I sought help online and found that this is called “Z Wobble” and can be caused by a bent screw on the inside of the linear module. I disassembled the printer, and found that the Left Z Linear Module behaves differently than the other modules - if I push down the moving bit with constant force, it moves unevenly and has different resistance through the process. I did not observe a bent screw however - I took it out and put it against the module’s wall and it seemed as flat as the module itself. Here’s a movie and sound from me applying constant force to the moving element: Microsoft OneDrive - Access files anywhere. Create docs with free Office Online.
I’m not quite sure what is wrong and how to fix it. I did contact Snapmaker support, we’ll see how that goes.
@Cousken what in the heck? I’ve never seen this before, it sounds like the motor itself is having an issue turning, is the shaft of the motor bent? I’ve never taken a rail apart so I don’t know what it looks like after taking the lead screw out, but it definitely sounds like the motor is having a lot of resistance happen, maybe it’s the bushing?
I’m not an engineer (software developer) but i have followed an engineer’s tutorial on how to disassemble it. I guess I’ll keep taking it apart and documenting. At best, i can spot something that’s off, otherwise I’ll just report it here as good as i can and hope for input
Good idea. Also if @Cousken you remove the metal strip, reattach the end plate and energize the rail and move it can you see or measure wobble in the lead screw? Does it make the same pulsing noise while energized and being moved in one direction for say 200mm?
PS in disassembling my two rails I noticed significant difference in my ability to slide the traveler back onto the rail from front. One was easy, other was impossible. Only way I could get the traveler back on to my rebuilt rail was to remove the lead screw completely. This is the rail where I observed the z wobble too. We will see if the bearing adjustment fixed it later today….
Hey Scyto! Thanks for your reply. I gotta admit i didn’t understand most of your message, many of those terms are unknown to me, i’m not a native english speaker.
Bearing gap?
I haven’t tried removing the rail guides, i assume you mean the two … pipes or cylinders the “platform” (what is the correct term for the moving bit?) moves along.
What i did do was take the motor with the lead screw attached out of the module. I tried moving the “platform” up and down the entire module and it seemed smooth like butter, so i don’t think the issue is there.
I put the “platform” back on the screw outside of the module. It could spin pretty freely by me just shaking the whole thing, i managed to get it all the way down to the motor this way (without actually touching the “platform”, just shaking / waving it in a circular motion so that the “platform” spins on the screw and moves down). So i don’t think the screw has any issues. There was a moment where there seemed to be more resistance, but nothing that had me worried.
Then, i tried grabbing the platform and moving it up and down the screw by force. Oh boy, that was hard. I observed the resistance here again, it’s definitional happening in the motor. Sadly, i didn’t have the confidence to disassemble the motor, it looked way above my pay grade. Is it something you think i should brave?
Another problem - at the “top” (opposite side of the module to where the cable is attacked) end of the module, there is a small metal pin. I happened to bend it all to hell. I understand that it’s supposed to push down the button when the “platform” reaches the top. I’m worried i damaged it irreparably. I bent it to more or less what i think it looks like - here i think some reference picture could def. help, @scyto , but i might have just wrecked the module.
My idea is that for now i can use this module for the Y Axis, since there two modules work together. Hopefully this is enough to eliminate the effects of this error. And then of course replace the module, hopefully by one provided by Snapmaker support as this is def. not a problem that i cause, i can’t imagine how i would have.
I’ll run off and make some videos of how it behaves.
Hi, sounds like you have checked everything, nicely done. Yeah I don’t know what the little round rails are called that the bearing runs on, but the are removable too and can be pushed out (so long as you unscrewed the square internal plate thing.
I was just hypothesizing if those little tiny round rails were warped in some way it would alter the pressure between that and bearings, (aka I am guessing!)
I hear you on how easy it is to wreck. I might have broke one traveler by over tightening grub screw and one end stop switch. It’s 10am here will take some pictures. Unless you are super handy with mechanical objects I wouldn’t advise opening the rail unless a)support have told you and b) you are ok to break it. I have 6 y rails (first set had slope, second set had wobble, third set - calibrated by support arrived but cable on one is borked) so I have plenty of spare components… it took me 3 days to figure out how to get one rail fully back together. I am sure Brent and a others can do it in minutes. Also if you want more of a real-time chat, come to the discord, much easier to share stuff.
I got some reference pictures online for the “end-stop” or limit switch here - Excessive play in x-axis linear module bracket - #28 by MooseJuice I actually do have some precision tools and am quite handy so it might just be ok - for a while untill i replace the whole thing at least. The button seems to click nicely when the platform reaches the end of the module. So no worries about taking pictures for my sake @scyto
Here’s some movies that in my mind prove the problem is in the motor module -
I’d love to join the Discord! Guess i missed there was one. Could you provide a link?
Discord its pretty quiet, but the folks are helpful and friendly.
Well you are obviously more mechanically inclined that me - i am still concerned at that pulsing noise as you move the lead screw - not one of the 6 i have had made that noise.
There’s a basic mechanical difference between a lead screw driving a lead nut and a lead nut driving a lead screw. Screws easily drive nuts; nuts do not easily drive screws. Of course there’s stiffness when you push on the lead nut.
Indeed, pushing on a lead nut puts compressive forces on the lead screw and can be a pretty effective way of bending it. If it was already bent a little it’s far more likely to bend even more.
The wobble to look out for is in the platform, wobbling rotation about the X axis in the Y-Z plane. It’s a fundamental design flaw of the SM. In the Y axis they’ve affixed a 300 mm platform on a 15 mm support, a 20:1 torque arm. At that ratio it doesn’t take much for the platform to wobble, even just from mechanical vibration.
Hello eh9, thanks for your reply!
I’ll try to explain more clearly - one of the 5 linear modules i have has bigger resistance to push than the other 5. Also, the resistance is uneven throughout the push if moving the platform all the way, and even stronger pushing it the other way. This is not the case with the other 4.
I didn’t really understand your last paragraph, as mentioned I’m not an engineer. I’ll give it more time and thought and maybe I’ll get what you mean, but wouldn’t mind if you dumbed it down for me. Even better, can you suggest steps to offset this problem?
Absolutely, it was the first people i contacted. I’m just waiting for reply, it’s the weekend after all.
I did reassemble the machine with the faulty module as part of the Y axis, and it seems to have minimized the wobble drastically. The remaining wobble might be due to the other issue people seem to mention here a lot. I do realize this isn’t really a solution, just a band aid, in worst case i am damaging my other Y module due to increased burden. One way or the other i am at getting the faulty one replaced asap.
Did you check / adjust the bearing gap? It seems to have made huge difference to the wobble on my rail (I put it back together yesterday). Glad to hear yours improving.
