Y-Axis randomly slipping since MK4 Upgrade
Ever since I upgraded my MK3S+ to MK4, the Y-Axis is randomly slipping during printing. The slip is always multiple centimeters.
Sometimes I can print for days without an issue, today it happened 3 times, at different stages of the same print.
The self test of the axes succeeds every time. Sometimes before a print it does the more violent recalibration of the Y-Axis. Not sure if that is normal or part of the issue.
This happened with FW 5.0.0 and is still present with FW 5.1.2.
I can move the Y-Axis smoothly from front to back by hand. I'd say I can move it slightly easier than the X-Axis.
Like this I do not even dare to try larger prints anymore. It is quite likely they will fail.
Before the MK4 upgrade I hade random collision incidents, but these were always detected and the printer automatically recalibrated X and Y and then continued to print. The MK4 does not detect the axis slipping.
By chance I witnessed the slipping once. It was on a fast travel. The motor made a high pitched noise, so I assume the stepper motor just slipped.
I did not modify any speeds or accelerations. Fast travel is at 200mm/s. After the slip the print continues as if nothing happened, but with an offset in the Y-Axis.
Any tips what I could try to find the cause of this issue?
Thanks, Reinhard.
RE: Y-Axis randomly slipping since MK4 Upgrade
I did some basic maintenance an the axes: Clean the rods, check cabeling, ... nothing I could see there.
So I did another attempt on my 15h print ... and it failed after about 10h.
Since this was during the night I didn't catch it immediately, and funny enough a couple 100 layer up it corrected itself and I have the same step backwards in the print.
I assume it detected a crash and re-zeroed the Y-Axis?
Next test was a hand written gcode file which only runs the Y-axis back and forth at speed:
G0 Y250 F18000
G0 Y0 F18000
a 1000 time. Runs for just over 30 minutes without any issues.
I was wondering why I did find the max speed in a generated gcode file to be F18000, where I would have expected F12000, since that would be 200mm/s.
I also saw that the flat side surfaces in Y-direction show a high frequency wave pattern, where the large side surfaces in X-Direction do not
RE: Y-Axis randomly slipping since MK4 Upgrade
I have now replaced the Y-Axis smooth rods and bearings. I also checked the belt tension, and I think it was a bit tight. Also the tensioner block might have been a bit loose. So after tightening the belt correctly I could now print a whole day without any issues. But the high frequency wave pattern is still there on flat surfaces in Y-Direction.
RE: Y-Axis randomly slipping since MK4 Upgrade
Check in the menu to see if there were any crashes on the previous print I suspect that's what causing the shift.
If there were crashes turn off crash detection and run the print again
I had an Mk3S+ that would crash for no reason after multiple hours of printing. I was never able to solve it even after months of troubleshooting and replacing everything including stepper motors and even the Einsey board. It would run flawlessly with crash detection off.
I finally after about 6 months ended up returning the printer and buying another printer which has had no issues. I asked Prusa to tell me what they found but I never heard anything.
FWIW I never had a failed print with crash detection off. I'm not sure in reality that the crash feature works very well because there would always be a small layer shift after the crash, so the parts were no good anyways.
Good luck.
RE: Y-Axis randomly slipping since MK4 Upgrade
After thinking about it for over a year one thing I didn't try that I should mention is that I suspect the issue was possibly related to the frame twisting or something as it became heat soaked. Hence the reason the phantom crashes would only occur hours into a print.
Maybe breaking the breaking the screws loose for the guide shafts when the frame was heat soaked and then re tightening them to allow the guide rods to move where the want. It's a stretch, but maybe worth a shot.
Or just turn crash detection off and move on. Like I said in my experience any print with a crash was junk anyways.
RE: Y-Axis randomly slipping since MK4 Upgrade
On my MK3S+ I had crashes on a regular basis, but the printer would always detect them, re-zero X and Y and continue the print perfectly.
The issue is that on the MK4 it does not detect the axis slipping and just continues.
Also my issue sometimes happen right after starting the print, sometimes many hours in. So it's not heat soak.
But as written above, replacing rods and bearings, and readjust belt tension it works fine again.
It most likely was the belt tension being a bit to tight. But the bearings were a takeover from the MK3 anyways, and changing them is not hard.
RE: Y-Axis randomly slipping since MK4 Upgrade
I had a similar multi-centimiter layer shift failure last week. Noticed the y-belt was loose. After fixing that it did perfect on a few long prints (18-32hr), then suddenly failed again on a small 2hr print. The y-belt was loose again, almost sagging down.
The issue in my case is that one of the belt anchors (the one facing back) is no longer able to grip the belt thight enough. You can see the gap in the picture where the belt moved, and I'm attaching a link to a video (hope it works) where you can see how easuly I'm able to make the belt slip.
Going to reprint those parts and I'm even considering adding some epoxy to lock the belt ends in place (but I know I'll regret it when I have to replace the belt some day)
Eddy
if the video doesnt show, this is the link to it on youtube https://youtube.com/shorts/NmOMUUI5RoI?feature=shared
@osre - check your drive belt pulley grub screws.
See Step 32 on: https://help.prusa3d.com/guide/2-frame-assembly_427481#428839
Cheerio,
RE:
Chcete-li @eddy
Máte zajišťovací šrouby M3x10 vložené do napínáku řemene podle pokynů k upgradu sestavy vozíku Y krok 39 a 40? Prodloužení pásu přes zuby mě vede k domněnce, že tyto šrouby chybí.
RE: Y-Axis randomly slipping since MK4 Upgrade
My issue was actually fully solved by replacing the bearings and re-tightening the belt corectly. Mine was a bit to tight. Since then, no more issues.
RE: Y-Axis randomly slipping since MK4 Upgrade
Thanks Osre, and yes that was about the 2 or 3rd thing I checked when doing the initial trouble shooting.
RE: Y-Axis randomly slipping since MK4 Upgrade
Thanks Miroslav - I bought the printer "pre assembled" so all the screws and grub screws where in place.
I'll be honest and admit that I went full-nuclear on my solution and actually epoxied the ends of the belt in place. I was just going to reprint some new parts (and get a new belt), but I'm thinking I might just to ahead and add some positive locking features to the model like a grub/set screw to really lock the belt ends in place - I know I'll add a few grams of weight but it's probably irrelevant for the hobby level stuff I do. I'll post my remix of the belt holders on printables, and yes I'll use the smallest blunt set screw I can get may hands on 🙂
Thank you all for the great feedback ... would any of your have an XL? I'm stuck on getting past the filament sensor test since the last update ... grrrrrrh
Cheers,
Eddy
RE: Y-Axis randomly slipping since MK4 Upgrade
Got the same issue with assembled MK4 shipped in February 2024.
Temporarily fixed by adding thin pieces of plastic onto the belt inside the holder and printed new Y belt holders.
Now I suspect I'll need the replacement belts for MK4.
Does anyone know where are MK4 X and Y belts available? Can't seem to find them in the spare parts list/webshop, only Mini and MK3 ones are available with explicit warning that mk4 is not compatible.