Calibration Fails after printing happily for a couple of years
Hi there, I have a Prusa MK3S that I bought in 2020. I was able to assemble, calibrate and test the printer, and it's been printing happily since Aug/Sep 2020. late last year, I printed two things back to back, the first item succeeded, but the second print failed - it's been a few months so unfortunately I can't remember what the problem was, but in any case, I started troubleshooting, and began my troubleshooting by rechecking calibration.
Now, whenever I try to calibrate the printer, it seems to fail - firstly, if I self test, the fans show up OK, but the X-Axis length test fails. I checked the usual suspects - moved the extruder all the way back to the left, and performed an autohome. I have even factory reset the printer, and updated to the latest firmware. However, despite this, when performing an X axis Cal, the printer moves the extruder all the way to the right, and almost immediately fails. Again, I checked the obvious suspects (Zip ties on the extruder cable bundle hitting the end stops, making sure the extruder is set back to it's left-most position at the start of the cal, ensuring the bearing rods are clean of any dirt, etc. I also checked forum threads like this one: https://forum.prusa3d.com/forum/original-prusa-i3-mk3s-mk3-hardware-firmware-and-software-help/im-stumped-self-test-error-axis-length-x-axis/ to see if there was anything else I missed, but I'm stumped.
The only thing I note is that although the extruder moves smoothly along the x-axis, it is MUCH easier to move to the right (your right as you face the printer), whereas moving to the left takes a noticeable amount of effort. That being said, it doesn't seem like there's any obstructions on the bearing threads. While incredibly tight, I've also been able to get a sheet of paper between the zip ties and the printer frame when the extruder is all the way to either side (so I'm pretty sure there is a thin gap there.
Also, if I instead try to select XYZ calibration as opposed to starting with a self-test, the bed calibration seems to fail - Again, despite checking the PINDA sensor's operation (and even reseating the sensor today), the bed calibration point on the front right always seems to catch the paper on the bed, and even start to damage the heated bed slightly! I have a feeling this is again, a symptom of an incorrect x axis, but I'm not sure.
I'm out of ideas. If anyone's got any better ones, I'd love to hear them. if you guys want pics or videos to show what's going on, I'll be happy to provide.
Thanks In Advance!
RE: Calibration Fails after printing happily for a couple of years
have you lubricated your smooth rods and bearings? do your X and Y idlers rotate smoothly? there should be no noticeable difference in effort to move in one direction, or the other
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: Calibration Fails after printing happily for a couple of years
Thanks - Lubrication was going to be the next thing I try - I'm waiting on a delivery of lubricant (although its' out of stock on the webstore so I had to go third party.) I'll check and report back. Sorry, are idlers the stepper motors?
RE: Calibration Fails after printing happily for a couple of years
At one end of the X and Y Belt assembly, you have a stepper motor, at the other end, you have an idler wheel, which turns the belt around and feeds it back to the X or Y carriage, as the motor moves the assembly
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: Calibration Fails after printing happily for a couple of years
Ah, I see. I think they rotate smoothly, but hard to tell exactly which part is giving resistance. I think what I am going to do (unless there are good reasons not to), is since the rails themselves feel very smooth but dry, I am going to remove the entire extruder assembly from the x axis rails, and regrease both the z and x axis (y axis feels ok since it's a bit more protected from dust, and still moves quite smoothly). Are there any reasons this would be a bad idea?
Is there also a good procedure to do this? Otherwise my plan was to take the top Z axis holders off, lift the entire x axis assembly off, remove the x axis from rails, apply lubricant and then put the whole thing back together.
RE: Calibration Fails after printing happily for a couple of years
A less invasive option, is to follow the Prusa maintenance tips.
https://help.prusa3d.com/guide/maintenance-tips_23200
proper functionality only requires a very thin layer of lubricant. overfilling the bearing cases, can cause the bearings to slide instead of rolling, which can be very destructive. causing grooves in the rods very quickly.
https://help.prusa3d.com/article/i3-printer-regular-maintenance_2072
If the above procedures are unsatisfactory, you can try disassembly.
you will probably need to remove the Z top brackets, and the Z motor retaining screws, in order to get enough space to remove the X axis ends from the lead screws and Z axis smooth rods.
I woud lubricate the Y axis whilst you have the |Lubrication handy...
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: Calibration Fails after printing happily for a couple of years
Ah thanks! That sounds perfect, much appreciated! Look forward to trying when my lubricant arrives...
RE: Calibration Fails after printing happily for a couple of years
Me again! I got my lubricant, but I've also since noticed that at least one of my x-axis rods has a groove in it - not sure if this is contributing to the resistance of the extruder movement as it moves to the right. But I figure I should probably try to replace the bearings and rods.
Is it advisable to replace all the bearings, rods, and belts for the printer at once? Shipping from the prusa store to the UK is pretty expensive, so if you have any recommendations (and suggestions on local stores in the UK, if that's allowed), I'd be very grateful!
RE: Calibration Fails after printing happily for a couple of years
https://lecktor.com/en/linear-rods/2-misumi-psfj8-rods-set-for-prusa-mk3mk2s.html
may be an option for the rods.
https://lecktor.com/en/bearings/1-misumi-linear-bearing-lmu8.html
Bearings
and if you want them, 2GT Timing belts
https://lecktor.com/en/15-timing-belts
NOTE, it is worthwhile getting good belts by 'Gates' or any brand name...
I have no connection with Lecktor, nore have I bought from them.
My normal suppliers seem to be out of stock of X axis rods.
regard 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