"Bump" in Y-axis

Yup, ,I’ve got the exact same problem. Following what Support told me to do this weekend, change the Y linear rails out with the X linear rail. See if the problem follows. This should be fun.

I was also told to do the same thing by support for a slightly different issue. Seems like they are really trying to avoid replacing modules.

Well, cost aside, if swapping linear rails around gets your SM running again, that’s lots faster than shipping across the planet.

I’d prefer the response to be “swap your modules while we ship you a warranty replacement”

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So I’ve noticed this same issue since day one. Does anyone have an update on how support will choose to resolve this issue?

This worked for me, I laid the printer on its side, loosened all eight screws attaching the bed to the Y linear modules, applied even pressure by pulling the bed, then tightened a screw on each module, then the remaining 6 screws. My theory is the screw holes have enough play that the mounts on each module are not in perfect alignment. Applying pressure with the screws loosened puts the mounts in closer alignment, eliminating the Y bump.


Sorry for the long delay in updates again. I ended up getting a replacement linear module. Unfortunately, the home position of the new module was ~1mm further forward than my other modules. Luckily, my X-axis and the one good Y-axis module both had the same initial position, travel range and speed, so I moved my X-axis to the right side of the Y-axis, then put the new module as my X. So far, this has eliminated the bump and I have not had the binding happen during calibration. I’ve been able to print two objects successfully since I finished rebuilding it yesterday, including one in the front left quadrant, an area I have never been able to achieve proper bed adhesion before. I’ve had the A350 for two months now and I’m finally starting to feel like I can use the machine. Hopefully this is the last time I have to deal with this problem.


Hi All. Just wanted to add my experience to the discussion. I had a similar issues with my A350 (it seems to be only the 350s - has anyone had the issue with one of the other sizes?). When moving from front to back, it bumped at around the two-thirds mark, then when moving from back to front it again bumped two-thirds of the way along.
I took the various steps people have described here and the bump went away whenever anything was loosened - if there was any give in the system it wasn’t an issue; only appeared when everything was tight.
With some reeeaally careful measurements with a caliper I worked out that one module was moving slightly faster than the other - only a difference of about 0.8mm across the length of the module but clearly enough that they got out of alignment, hence the bump.
I swapped one with the X axis with no luck, but then when I swapped out the other it resolved the problem.
So now I’ve got what is clearly a (admittedly only slightly) defective linear module on my X-axis. Not sure whether I should pursue a replacement or not. For my purposes, an error of 0.8mm over the ~35cm length isn’t going to affect anything much, but I feel like it’s a bit of a poor effort when the company put such an emphasis on precision in their advertising.


Is the .8mm over 35cm consistent? like if you do a series of 100mm measurements is it 0.23mm out from 0 to 100mm, 50 to 150mm, all the way to 250 to 350mm?

If the pitch of the leadscrew is off consistently then the steps/mm can be adjusted.
For your example of a travel of 350.8mm vs commanded 350mm, instead of 400steps/mm, that would be compensated by changing the firmware to 399 steps/mm
M92 X399

If the pitch varies and is not consistent across the length of the leadscrew I would be requiring a replacement as that’s going to potentially leave visible artifacts in laser and cnc projects.

One or both of those modules is defective. You’re taking about around 0.2% difference in lead screw pitch over its length. A decent quality acme-threaded lead screw should be something smaller that 0.1%. (Acme threads are what’s in the linear module.) High-precision ball screws are at 0.01% or better. It’s possible that you’ve got one module at +0.1% and another at -0.1%, but while possible, that’s quite an unlikely outcome.

Snapmaker had a known batch of modules with out-of-tolerance lead screws. A manufacturer return may be in your future.

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LOL…I forsee them “solving” this by selling “matched” leadscrew module pairs. Like buying your DIMMs in pairs for computer builds.

As an update to mine… I’m seeing very mixed results. After seeing the exact same behavior between testing the laser and rotary tool, I tried loosening the screws that hold the platform and moving in the Y direction back and forth then re-tightening the screws to the platform. This seemed to work so I attached the 3d printing bed. When it tried to level it was horrible grating and grinding. Absolutely terrible. Worse than ever… then after a bit of back and forth with it… it seemed to be fine. Idk what’s going on

Hello friends,

Sorry to see how big of an issue this is, but I’m glad I’m not alone. I’ve experienced the “Y-bump” since day one at the similarly stated 2/3rds mark but inconsistently, but avoided issues in my work with smaller prints. Now with larger laser projects I need to solve it. Thank you to those who conducted creative experiments to determine the difference in lead screw tolerance in the linear modules. I will be taking apart my A350 to determine which modules I might switch to have a perfectly matched pair for the Y-axis, while I submit a ticket for a potential replacement.

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Not sure it helps with another post saying “I have the exact same problem”… but I do.
I have measured the alignment of the Y-axis and they have exactly the same distance. I tried to loosen the screws and tightened again. Tried to swap the Y-axis linear modules. Same problem. My modules are perfectly aligned.

Also confirmed now that the Y-axis linear screws travel different distances. One seems to be 1 mm ahead of the other even though they are the same in the beginning. The “bump” happens when they “sync” (in a not so nice way) again.

Has anybody actually got some feedback or reply from a Snapmaker official?

I would suggest to swap your axis till you find two pairs of matching ones.

Hi all, I’ll admit I haven’t read every post so I apologize if this has already been said. I was having this problem, especially when leveling the bed for 3d printing. I found a solution that has been holding up with no switching of linear modules necessary.

I applied blue Loctite (removable) to the screws. Screwed down tight then backed out about a quarter to a half turn for each screw. Loctite has kept the screws from backing out further and I have had many sucessful 3d prints and accurate laser etchings. Thought I’d share. Thanks.


I have read a lot about switching out axis modules etc. with this issue. Since I had this Y axis clunking myself and being and old machinist/engineer I discovered the problem is debris under the steel bands that cover the lead screws.
I cleaned the surface under the bands and cured the issue. The debris in my case came from surfacing the router table creating a large amount of dust.
When the axis travels it lifts the bands an rides on the extrusion. The debris cause the axis to bind thus causing the misalignment between the 2 slides.
I used compress air to blow the debris out of the covers. All is good now, I never would have found this if I had not run my finger down the band And felt the lump in the band.
Hope this helps

Nice shot! :grinning:

Could you please share some photos of the debris so that I can forward them to our mechanical engineers and ask them to look into this issue?



The debris came from surfacing the milling table (sawdust essentially).

It created some fine particles and I never saw them but the dust was all over the machine.

I must have gotten under the foil and between the slide.

My suggestion is to develop bellows to cover the slides.



The tightness of the steel strip can greatly affect the dust-proof performance of the linear module. We have conducted many dust-resistant tests with different degrees of tightness of the steel strips. And we found the optimal tightness to achieve the best dust-proof performance. We have also conducted this test on more materials (POM and Beech Wood) to ensure that steel strip can protect the main parts from dust and dirt in most scenarios.

As for the metallic debris, you can remove it with rags. And the debris will not fall into the linear modules.