Ender 3 Mod - Y Axis Tensioner

by Cornely_Cool Sep 13, 2018
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Tolerances are off, It was extremally tight sqeeze even after sanding it down,broke when tried to loosen it uop... rubbish..

Tolerances are ok, and are the same for all my tensioners.

If you break the screw is because you print it in vertical, if you print correctly in horizontal is practically impossible to break, due to the layers orientation. The body is over-dimensioned for the stress that have to support, so I dubt that in normal conditions you can break it...

Please find on the internet how to calibrate your machine and start learn...

Anyway, thanks for be so polite...

Hi, I've just installed your CR10 X tensioner on my Ender 3 using the original M8 screw and it fits perfectly. Will it be possible to print the same M8 screw for this one?

Thank you!

EDIT: I printed it for testing and it worked

Cool im curios it too thank you, does bed hit this one when goes full front abother design whic i printed bed hits tensioneer and i need to modfy it

The bed doesn't hit the tensioner in my case.

thank you ill try :)

Here is a tip if you have trouble getting the bolt through the spacer. Heat up an M4 screw with a lighter and melt it through, then it'll fit like a glove.


these fit together real nice, I printed as they came up in cura, as shown in your pics, vertically, however, the slot in the body pinches the bearings/rollers so as they cannot rotate freely, also, it almost has the belt too tight without even putting the knob on though. so that kinda defeats the purpose of having adjustability. Thanks for the effort though, I printed the y axis tensioner looks like it wont have the same issues. thanks.

Thanks for your feedback!

Can you show me a photo of where the slot pinch the bearings? Just for understand...

Is better if the screw is printed horizontally, give more strenght.

Best I can do is hold the y axis body against the x axis body, the y axis body is perfect, i measured the slot in the x axis body to be about 1.25mm narrower than the on on the y axis body, and yes I get the strength thing I didnt realize that was the recommendation until after I printed

Ok, so the problem is on the X axis, not in the Y...so we are speaking of another tensioner

i dont get it how people are happy with this. was there a previous version that was different? the bolt is not fitting into the body (that's for start)
then the bearing do not fit between the bolt 'fingers'. oh come on

Man, the opening between the 2 arms of the screw is 9.8 mm, and I will keep as it is due to the fact that if you need some more clearance, you can sand it a little (I prefer to have a tight fit on the bearings).
For the body fitting, I can say that, is a common problem on printers that have not been tuned correctly. On the model, the clearance is about 0.1 mm all around the screw, so if you can not reach this tolerance, is a waste of time). The main mistake that some users normally do, is to print the screw in vertical instead of horizontal...

Anyway, thanks for your feedback.

i tested/printed many versions of tensioners. so far this is the only one that is having this kind of issues really but ok:)

I loved the design but have been unsuccessful with this thing. There are a few issues for me. Firstly, the inner part will not fit/slide into the outer mount. It is just too big/tight. If I print at about 97% then it will fit in - quite some difference. But there's another problem even at 100% - and that is that the pulley wheels will not fit inbetween the two arms - it's just way too tight, and the arms snap off because I have to put a LOT of force on them to try and slide the wheel in. So basically that arm-mount for the pully needs to be bigger. So, print at 103% it will now allow the pulley in but of course the arm/screw mid part is now way way too big for the outer mount. So, increase the outer mount size and it no longer fits onto the railing. So, it's a bust for this one. Basically what needs to happen is that the inner screw/mount holding the pulley needs to be redesigned so the pully spacing is bigger, but at the same time the diameter of the whole thing is smaller so it fits into the outer mount. And/or the hole of the outer mount through which the mid part goes is made quite a bit bigger with much more tolerance.

I saw in the picture you printed the inner part vertically - try printing horizontally. I printed 6-8 of these horizontally when testing prototypes w/ the designer. When printed horizontally, I've never had internal parts-fit-to-each-other issues, and use 100% scale for everything.

Thanks for your post. I printed it horizontally and it works fine for me... Vertically doesn´t

Thank you for making this mod. Any chance you could create another version for the 4040 Y axis extrusion of the Ender 3 Pro? I'd be happy to try it out, and would appreciate it a lot. Cheers


Here it is mate! I will wait for feedbacks...

Ender 3 Pro Mod - Y Axis Tensioner

I love this design, but haven't had any luck fitting the screw into the body, I've tried 2 PLAs and Hatchbox black PETG, always too tight.

Can you post again the GT2 pulley version with M5? I'd like to have the GT2 version on both axes. Thanks.

Great design but I'm having issues with the tolerances between the screw and the body. I've seen your videos on the CR-10/Ender 3 X-Axis tensioner how they're coming off the built plate perfect for you, but no matter what I do I can't get them to fit together (reduced layer height, speed, temperature, scaling, etc). The screw and the cap work well after a few twists.

Part of the reason I'm printing these is my belts are slightly too long and can't be tightened enough to proper tension. Though I'm only out +0.1-0.2mm, it's made it too large. Is it possible for a "low tolerance" version of this and the X-Axis tensioner too?

which material are you using? Several users reported that the same problem is more "evident" with the PETG. With PLA or PLA+ I never had a problem. Be sure you print the screw in horizontal instead of vertical.

Between body and screw there is 0.1 mm of clearance all around, so, if you have a 0.2mm tolerance on your machine for such a small piece, you are already out...

Standard PLA which has proved accurate enough on another printer. I've also printed the screw horizontal to ensure strength and because that's what your instructions said.

I've looked at the files SLDPRT you've released for the CR10/Ender X-Axis and I don't think there's 0.1mm clearance the whole way around the screw. It seems like on the flat parts there is, but the threaded parts seem to be the same size. I need to investigate more in Fusion 360 though which can be painful. Update: Okay, there is a 0.1mm gap even on the threaded/curved part. Dimensional inaccuracy is definitely my problem and your file looks good.

Unfortunately having extra long belts courtesy of Creality means I can't really do much to improve my accuracy until I get something like this printed.

Hey try putting a zip tie on your belt to make it shorter temporarily. Or not so temporarily. Fold the end over so the teeth interlock and put a zip tie on it. Now you will have a end and it will be shorter.

Great thing, printed both X- and Y-axis.
Is there any chance that you put a hole in the screw part to fit a hexagon M4 nut?
Would be awesome!

There is no mechanical reason for put a nut.

Oh, so you just put the screw in? I got some M4x20 and put them on without a nut by now.
If I think about it, the tension in the direction of the axis should be enough to have the screw fixed.
I wondered why you didn't at least make the surface flat where the screw comes out but I guess I'll just leave it as it is now.
The screw shouldn't move by the vibration induced by the printer as it is pressed against the screw-part of your design when the belt is tensioned properly.

Would be nice though if we would use a printed part to replace the screw. If we don't need any fixation anyway, we could keep it in the RepRap spirit and just use a printed part where we can :)

In the old versions of my tensioners, I foresee also the nut, but just because another user mention it... that versions were printed in vertical, and the seat for the nut make the section too weak for be used...
The new version is printed horizontally, potentially I can also add the nut seat, but is really useless! The screw is screwed directly into the plastic (the hole is slightly smaller than the screw), and will not become lose with the time (same fit on all the versions of the tensioners, and never had a screw losen)...is not affected by torsion movements, because the sprocket wheels are working on bearings.
So, my point of view is... if one piece is useless, there is no point to use it!
Sorry, but I don’t understand your point about the flat surface...
I saw a remix of one of my tensioners, where one user made a plastic pin instead of a screw... i can understand the RepRap spirit, but anyway, in my opinion, one screw is ways better than a piece of plastic!

Been following this for the last few days as it was getting really close to what would work for my Ender 3.

I got my Ender 3 about 3 weeks back and have found that the recent revision is just different enough that none of the existing Y tensioner options would work well with the stock F688Z bearing. Creality squared up the roller bearings on Y-plate which now places the front left roller bearing directly across from the front right.So for this tensioner to work on my version the eyelet would need to be removed to match the right side of your "Body" part.

Making this modification would also make this suitable for the X-Axis as well (at least for my revision of Ender 3).

I can take pictures and measurements if it helps at all.

EDIT: Added photos

Edit2: Looking at this more, this current design is getting real close to being able to use the stock Bolt and Nut along with bearing. The side opening in the Body is wide enough to facilitate the head and nut. The "Screw" part would just need to be modified to fit the 7.5-ish mm wide bolt with 13.7-ish mm head.

Thanks for your comments and for the photos, now is more clear that the fixing system must be different than X axis version; I uploaded the new files, so this version should match the design of the Ender 3.
Is not possible to use the M8 screw, because it will make the screw part become too weak in the holes area, so i prefer to go on with solution of M4 and spacer (M4 because in this way at least the screw model can match between my other different designs).

Anyway, at the end of the "beta" versions, I will release also the Solidworks files, so you will be able to modify them as you like!

Let me know...

Looks Awesome! Thanks! Got the new body printing now and will report back after work.

Not sure if you have an X Tensioner out there, but I'd suggest keeping your last version for that. It's working perfect on my X.

Please, can you take the dimension in the attachment? Seems the new double support of the ender 3 is different than the old one (and is more correct, because make the belt stay parallel to the v-slot profile...

20mm between top bolt and lower bolts on center.

Hi Cornley_Cool were you going to do one more tweak based on the 20mm measurement?

I think it is already 20mm. I have it printed out and working fine. I suppose the "axle" hole could move up a mil (or half mil) to more center the belt on the rail. But the upper teeth have JUST enough clearance to not scrape.

Hi, thanks for your feedback!
The actual position is the same as the orifinal tensioner, this is the reason why i didn't modify again...

anyway I am not a fan of the "inclined belts" as per Creality projects.

Makes sense. agree on the incline - Some of us tilt the original creality tensioner upwards in the slot to get closer to parallel vs inclined belt since it gives you some amount of play by not fully tightening the bottom tnuts. That way it's possible to get very close to parallel or level. However this end of the belt being parallel doesn't matter as much as the end between the motor and the y carriage. Will print and try out - I have been using your slightly older single height version which worked great for me.

No, I think is ok as it is.

Anyway I didnt receive any feedback...so, I still waiting to know if is ok or not.

Works great, and posted the make! https://www.thingiverse.com/make:549949

Ender 3 Mod - Y Axis Tensioner

Anyway, as already wrote by another user, seems the screws need to be lifted a couple of mm to make the belt parallel to the extrusion beam.

Yes,Lifting the screw a couple MM to make belt parallel to beam is cosmetic but not necessary for function, if belts are not rubbing.

Right now, my belts just barely rub but that is because it is mostly in center of the channel. (see pics) If others have printers where belt is more off center offset, they will rub, and this is where being parallel to extrusion would help.

Added a version 2 of the body with a 2mm offset....in case you want try it!

You can find the X tensioner in the Remix Link, is done for the Cr-10, but can be used for the Ender 3 and similars too!

Hi, so the stock bearing I think is M8 Size, but caliper measures 7m (but I'm not sure how caliper measurements translate to M8). The reason I think It's M8 is because its on the BOM: https://github.com/Creality3DPrinting/Ender-3/blob/master/Ender-3%20Mechanical/Ender-3%20BOM.XLS

Note that Ender-3 is open source now. All the drawings, specs, parts, etc are here:

I do have another GT2-20t pulley (same stuff that I used for the X-Axis) that I can use. This may make it simpler. Which do you think is better? the stock M8 or the Gt2-20t with 5mm bore? (same as X axis.

For me, the best solution is the Gt2 pulley, don’t know if there is enough space for a M8...

Okay cool then gt2 16t 5mm bore should work great. Just like it did on the X axis.

Oh and this tensioner uses m5 hardware but has a 3d pritned bushing for the m8 stock idler pulley. Just an idea.


ENDER 3 Belt tensioner

Ok, updated the files, now you have 2 versions, one for the GT2 pulley, and one for the bearings 4x15x5mm (what i used for the Cr-10).
The pieces of the 2 versions are not compatible, due to different size of the "wheels".

In case you want to use the original bearings F688Z - 8x16x5mm, you just need to use the "bearing version, with a spacer (i didn't draw it because i don't want loose time in find good tolerance for the bearing side...), so, basically is a tube with 4 mm internal diameter and 8mm exterla diameter; lenght will be 9.5/10 mm.

To be considered that the belt position is changing between the three versions, due to the difference in diameter of the wheels.


Thank you for volunteering your time and skill to design a part for a printer that you don't even have. Much appreciated. Wanted to check one last thing as typing is easier than printing - the updated parts were designed so that the belt goes over the extrusion lip on the top right? and returns "inside" the extrusion at the bottom? It's basically opposite of how the X-tensioner works with the belt outside extrusion lip on bottom and inside on top. Pictures attached for clarity.

Ok, so now you hve only one version, that use the OEM bearings, a M4 screw and an adapter; The bearing are at the same OEM position, so should be no problem.

If you want use a GT2 pulley, you will need to draw a new body, with an offset to recover the diameter difference.

I have a dubt about the lenght of the fixing braces, in the Cr-10 I had to make them shorter due to interference with the bed wheels in the maximum forward position of the bed, please check this for me!


You are absolutely right! I did not realize that the wheels do interfere and does not allow the bed to fully move to its build area. Note that the right side wheel is further forward than the left. I've attached the Y plate from the open source file. The Bed size is 235x235mm with 220x220 official printable area but many people can do 235x235 as long as they center the nozzle perfectly.

Body modified, reduced braces lenght of about 7 mm ( if you can/want, try to print the pieces, sorry but I don't have time to check all the drawings of another printer...), anyway the body should be strong enough, so no problem.

If this is not enough for allow the full movement, probably will need to go for a body sypported on the low part of the frame ( like I saw in other projects, but really looks "bulky" so I prefer not to do it if not strictly necessary! )

Hi Corely_Cool - I am an idiot. I messed up. I did not account for the bed coming forward and how far the wheels come forward. See pictures, there is no room/clearance on the right side.

So actually your Cr-10 X-tensioner would have been the better place to start, and shorten the left side a lot (or have the v-slot protrude out more to hold the tensioner)

I'm sorry. I understand if you don't want to work on this anymore.

note that in my pics I have my belts quite tight using the stock tensioner.

Ok, design updated...at the end of the story it looks like the X axis, but with shorter braces...
let me know

Works awesome! Take a look. Looks so clean and professional! Note I have a older ender-3 with offset wheels. Newer ones have even wheels and a double sided tensioner. So this may not work with the newer ones.

[EDIT] - I scrolled up and saw someone else commented!

This works perfectly, but maybe you can keep the GT2 20t version up? So people can choose whether they want to use original hardware with the spacer, or GT2t. Because while I do like the original hardware, I think the Gt2 closer fits the belt (like you originally said) and may better constrain the belt motion from wiggling back and forth. I may want to switch back to GT2.

I also saw your comment about M8 version not recommended - I understand that - and observe that when printed on its side rather than vertically the layers are stronger. Especially if you increase the perimeters, so the strain is stretching the filament, not trying to separate the filament layers.

Since we're at a point where its out of beta, I will post your thing on the Ender-3 FB forums!

I am a little lost in the comments, since they are not in cronological order!
The differences between the new and old serie of the printer are clear, the last design of the body will cover both of the models and will look more “fit” for the v-slott 4020.
Try print it out!

I have to modify the position of the bearings, because the belt is not aligned with the v-slot profile!

I see... so, basically the functioning with the original bearings is the same, with smaller bearings or gt2 pulley will result in an offset of the belt.

I will take a look on it.

Anyway, can you take some pictures in the motor side of the Y axis?

Hi, This is a picture of the motor side. Note that mine is not stock, I added a top idler pulley to align the top of the belt. (https://www.thingiverse.com/thing:2919244)

Ender 3 X & Y Axis Idler

So, I tried printing it and fitting it on my Ender-3. I fitted your updated CR-10 X-axis tensioner to the Ender-3 with M5 hardware and a 20t 5mm smooth idler and it fits beautifully and works perfect.

Some notes

  1. The screw/puller is sized for a M4 screw. However, the Ender-3 uses M7 screws for both the Y and X axis.
  2. I thought, oh no problem, I'll just print out the puller/screw from the CR-10 X-axis tensioner which is sized for M5! So I did htat.
  3. I then realized when I couldn't jam the CR-10 M5 screw/puller in to the body (but the M4 one fit in just perfectly and fine) that some top groove dimensions are actually different and the CR-10 M5 screw/puller does not fit into the Ender-3 Body. The CR-10 M5 screw is too small on the groove. See attached pictures.

So I guess my feedback is, may I have a screw/puller for M5 threads too, that fits in this body? Thank you in advance!

And also one random thing I noticed from the Cr-10 X-Axis mod - It works perfectly with the idler screw threaded in the plastic, but may work itself loose over time? Maybe a nut trap at the back? This is the only only thing I can think of improving, it works perfectly fine without it.

As I don’t have this printer I supposed the components were the same of the CR-10, so :

For my CR-10 X axis I changed the original bearings with a GT 2 pulley, that have different overall dimensions.
For this tensioner i considered the original double bearing, that is why you cannot swap body and screw (the central slot of this version is 11 mm (for double bearing) the cr10 version is 10mm (gt2).

The thing of the traped nut, i decided to go without it, because I saw in the previous versions, this solution was reducing the strenght of the screw (printed in vertical). Anyway, i used the version without nut for quite long time without problems (at the end of the story, the pulleys are working on bearings, so they don’t turn on the screw).

So, basically, this printer have the same oem tensioner for both of the axis?