[Closed] Z-axis failure  

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lcemoore
(@lcemoore)
Active Member

Have to get advice on a failed print. It appears that the z-axis motors just stopped moving during the print.   Before cancelling the print, I observed the z-axis motors slipping with no movement on the axis.  This is the third print on this printer, but the first time this has occurred. After stopping the print the z-axis seemed to move smoothly up and down using the controls.  I then lowered the z-axis to the build plate and the controller reported z-axis at +3.8, this seem consistent with z-axis slip

Any ideas.

Maybe related, during x/y/z calibration the machine will not do the upward Z move on 4 out of 5 attempts.  It does seem to work if I move the Z-axis near the top before starting the calibration.  The z-motor threaded shafts seem to move freely by hand when deenergized. 

This topic was modified 1 year ago by lcemoore
Posted : 22/09/2019 2:49 am
charles.h13
(@charles-h13)
Famed Member

If you XYZ calibration fails I would start there by disassembly and retracing those steps.  It worked for me.  

Posted : 22/09/2019 4:55 pm
lcemoore
(@lcemoore)
Active Member

I am currently on a quest to locate the gremlin.  I tried printing, re-slicing and printing the same piece and it failed at exactly the same Z-height.  I then made a test tower which did not jam up, but did print a very wide layer at the same Z position.  I checked the gcode at those heights and it seems to be fine, but there is a ~1 mil high, very wide layer at the same z-height the previous two prints failed, but the printer got past it.  It looks like it had a problem getting past that position and printed a few layers worth of filament without advancing along the z-axis, but it would have to have done that over multiple z-height increments to get the effect.  Unfortunately I stopped the print early, or else I could have verified the theory by comparing the printed height with the designed height. 

You can see in the image, the wide band on the tower at exact same height.   I inspected the lead screws for damage and didn't find any.  I put pieces of tape on the dust caps, which are currently about 5 mls above their respective motors.  The dust caps loose synchronization concurrently with the fail.  I have not been able to see it happen yet, so I can't yet say which shaft is hanging up, but that is where I am looking.

 

 

Posted : 22/09/2019 7:10 pm
Tim
(@tim-m30)
Illustrious Member

The lead screw dust cover nuts (aka jam nuts) can wedge and jam the motors.  The T-nuts can also jam, but less likely.

The most common problem is something is snagging a wire or interfering with the X-carriage as it raises up. A wire tie hitting the power supply or Einsy case, a spool holder that is installed wrong, or even a screw tip that goes through the vertical frame to hold an accessory.

This post was modified 1 year ago 2 times by Tim
It is always wise to get more than one opinion......
Posted : 22/09/2019 10:49 pm
lcemoore
(@lcemoore)
Active Member

'aka' jam nuts, got that straight. 

All your points of contact are definitely a possibility, but I been over every possible point of contact many times now (2 days worth of effort), so I'm sure it's not a point of contact other than maybe the duct covers.  Once the JAM NUTS were moved up, I  loosened the z-axis tops and cycled the z-axis  at least a dozen times and tightened up the top caps.  So for it seems to be printing and calibrating correctly.  3 tall prints accomplished so far with no errors.

Good luck to me.

Thanks for your inputs

Posted : 23/09/2019 12:13 am
Tim
(@tim-m30)
Illustrious Member

If the issue continues, post up photos of the frame, rear of the extruder, the cable tail, and spool holder you're using. All angles. Whatever it is/was is mechanical; maybe not obvious to you, maybe obvious to others.

It is always wise to get more than one opinion......
Posted : 23/09/2019 5:29 pm
lcemoore
(@lcemoore)
Active Member

@tim-m30

Will do...  Thanks

Posted : 23/09/2019 6:07 pm
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