slight Y move on pure X

[balmy oracle]

A printer with about two years of use. A slight waviness appeared on the print, and after inspection I found a stretched belt (the Kevlar core had worn through). After replacing it and repeatedly checking the length, tension, and path, nothing changed. I also checked gantry squerness and do de-racking The attached video should explain a lot. What could be the cause?

[sly burrow]

Retune your belt comparison and do IS tuning

[balmy oracle]

it`s not ringing like waviness (i make IS and nothing changed) its something else that i want to figure out

[sly burrow]

Without a picture or video of a print it’s hard to tell the video is hard to determine what is happening

[balmy oracle]

Its not about print quality but unexpected movement of gantry. This top down view should explain a lot more. this supposed to be pure x move.

@sly burrow

[sly burrow]

Check and make sure both police are tight in the grub screws. Haven’t come loose on the motors for A and B

Also make sure motor shafts aren’t bent also could you take a video of you pushing the Y axis forward and back without touching the belts and see if the x moves left or right?

[sly burrow]

With motors disabled

[pulsar pendant]

Check the M5 screws attaching the X beam to the printed XY joints and the M3 screws that attach the joints to the rail carriages.

This almost looks like the X beam assembly has lost its rigidity and is kinda twisting around.

[balmy oracle]

pulley are tight and shafts are straight

[balmy oracle]

I checked mentioned screws in step "de-racking", I'm also recheck it a moment ago. X beam seems to be rigid as new. I'm about to replace just in case all pulleys and bearings in gantry

[sly burrow]

Something is wrong the head shouldn’t be wiggling back and forth like that

There must be binding try taking the belts off and check for binding and tram everything

Make sure linear rails aren’t loose and that there is no binding (easiest with belts off)

[deep cargo]

It isn't unusual for things to move a bit in one direction when pushed in the other (X or Y) with motors unpowered. Just a slight difference in how easily the A and B motors / belts turn over.

[sly burrow]

It’s wiggling back and forth tho if it moved one direction maybe and even then it shouldn’t but back and forth is wrong

[deep cargo]

Not really. At least what's shown in the last video is not a problem.

[sly burrow]

The same movement is happening with motors moving the gantry and that’s the problem so there is something corresponding to this across pushing it by hand and the motors moving the gantry

[deep cargo]

Doesn't look like the same thing at all to me.

[sly burrow]

Can you do a belt comparison with shake n tune? Could you also send more photos of the belt paths

[deep cargo]

At least from looking at that top down view (the second video) it seems like is pushed forward (to the left in the picture) when toolhead is at either end in X (or backward when it's in the middle). If everything is verified to be square and parallel and A/B belts are tensioned correctly, I'd suspect something could be wrong with the belt path in the X/Y joints, and the belts aren't parallel between the toolhead carriage and those joints.

[balmy oracle]

Bełt route

I make a test maybe is worth showing. I'm manually pulling both belts at the time

Front view

[sly burrow]

Is the gantry parts tight on the linear rail blocks

[sly burrow]

Also the belts don’t look like they are in a straight line might be the angle bit towards the xy joint it looks like there is a gap between then they should be in a line looking down

[balmy oracle]

yes

[balmy oracle]

which photo?

[sly burrow]

This video

[balmy oracle]

You mention this?

[sly burrow]

Yes

I believe they should be more in line

I could be wrong I haven’t looked at a stock gantry in a while

[balmy oracle]

its because i have 20T pulley 16T should be smaller and upper belt would be shifted a litte bit left (in this case)

[sly burrow]

Ok are the pulleys the same size on both motors and are they the correct tooth spacing for the belt?

[deep cargo]

If the belts aren't parallel from the toolhead carriage into the XY joint idlers, something is definitely wrong there (and could very well cause these issues). And unless there's something going on due to the camera perspective, it looks like they aren't. Like some idler is the wrong size or not mounted right, or a belt is riding on the edge of it.

[balmy oracle]

yes pulleys the same size, this setup prints 5000m of filament, i have got this issue recently

[deep cargo]

even if they're the same size, are they the right size? (20T for the toothed one, a pair of F695 bearings for the flat one)

Could very well be you've had this issue forever, just that it got more noticeable with a bit more belt tension after you changed those or something.

Or the belt isn't going where it's supposed to over one of the idlers (the flat one is really hard to see, let alone take pictures of)

[balmy oracle]

yes im sure they are the right size.

[deep cargo]

in any case, if the belts aren't parallel (when looked at from straight above you shouldn't even be able to see the lower one), that is a problem, and if they are out-of-plane going into the xy joints, that is probably where that problem is.

[balmy oracle]

I will check this later, now i need to go to work, thanks for help

[balmy oracle]

After a search, I decided to take the gantry apart, clean it, and check the bearings and pulleys. And I think I may have found the cause.

[deep cargo]

That could certainly explain it.