Tall thin parts get knocked off the bed  

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snaslund
(@snaslund)
Active Member

Cant quite figure out whars going on here.  Im printing the Lack V2 enclosure file #2 which is tall thin parts.  Using PETG and print quality looks fine, decent bed adhesion but once its about three inches high, i get a collision that knocks the parts loose from the bed.  I suspect the hot end is hitting a small zit on the part but overall Im not seeing any significant blobs.  Tried this print three times now with same failure and I am using Prusa gcode.  Anyone have ideas?

Posted : 13/08/2020 6:38 am
snaslund
(@snaslund)
Active Member

Also, I cleaned the bed right before starting the print with IPA and I can here the snap when it happens.  The remaining parts are stuck to the bed pretty well.  Not sure what could be causing this except for maybe flawed code, problem seems to be with the same part at the same point in the printing process so it does not seem random.  Might try to reslice the file and see what happens but Im sure lots of people have used this code before.

Posted : 13/08/2020 6:42 am
snaslund
(@snaslund)
Active Member

So, i resliced the file using Simplify3D and im still having the part get knocked off the bed once its about two inches high. Seems like little nibs on top cause a collision.  Any ideas about eliminating those?  This is atomic brand PETG and I am running is at 245 which is mid to low end of the manufacturer’s range.  The nibs are very rare and dont show up on the sides of the print ever.

Posted : 14/08/2020 2:33 am
bobstro
(@bobstro)
Illustrious Member

If you are over extruding, filament can build up on top surfaces. PETG is particularly sensitive to this. Try calibrating your extrusion multiplier for each filament and see if that helps. I've got some notes here on the subject.

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 14/08/2020 2:35 am
towlerg
(@towlerg)
Honorable Member

What skirt size are you using? I the skirt connected? Mouseears?

Posted : 14/08/2020 4:40 am
snaslund
(@snaslund)
Active Member

@bobstro

Thanks, will check the extrusion multiplier today.

Posted : 14/08/2020 1:53 pm
snaslund
(@snaslund)
Active Member

@towlerg

I think bed adhesion is pretty good but will try that if nothing else works.  I think the root cause is little zit being collided with on top of part.  They appear on corners where the hotend makes a z hop off the part.

Posted : 14/08/2020 1:55 pm
towlerg
(@towlerg)
Honorable Member

@snaslund

Don't forget that the nozzle is hot enough to slice through small blobs.

Personally I almost always use a skirt, it uses little plastic (as a percentage of total), adds a few minutes to the total print time, the only downside being a little post printing processing. Make sure the skirt is actually attached to the first layer, can't remember the parameter. 

Posted : 14/08/2020 7:01 pm
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