Design Shifting Mid Print

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Design Shifting Mid Print

Postby Radioman1017 » 2017-Feb-Sat-13-Feb

Hell all,

Very confused about this problem.

I'm trying to print the eye piece for a Deadpool mask. There are no flat sides at all so unfortunately, I have to print as flat as possible with a lot of support. I'm slicing and creating the gcode with Simplify 3D.

I purchased the file here:

https://www.etsy.com/listing/470615228/ ... _active_40

The specific piece I'm trying to print is the right eye piece.

This is what it should look like, pre-support.

Eye.PNG


I tried to print this, twice last night at .2mm layer height, 20% infill.

IMG_0446.JPG


The one on the left was the first print. The extruder shifted twice, giving me that three stair step pattern. I reset, re-ran the slice and created fresh gcode and tried it again. It only shifted once the second time but it's still happening.

Now, to be clear, the print itself is NOT shifting. It's not on a glass bed. It's printing on my Printrbot Metal Plus. It's like the design is suddenly deciding to move everything over at these random spots.

I have no idea what could be causing this or how to correct. Can anyone assist??

Mark
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Design Shifting Mid Print

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Re: Design Shifting Mid Print

Postby RetireeJay » 2017-Feb-Sat-16-Feb

The printer relies on the steps in the stepper motors being executed perfectly to keep track of its location.

If something gets in the way of motion on one axis and jams it (like a cable snagging on the bed) then it can throw the whole location for that axis off. If you are near the printer during this type of problem, you will hear the motor "grinding" when it hits this jamming point. Alternatively, if the printer is asked to move beyond its boundaries that are set in firmware (which are configurable in EEPROM setting in some versions of Marlin) then it may silently refuse to move while losing step counts. But that doesn't look like the case here because the largest requested motion seems to happen on the first layer.

The sudden, large, and infrequent shifts are evidence that the drive to the motor is probably adequate; if the motor were truly under-powered then the shifts would be much more frequent and also in random directions.

You might want to check your lubrication. Do the X and Y axes move reasonably smoothly when the power is off and you move them by hand?
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Printrbot Plus operational January 2013
Brass threaded rods (5/16" X 18) & nuts for Z axis
GT2 belts & pulleys
Cable chain to reduce probability of fatigue failure in wires
E3D V5 Hot End, 0.4mm nozzle, also 0.8 and 0.25 in use occasionally
PB fan mount + 40mm fan -- using printed mount adapter, not the E3D supplied fan
Injection molded extruder gears
Optical Z "endstop" (custom designed and built)
Have used many pounds of T-Glase filament. Now also doing some work with Ninjaflex SemiFlex
Print on glass with Scotch Craft Stick or other glue stick
"My next printer is..." Prusa i3 MK3
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RetireeJay
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Re: Design Shifting Mid Print

Postby Radioman1017 » 2017-Feb-Mon-23-Feb

Hey Jay,

So I was sitting next to my printer doing a print and heard the ratcheting that you were talking about. The extruder then was off considerably and the print failed. The extruder was pretty far to the right side when this happened but I don't see anything blocking. Lubrication seems fine. I just had this printer refurbished by Printrbot last month. Where might the lubrication be bad? Under the center arm on the X-axis or on the motor or threaded road itself?

mark
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Re: Design Shifting Mid Print

Postby RetireeJay » 2017-Feb-Tue-08-Feb

If you move the X axis by hand (with the power off), does it move smoothly from end to end? You will feel some drag from the motor (even a little "cogging" as the magnetic poles move past each other) - but the resistance to motion should be consistent from end to end. There should be no clicking or popping sounds. If the resistance to motion is not consistent or you hear clicking & popping, then it's worth disconnecting the belt and running the test again with the motor disconnected. In this condition, there should be virtually no resistance to motion from end to end; give it a shove and it should move a ways under its own momentum. If it progressively jams up as you approach one end, it may be that your rods are not parallel. When you force rods that are not equally spaced though bearings, you can get high resistance to motion as well as clicking and popping sounds.

Another, entirely different approach is to look for anything that is jamming the motion that has nothing to do with lubrication or rod spacing. Maybe a cable interferes. Maybe there's something on the drive belt that is worn or otherwise interfering with the motion.

Or, maybe the print itself is somehow getting in the way. If you're seriously over-extruding, you can build up successive layers of "plowed up" material until it interferes with the motion. Or, if the print is starting to lift off the bed, the warped part of the print could jam the motion.

I've experienced all of the above - but I can't think of any other axis-jamming problem in my experience.
  • 0

Printrbot Plus operational January 2013
Brass threaded rods (5/16" X 18) & nuts for Z axis
GT2 belts & pulleys
Cable chain to reduce probability of fatigue failure in wires
E3D V5 Hot End, 0.4mm nozzle, also 0.8 and 0.25 in use occasionally
PB fan mount + 40mm fan -- using printed mount adapter, not the E3D supplied fan
Injection molded extruder gears
Optical Z "endstop" (custom designed and built)
Have used many pounds of T-Glase filament. Now also doing some work with Ninjaflex SemiFlex
Print on glass with Scotch Craft Stick or other glue stick
"My next printer is..." Prusa i3 MK3
User avatar
RetireeJay
My next printer is...
 
Posts: 4941
Joined: 2013-Jan-Wed-13-Jan
Location: Greenville, SC
Reputation: 496


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