Zones of my print not printing

[Sunrider 0]

So i just got my printer 2 weeks ago and it did a pretty good job on the first prints i've done, wich they were quite small. I started printing larger things a few days ago, wich it was what i bought the print for. And i seem to get this kind of under extrusion problem in some parts of the print, only at certain hights, because as you can see in the image it kinds of corrects itself in the next hights

any guesses on how to fix this problem? 

ive read that it might be a problem of the retraction being set too high, but i dont think it might be that

[gr5 2,265]

That seems extremely specific - that underextrusion.  It goes from good extrusion to massive (maybe only 20% extrusion) underextrusion (80% less than normal).  Well first thing to try is to slow it down.  You can experiment live printing - most printers have a TUNE menu while it's printing where you can reduce the print speed to say 50%.

 

By default I think cura prints infill at 2X speed so it could be this is where it switches from infill to outer wall and it takes a few seconds to get back up to pressure.  It could be your infill is even worse underextruded.

 

I'd look at the part in preview mode in cura carefully to see what's going on here.  use the "play" feature and the horizontal scroll to see exactly the path the head makes.

[Sunrider 0]

29 minutes ago, gr5 said:

That seems extremely specific - that underextrusion.  It goes from good extrusion to massive (maybe only 20% extrusion) underextrusion (80% less than normal).  Well first thing to try is to slow it down.  You can experiment live printing - most printers have a TUNE menu while it's printing where you can reduce the print speed to say 50%.

 

By default I think cura prints infill at 2X speed so it could be this is where it switches from infill to outer wall and it takes a few seconds to get back up to pressure.  It could be your infill is even worse underextruded.

 

I'd look at the part in preview mode in cura carefully to see what's going on here.  use the "play" feature and the horizontal scroll to see exactly the path the head makes.

Now that you say that, i think the problem might be related with another problem i have, where as soon as the hot end gets hot filament starts to extrude by itself, i know this is a normal thing to happen, but it extrudes quite a lot of filament, and it does this everytime, so filament comes out the nozzle even when its not supposed to, when the head is travelling for example.

[gr5 2,265]

9 minutes ago, Sunrider said:

so filament comes out the nozzle even when its not supposed to, when the head is travelling for example.

That's relatively normal.

 

There is something called "retraction" which is turned on by default in cura.  It retracts the filament a little bit when the print head goes over a gap.  If you retract too much you get air in the nozzle and you get over and underextrusion.  If you retract too little you get little strings across gaps where you don't want them.

 

Basically the print will be most perfect if you never speed up or slow down the printing speed but sometimes you have to stop when you go across a gap.  Cura by default does lots of speed changes which can cause under and overextrusion each time there is a speed change.  So I always make all the printing speeds the same (but the non-extruding "travel moves" as fast as possible).

 

[Sunrider 0]

Imma try that, thank you !