X axis homing issues (MK3S)
I have a MK3S for roughly 6 months now, and have had a great time with it so far. Prints have been great in PLA, PETG and Nylon.
However, about a week ago my printer stopped auto-homing correctly on the x-axis. When attempting to autohome the X axis will not move left from where it starts. It will move the back-and-forth right-and-left to the initial position, but it will not initially move all the way to the left (point 0.0) like it used to.
If I disable steppers I can manually move it to 0.0, and then autohome is "correct enough." If I leave crash detection on, though, it will detect a "crash" and stop printing. If I try to resume the print it autohomes incorrectly and won't start from 0.0. If I disable crash detection I can get decent print. I was able to print a new right (idler) X-axis end to replace the existing one which I noticed had a crack in it. However, a second print did experience one shift in it, but largely printed fine.
Before replacing the X axis bearings I did notice it did seem a bit harder to move the X axis left, but certainly not too hard. After replacing it seems like both directions are moving similarly.
I have tried the following (in no particular order):
- Replaced the X and Y axis bearings (both sets seemed fine after removing)
- Re-tensioned the X axis belt (a couple of times)
- Reprinted and replaced the right side X axis (idler) end after noticing some cracks in it (though, they were there for plenty of successful prints too)
- Checked both the X and Z axis rods (both sets seem straight by rolling them on a flat surface)
- After "manually" homing the X axis done multiple complete 0-250mm X axis movements without issue
Does anyone have any more ideas? These seem like the most likely culprits so I'm a bit stumped. Is it possible the X axis motor needs replacing?
Best Answer by rmm200:
Still sounds like binding. If you replaced the bearings - and greased them - check for them being clamped too tight.
The axis should move freely both directions with power off.
Too tight U bolts on Y and too tight screws on X seem to be common. And don't forget the idler wheels have bearings too.
My setup: i3 Mk3S with Lack enclosure. PLA, PETG, Nylon. PrusaSlicer. Windows 10 & Ubuntu Linux. Sketchup & Fusion 360. OctoPrint on a Raspberry Pi 3 B+.
RE: X axis homing issues (MK3S)
Still sounds like binding. If you replaced the bearings - and greased them - check for them being clamped too tight.
The axis should move freely both directions with power off.
Too tight U bolts on Y and too tight screws on X seem to be common. And don't forget the idler wheels have bearings too.
RE: X axis homing issues (MK3S)
Just summary about homing: the normal x axis home position is detected by stalling the extruder to the mechanical left end position. Stalling the stepper motor the motor current increases and this is detected by electronics as end position. So if durin the calibration move the movement resistance increases the current over the set threshold for stalling ,it detects a false x home position.
So bearings (greasing), rods (their exact parallel positon) and the belt (tension) has to be checked and adjusted.
even an old man can learn new things 🙂
Standard I3 mk3s, MMU2S, Prusa Enclosure, Fusion 360, PrusaSlicer, Windows 10
PRUSA MINI+ Prusalink + Prusa Connect
RE: X axis homing issues (MK3S)
Still sounds like binding. If you replaced the bearings - and greased them - check for them being clamped too tight.
The axis should move freely both directions with power off.
Too tight U bolts on Y and too tight screws on X seem to be common. And don't forget the idler wheels have bearings too.
This is good advice. I don't recall seeing this in my debug searching, but I've backed off the screws on the back of the X axis housing so they are less tight. It does seem to move a bit more freely now. I also loosened the X axis belt just a hair as well.
I've started a 5 hour test build (benchy with 0.07mm layers) to see how things go. I'll definitely post an update soon.
As a bit more background: After I posted my message, but before the replies, I did perform a factory reset yesterday, went through the setup wizard, etc. It helped temporarily; I was able to get one simple print (~1 hour) out. However, after getting 1-2 hours in to a longer second-print the same issues (crash detected, autohome on the X axis failing) reared their ugly heads. So, it seemed at first like that could have played a role at first, but likely didn't.
Finally, thank you @zoltan for the background. That was one of the reasons I wondered whether a faulty motor could be causing the issue. I took a minute to measure the inner and outer spacing on my X axis rods with my (cheap) digital calipers as well. They appear to be OK; at least as much as I'm willing to trust my skills with cheap calipers. 🙂 (The measurements were <0.1mm different, and that I'm chalking up to the aforementioned poor skills and cheap digital calipers.)
My setup: i3 Mk3S with Lack enclosure. PLA, PETG, Nylon. PrusaSlicer. Windows 10 & Ubuntu Linux. Sketchup & Fusion 360. OctoPrint on a Raspberry Pi 3 B+.
RE: X axis homing issues (MK3S)
Also - HOME is as Zoltan said, where the printer smashes the extruder far left, and the bed far back; then it moves from that "home" to a spot roughly centered above the cal dot on the heat bed. This second move will depend on the last successful XYZ calibration. And changing belt tension changes the calibration; so recommend you do another XYZ after your belt adjustment.
RE: X axis homing issues (MK3S)
Thanks everyone for your help. The issue does appear to have been related to the tightness of the screws on the back of the "X axis / extruder mount." I'm not sure why it came about so long in to use other than maybe the bearing just finally warped enough to cause the issues. My Benchy print failed, but that was a bed adhesion issue. I then did my 13-14 hour print to be sure, and it turned out great.
@tim-m30 - Always a good point to bring up. Basically, after any change I made I re-ran the calibrations, if not the whole "first time setup" just to be safe.
My setup: i3 Mk3S with Lack enclosure. PLA, PETG, Nylon. PrusaSlicer. Windows 10 & Ubuntu Linux. Sketchup & Fusion 360. OctoPrint on a Raspberry Pi 3 B+.