I replaced the 5/16-18 threaded rods I had in my repstrap with 8mm two start lead screws. These are precision threads, unlike run of the mill threaded rods. I also replaced the vinyl tubing I was using as a coupler with a 3D printed one that works similar to the type of clamping couplers you found. I have an 8mm bearing mounted up top to keep the rod running true, and I also carefully adjusted my motor mounts to get the shaft of the motor, and the screw 'nut' in the gantry perfectly in line. I then adjusted the bearing up top to also be perfectly in line. Made a BIG difference, my Z 'wobble' is almost totally gone now. You'll always get a bit of wobble from SW round off errors, especially if your layer height isn't a perfect multiple of the steps/mm.

The First 10 Seconds i thought i was watching EEVblog because of the Voice. 😆

didnt know dave jones [eevblog] had another channel..

This was extremely helpful! I didn’t know what to search for on google for the longest time and searched for “layer lines” which kept me from the right solutions. Z banding or z axis is what I should have searched for. When you don’t have the knowledge you tend to search for what your uninformed vocabulary makes of what you see.

Dude, your channel has been so helpful, the amount of information you provide compared to other channels is great, some parts others haven't even mentioned!

The job of he coupler is not to act as a spring (although it does). It principal purpose of the coupler is to handle misalignment so that the shafts don't have to be perfectly aligned. If you want the coupler to perform better, make sure the far end of the shaft is in line with the motor shaft.

Good tips! I've been doing taller and straighter prints lately and have noticed a perfectly periodic Z wobble. It's very slight, but noticeable when the wall should be dead straight. I think I can resolve it with some of the info you gave here.

A great set of videos. you are appreciated. in regard to the z axis coupler . I note the importance of keeping the shaft and rod apart to allow a bit of flexibility in the coupling, and I appreciate that the print results determine whether something is a good hypothesis or not, however something that may be a second order issues is the spring in the coupler.. In winding up the platform the coupler goes into compression, ie shortens slightly and on stopping of the rising it will bounce upward from the release of pressure (acceleration). I suggesting thinking about the oscillation that may occur at the abrupt halting of rising or lowering and if this reflects in the print as Z banding.

Add a ball form a ball bearing inbetween the stepper axis and the threaded rod. Thus is stays mobile like before but does not allow for z oscillations.

Awesome this helped a ton!... also figured out that when my extruder was pulling the filament it was cause these issues as well

You're correct in there should be a gap between the stepper motor shaft and the threaded rod. If you look up how to install a Helix Flex coupler, more importantly the exact one's you install no matter the brand, they give specs on the max shaft insertion length for the particular coupler. They'll also give specs on the max off center distance it will correct for. They're not all made to the same specs. In addition, proper installation of the Helix coupler is done by first setting one side. Generally the stepper motor side. Then insert the other shaft, in this case the threaded rod. Before tightening, you must spin the coupler to allow it to fully expand and find center. Then you tighten it. It's amazing to me, in this day of Google, no one has taken the time, a shear moment to search how to install them properly. Especially if you find you have an issue in that area. Most continue to go by trial and error. Then pass on findings. Which may or may not include complete let alone correct info. It boggles the mind sometimes. Or rather mine. And gains a shake of the head... I've found even the manufacturers don't know how to install these couplings properly. Just mind boggling... And yup there goes the head shake just thinking on it. lol

Been watching your videos on this playlist from the first onward (14 so far).. what a wealth of knowledge, thank you so much.

Really nice and exhaustive vid, man. Thanks for sharing the knowledge. 👍🏻

Interesting, I'm having similar randomised wobble too. I'm using a printer with a ply frame, it's well attached and I've replaced my couplers with printed self-centering ones (which got rid of the sinusoid all Z wobble). I also plan to upgrade to proper lead screws but I'll definitely check the motor wobble. Though the randomisation suggests it's nothing to do with Z being off-centre. I'm also making silicone bushings to replace the z levelling springs.

Great analysis! I know my printer suffers from at least one of these issues, so it's time to start tinkering! Thanks for such an in-depth look at the z-axis.

I am having the exact same issue here. Finally an actual helpful video

Thanks I had this problem. Now my prints are better looking.

Cheers Dude. Turned out my lead screw was bent slightly. Managed to get it straight again after trial and error. The bend with minimum effort

Hi there, thanks for the information. Having worked in industry, I can tell you that flexible couplings are actually used to mitigate a miniscule amount of axial misalignment over a short distance, say between a motor and pump directly coupled together and not a long shaft like these used on these machines as any misalignment gets amplified. Even then, the motor is still always aligned to the pump using various methods. Also, because as you say, these couplers are springy, any vibration in the machine could potentially mean your z axis can bounce around. Because threaded rod is usually undersize and inherently pants in a linear motion, what I've done in the past to get by is to drill the centre of the rod 5mm. then, cut with a hand saw down the length of the rod along the hole you've just drilled essentially splitting it to 2. then thread on 2 nuts along the split, insert your motor shaft and tighten the 2 nuts against each other. this clamps the split end on the shaft coupling it. I've drilled mine on a lathe with the end supported in the bore to stop it and aid accuracy. done well, the Motor shaft fit can be tight enough that it actually holds itself in under vacuum! works well for me and a very positive coupling. in an ideal world, the shaft should be supported both ends and the motor coupled directly onto the end, this is his I've seen it done on high end routers and mills. food for thought!

I have a Da Vinci Pro and have made many bed calibrations and 20mm test cubes that look nearly perfect, especially in the Z axis, but when I print anything else I get noticeable banding, mostly on rounded/curved models. Any help would be greatly appreciated. Thanks!

i had lines/ridges start to appear over time,finally decided to figure out why... i just changed to couplers that look like the ones you have exactly others were thin blue ones that came with my cr-10 clone... i did find one of my grub screws was loose on one motor next to extruder also which may be the main reason i had issues. there was only one grub against threaded rod anyway.. these new couplers have 2 grubs screws for motor shaft and 2 for rod... i am doing a print that turned out not so perfect yesterday...hoping this fixes the issue... ps i think i heard these couplers with rubber built in mounts can fail... Has that happened with yours? thanks again

Is it fairly easy to bend a stepper shaft or is that merely a manufacturer defect if you're so unlucky to get one? I have a delta and am just about ready to throw in the towel with this thing. Everything prints just fine except when it starts the outer shell, it leaves a blob and gradually smooths into the surface as the layer carries out. Esteps are calibrated to perfection, tried printing at hyper speeds (100-120mm/s), 2.5mm retract @ 45mm/s, and even tried a negative value in retract restart (but that made it worse).

Great video's! keep up the good work!

great video. 5 start lead screw would be crazy fast...think thats what im going to do on my big build

I agree about the couplers pushing over

Great video! Those motor holders are the same as what I am now using, after the original warped under heat and pressure. Also think I will leave a space between the shaft and rod, always wondered if you should or shouldnt.

While the human eye is an incredibly precise instrument, the proper tool for the proper job is always good advice to follow. A micrometer is a must-have for accurate and precise measurements of parts. The threaded rod, for example. Measure everything, and return or toss out-of-spec components. A dial indicator, likewise, is a must-have for accurate and precise measurements of parts and assemblies along their long/longitudinal axes, such as stepper motor shafts, threaded rods, and stepper motor, coupler and rod together. Measuring at the furthest point from the fixed base yields the greatest precision as any angular deformation/mis-alignment is exaggerated. A weighted or magnetic mount for the dial indicator is also a must-have accessory. As with most things, you get what you pay for. These are tools that will last a lifetime, so buy quality the first time. Buy quality parts. Measure for precision before assembly. Then measure your assemblies as you build and you'll be all but guaranteed of a good result.

sounds like EEVblog

Excellent video, thank you!

tip for reducing headaches in the future: the reason why consumer electronics manufacturers use locktite blue on fasteners is because it prevents the fasteners from loosening up due to vibration, this is critical to know when assembling an ender 3 since the fasteners keep coming loose on mine and an adhesive reduces the need for maintenance drastically. some say that loctite blue serves to show if a warranty is void, but you would need to unscrew the screw and break the seal to check it, so i doubt that. this is also why rivets are better than bolts

I have a home made 3D printer. I am facing issue with my z motors, as they are not moving up as expected and endup crashing into previous layer. I am currently moving z motors by hand clockwise to avoid this issue but it is not giving output as expected kindly advise if there is a way to fix this issue by increasing z motor position after each layer by changing printing configuration in Slic3r or in Merlin firmware. I am using Slic3r for gCodes and PronterFace for printing

waw, overall best explanation. You gave us really comprehensive review. thank you

Otro detalle a tener en cuenta, es el tipo de varilla que se usa. Si es varilla de acero inoxidable o varilla rectificada. Hice girar las varillas de mi impresora en el eje z y encontré que éstas mueven todo el carro. Ahora voy a comprar varillas rectificadas a ver si tengo una mejora.

Where did you get your z couplers?

Can you please show the link where did you get the couplers from?

Do you have a source for the clamping couplers?

Very informative video!!

How do you drive the stepper motor to check that the axis is true?

Hello there - just found your channel by accident :) Thanks for all these useful tips - I am still improving my i3 more and more! I have one question - my z-axis motors are really slow in comparison to yours in this video... I mean for printing it doesn't matter but the movement for homing takes too long in opinion ... Any hints how to increase the speed? cheerio and greetings

Just use aquarium air tube as coupler and done with it

Where do I get one of those metal couplers for the threaded rods? Seems like that would make a huge difference from the rubber tubing mine came with.

Great video! where did you buy the couplers? i have the same printer. thanks!

Thank you for your troubleshooting tips and advice. I am looking forward to getting my 3D printer up and running. As soon as it shows up at my door! lol It is on a slow boat from neverland.. I noticed in the kit I am getting, I am looking at the pic of it and there is no coupler from stepper motor to the Z axis. I am curious how they attached the threaded rod to the stepper.. A side note.. You talked about the Z axis rod and checking to see if it is bent.. I worked for a company that made dot matrix printers and one of my many jobs was to check for bends and correct any rods that were not within tolerance. If I remember correctly, I had .003 - .004 to play with. That task got pretty boring pretty quick..

Well, if you are using a flexible coupler without proper support, what do you expect?

Nice work, I like your videos.

Are you sure.. Need gap in the screws and the motor shaft?

I also noticed that on my couplers I don't like the fact that the grub screws are at 45 deg pushing the rod to one of the sides. Wondering if making a extra support for the threaded rod on the top and bottom (close to the coupler) with a bearing wouldn't help. It would force the rod to be straight and any wobbling would be caught by the coupler.

Perfect :)

thanks a lot!

Noticed that you don't have any fixation at the top for the threaded rod. Is that a mod? Maybe it's a good thing that it can turn freely, if fixation aren't aligned 100%. I have just bought my own Prusa, and it need some updates but first I just need to be able to print. Was not as easy as I thought :)

My Z-screws are in pretty poor shape. I'm thinking of abandoning M5 rods in favor of proper lead screws.

Hey :) In the end of the video(8:48), you showed the z motor spinning and it makes a little whining sound. I just built my i3, and mine's whining sound is a lot louder than yours(during fast movements such as homing), do you think it's caused by some of the problems you memtioned?

M5 inox threaded rod & few inches of silicone aquarium air pipe instead of a couplers solve most of all problems on Z axis

Have you put any thought into changing your 5mm rods to ACME threads.(Z axis) Quite a debate whether it makes a difference.

Hey would you recommend the replikeo kit based on your experiences? I'm getting into 3D printing but only have a M3D printer at the moment. I fancy getting a bigger printer and the Prusa i3 looks like a good shout?

For those looking at printers from china, expect to do a lot of work in this area. some of the printers from Banggood have had errors up to millimeters in the straightness of the screw rods or tie rods causing in a worst case scenario complete seizures. Check before assembley and replace or straighten rods and up grade couplers and oversize sloppy bushings and you will be on you way to having a half decent printer

I just watch your videos because of your accent :D

Is it just me or was there a bit of delamination in the z motor bracket even before he snapped it?

Another common problem in this case, is an unlevel bed. IF one side of your bed is slightly higher up than the other, it can cause the Z offset for that one side to be inaccurate.

Still relevant 7 years later

Looked a little bit better

really like your videos :)

Best improvement for this - Buy a proper cnc threaded rod , they are quite cheap these days .

Oh Hi Dave xD

My issue was a broken lose z nut

I couple my 5mm threaded rod to the stepper motor using a piece of silicone tube.

was this printed at the printers max resolution?

go belted z!!

i have never use a 3d printer with treaded rod

Ozzyman has a 3D printer haha

Where can I get the new coupler

My 2 cents: Let the screws rest on the motor shaft, that way you remove any springiness, and the entire weight is taken by the motor bearings. Next, make sure you Z guide rods don't move in their respective holes. Even if the screws are bent and wobble, they are lose on the top and the guide rods should prevent any movement, even if the screws move.

i noticed a lot of australians are into 3d printing compared to americans

You sound just like EEV

Add a bearing at the top to reduce movement on prusa and prusa Chinese clones

I think it is a bad idea leaving gap between the shafts.

New Couplers are ordert and the print for the new Motor Mount will be printed. www.thingiverse.com/thing:639225 By the Way. Test the Filaprint Build Plate, it is unbelievable awesome. A big THX :)

LIP SMACKING 🤪🤪😵😵😡😡😠😠🤬🤬🤬🤬

I wouldnt even buy an ugly printer like this.