Z Wobble

itisnot_me · March 2019

As you might know the z screws are not straight on the A5. With that it does create z wobble. While not a show stopper I have been dialing in my A5 to be as perfect as possible. I am getting so great prints but it seams like my last thing to fix.

So, does anyone know of a successful method where they almost completely eliminated z wobble? Some people have add on mods that hold the tops of the screws close to in place but idk how well that works with the screws still bent.

Der_Muck · March 2019

For what do you wanna fix it? When the bearing is straight the Z wobble doesnt infect anything at all.
You can try to unlose the screws of the Z motor a bit, set Z0 and than screw the screws thight. That should center the motor little more. I only have a little wobble when Z is on the ground with that now.

Dont mount anything on the top there, you will get some force on the bearing and that effect the print.
There is no bending, I think its the gab in the thread of the brass bushing and the flexible clunch of the motor.
So one side has to be free, thats ok and what the chinese engineers thought.

itisnot_me · March 2019

I would like to stop some z offset/banding/wobble that happens on prints. mine it not really all the bad but I am working for perfection on my prints.

Der_Muck · March 2019

Did you change the bearings on Z? And did you use right lube for the thread and the bearings? The original lube is to sticky, change the blue lube to a litium base fat or a PTFE oil.
Normaly the light wobble of the Z thread doesnt effect the print. I would try to center the motor as I wrote, that can reduce the wobble. If you have bad wobble, maybe the flex. clunch is not good any more.
The system of the JG has its limits of quality and accuracy, a round 8mm bearing is never so accurate as a linear guide.
But again, the wobble is caused of thread clearence. If you can find the right position of the motor, the screw drive will be centered and the wobble is reduced to a minimum. A change to a ball screw drive is not passible because of the build size and its to expensive for that printer. Its more to use in a self build printer unit in combination of a linear guide.

itisnot_me · March 2019

I can try you relube the threads and lube the rods. For the threaded do i need to do something special to remove the current stuff or just apply more on top.

I currently have this one

I did not change the bearings on the z and only have on X. dang it was such a pain to change it out though. Thought i was going to break

I mean my prints are pretty dialed in but there are sometimes that that i see the shifts. I believe i have too high of standards. You can see below the slight lines that i am talking about.

Image: https://jgmakerforum.com/uploads/editor/la/k7oc5p36dm0l.jpg

Der_Muck · March 2019

That is not the fault oh Z wobble, its can be that a bearing is to tight to move freely or a sticky lube.
I used PTFE spray on the thread to weak the blue orig. lube and than wiped it away. After that I used universal lube.

Is it PLA you print? It looks like nothing comes out of the nozzle. Try a retraction test with Z hop than you see what your problem is and if the settings are ok: https://www.thingiverse.com/thing:909901

The layers should be look very equal to the others and the tip should also look very nice with PLA. Try to break the tips to see the layer adhesion. After ajusting you will have much higher quality.

itisnot_me · March 2019

Alright so i was thinking that maybe my issue that i have could come from the bed movement.

Do you think that if i was to secure the bed without springs and made it stationary that I could reduce the thing that I call wobble on the print. I mean I already have the bl touch installed and it auto levels on every print. so i do not see why the springs are needed.

this is a closeup of the latest print https://photos.app.goo.gl/u4BQBW8FQa1VjREf7

Like i mentioned its not a show stopper and is shown more on pictures that in your hand, but its something that i want to reduce so i get cleaner prints

Samuel Pinches · March 2019

I'm very certain that some of this wobble comes from the long springs and screws that the bed is mounted on. I replaced these on my A5 with solid nylon spacers, which meant I could tighten the thumbscrews, making the entire bed very solid. That improved my print quality. However, you will need to find the right height of spacer for your bed. I just use mesh bed levelling to compensate , and I keep my bed fixed in place.

If you have a bltouch I think you have the perfect opportunity to try it also.

itisnot_me · March 2019

how much clearance would i need for the bed to the the case?

Samuel Pinches · March 2019

I think you need a minimum 8mm spacer... not sure what that works out to be though.

itisnot_me · March 2019

I had the spring compacted to about 10mm and it was either rubbing on the top of the case or very close. I think that if i have about 16mm spaces in place of the springs it might be enough clearance to not drag on the top of the case. I will head out later to try to find some

beata · April 2019

I have an (admittedly tidy) scratch on my top cover due to lowering the bed too far. I'll have to give this a try too.

itisnot_me · April 2019

@beata I found that the 1/2" nylon spacers from Lowe's worked but you either need a bltouch (or some bed leveler) or you need to modify the z endstop switch lower to account for the height difference. Though I didn't see a difference in the wobble that I have seen I think it's more baked into the machine as it's in the same spots every print

beata · April 2019

A quick measure with the springs removed, between rail and bed, raised with craft magnets, 16.5mm - 18mm. 5mm clearance between bed and top of base. With the out-lier in the same corner I had trouble with previously.

Gandy · June 2019

itisnot_me, did you find a solution to this? I'm having similar results on my print, already with nylon spacers applied. See https://jgmakerforum.com/discussion/731/inconsistent-layer-stacking

itisnot_me · June 2019

@Gandy sorry I have not. And it pisses me off to no end. If I could solve it I might actually like my printer again. I also don't want to sink more money to buy none bent rods. Also replacing them is super labor intensive.

Gandy · June 2019

Sorry for hitting a nerve here, I can totally understand how this sucks, facing the same issues. If the lead screws turn out to be bent, I might try to bend them back, if that fails I can still order replacements. I'm not exactly looking forward to that, either, so I'm still trying to figure out what else could be wrong.

mgrabow · June 2019

I agree the Z wobble is something I want to fix as well. and its a "just because" thing.

itisnot_me · June 2019

Same. At this point I'd say its baked into the printer aka a hardware thing. As no matter what I tried it would not disappear.

Gandy · June 2019

I bought mine in March in a flash sale. I'll go ahead and contact jgaurora for a replacement part.

itisnot_me · June 2019

Let us know if it goes away

poikilos · November 2019

Has anyone on this thread tried replacing the "stretched" motor couplers on the z axis (as indicated by the z axis lead screws wobbling during z axis movement), or adding TL-Smoothers? If you make one change at a time, we can narrow it down.

itisnot_me · November 2019

replacing the motor couplers didnt make a difference. Also i installed 2208's so useing TL-Smoothers were out

poikilos · November 2019

(The bold parts are just so nothing gets missed in my long post--it doesn't imply anything else.)

@itisnot_me If you provide a link to the model(s) (for original photo and closeup) I can test them before and after I make some upgrades to my A3S (version without exterior SD card slot) which is mostly the same as the A5.

There is also [JGAURORA A5 Z Gantry Stiffener ](https://www.thingiverse.com/thing:3199105) (still requires buying at least a cheap type of lead screws, but you install them outside of the printer which is not as labor intensive as repacing the lead screws inside) which may help if there is any z wobble related to the connection of the gantry to the chassis (make sure the screws that connect it are tight for now--mine were missing on a used A3S!).
:edit: You mentioned that tightening your bed screws caused them to rub up against the case. When my gantry screws were missing, tightening the bed screws caused them to be that close, but not anymore.
:edit: You mentioned that you thought the springs were causing wobble. If you don't want fixed spacers, you may be able to get more stability and keep the springs if you use guides such as JGAurora A5 Spring Guide.
I thought of a Z wobble test: If you print some kind of straight pillar such as any calibration test, [with a cylinder](https://www.thingiverse.com/thing:35088) for easy diagnosis, you can fairly clearly confirm whether there is z wobble caused by the z lead screws if part of a layer protrudes, but the opposite part (imagine a mirror along the width of the protrusion but in the center of the model) is indented consistently (for each layer that has a protrusion).
If the height of the model is not what it should be (off by more than about 1/2 of layer height which could just be rounding to nearest layer by the slicer) that probably indicates motor skipping on the z axis (due to poor lubrication such as the stock blue grease)--you would have to measure a model with accurate calipers to confirm that. I think that is the bearing issue @Der_Muck mentioned, but if he could clarify which bearings, that would be helpful.
Maybe the rods (actually you probably mean the lead screws) are bent, and getting non-bent ones may be the solution if so (if you still see the wobble after you replaced the couplers, which I have but haven't installed yet), but there still may be other issues: Der_Muck asked whether the filament material is PLA. The prints look very shiny, which makes me concerned it is PETG (which has a set of issues with some solutions I know). His concern about whether extrusion is steady is valid, and material makes a big difference with extrusion and retraction. If you specify the filament type, I can comment further.

Z Wobble

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