally damage the cable strip when moving along Z axis. Anyway, my frame is already finished, so it makes no sense for me to take it apart and move gantry.
Thanks again, here's a movie of it working: youtube.com/watch?v=mNse11SiS-E

Going to go for the ribbon cable next, phone wire works, but it looks really ghetto :(
Looks great. Parts are printing now. I post results when I run into problems or it is finished :)
i will like to get my hands on a set of acrillyc cut parts... can eny one help me? were i can go to get them? thank you :))
Finished building and first testing of a Mendel90. It is a great design Nophead!

I had just one problem: the x-bar clamps don't clamp the rods tight enough, so if i tighten the x-belt the rods move. Maybe you can increase the gap a little so it is possible to secure the rods a little more. I know that my printer was printing a littlebit to little plastic and therefore the hole
s are a bit large. But i think it would be an easy improvement.

Personally i really prefer a vertical x-axis and i am working on one compatible with this printer.

Thanks for your great work!
Not that it would be practical, but if you printed the two support sheets (like a series of puzzle pieces), this printer would be over 80% printable ;)
22/3/12 Improved Wades extruder:

Front moved back to allow for deeper hobbed bolts.

Added upper support web and reduced the lower one to one layer.

Added composite STL.
I've started gathering parts to begin building the Mendel90. I got the python scripts to run OK using your instructions, and have been able to view the plans in OpenSCAD.

One thing that puzzled me was the polypropylene strips. I can't see them in the model or find any reference to them in the blog.

Where do they go and what are they for?

Thanks.
Those are the purple strips that you can see in the model. They are mentioned here: hydraraptor.blogspot.com/2011/12/mendel90-axes.html under the Cables heading.
Woo! Printing this now! Thanks for posting the design. I am going to laser cut the sheets at school. I will let you know how the build goes/contribute where I can. Thanks again.
it seems for me that z-coupling and x-idler-bracket models mave problems with though holes. It`s a bug or a feature?
They have a support layer because they have a smaller hole on top of bigger one. That would mean printing the smaller one in mid air.

They are one layer thick and easily removed with a drill or a penknife.
thnx. was thinking about that.
Thank you for this great design, i would love to build one, but i have one question (if its been asked already, i'm sorry)

Is there a way to easily convert a prusa into a mendel90. without having to replace a lot of parts?

It seems like the X-carriage and vertical parts could be the same exact parts..

Also: Will this appear on reprap.org once you feel the design is "finished" ?

One more: Could you compress these into a few "plates" like the prusa design?
Sorry, none of the printed parts are compatible with the Prusa. I swapped the smooth rods and lead screws at the X-ends, the spacing is different and so is the x-bar spacing.

I will put the instructions on reprap.org. Whether it appears on the front page is up to Dr Bowyer.

It is easy to combine parts onto build plates with openscad. The problem is Skienforge only has one infill direction per layer, so bridging does not work properly. When one parts needs a bridge lay
er they all get it. If two parts need a bridge in opposite directions on the same layer one is not right.

I also print some pulleys at a different layer height and some parts with 100% infill.
Slic3r does proper bridging, where you can have multiple bridge directions in a single layer. Works very well, and the output of the newest version is on par with what skeinforge can output.
I will have to give it a try soon, but I need to do some work on my code as don't use E codes, just extruder on / off.
Thank you for the answer, i might (with your consent) design a similar model that is more compatible with the prusa parts, so that it's convertible, if it's possible obviously, but for now i don't see many problems.

Are there any concerns that you are aware of to take into consideration if anyone would be trying that?
You don't need my consent to make your own design variant. If you look at my blog you will see each change I made was for a reason.

I am not sure what advantage there is making it compatible with the Prusa. Anybody who already has a Prusa should be able to print the new parts easily enough.
I'm working on building one...it's really hard without documentation. I got a few questions.

Should the templates work for MDF? The numbers are for the sizes of holes in mm, right? What are the 2 8mm holes on the base?
Are the microswitches in the BoM the endstops? Why only 3? In this picture, I can see 4, 2 on the Z axis, 1 on X and 1 on Y. Shouldn't you use 2 on each axis?
Where do the
ball bearings go? I can only think of 3 places, the extruder pinch wheel, X idler, and Y idler. They are also known as 624 and 608 bearings, you should put that into the BoM.
Why so many kinds of screws? Can you try to consolidate them?
What would the screws be in SAE?
I will do the documentation as fast as I can but it takes time and I have other things to do. Some of these questions are answered on my blog.

The two 8mm holes are in case the motor has two shafts.

The templates will work for MDF but I use 12mm so the gantry would end up 6mm further back. I also use No6 wood screws which have smaller pilot holes . Best to wait for me to publish the source as that can generate any permutation.

The ext
ruder uses 3 608 bearings, one 624 on the X idler and 2 on the Y. The BOM is generated automatically from the ball bearing dimensions. I will have to add another field to get the type in there.

Yes the microswitches are the endstops. You only need one on Z. I use the top and everybody else uses the
bottom. I am going to redesign the bottom limit to be simpler and will probably change that to a full size microswitch because lower force ones are available. A high force one may lift the x end.

The screws have to be the right length in most cases. For example they can stick through the base and
would look ugly sticking through the frame. There is one that is far too long on the y-idler to avoid yet another type.

I don't know anything about SAE screws and find them impossible to Google, unlike metric where I can just do "M4 nut size".

With the source files you could put in the size of SAE
you want to use and everything would change, the plastic parts and the sheet pilot holes, etc.
Could you consolidate between M3 and M4, and between cap, pan, and hex heads? If you put feet on the corners of the base, you could level the whole machine as well as put screws through the bottom, eliminating some of the smaller lengths.
Some need to be M3 because they go into motors. Some need to be M4 because they go through bearings. Some need to be hex head because there is no room to get an Allen key or a screw driver in, but you wouldn't want them everywhere as they are slow to put in. You can substitute pan for cap but I find cap easier to fit when the other hand is holding the nut. And I personally don't like ugly machines like Mendel where some of the bolts are far too long. They only cost pennies, even in small quantities so it makes very little difference to the total cost.

For the Huxley90 variant the frame screws are M3 so there are few M4. The Sturdy90 variant with 10mm rods uses mainly M4.

I don't want to stand it on feet because it will bow and sag unless a very stiff material is used for the base, or you make a torsion box under it.

There is no need to level
the machine. It can print on a slope. It just needs to keep the alignment of the Y axis to the Z to within a small fraction of the layer height, which when people print 0.01mm layers is not much at all.

Everything is configurable, but changing it changes all the sheets and parts. This is really ju
st an example of one of the many machines this design can produce.
Oh, and what's the 22mm long smooth rod for?
The Wade's idler axle.
The latest Prusa just uses friction fit for the bars. I haven't had a problem with one screw one prototype.

Yes the y-idler was missing, thanks for spotting it, I have added it.
why didn't you use greg's hinged instead of wade's?
I don't think Greg's idler bracket is strong enough when printed with ABS, Greg only uses PLA.

I don't need to raise the motor because the bolts have captive heads, so I have no need to get under it, and I prefer to keep the centre of gravity low.

I have no reason to open the idler and prefer to keep it in place once the spring tension has been set. It doesn't close fully like the original
Wade's so it is easy to load filament, just push it in and turn the wheel.

If I need to clean the hobbed bolt I take the nut off with my fingers and remove the bolt and big gear.

The mounting holes are still on 50mm centres, so you should be able to fit Greg's if you want.

More details here: htt
p://hydraraptor.blogspot.com/2...
"I don't think Greg's idler bracket is strong enough when printed with ABS, Greg only uses PLA."

I'm using a Greg's printed in ABS, stiff springs and bolts tightened almost all the way. No problems so far, and it has turned out just as reliable (with a proper filament guide, thingiverse.com/thing:17030 ) and a lot more convenient than a Wade's. Plus, it looks sexy. ;)
so, I read all the 4 posts about mendel90, questions:

1 - in your design, the Z and Y motors get much near headed bed than the prusa, might happen some overheating problems?

2 - you made this Z limit thing with rubber washers, and stuff, don't you think the one gregfrost did on his X end motor is something simpler? you could add something like that to the x idler bracket easily and solve the problem with no extra hardware, etc...

3 - you talked about the prusa heated bed not get corners heated enought, Triffid_hunter told me that using about 4 sheets of aluminum paper between the glass and the pcb could help, what do you think of that?

4 - what height do you think Z axis could go using this design and still be stable? m
aybe 30 cm?

5 - do you think the best frame would be acrylic or MDF for this printer?

6 - could you post some pics, vids, etc of your mendel90 printing and the results of the prints?

great job =)
Here is picture of a Huxley extruder gear printed on Mendel90 with 0.3mm layers. lh4.googleusercontent.com/-DGCMaGYS74Q/T0oVIUu4nPI/AAAAAAAAGA0/ZC19w2KwE60/s800/CIMG0528.JPG
do you think this could be made with aluminum sheets instead of MDF or acrylic? if yes, what thickness, 4mm?

thx
Yes it could be made from aluminium. I think the base would need to be thicker than 4mm to take the tapped screws and should be tooling plate to be flat enough.
man I'm really considering on making one of these as my new printer =)

tell me, adding feet to it (like prusa has) would be a bad idea?
Putting feet under the base would encourage it to warp. It needs to sit on a nice flat surface though, like a desk. If not I would make the base rigid, perhaps from 10mm aluminium and add three rubber feet.
your x carriage looks nice but there is no fan holder, are you gonna add it later or you think it's not a necessary thing to have?
I haven't use one since I started using heated beds. It should be easy enough to add one though.
1. Stepper motors are rated to run at 100C so the only limitation is when the brackets melt. There is no problem with an open design like this. Even when I box my machines and run them with a chamber temperature of 45C, the motors only run 60-70C. That it fine for ABS brackets.

2. Yes a few people have pointed that out. I will redesign it.

3. Yes that could help. It needs some with an without measurements to show if it worth doing. The PCB already has a layer of copper on the top which will have similar conductivity to several layers of AL foil. The foil may increase th
e coupling to the glass because it is soft. Removing the silk screen would achieve the same I think.

4. You can simply make the z-bars bigger diameter and rebuild the files. With say 10mm bars I don't think 30cm would be a problem. You could also fit two sets of Z-bar clamps, slide them to the top
for big builds but bring them lower to not compromise small builds.

5. MDF is a lot cheaper and easy to work with. Acrylic looks nicer and is lighter for the same stiffness I think. I am waiting for some acrylic parts to arrive to test this version. Acrylic will also be more stable in changes of hu
midity, but I think you can seal MDF with acrylic paint to achieve the same.

6. Yes I will do that when I have hooked it up to some standard electronics and firmware.
What is your estimated cost of the unprinted parts?
The cost depends a lot on where and how you buy the parts but is should be about the same as an LM8UU Prusa. Same motors, electronics, and bearings. The rods and belts are slightly shorter in total I think. The frame is cheap if you use MDF and probably similar to the Prusa studding. The fasteners are more numerous but smaller ones, and don't cost much anyway.
Thanks, so what was your overall cost?
I paid about
£13 for MDF. Everything else I already had. I keep a small stock of motors, bearings rods, belts, fasteners, etc, some of which I bought a long time ago, so it would be hard for me to find all the prices.
Thanks I appreciate it
nophead, from dxf file frame base is almost 1.2mx1.1m in dimensions. Is it really that big?
No the sizes are as stated in vitamins.txt. I have just loaded the base into Rhino and that is correct at 468 wide It looks like whatever you are viewing it with is taking the units as inches instead of mm. Are DXFs dimensionless like STLs? I have never used them before.
Check again. I measure it at much closer to 450mm... using Qcad to measure.
This looks fantastic - I'm excited to build one, with a few slight modifications. When will the .scad files be available?

Two questions -

1) The bolts in the base dont' appear to have nuts on the bottom side, are they supposed to be threaded in the MDF/acrylic?

2) I can't see in the smooth rod holders how they are adjustable to make sure the rods are parallel. I know you have mentioned this feature - is it just mi
ssing from these renderings, or am I missing it?
The scad files will be up when I have finished the build scripts and sussed out git. Hopefully this weekend, but I have to make two new hot ends first.

1) Yes they are M4 tapped for acrylic and No6 wood screws in a pilot hole for MDF. You can also tap MDF M4 and it works very well.

2) If you look at the bar-clamps.stl you will see the screw holes in the base are actually slots with 2mm of movement side to side.
Are these printed parts the same as for the MDF version?
More or less. The hole sizes might be slightly different as the screws go from M4 to No 6 wood screws. However you can actually tap MDF M4. The sheet drawings will change as the sheets are thicker, which moves the gantry back a few mm, and the pilot holes get smaller. Also the BOM changes of course.

Note that the MDF version shown on my blog is slightly bigger and uses 10mm rods and bearings.

If you wait a couple of days I will publish the source with scripts to make all the STL and DXF files and the BOM. You specify the build volume, sheet materials, motors and rods, etc, and it makes custo
mised versions of all the parts.
Added a bill of materials.
I added the sheet drawings in DXF and PDF.
Hi Nop head, it's like my happy day to see this! Will you also be providing one for

M6 rods/NEMA14s as originally forecast as NEMA14s are a lot cheaper than NEMA17s.

I know, some people are never happy! Sorry about that.

Are you also going to provide the dimensions for the acrylic/MDF? are they different for the M6 version vs the M8 version. I was going to get some M6 threaded rods from Screwfix this week as well!
Where can you get NEMA14's cheaper than NEMA17, I have always found them more expensive?

With the source files you can chose any combination you want but all the sheets and plastic parts will change. As one of the predefined configurations I have a Huxley sized machine with M6 rods and NEMA14. It needs a small extruder designing as it looks a bit silly with a full sized Wade's and the
re is no justification for using the smaller motor on X unless the extruder is lighter.

I am currently working on scripts to build all the files automatically as it takes a long time to export everything by hand.

I will add the files for the acrylic M8 version to this thing.
Where's the .scad files?
As stated I will publish them soon. Probably as a link to github.
I wonder why there are no printable 3D printers in the Thingiverse Features Things O:-)
The other difference with Printrbot is the vertical carriage / x-axis. That gives smaller printed parts but I prefer to have the carriage horizontal with a low centre of gravity.
I was thinking of it as a sort of upgrade path. A printrbot is meant to introduce people to 3dprinting on the cheap, and if they eventually want better performance but don't want to build a new machine from scratch (possibly recycling parts like the motors and electronics) they could easily convert their printer to something that more closely resembles the mendel90.
The unique thing about a Printrbot is that it is a Mendel style machine with no frame and the Z and Y axes are unsupported.

If you add a frame you would end up with a machine like this. You don't need the chunky Z motor brackets and the studding connecting them. You wouldn't use the Y-axis where the rods move and the bearings are stationary because that makes the Y carriage (and hence the depth of the machine) bigger a
nd heavier.
I did a quick search using the tag system and of the 63 things that were tagged "3d printer" the following printers have been previously featured. the maker bot cupcake, the makerbot thing-o-matic, the ultimaker, and the CUBE(printable). did some more poking beyond that and found the reprap wallace(printable), the prusa air2, and the 3D printed full size makerbot(printable).

there is probably more but the prusa and reprap tags are used so liberally(basically any thing that can be printed with a prusa seems to have a prusa or reprap tag) that wading through and finding the original upload is beyond my attention span.

p.s. have you considered making a version of the me
ndel90 that bolts a mendel90 frame to a wallace or printrbot?
Awesome! Definitely looking forward to seeing the other sizes, BOM, etc. Keep up the great work! :D
Awesome! Definitely looking forward to seeing the other sizes, BOM, etc. Keep up the great work! :D
congrats on the release! looks really well thought out like everything else you've given this community :D
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