Z-Axis grinding after print finishes
Hello!
I've had my i3 Mk3 for a few years now, and haven't run into any real issues before. However, recently I'm noticing a strange issue. For maybe one out of four prints, when the print is finished and the toolhead begins to lift on the Z-axis, a loud grinding sound is made. The toolhead/X-axis assembly increases in height much more slowly than normal while this grinding sound happens. This doesn't happen on every print, and it has happened across prints with different heights.
I've cleaned out the trapezoidal nuts (compressed air, cloth, brush) and cleaned the lead screws (brush). Whatever this issue is, it's also showing up in my prints as small bulges (I'm assuming the issues are linked as the noise and the bulges both cropped up recently). Images are linked here: ( https://imgur.com/a/y8PJHFE).
Has anyone else experienced this issue?
RE: Z-Axis grinding after print finishes
have you lubricated your smooth rods and bearings?
Joan
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK
RE: Z-Axis grinding after print finishes
I haven't, I can give this a shot and see if it helps!
RE: Z-Axis grinding after print finishes
https://help.prusa3d.com/guide/maintenance-tips_23200
this knowledge base article may help
regards Joan
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK
RE: Z-Axis grinding after print finishes
Thank you! The link was very helpful. I've cleaned and lubricated all of the rods. Unfortunately, it didn't help in reducing/eliminating the issue.
I've now tried the following:
New nozzle
New SD card
New filament
Cleaned/lubricated rods
Cleaned trapezoidal nuts
Cleaned lead screws
I'm unsure where to go from here. I could order a set of replacement trapezoidal nuts and see if that helps, but other than that I can't think of what to try.
RE: Z-Axis grinding after print finishes
I've replaced the trapezoidal nuts, but the issue persists! Interesting. On a recent test print, I had the grinding noise come up again. The gantry looked straight before the print but after the grinding noise, it looks like it is not straight. I ran the z-calibration afterwards because it looked like one side of the x-axis gantry was lower than the other, and the z-calibration confirmed this. It looks like the left side was lower than the right.
Could the grinding noise be because the left axis is rotating slower than right, and they are fighting each other?
RE: Z-Axis grinding after print finishes
Could the grinding noise be because the left axis is rotating slower than right, and they are fighting each other?
Yes, both steppers have to rotate at the same rate, if one isn't moving as well as the other or isn't moving at all the X axis gantry can tilt and that will cause stress on the motor that is rotating.
Based on what you've said I can think of 4 issues that may be your problem.
1) Connectors or wiring
2) Failed/Failing Stepper Motor
3) Vref set too low
4) Failed/Failing solder joint on Rambo
My best guess is you've got a poor contact where the stepper plugs into the Rambo board, check your connections and see that they're tight. You might even want to swap them and see if the problem goes away, stays with the same stepper or changes to the other one. If the problem remains the same then it could still be the connector, vibration may have cause the connector to open and no longer make good contact, or that stepper is failing. If you swap the cables and it changes the problem stepper then it could be a failing solder joint on the Rambo.
I include the Vref for completeness but it's unlikely the problem, this is set by Prusa and if that were the problem it would likely affect both motors. My bet is this is something in the connections or wiring. I had a similar problem with Ender3 on the X axis, most prints would work fine but occasionally the X axis would shudder can cause a layer shift. I replaced the connector and it's been fine ever since.
Cheers
-Bob
Prusa I3 Mk2 kit upgraded to Mk2.5s, Ender3 with many mods, Prusa Mini kit with Bondtech heat break, Prusa I3 Mk3s+ kit
RE: Z-Axis grinding after print finishes
I figured it out! Thank you to both Joan and Bob.
I tried changing the connection for each z-axis stepper motor to see if the problem would swap or if it would stay the same, and it ended up staying the same. Then, I tried a test print at a different location on the bed, and found that changing the location made the problem markedly worse. If it was solely a z-axis issue, I wouldn't expect changing the location to have an effect.
I checked my bed-levelling, and lo and behold... my bed was apparently wildly uneven. After tightening the screws (I'd done the Nylock-style mod a few years back) and ensuring the bed is level... my prints are back to normal!
A little anti-climactic, but the problem is solved. I'm unsure how the bed being that unlevel would lead to the z-axis lead screws not moving in sync... but I'm happy i'm back up and running! Thanks again for all the help!