random dotted layers

[notlob 0]

Hi, apologies if this has been asked before. I have ironed out most of the problems I've had with my Ender 3 Pro, but with about one print out of 3 or 4, I get a dotted line across part of one or a few of the layers, with the rest of the print being OK. If you look at the attached photo, it is near the top of this print just before I cancelled it. 

 

Any ideas what it could be ? I've levelled the bed (which has improved the general smoothness of the print), but not helped with this. 

Any help greatly appreciated

Thanks

John

[JAGQueen 0]

I just solved this problem with my CR-10.  Essentially you are getting a hiccup with your filament feed.

 

The bad news is that there are many causes, apparently.  I just ran through them, so...

 

The three most common are a partially clogged hot end, a dirty/not feeding well extruder and a kink in the feed line.  The CR-10 uses a Bowden tube, that white tube from the extruder to the print head.

 

The first thing to do is to raise the print head a good distance up over the bed so you can see the underside.  Then manually heat up the hot end, usually this is done by the filament load/unload routine.  Then manually disengage the filament and push on it.  If you get a nice stream out the hot end with just a moderate push on the filament, everything is fine and your problem is elsewhere.  Mine was not.

 

So I tried cleaning the nozzle, like they recommend here: https://all3dp.com/2/3d-printer-nozzle-cleaning-the-easiest-way-to-do-it/

 

That did not work.  So I tried changing the nozzle, which just made things worse.  So back to the original nozzle.  In any case, back to the problem solving.

 

If cleaning does not work, the next step is to try cleaning and adjusting the extruder.  This is especially true if you unload the filament  and there is a flat spot, or if the filament does not have indentations where the extruder was digging in and advancing the filament.  Here is an article on it: https://www.fargo3dprinting.com/how-to/clean-3d-printers-drive-gear/

 

If that does not work, try pulling the filament, clip it off so you have a clean end, and then manually feed it slowly, feeling for tight spots.  That is how I found the kink in the Bowden tube and then wound it so it was straight with electrical tape.

 

Presto, I now am back to great prints.  Still not sure how I bent the bowden tube...

[notlob 0]

Brilliant, thanks so much for the detailed reply. I'll try these steps this weekend.

Many thanks

John