Self-Test Y-Axis Issue - Y Axis can't remember where it is  

RE: Self-Test Y-Axis Issue - Y Axis can't remember where it is

Posted by: @echonuevo

New issue with my Prusa Mini has me stumped. I am unable to complete a Self-Test - consistently fails Y-Axis.

Mini has 200+ hours on it. Problem noticed on Firmware 4.0.5, still a problem with latest firmware update to 4.2.1 (took time off after previous tinkering efforts failed). No longer able to print. Cleaned printer regularly with canned air, and Y-Axis belt tension seems okay to me. 

Trouble-Shooting discoveries: 

1) Boot up the Mini after resetting from Auto-Home Calibration Test => Y-Axis says its at -3

2) Perform an Auto-Home Calibration Test => Finishes at same position, Y-Axis says its at 24, print bed appears to be where it should be

3) Press "Reset" button, wait for reboot, Y-Axis now says its at -3 (same position hasn't moved)

When I manually scroll the print bed toward me (i.e. Y+), the print bed reaches its physical Y+ stop (which should be +180), but the reading will be shy of 180 (like 150 or so) and I keep spinning the dial and the motor clunks repeatedly against the physical Y+ stop until the dial reads 180. Then I can manually send the print bed back (i.e. Y-) until it reaches the Y- stop (~-3) okay. I can then bring the print bed forward to 180 no problems and back to -3 no problems and repeat at nauseum, but if I repeat the Self-Test it still fails on Y-axis.

Note I am always able to perform a Auto-Home Calibration and the print bed ends up where it ought to be at Y = 24, regardless of where the print bed is before I start the Auto-Home Calibration. 

Please help - I'd like to get back to printing robots and cats with my toddler son. He misses his "Prusa-Robot". 

Thanks - 

J. D. - 

 

After each reset you must always perform a reference run (homing G28) of the axes so that the printer head knows its correct position in the axis system. After homing the position is X176, Y24, Z2. After that you should be able to position in all 3 axes from 0 to 180. If this is not the case, either one axis is stuck by an obstacle or the mechanical travel is too short.

Also check the belt tension and lubrication of the linear bearings and that the belt pulley is firmly seated. The belt must not be too loose, otherwise the axis can loose steps.

RE: Self-Test Y-Axis Issue - Y Axis can't remember where it is

Hi @karl-herbert , thanks for responding. How does one perform a "reference run - homing G28"? Is that different than performing an Auto-Home Calibration Test? I have performed the Auto-Home Calibration test and the Y-Axis ends at Y24 as you indicated, but then if I immediately do a Self-Test the test will fail (Y-Axis failure), or if instead I try and start a print, the print will fail (Y-axis failure). 

Is a "reference run" a different operation from a Auto-Home Calibration Test? 

J. D. - 

RE: Self-Test Y-Axis Issue - Y Axis can't remember where it is

@echonuevo

You can find some information about the "Mini Self Test" here: https://help.prusa3d.com/en/article/selftest-mini_112055
If this does not help, I would contact the Prusa Chat (Login with your Prusa account and select eshop).

RE: Self-Test Y-Axis Issue - Y Axis can't remember where it is

I believe it's in menu -> calibration -> Home? Or settings? Not sure and cannot check right now, MINI is printing. Home command is definitely somewhere in menu. It also gets executed before every print (Home with MBL, Home without MBL).

RE: Self-Test Y-Axis Issue - Y Axis can't remember where it is

I have the same issue. It started showing up with firmware 4.2.1. The printer was working ok before I upgraded. It does not get fixed when I select home. I have to disable the steppers and manually move the plate to zero before a print now. Also, my prints are now failing because the y axis forgets the zero position during the print.

RE: Self-Test Y-Axis Issue - Y Axis can't remember where it is

@humberto-r

This is exactly what is happening to mine. I could've taken that same video on my Prusa Mini. I had an inkling it was software. I will be rolling back to a previous software build and see if that helps. 

J - 

RE: Self-Test Y-Axis Issue - Y Axis can't remember where it is

@humberto-r

@echonuevo

I would contact the Prusachat and also link this video.
A firmware update should not produce errors of this kind.
I hope that the problem can be solved quickly for you!

Basically, all CNC controlled machines require a so-called "reference run" after switching on or after a reset, so that the machine can set an initial zero point. The system remembers this point until it resets or the machine is switched off. During operation, the machine must neither shift this "zero point" (unless this is planned by programming) nor delete it.

RE: Self-Test Y-Axis Issue - Y Axis can't remember where it is

@karl-herbert

Hi having same issue printer makes loud noise as though hitting it's full travel stop and keeps saying it's at -3 for Y axis but has no travel when you manually adjust, if I do auto home it says Y axis is at 24 but test says fail and keeps failing prints. My teenage son who's printer it is is getting very disheartened by it as it's only 4 months old and now can't print any help would be greatly appreciated Chris

RE: Self-Test Y-Axis Issue - Y Axis can't remember where it is

@crazee99

Did you run the self test again? What does the printer report there, or where does it get stuck?

Are the linear bearings running smoothly and is there no blockage in the area of the guide shafts - SPINDA correct adjusted - belt tension ok -  pulley well fastened (no loose screws)?

RE: Self-Test Y-Axis Issue - Y Axis can't remember where it is

@karl-herbert

Run self test again and printer says fail mini + , Y axis belt tensioned and not over tight slight deflection when pressed, bed makes loud clicking noise as though it wants to go further on it's travel spectrum but because it's starting in wrong position can't adjust bed axis to start at correct position. Has been fine until last week , checked for foreign objects and clear , bearing's are clean and lubricated,no slack in plates as only just 4months old all other axis correct but due to Y axis fail it keeps messing every print with layer shift???

RE: Self-Test Y-Axis Issue - Y Axis can't remember where it is

@crazee99

Have you checked the flatness and alignment of the print bed (no axis skew)?

https://help.prusa3d.com/en/article/xz-axis-skew-correction-mini_158518

You may also want to check all connectors on the printer board. A factory reset and reflash the firmware can often be helpful as well.

If you get stuck, I would contact the Prusachat.

good luck 👍 

RE: Self-Test Y-Axis Issue - Y Axis can't remember where it is

@crazee99

This has been explained several times here in the forum. There is no sense to remember any position between the switch off and switch on,  because during this time period you can move the extruder and the bed manuály and not having electricity the printer can not register how far did you move it. When you switch on, it sets the starting values which is for y -3. Each print starts with nozzle homing, which means the printer sets the starting  x,y,z values .

So the printing incapability could be caused by something else.

Would be better you to exactly describe your problem not 'I have the same' like. It is not always the same.

Add on. Do the selftest more times and check if the coordinates staying the same. do not reset the printer after calibration.

During homing  after the bed finds the physical "zero" position it is moved by those 24 steps not to be in physical contact with the frame. Try to find on google sensorless homing.

RE: Self-Test Y-Axis Issue - Y Axis can't remember where it is

Hi thanks am going to do a strip down and check all connections and clean everything then rebuild as new start up , firmware version is 4.2 printer was running fine and started making grinding noise on heated travel when it reaches end of travel even when I have auto homes it to requisite position of Y-24 from Y -03 so confused about why it is running out of travel but will post back when I have rebuilt it thoroughly thank you