MakerBot Print is our newest print-prepration software, which supports native CAD files and STL assemblies,
allows you to interact with all your printers via the Cloud, and many other exciting new features.

Download Now


CR-10 Mod - X axis Tensioner

by Cornely_Cool Apr 9, 2018
Download All Files

Thing Apps Enabled

Please Login to Comment

I had trouble fitting mine, but managed it by removing the x axis mounting screws. Then when the belt was fitted into the slot, remounted the motor.

The design has been done around my machine, and I can say that fit most of the others (you can see the photos of the makes).
Unfortunatly,sometimes creality (or other brands), send out the printers with slightly shorter belts (production issues? end of the roll? I don't know why...). You can either change the belt with a longer one, or use a different model/remix of the tensioner.


will this work on a cr10s pro?

The shape of the plates is the same, and the v-slot is same size... so I suppose it can be used on a cr-10s pro.

Hello, is it good also for ender 3's stock bearing or I must to put necessarly a gt2?

The ender 3 stock should use the same bearings of cr-10, so you have 2 options...version F688z with m4 and spacer, or F688z with the oem M8 bolt.

this print is a hard one! i have attempted 6 times now with CT-10 X tension Version F688z + M8 version.

my issue is the knob doesn't screw on all the way. the tension bolt doesn't even go in 10% to the X part. my printer is fully calibrated and running well.. i have no idea why this model has been pain in the arse. :(

maybe post a pic of the print...if there are some macro mistakes we will notice.

Print the screw, in horizontal, the knob in vertical.
Slowing down the speed, you will increase the precision.

First of all: thanks for sharing this, I really like idea, execution and looks. Which is why I definitely had to at least try to print this. And failed miserably.

+1 for the need for higher tolerances (.2?) even though you seem to see this as a complaint and that means I'm unable to peoperly calibrate / use my printer. The irony is that I'm trying to improve the printer with -- among other things -- this tensioner, so obviously I came here with my printer not working perfectly (yet?) ...

Thanks, but anyway the base idea is not mine, it start as a remix, that evolved during the time!

For the “tolerances” issue, my opinion is that is already good as it is, due to the fact that if you have too much clearance between the screw and the body, the scrw will not stay coaxial to the horizontal axis, but it will be allowed to work a little inclined. The result is that potentially you will have the belt that “travel” left and right on the pulley during the x axis movement (you can see well this effect on the Y axis idle pulley).
Another issue can be the knob that will not tight well the screw as it is now...

I will consider the fact to prepare one model with bigger tolerance as also other people requested, maybe just for test...
...as always, when I wil have some spare time!

Hey man can you perhaps make it about 5-8mm shorter for those of us with the SHORT cr10-10s belts that it does not fit on. PLEASE PLEASE

For have it shorter, you will have the body weaker...

5-8 mm is not possible, I have 2 mm "extra" where I can play (GT2 Version)

Anyway, for a couple of bucks you can buy meters of GT2 Belt...

When I will have time I will check what is possible to do...

I just want to thank you for the design and the source files. I may try to adapt for my Anet E16.

No prob man, you are more than welcome!

It was extremely difficult to print this properly (I am using PETG, and I realize this is easier in PLA, but sincerely, a part that is going to be under stress is better printed in PETG).

Anyway, my printer is quite well calibrated and I tried several prints tuning my settings (5 for the knob alone) and it still wouldn't fit.

What finally did it, was to get the knob with a 45 deg. angle, put some supports and print it that way. The outside is not perfect, but at least it fits.

Now, after looking at several other similar parts, I recon the issue with this one is that the insets for the screw part are not done in a way that is ideal to be printed - they are basically very thin overhangs and thereby extremely difficult to print in PETG or ABS. This one: https://www.thingiverse.com/thing:3270228 has much better insets to print (but otherwise is not as good as the one from Cornely_Cool).

I will look at the source files kindly provided by Cornely_Cool and see if I can alter the insets in order to print better.

All in all, it's still a great creation, and I thank the creator, it's just very difficult to print properly.

Ender 3 X Belt Tensioner 1.3 upgraded

Finally some more constructive message than usual complains...

First of all, if i must be honest, I never tried print this version in petg, due to the fact that the Pla version is more than enough solid for resist under stress...basically, everything depend by the printing direction of the screw.

The knob fitting is a problem that has been barely mentioned in the comments, and also in my tests has never come out as a problem, but ok!
I print all the pieces without supports, especially the knob, that is cylindtical and to be positioned in vertical...

I don’t think I undertood exactly what is your poi t on the threads “not done in a way that is ideal to be printed”, the threads are just a kind of trapezoidal threads, with some fillet on the internal edges, nothing of complicated, and yes, during the print are overhanging a little, but are sequential overhangs that should not affect the result (due to the tolerances given in the model.

i can imegine that the real problem is the matching between the model, and the petg or abs, that have different shrinking factor than pla.
If you have the possibility, will be interesting to try print in pla, and see the result....

The model you post is a derivate of the original model on fessyfoo, model, threads and guide system are the same.
The first versions of my modified design (I also started with the fessyfoo desig...) was practically the same, but I just correct what in my opinion were some weak points of this kind of model, as the triangular threads (with much more tolerance, so much easier to print, but also with more residual clearance when fitted), and the fact that the screw must be printed in vertical (so, layers in wrong direction compared to the tensioning axis); another issue i found is that the knob is too small to be able to tight correctly the tensioner (at least for my hands ;-P ).

Anyway, the source files are online, so feel free to study and modify them according your needs! I will wait to see your mods here on thingiverse!

Thank you very much for this great design, sir! Makes a lot easier to adjust the belt. For those who said that it's not fit or whatever, just thank the designer, adjust and calibrate your printer properly. It fits great. Again, thank you!

Hi, that looks like a well engineered design, thank you!

I was wondering if you could create a version that is compatible with the bearing and screw supplied with the Geeetech A30 printer. It comes with an M5 screw and two F625Z bearings, so the only change necessary is to decrease the diameter of the bearing holes in the "Screw" to 5mm, as the outer dimensions of the bearing are similar to the F688Z.

Just Wow! Thank you so much.

If I will have time tomorrow, I will upload the model you are asking for!

Stay tuned

Comments deleted.

Nice design, thanks for sharing.

Unfortunately the stock belts on my CR10 and CR10s are too short.

Also I recommend screws that are longer than 20mm (25 would work), 20mm doesn't make it all the way through.

i have a Stock Ender 3 and would like to print this model, i am not sure which version i need to print without needing to pay any addtional parts. i have added a photo of my current x Pully. by looking at it i should print the Version F688Z + M8?

Yep, should be the M8 bolt version.

Cool design however the screw wont fit the body.

Post photo please.

And i cant screw it either. Printed the screw horizontaly and vertical.

Hi, from the photos seems you are too high with temperature or you are over extruding (all the extrenal surfaces presents “blobs”, so I suppose the internal side and the screw threads are with the same finishing), and probably this will “cancel” the tolerances.

Die idee ist gut aber die umsetzung ist schlecht. Die Toleranzen sind einfach zu klein. Wenn man die Teile virtuell zusammen baut stellt man fest das zumindest bei der F688Z X Tensioner version kein spiel vorhanden ist. Wenn man es trotzdem druckt barucht man trotz 100% drucker genauigkeit einen hammer für den zusammen bau...

H i,
I still not understand why people write a comment without being able to use a printer..
All the pieces has been tested several times, and everything fit correctly.
Here you can find two videos I made time ago about the fitting of the pieces right off from the bed :



There is a tolerance on 0.1 between body, and screw, and same tolerance on the thread.
If you cannot print it, is not problem of the model, believe me!

Hallo, könntest du nicht eine Version mit 0,4mm Toleranz machen? 0,1 mm ist einfach zu wenig. Ich verstehe nicht warum man sowas so genau bauen muss. Die Teile können doch ruhig ordentlich spiel haben.
Natürlich könnte ich die extrusion runter stellen aber dann könnte ich auch stabilität verlieren. Bei dir scheint wohl die extrusion recht wenig zu sein. Zumindest ziehst du ordentlich Fäden. Und ich glaube das ich mit mehr als 5000 Stunden und 6 eigenbau 3d Druckern genug erfahrung habe.
Also wenn du mehr toleranzen einbauen würdest, hätten andere nicht das Problem wenn Sie ein anderes fillament nutzen, andere extrusions werte haben oder andere oder abgenutzte Düse verwenden.
Ich baue dein F688Z X Tensioner grade so um das er an jeder Kante 0,2mm spiel hat.

PS: Bei einer DIN M8 Schraube und Mutter hat man schon mehr spiel als 0,1mm. Verstehe mich nicht falsch ich mag dein Design aber 0,1mm Toleranze ist viel zu wenig.

I respect your opinion, but a model with 0.4 mm of tolefance on a sliding part, is completely useless (especially on the threads...).
When I designed this version, i printed several “beta” versions, for find the best compromise, and this is the state of the art.
On my printer (a Cr-10) the pieces come out from bed already on and ready to fit... and I am not a master in printing!

0.1 mm is on the radius, so on the diameter you have already 0.2 mm.

Anyway, on the files page, you can find also the Solidworks models, so you can edit them as you prefer.


Slightly confused as to currently which files are appropriate for a stock ender 3? Thanks

Depend what hardware you want use...

If you want use the standard bearings, go for F688Z version (m4 or m8 screw, depend which one is already installed)
If you have a gt2 idle pulley available, go for the gt2 version.


First off: AWESOME tensioners - both X and Y. Everyone should use these as they're a "must-upgrade" on Ender 3's, CR-10's (all variants.). Thank you so much for putting in the time and effort in designing such quality replacement parts... !!!

Now to my request:

Any chance you can give us a version that takes the same 20-tooth toothed GT2 toothed pully you used, but with only a 3mm bore, rather than the 4/5 mm ones you have done so far? We're having a helluva time in my country to get toothed idler pully's and can seemingly buy 20 toothed ones only with 3mm bore...

Or supply the files in some form we can edit with 123D Design or even FreeCAD?

Thanks again for a great project.


Thanks for your comment,

the editable files are already online, but are Solidworks files.
In case I will prepare for you a version of the screw for a 3mm screw!

thks, also need one :)

Ok, files stl added, for M4 and M3.


Has anyone tried the CR-10 Mod X and Y tensioners on Ender 2 as they are close in design?

on the Y axis, should be ok, the same tensioner of Ender 3 :


On the X axis, will be ok the same of Cr-10 (just pick a version, as per your needs...)

Ender 3 Mod - Y Axis Tensioner

this is the best X tensioner design for the cr-10. any intention in making a Y tensioner like this? hopefully for the cr-10 s5?

I've been looking for a good Y tensioner that doesn't require you to saw the oem aluminum bracket but no luck

thanks man, the Y tensioner for the standard Cr-10 in already online : https://www.thingiverse.com/thing:2869114

For the S5 version, I have some request, so I will prepare something as soon as I will have free time :-P

CR-10 Mod - Y axis Tensioner

that's great man!

btw, there are some designs here for the s5 Y tensioner that uses the aluminum bracket, some s5's have a 2 piece bracket, and some are single piece. ideally the tensioner shouldn't need to use the bracket, just the printer frame

see this design: https://www.thingiverse.com/thing:2650218/comments

it uses the aluminum bracket, but as you can see from a pic I posted there in a comment, mine has a single bracket, so I would have to saw it and drill holes in it to use this design.

I ended up making a simple remix of another Y tensioner so it wouldn't need the bracket, but it still needs a metal screw and nut, and I would love to have a Y tensioner like your design, that uses a 3d printed screw.

looking forward to it, cheers mate

CR-10 S5 Y Axis Tensioner

First post here, had to say how much I Love! the look of this tensioner, it was one of my first prints.

But it failed using PLA. I printed at a really low temperature as I'm a neewb, the x is still working, but I went back to factory for the Y when it broke (likely User error). If your just getting started, stay with the factory for a bit until you learn how to melt the plastic together, Then make sure you match the color of the guts to that of your frame, it looks really sharp.

Will come back and donate when I have a better print. Thank You for such a slick design!

Thank you! I´ll try one of each in every one of my printers. CR-10 GT2 | Ender-3 M4 | Ender-2 M8

I want to try the belt straightener too

Did you try it on Ender 2 ? I'm also curios if Y tensioner fits. :)

Hello, I’m curious is this will fit a cr-10 mini.

The pieces are the same of the cr-10, so, yes it will fit!

I printed this for an Ender 3 - works great! Thank you.

The only thing I had to do was increase the size of '[_Mk6__-CR-10-F688Z-_XTensioner-_Knob' to 102% in size for the smooth turning of the knob.

Probably because you printed the screw in vertical...

Thank you for source files, you are a saint for releasing them!

Nice design, I have GT2 pulleys with 4mm hole in your opinion I can use your GT2 version, thank you.

You can use the GT2 version, but you have to modify either the .stl or the .slprt files in order to reduce the diameter of the holes for the screw (that should be 5mm in the models)

Thanks for the reply but I'm not able to make the change, does nothing ...

Anyone else finding the belts too tight for both the X and Y axis belt tensioners? I'm able to fit the X axis belt tensioner but it's put on really tight that I feel like I have the unscrew it all the way and even then the X axis doesn't feel that smooth. With the Y axis belt tensioner, I can't even fit the belt on. Do you have any suggestions as to what I can do to fix both problems? I'm using the CR-10S.

Unluckily, some machines arrive with shorter belts, so the only thing you can do is change the belts!

Would you happen to know the dimensions of the belt I would need? Also, I've read that the parts with M8 screw is for the stock parts. What's the difference between stock and GT2? Love the design of your belt tensioners by the way.

The belt you need is a classic GT2 belt 6mm wide and 2mm pitch; you can find it sold by meter, is quite unexpensive.
For the gt2 version, you need a idle gt2 pulley (with or without theet) wit 5mm hole (and relative screw, of course).
The OEM version is designed for the stock hardware, so the two original bearings and the original M8 screw.

I am currently using the stock hardware. Would I still need the GT2 Belt for both the X and Y axis? Also, what's the difference between the idle GT2 pulley and the stock hardware? Is the GT2 pulley better in a way? Thanks for all the help

In my CR-10, the belts are long enough to use the tensioners in an intermediate position.
For this machine, and the S version, the belts are gt2 6mm wide and 2mm pitch. If your belts are short, and you want to use my tensioners, you will need to replace the belts, otherwise, you will need to go for sifferent tensioners.
Actually, no big differences between gt2 pulley and oem bearing, except for the working diameters.

Thanks for all the help

Any chance you could add a second 20t idler to align the belt to the axis? I hate the creality design of the belts not being parralel with the movement direction.

Yep, I’m working in it!

Thanks you for your work!
I mounted the two with the piece for the original screw and everything perfect.

Comments deleted.

Please explain what you break, and post photos...

Hey man nice work! Do you have a matching Y axis tensioner?

of course...you can search it in my profile!

I am interested in making (Version GT2). Can you please tell me if this is the correct pulley to purchase?

GT2 Idler Pulley 20 Teeth 5mm Bore for 3D Printer 6mm Width Timing Belt


I assume that I will also need some M5 nuts? Washers? Locknuts?


Is the linked ^^ GT2 pulley the correct one to use to replace the stock bearings?

I just built one. I see that no nut is required. Thanks for sharing this.

Thanks for the feedback!

hello, I'm about to print the F688Z version for my Ender3. You mentionned that the screw needs to lay down for more strength. the other parts can be standing ? thanks

I never tried that version, but yes, the screw lay on the bed, the other pieces in vertical.

Do I need extra parts, such as nuts and screws? Or I can use only the stock CR10 parts?

If you want use the stock hardware, you can consider the model with the M8 screw.

Thank you, I'll print the parts, upgrade, then post pictures here

Thanks for your time on the design, love the look but having trouble on fitment. I printed the parts and while the cap & screw fit together nicely the screw does not fit into the body once your fit the tangs of the screw in. I had to print the screw at 97% scale to fit into the body. Typically I would figure this as an over-extrusion but I've calibrated my printer through the eprom after measuring filament extrusion differences. Any thing else I might have missed? 2 line wall count, 0.8 wall thickness, 0.2 layer height, Ender 3, 1.75 PLA @ 195/65.

I've tried printing several different X-tensioners and have always encountered the same issue. So I can only assume it's something to do with my printer/settings. Is it best to scale the body so the original screw and nut fit in, or the screw and nut so it fits the original body?
Also, would slicer make much difference? Which one was used originally for this?
Anything I should check?

I've been using:
0.2mm layer height
3 walls, top and bottom layer
60mm/s print speed
50% infill
PLA+ @ 215/50

Try slow down to 40mm/s, the temp seems also high.

Anyway, if the pieces don’t fit, you may heve some dimensional issues, so check the e-step of the extruder, the jerk and especially the accelerations!

Thanks for the reply.
Recommended temp for PLA+ is 205-225. I did a temp tower and 215 seemed the right spot. I can try lower temp as well as printing slower.
I will also check the other things you mentioned.

There has been one that I found printed without issue for me, however Ender have perhaps shortened the belt between it's design and my printer as I couldn't stretch the belt tight enough to get the screw through the body and thread to hold the belt.

In Cura I have the following:
Print acceleration 500 mm/s
Travel acceleration 5000 mm/s
Jerk control enabled
Print jerk 20 mm/s
Travel jerk 30 mm/s

I will keep playing and see how I go.


I had the absolute same issue - though to be honest it seems to me, that there is just some tolerance missing. I modified the screw just at the relevant dimensions and it fits and works really well now! To be honest I feel like there are just some tolerances missing. Other than that I am super happy - thanks for the design and ESPECIALLY the CAD files! I love the model, but for specifically my Nut-mounting I had to do some tiny modifications, which was easily done! Thanks!

I print the pla+ (sunlu) at 200/205 and come out perfect. anyway, every printer has its own parameters..., so, if you already check the best temp for you, use that one.
Just for give you an idea, my acceleration is 1000 and my jerk is 7.
about the lenght of the belts, all my projects are based on my printer, so everything has been designed for match my machine. If your machine has shorter belts, i cannod do much...(or better, I can do it, but is to modify the drawings, but I really don't need it!).
If you want to modify and remix the parts, you can find the solidworks drawings attached, and you can create the model that match your needs, without any problem.

Thanks once again for the additional info.

I have only had the printer a couple of months and have assembled it, levelled the bed and off I went :-) The results so far have been good enough for me as I've only really printed figures. Now I'm looking at more mechanical prints I can see it's time to do some calibrations and make sure everything is set right.
I've just been using a profile from a FB group that most seem to recommend and have made one or two minor adjustments to it.
With regards to the belt, it's more an assumption based on other comments I've read on some of the other tensioners that seems to make sense. It also seems that Creality make small modifications to the printers over time. However, once calibrated that may prove incorrect.
Looks like I may need to give myself a crash course in 3D modelling and adjusting others parts. Understood that the parts work for yourself so there isn't a need to modify them.
I will start with calibrating the printer extrusion, x, y and z axis and go from there.

Thanks very much for the feedback and suggestions!

I don’t want to seem rude by telling I don’t need to modify the model. Just I work enough on this tensioner, I made several versions and enough print test for decide that this will be the final design.
For the fitting issue, I may be able to increase the tolerances for who is not “precise” enough, but Where will be the funny part of the perfect setting pursuit?


I didn't take it as being rude at all. Sorry if I gave that impression. I definitely appreciate the time and effort people put in to creating these models and sharing them for the broader community to use :-)

Maybe add CR-10 / Ender 3 in the title for noobs like me ;)
I was curious if this fits my Ender 3. Other tensioners I tested broke mid print after a couple of prints, so I'll try yours!

Is important to print the screw laid on the bed instead than vertically, to give the layers the correct orientation to improve strenght.

I will put "ender 3" in the tags to facilitate the search....

Never tried that actually, but it makes a lot of sense. Strength along the layers should be higher than inbetween. I'm an engineer myself, so my job would have been to think about that orientation myself lol.
Anyway really great design. Printed in two colors as well and it just looks fantastic. Also the threads work smooth directly after print.

Comments deleted.

Can anyone tell me if this will fit the S4 that runs a 10mm wide belt not a 6mm

Does the s4 use 10mm belt also on the X axis?
I remember the wider belt was on the Y axis only...

Any idea why Simplify3D hangs on calculating infill ?
First time Iam encountering this

Hi, I uploaded new stl this morning, because seems the previous files were a little too big (export made with really high resolution).
I already try to slice this files and I didnkt have any problem, so I don’t know what to tell you...

Tried again in Cura 3.4.1 and there they worked fine and will soon be done printing.

Hi Cornely-cool

I see that you simplified the design of the body and the screew...


I’m doing my best for give a nice and practical design!...at least I’m tring doing it!

How thick are you printing the walls for the body piece? There is no way that the screw that I printed (cleanly) could fit all the way into the body. The body ended up cracking eventually and I had to cut away pieces of the body to remove the screw. My Cura settings have the wall thickness at 1.2mm but a Wall Line Count of 6 - I'm wondering if this is way too thick to allow the screw in?

What do you recommend for the Wall Line Count? Thanks!

Hi, i use 3 lines for walls all around, 0.2 layer, 0.4 nozzle. 205/65. The print speed of the pieces in the photos was 30 mm/s material pla+.
I made several printing test, and every time the fit was ok, so, no problems on the models.
The number of the walls is not affecting the external dimensions, but only the strenght of the piece.

Something is wrong with your settings (maybe post a photo of the prints), check the step/mm of the extruder, maube you are overextruding material, so the pieces come out bigger than normal.

Just printed this with no problems. The cap screws on just right with no play or tightness. The screw component is a little snug when inserting it into the housing, but that's fine as it will loosen with use. Excellent design, thank you. I printed with PLA.

Thanks for the feedback mate!

Hello, is it possible to update the screw and nut for https://www.thingiverse.com/thing:2940114/comments? So, I can use for my Anet E10 this X axis Tensioner with same nut.

Anet E10 / E12 Mod - Y Axis Tensioner

Ok, I added the new files to that page! the Stl are marked as "Mk2". I didn't print them because I don't need them, so please if you will print them out, just let me know if everything is ok and please send me some photos so I will add to that page too.


Thanks man! I'll print them soon...

Comments deleted.

The parts do not even come remotely close to fitting together. My printer is calibrated for maximum dimensional accuracy.

I tried to print the nut and screw slightly smaller/bigger but nope, still doesn't fit, at all. Thanks for wasting my new PETG!

You blaming the maker, don't be such a sad person. Every thing you make is down to you, and PETG is cheap. Its your own fault not the maker and you should be thanking the maker for the time and effort he has put into it.

Lmao I already made my own

I'm sorry to read your messages mate! For double check what you write, I'm printing (now in progress) again all the pieces (I downloaded stl from thingiverse) and will check the fit.
To me, all the pieces fit correctly and with minimum clearance; in drawings there is 0.1/0.2 mm of clearance everywhere, and from my tests (I'm using this tensioners on my printer, so...) the tolerances are ok (i already reprint all the pieces some days ago after one user wrote me about one interference, common in X and Y tensioners, that I fixed the same day).

Just finish print a screw and a nut, I try the fit, and is ok.
Pieces just removed from the printer, no post processing, just removed the brim on the base (is by default in my slicer profile).
Now i am printi g the body, just for double check also that fit!
I print at 0.2 mm layer! 40 mm/s in pla.
I will let you know the further results.

Fit Test Screw/Nut ---> https://youtu.be/hGHBk1Jx-E4
Fit Test Screw/Body ---> https://youtu.be/Y-v41Rapck0

So, I think this will answer to your message... The pieces fit correctly.

Comments deleted.

Have tried printing this mod a few times and it does not fit together,also the Y axis tensioner as well,neither one will screw together nor will the screw slide into the carriage at all,have even tried resizing parts to get the to fit but still nothing.They come out looking perfect but the threads don't match and again the screw will not slide into the carriage.I have a Tevo Tornado that I really want to use these tensioners on.Please Help.

as wrote by one user in the Y - Axis tensioner page, he found an interference between the screw and the body! this has been already solved this morning and I already uploaded the updated files for both Y and X axis models!

For the threads, I cannot find any problem!, I just re-print again today the parts for double check (after discover the interference), and the threads match perfectly to me, no issues.

The tolerances i used are around 0.1/0.2 mm so maybe depend by the precision that you can obtain with your printer.
Just printed today a 20x20x20 Bench cube, and I obtain 20.02x20.06x19.99, so I think my machine is quite calibrated.

You were right kinda...Bed level was off a little so it did make a difference but still the screw does not fit into the body.I have tried printing it at .2,.16,.12,.08mm all don't fit without modification.I have to use a dremel to make a channel in the grooves on the screw to get it to fit as well as take some material out of the body to get the screw to fit.I printed a 20x20x10 cube that came out perfect so I know my machine is accurate.Can you take a look at the gcode and make sure it's correct?Thanks

Just reprint the Y screw, and fit perferctly with the body and the nut, no post production needed

hi im looking to print this out but i saw you used a GT2 20t pulley what was the Bore of the pulley you used?

Does it fit CR-10 S4?

yes, the X axis is the same.

Having you seen it getting loose over time, or the parts deteriorating? What material did you use? Do you have to tighten it form time to time?

Nice job, can i reused the stock pulley ?
can i reused the stock belt ?

out of subject : where do you buy the 2nd z axe ? is it not tricky to installed?
do you got cr-10 or cr-10s ?

I change the pulley because in my opinion the original one is a completely wrong project from creality.
On one side you have a GT2 20t pulley on the stepper motor, and on the other side they foresee two bearings with bigger diameter than the gt2 pulley....that is also the reason why the oem belt scratch on the V-slot profile on the tensioner side.
Anyway i think you can use also the stock pulley ( but with the limits described above ). The belt is the OEM.
I got a Cr-10 and installed a dual z upgrade from amazon ( easy to install, but of course you need some DIY basic Skills for the mechanical installation, and need to open the control box for pass some extra wires )
Furthermore I installed a timing belt between the 2 z rods by using 2 GT2 pulleys 20t (hole diameter 8mm for install on the rods) and a GT2 belt of 760mm that fit perfectly without any tensioner.

Now is almost 2 months from the mod, and I didn't had to touch again the Z axis alinment.

Thanks for uploading the Cad files as well. Supper usefull!

This looks really good.
I don't actually need it, but I'll make one just the same cos I like it :)