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Tevo Tarantula Single Motor Dual Z Axis

by NinjaCookie, published

Tevo Tarantula Single Motor Dual Z Axis by NinjaCookie Jan 4, 2017


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These parts are designed to give the Tevo Tarantula Dual Z axis from a single motor. I won't go into the pros and cons here, as it's complicated. No more motor couplers though, so makes things easier! It is a little more fiddly than dual motors, although requires no extra electronics.

They are remixed from the excellent brackets by thingirob. I have remodeled these parts completely so they do look slightly different.Please note I have added tolerances where the original parts had none, these should print fine without scaling.

You need 2 of the Z Nut holders. I have included x2 in the name, but just to remind you.

Please note the photo I have included is v1. I have updated the designs since then to improve them based on my experiences.

Additional Hardware

You will need the following parts to put it together. Many of the screws etc. were spares from the kit, or left over from other changes I have made for the printer.

  • 900mm closed loop GT2 belt. I found a seller on AliExpress that made these very cheaply. Link may disappear if they stop selling them.
  • 4 x 608 Bearings
  • 2 x 400mm lead screws. Threads need to match. Also need standard brass nuts.
  • 2 x 8mm bore 20 tooth pulley. Seller I used
  • 5mm bore 20 tooth pulley for motor. Seller I used
  • 2 x Smooth Idler Pulleys w/ 16mm diameter. I had these so no seller, although commonly available. Basically same pulley used on other axes of Tarantula.
  • 2 x 25mm M5 Screws. Can be longer.
  • 2 x Nylon spaces or nuts.
  • M5 washers (to use to space idlers correctly. I used 4).
  • 2 x M5 nuts, ideally nylock nuts.
  • Nema 17 motor from original Z axis.
  • 4 x M3 screws to mount Motor (should already have these with original brackets).
  • 8 x M3 screws and nuts to mount brass nuts.
  • M4 T Nuts and screws. I won't include the amounts, however I would suggest using a minimum of 8 on each bracket, and 2 for each of the Nut holders. This would be 44 of each.
  • Optional 2 x 8mm lock collars. The screws are held in place by gravity, however you can add lock collars underneath the upper bearing bracket. I do not use them, as in the event that the print head crashes into bed, the screws lift out of the bearings and prevent damage.

Putting it together

Brackets and Lead Screws

  1. Put together the printer with the brackets as normal. Take care to try to align the brackets as best as possible.
  2. Insert bearings into relevant spaces in brackets. Should fit well, although may need some sanding depending on how well your printer is set up.
  3. Add brass nut to Z nut holders. Use M3 screws and nuts to securely fasten.
  4. Attach 8mm bore pulleys to end of lead screws and tighten grub screws well.
  5. Insert Lead screws through upper bearings, then thread on Z nuts, finally push lead screws into bottom bearings. If using 400mm screws, none of the screw will come out the other side, this bearing just supports it at each end.
  6. Secure z nut holders to X axis. Care should be taken here to measure the distance from each side to a fixed point on the frame (top or bottom, not the bed), to ensure it is square. Use the lead screws to adjust up and down manually. It is easiest to have the T nuts in the slots properly, but leave them loose while adjusting, and tighten only at the end.

Motor Mount

  1. Attach stepper motor to motor mount. M3 screws should still be a little loose, letting the motor move along the slots.
  2. Mount should then be attached to frame. Position as centrally as possible.
  3. Add pulley to Motor and try to level with pulleys on lead screws. A straight edge like a ruler can be helpful here.
  4. Push M5 screw through relevant hole for idler pulley. Add the nylon spacer (or nut if using instead), then add washers (2 for each). Finally put on the pulley and add final nylock nut. These also need to be checked for height against the other pulleys. You may need to add or remove washers to get the heights right.
  5. If the X axis is straight now, you can attach the belt. This should be threaded around the pulleys as show in the pictures. The last pulley can be a little tight due to limitations in the frame, but should go over without too much trouble.
  6. Tension the belt by pulling the Motor back in it's slot then tightening the screws. Given how this works having really high tension is not as critical as it is on the other axes.
  7. Manually rotate the motor pulley (with care!) to ensure the mechanism moves freely, and doesn't bind up.

Firmware changes

You need to invert the Z motor direction in the firmware for this to work correctly. That is the only change you need to make (unless you have changed thread pitch at all).

Important Notes

It has been pointed out to me that unless alignment is perfect, having the screws supported on both end will lead to binding. I don't have a problem with this myself, however if you do, the best thing is to simply pop out the bottom bearings and not use them.

As with any modification to a printer, make sure you test well, through the whole range of motion of the Z axis to ensure it moves freely and does not bind.

You may need to up the current to the Z motor slightly, as it is working a little harder than it was.

I needed to buy a longer Motor wire due to moving the Z axis. Depending how you mount your electronics, you may not need to do this.


I greatly appreciate any feedback you have! If you have an problems, I am happy to help where I can.

Improvements from v1

  • Removed some material to improve strength.
  • Added ribs to upper brackets to improve strength.
  • Fixed an alignment issue with some holes.
  • Adjusted hole spacing under bearing blocks so all previous holes present.
  • Increased travel for motor to allow more belt tension if required.

Print Settings


Tevo Tarantula


Doesn't Matter








Recommend Concentric supports for Top brackets as easier to remove. Z Nut holder does not require supports.

Unlike thingirob brackets, I have allowed tollerance in these parts where required, so should be able to print at 100% scaling.

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Hi, I see you are improving your design. I recommend you to put radiuses where the bottom plates meet the perpendicular walls to help spread the stress as mine cracked at those places. My layer adhesion sucks, but even with good adhesion, this would be an improvement. I like your design, I am using it just as bottom brackets for untill the loop belt arrives.

FYI - if you want to keep a mechanical end stop just you can with this mod. All you have to do is remove the right angle aluminum bracket on the 2040 extrusion and cut part of the original acrylic mount so it clears part of the bottom mount. That's what I have done on mine and it works without any trouble.

Would this work equally well with thingirob's bottom brackets in stead of yours?
The underside of the lead screws would be floating in the air as in the original Tarantula setup.

Can I use Idler pulleys with teeth?

It is possible but in this case it is not required, the idlers are on the smooth side of the belt. There are arguements against using toothed idlers as they can cause issues when it comes to tensioning. Better people than me have argued this online.

Does that motor eat up some of the Z build height?

It does unfortunately. The next versions moves the motor so hoping to eliminate this as much as possible. I will also include an adaptor to reverse the motor mount if people prefer.

Will that not save some printable Z height if the motor is brought to the top like other people have done? (i.e. when the board stand off were used)

Yes it would, hence why I am planning to include it in the next version. Up to people to decide how they wish to orient then. For me personally I prefer the motor below due to an enclosure.

Great design. I've just finished printing top brackets. Left side bearing hole seems to require sanding to fit bearing in. Right side is fine.

The tolerances should be the same on both so could only put that down to printing differences. In all the versions I printed, some needed it, some didn't. Tolerances with 3d printers are always tough to crack.

I wish I had the foresight to see this issue before printing and installing all these parts, but I am now at a standstill. Where does the -Z limit switch get mounted?

My apologies, I have autolevelling so did not plan for the limit switch. It is something I am considering for the next version

For those interested in bottom mounts mounted by screws onto the 2020 and 2040 extrusions, I've made them here: https://www.thingiverse.com/thing:2504887

Bottom Mount for Tevo Tarantula Single Motor Dual Z Axis

Do you have the X axis motor mount plate design. From your pictures. Mine snapped from the screw holder being to tight up to it.

There are a bunch of designs on here to look at. Part of the reason I left them off my 3d model was because so many people have different variations. The designs I made work, but are a bit lousy, with too much flex in them. I am working on a simple 3 wheel design at the moment which I will update at some point. I suggest you look around and find what works for you.

I made this so you move the motor out of the way and do not need to change the motor settings in the firmware https://www.thingiverse.com/thing:2450016

motor mount
by XennoNL

This is a great simple idea. The whole mount being in the centre at all causes issues with cabling, bowden etc. so it's not idea. Have a version 2 in testing at the moment that fixes the issues of the first I hope.

Sorry to be smothering you like this but I am really holding on for the update any tentative timeline for the release?
Thanks and great work!

I am almost at the point of printing this one off so if you think you will be ready to release version 2 (3?) and it uses the same part list I will hold off. Any update?

i really like the look of this
i have now ordered most of the parts listed in the description

thanks for this

Just wondering would it be possible to change this to a gear setup? might solve the torque issue with single motor having to handle all the load

This is something I have considered, however I'm not a massive fan of small 3d printed gearing. Getting meshing to work well can be a problem. Would definitely be a good idea though if this can be fixed.

i have been using this mod for a while now. with good results. but there are some modifications needed to make it better.
1 maby you can think of a way to move the stepper motor out of the way maby with an extra bracket so you can mount it upside down? that way the teflon tube does not get tangled and you have extra printing hight.. maby incorporate the motor bracket into the top right bracket?

2 the top bracket need to be shorter because now the wheel guide plates hit the brackets on the top.. and block 20mm of printing realestate :)

thanks for this great design!

Thanks for the feedback. I'm testing version 2 at the moment which fixes these issues and reduces the need for supports. Plus integrates the tensioner mechanism as well. We'll have to see how it works.

how do you invert the motor firmware?

Jul 6, 2017 - Modified Jul 7, 2017

Hi, like the design. Was working on a similar one, but will be using this instead. Read the comments regarding the danger of binding due to misalignment of the bearings. Did a quick test of some chinese 608Z bearings I have. And I found they will allow enough angular misalignment that I think this shouldn't be a concern as long as the prints are dimensional correct. Or printed in the same orientation. Any chance of you publishing the cad files? I'd like to design a Y-carriage with a back plate that integrates the Z-nut mount. And having the cad files would make this easier.


Thanks for doing this awesome mod! A quick question – where can I get the STLs for the brackets you used to raise the y axis as shown in the center of image 3? I can't seem to find them in the Files section. Thank you :)

Thans a lot! iv made it, and realy love this mod all fets and woks great.(Модернизация прошла успешно, работает на ура, жесткость возросла в разы. вобщем рекомендую запариться)

Какое количество шагов в конфиге указано у вас, или подскажите как посчитать при комбинированом варианте ремень и ходовой винт?????

Is it possible move motor off the printing area to top to top rail because i have fanduct which need space on top so i cant print high prints because fanduct hit motor

Does it really work?

Yes, I have been using it on my printer for several months now. I am still making improvements to the design and hope to post an update when I have finished my work putting in a v6 and printed the parts again.

How much slack do I need to take out of the belt? I would like to run the motor with a 16-tooth gear and the lead screws with 60-tooth gears to get more precision out of the whole thing.

Given that arrangement I would say you would need a different length of belt. Would need to run the figures through my system, but I would expect you need something longer given the larger diameter gears on the lead screws. Saying that, I don't think you can get that much more precision out of the system given the moving build plate and the gantry. I'm not sure of the maths but the 20 gears given precision at least down to 50 microns. I doubt you will get more precision that that out of this printer.

Does this work with the stock lead screw length(375mm)? Or do you really need a 400mm one?

how you mount z endstop i can't mounted it

You will need to use longer screws, and perhaps use a different setup. There are a number of the on here. My apologies, I use automatic leveling, so don't have a physical Z end stop anymore. I will have to consider this in the next version.

My printer is going to arrive in a few weeks and this will be one of the first things I will make.

P.S. Like your username

A very nice project

Are you going to publish the x-axis drawing suitable for the project

Hi, not sure what you mean? I have included the brackets to lift the X axis. There are a bunch of other X axis mods that will suit this.

I want to remix this for another printer can you tell me what the distance center to center of the lead screws so I can adjust the belt length required?

Yeah, no problem. Center to center of screws is 350mm.

how easy is it to print the bottom right and left brackets with the overhang that they have? i am not sure my printer would be capable of such a feat, but i really do like this design.

Jan 25, 2017 - Modified Jan 25, 2017
NinjaCookie - in reply to reicha23

It needs supports unfortunately. I did have a version which didn't but was so much plastic wasted. I am working on a version that uses Pillow block bearings, so should avoid the problem of printing the brackets like this.

I am looking forward to seeing this new version. Do you have any time in mind when that one will be done? I am definitely going to use this design as it is one of the best I have seen yet. I have been wanting to convert to a duel z for quite a while and this looks like the one i am willing to try.

Sorry for not getting back to you. I'm still working on it at the moment, I've had the board of my printer die on me, so had to get a replacement. It's back up and running so will be printing my first set of test pieces this week. Hope to have an update by the end of the month.

Im curious if you already made any progress in the pillow block bearing design :). Im planning on buying some of them to create a dual Z on my Tevo

looking forward to it. I think I'm going to be buying the parts for the upgrade here pretty soon.

I just found this and it looks so much more stable than the other z axis I found on here. Now I just need a longer belt and some bearings (the other one uses those pillow blocks).

Thank you for this. I was going to start designing this myself.
As far as the bearing bottom and top, you could use Bore Diameter Mounted Bearings Ball Bearing Pillow Block (http://www.ebay.com.au/itm/Dia-8-10-15-17-20-25mm-Bore-Diameter-Mounted-Ball-Bearings-Pillow-Block-Great-/142140997733?var=&hash=item2118438065:m:mv7OnicwOF4mN2o4JfNCVeQ)
This would allow for slight misalignment.
Have a great day

Jan 4, 2017 - Modified Jan 4, 2017

There is NO DISCUSSION compared to two unsynchronized Z steppers which IS A DESIGN ERROR !
I did that 10 month ago for my Geetech Prusa (one of the first improvement) and put it recently here as it applies to any Z bed.
I did it in a simpler manner as I don't need idlers.
BUT YOU MUST NOT hold the lead screws at the bottom as it is unnecessary because it adds a constraint that that will require perfect alignment otherwise it will lead to binding.

At last common sense seems to reach the 3D printer hobbyist :)

BTW: The Tevo Black Widow uses the same setup as yours, you should mention it.

Thank you for your feedback. I agree that the 2 motor solution is not good, and within the confines of this printer, this is the best solution I could come up with for now.

I understand your point about alignment, and don't have any issues myself. I will update the description to suggest that if you have a problem with binding, then remove the bottom bearing. That should be sufficient.

Jan 20, 2017 - Modified Jan 21, 2017
ant0ny - in reply to NinjaCookie

Removing the bottom bearing with your current design will cause more issues. Where people (including my own printers) remove the bearing to negate any Z axis shaft wobble is when you have 2 Z motors and so the forces on the shaft are released but the shaft is supported by the motor and coupling... this is proven as a sound solution to the common problem of not stright leadscrews.

If you remove your bearing on your setup as you have it now the belt tension will try to push the bottom of the zaxis leadscrew in the opposite direction to the belt tension which in turn will cause all sorts of forces not wanted on the Xaxis.

MKSA's design will fail eventually (without bottom bearing) as it wears his bearing out but I would consider this an acceptable loss due to the cost etc but for people using his design idea with less mechanical knowledge will end up hitting issues which will take them a while to discover.

Tevo Black Widow is the same as yours in principle but in reality uses the Openbuils C-bean Actuator as the base for their Zaxis, which is a very robust system designed for systems up to 1m+ in each axis.


Oh and I just forgot to add I like your design and I will build one of these soonish but most likely a remix with the ideas discussed but with a better mechanical approach in relation to removing the bottom bearing.

Yes removing the bearing can cause potential issues, but only under very high tension from my test. Why you would need to put this design through that I don't know. I'm currently reviewing it myself using pillow block bearings as mentioned previously. This would help with the alignment somewhat. I have looked at mksa's design and the parts for his I don't think would stand up to tension that well. I have followed the openbuilds actuators for some time and they basically all run one the same principle but with higher manufacturing tolerances. I'm still testing this, and have had mine working really nicely for a while now. I will be interested to see what you come up with regarding the bottom bearing.

Finally, my ordered parts have arrived. I had ordered both the regular bearing and the Pillow block as you and Milabar mentioned. ("I'm currently reviewing it myself using pillow block bearings"). Will you be uploading the STL that uses the pillow bearing or should I figure that one out by myself? I have all the parts as you mentioned. but a bit confused based on all the discussion. I feel its a good design and worth building...

Comments deleted.
Jan 22, 2017 - Modified Feb 2, 2017
ant0ny - in reply to NinjaCookie

Pillow blocks are good idea but maybe not needed as long as you have a way to align the top and bottom bearings.

If someone was to adopt a single bearing then the self aligning type bearing blocks cant be used on their own for the obvious reason.

As far as the argument for the tension it comes from 2 thoughts. 1 people who build and modify their printers are not all engineers and don't always have a feel for how tight to have their belts. So a safeguard. 2 Scale-ability: bigger and cheaper beds are hitting the market and the beauty of an open builds system is you can adapt. Then if you start to add duel extruders etc etc all add weight to the X axis and Z axis has to cope.

If I was to through a spanner in the works here... if you wanted a better linear Z axis with minimal "Z wobble" or "Z banding" then you would go with Z axis driven by Belt only and not leadscrew. The issue here though is when the motors are "off" there is nothing to hold the weight of the X axis up and it drops.

I just deleted repeated comments of mine... weird.

Thanks, I appreciate the comments. Given the nature of using a low cost 3d printer, aligning the top and bottom bearings isn't so easy. Like you say, most aren't engineers, so won't necessarily have items such as dial indicators to help them get the alignment just right. This is why I am looking at the pillow block route, given that I can forgo the big print of the brackets potentially, only needing the 1 add-on. I am also considering Thingirob's gimballed nut to help as well.

Understand the tension, however the main person I have made this for is me. The group wanted me to release this, so that's what I'm doing, but had never really planned to do so. Hence why X Carriage weight etc. are less of an issue for me.

For the best X axis, I would say dual ball screws are the way to go, not belts. But then there is the added expense. I think the dangers if a belt drive outweigh the benefits, mainly for novices though, especially when weight gets added.

Yes I didn't mention ball screw mainly because of cost and also size there seems to be very little in smaller sizes. From what I have read belt driven Z axis gives very good results...not that I have seen it myself.

FYI someone pointed this at me yesterday while talking about your design... http://3dwrx.com/TrueUp/DIY/ some neat little ideas about the position of things and the clean lines. The idea about the z axis slide blocks is an obvious mistake... just use the openbuilds "plate and wheels" would make this pretty good.

Thanks, I appreciate the comments. Given the nature of using a low cost 3d printer, aligning the top and bottom bearings isn't so easy. Like you say, most aren't engineers, so won't necessarily have items such as dial indicators to help them get the alignment just right. This is why I am looking at the pillow block route, given that I can forgo the big print of the brackets potentially, only needing the 1 add-on. I am also considering Thingirob's gimballed nut to help as well.

Understand the tension, however the main person I have made this for is me. The group wanted me to release this, so that's what I'm doing, but had never really planned to do so. Hence why X Carriage weight etc. are less of an issue for me.

For the best X axis, I would say dual ball screws are the way to go, not belts. But then there is the added expense. I think the dangers if a belt drive outweigh the benefits, mainly for novices though, especially when weight gets added.

Awesome. Thank you!!!