Y Axis not finding home, weird calibration errors, self tests A-OK?
I'm having issues with my new Mk3 kit. I assembled it and it tests out OK, passes all self tests fine. I go to test print the Prusa logo plate and the print head gets almost all the way around the outline of the base on the very first layer, then stops with a crash detection (although it is hitting nothing). It's always in the same spot while it's moving toward the back of the build plate on the left side looking from the front. It then does this weird kind of reset where the base plate moves back and it tries to keep printing about 3 inches back on the plate. I've checked for obstructions, zip tie heads and the like and everything moves freely. When there's no power applied things move fine with no obstructions.
The printer also seems to "forget" where it is during the print head adjustment test when I run it; what I mean is the first one goes fine, and it deposits the initial line along the edge of the build plate then goes to the back and starts laying down the zig-zag pattern, and completes it successfully; it's hard to get it where I want in one pass, so when I run it again instead of running the build plate all the way back to the back so it can do the pressure leveling line across the front of the build plate it just kind of plops it out in the middle of the build plate, goes to the back (with lots of skipped stepping noises when it hits the back) and then tries to start all over again.
When I do the nine point bed leveling calibration it also will "forget" where it is, and starts half way through the plate instead of up front (failing to move the build plate all the way to the back). It will get to the back of the build plate and start step skipping but the printer fails to recognize it's all the way forward, and keeps acting as if it's going through a successful 9 point measuring. Sometimes the PINDA probe appears perilously close to the build plate locating posts and may even bump them slightly on the way by with no crash detection, btw.
I'm thinking I might have a bad Y axis stepper motor despite it passing self tests but could this be a logic board issue? Where to go from here?
Help?!?
RE: Y Axis not finding home, weird calibration errors, self tests A-OK?
Update: Thanks to a helpful suggestion on the FaceBook Prusa group, I turned off crash detection and the printer is functional.
I am still left with the question of "why"? The printer is cranking out prints now and aside from some filament binding on the spool (not the printer's fault) is working fine. I've had suggestions to lube the bearings on the Y axis up to and including disassembling the printer and packing the bearings with lithium grease (contrary to the Prusa instruction manual). Is this really necessary? Why is it working fine once I turn off crash detection? My calibration tests tell me I have below the minimum skew and the Y axis bed moves freely when powered down.
RE: Y Axis not finding home, weird calibration errors, self tests A-OK?
@richbusby
Hi Rich,
I purchased an Mk3 (fully assembled and tested) a couple months ago and I am having the exact same issues. It is a bit frustrating so I understand what you are going through. For me it is not happening all the time. I went for several weeks without any issues and then today it happened again. When I tried going through the xyz calibration, it would fail on the Y axis travel test. I turned the machine off and then on its side to see if there was anything interfering with the Y axis but everything looks normal. I moved the Y axis back and forth several times and it certainly doesn't feel like its moving freely to me. When I move the bed away from the LCD display, it is tight but moving it towards the LCD, it seems to move somewhat easy. I was tempted to remove the Y axis belt to get a better feel for how freely it does actually move but i decided to retry xyz calibration before tearing things apart. This time the calibration passed and I was able to start printing again. I also checked 8.5 View XYZ Calibration details from the HANDBOOK which includes the perpendicularity test. Everything seems to be normal. When I scrolled through the LCD display to explore the number of crashes, I had something like 37 Y axis crashes to date. The thing that really bothers me is when this condition does happen, the Y axis is hitting the stop and the motors vibrate like crazy. When i try to home the machine, it cannot find its way home and again I get this violent shaking and vibrating. This cannot be good for the machine.
It seems to be working right now but I am certain it will come back. I like the idea of turning off the crash detection but like you, I would prefer to understand why this is happening and if there is something that can be done to fix it. I have not had much luck with the customer support people at Prusa on simple problems so I was reluctant to go down that path again with what seems to be a more complicated issue.
I was also having trouble finding any warranty information. Does anyone know what the Prusa warranty policy is?
I am sorry I wasn't able to help you fix your issue but I thought you might like to know that you're not alone. Also, that my factory assembled and tested machine is doing it too.
Scott
RE: Y Axis not finding home, weird calibration errors, self tests A-OK?
@scott-7
Thanks for the reply. I've received a few suggestions to take the bearings apart and lube them with bearing grease contrary to the instruction manual and have half a mind to try that. If the thing is overly sensitive to resistance on the Y axis that could be the issue. When assembling my kit, I was surprised they did not have a step to lube the bearings (having an automotive background I expect bearings to get greased!) but wanted to follow the instructions to a "T".
RE: Y Axis not finding home, weird calibration errors, self tests A-OK?
@richbusby
Hey Rich,
A friend of mine is stopping over tomorrow to take a closer look at my Y axis. I will let you know if he discovers anything worth posting. It doesn't appear that anyone here is interested in helping you with your issue. Do Prusa employees monitor this forum or are we on our own?
RE: Y Axis not finding home, weird calibration errors, self tests A-OK?
If you want support from Prusa - click EShop above, log in and / or register, and a Chat button will show up.
Folks on this forum are just other users like yourself. Terrible place to expect Prusa support.
Most common problem new users seem to have is tightening the UBolts of Death too tight. That crushes the bearings.
Any binding is easy to feel. Just power off and move Y from end to end. It must be smooth both directions.
A bit of oil on the rods is OK as a temporary measure to check binding. And I do mean temporary. Lubricate them correctly as soon as you can.
Turning off crash detection is pretty much a terrible idea. It just hides your problems. They will bite you in the end.
RE: Y Axis not finding home, weird calibration errors, self tests A-OK?
If you want support from Prusa - click EShop above, log in and / or register, and a Chat button will show up.
Folks on this forum are just other users like yourself. Terrible place to expect Prusa support.
Most common problem new users seem to have is tightening the UBolts of Death too tight. That crushes the bearings.
Any binding is easy to feel. Just power off and move Y from end to end. It must be smooth both directions.
A bit of oil on the rods is OK as a temporary measure to check binding. And I do mean temporary. Lubricate them correctly as soon as you can.
Turning off crash detection is pretty much a terrible idea. It just hides your problems. They will bite you in the end.
Thanks for the pointer on how to get Prusa in a chat window. I don't think it's unreasonable to ask if Prusa support monitors this forum.
Ultimately I found out that the belt gear on the Y axis was installed too close to the stepper motor face. When it was cold things moved OK, but after printing for a while friction on the face of the motor/gear contact face caused binding as things expanded. It didn't help that a wisp of PLA made it's way into the gap and gummed things up. With the belt off everything moves super smooth with no binding so I've cleaned it up, put a smidge of grease on the back side of the gear and reassembled everything ensuring a gap between the head and the motor. Benchie printed just fine.
RE: Y Axis not finding home, weird calibration errors, self tests A-OK?
Hey Rich,
Glad you discovered what was causing your issue. I am pretty confident I resolved mine also. My friend discovered that there was some sticky residue on the Y axis rods. It appeared to be almost like a tape residue. We cleaned all the rails with some isopropyl and it has been working great ever since. I actually forgot that I turned crash detection off and after reading the post above, I will turn it back on. Have you turned yours back on?