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y-axis not homing before prints or after crashes  

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connor.d
(@connor-d)
New Member
y-axis not homing before prints or after crashes

I haven't used my Mk3 printer in a while (I only use it for printing enclosures for electronics projects and they take a long time). I have just powered it up today and flashed the most recent firmware on it. I noticed that the y axis sometimes doesn't reset when starting a print or between crashes. The printer will then continue under the assumption that the bed is homed and therefore tries to move the y-axis out of it's range, causing a rather loud noise due to high resistance for the motors.

I have spent the past two hours troubleshooting and re-calibrating, I am still yet to find the cause of the issue. One odd thing I have found however is that the belt tension values for the y motor make no sense, it's reading ~210 with really low tension in the belt, I don't know if this is because the y-motor has become damaged from the out of y range problem. This printer really hasn't seen much use as I've already mentioned, so I don't imagine the y-motor would have been damaged under normal use.

Thanks,

Connor

Best Answer by Olef:

The motor stalling is how the printer senses home has been reached. If you did not have smooth and easy bed travel all the way from one end of the rods to the other then that was your issue.

Posted : 07/09/2019 4:06 pm
connor.d
(@connor-d)
New Member
Topic starter answered:
RE: y-axis not homing before prints or after crashes

Update: I have done some troubleshooting and I think I may have fixed the problem. I disconnected the motor to check the resistance to movement of the bed itself. With the motor disconnected the bed was still quite stiff so I disassembled the bed to take a look at how tight the u bolts were, I loosened them all up completely and re-tightened them whilst feeling how much they could move. Now I have put everything back together I've checked the belt tension numbers and the y is around 245 now.

I have not seen an autohome fail yet after quite a bit of cautious testing. Is it possible that the motor was stalling and firmware just wasn't checking if it homed or not? Despite my issue being fixed, I'll leave this thread unsolved as it seems like something the firmware should absolutely check for.

Posted : 10/09/2019 8:33 pm
Olef
 Olef
(@olef)
Honorable Member
RE: y-axis not homing before prints or after crashes

The motor stalling is how the printer senses home has been reached. If you did not have smooth and easy bed travel all the way from one end of the rods to the other then that was your issue.

Posted : 11/09/2019 1:42 pm
connor.d
(@connor-d)
New Member
Topic starter answered:
RE: y-axis not homing before prints or after crashes

Okay, that's interesting, thanks for letting me know. It's odd that I've never seen this behaviour before.

Posted : 11/09/2019 7:51 pm
connor.d
(@connor-d)
New Member
Topic starter answered:
RE: y-axis not homing before prints or after crashes

Update: Although the initial issue was fixed, I was still struggling with an overly stiff y-axis even when the belt was completely loose. This was causing y-axis shifts in prints.

I have now seemingly reduced the y-axis stiffness considerably simply by cleaning the linear rods, and then applying some oil. The y-axis now slides when the printer is held at 45 degrees whereas before this didn't happen even at 90 degrees. So if anyone else ever comes across this same issue, just clean your rods.

Thanks,
Connor

Posted : 15/09/2019 10:31 am
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