Please analyze my print(s)

[gr5 2,167]

Well not "at the same time" but you do get it on the same model. Because of the lag or delay, as you slow down for a sharp vertex (corner) you get some overextrusion as the extruder is slowing down but there is still pressure in the head. Getting overextrusion before the corner means you must get underextrusion somewhere else. The somewhere else is as you start the next corner - again there is a delay so the pressure isn't building back up fast enough in the nozzle as it starts the next line.

As long as you print at typical speeds the delay isn't a problem. The slower you print the less under/over extrusion you get.

If your part overall is "underextruded" it will be more noticeable *after* a sharp corner. If your part overall is "overextruded", well this is more rare, but it will most likely happen just *before* or *at* a sharp corner.

 

[Nicolinux 288]

Ok, I understand it now.

 

If your part overall is "underextruded" it will be more noticeable *after* a sharp corner. If your part overall is "overextruded", well this is more rare, but it will most likely happen just *before* or *at* a sharp corner.

 

Very good explanation. Another thing for the cheat sheet

 

[illuminarti 18]

Another way to think about this under/over thing... if you try to print very fast (in volume terms), then you get very high pressure in the nozzle. This pushes back on the filament, causing you to get under extrusion, because the extruder motor can't push as much filament out of the hole as you are asking for. As noted before, this can amount to a 10 or 20% deficiency.

At the same time, the pressure in the head is such that in the parts where you want less extrusion, such as on the slow parts going into and out of corners, or on travel moves, the plastic oozes out anyway, causing local over-extrusions.

 

[Nicolinux 288]

Man over/under extrusion is a b***h. So the only way to fight it is to print slower/colder or faster/hotter and with a smaller layer height.

I wish Cura would be a bit smarter about this and provide some tipps. I noticed that it does some sort of logic for that. I entered by accident 0.7 layer height with my .4 nozzle and Cura warned me about the print speed. Wich is nice. David should add more of these warnings. Maybe the cheat sheet will help him

 

[gr5 2,167]

So the only way to fight it is to print slower/colder or faster/hotter and with a smaller layer height.

 

To reduce underextrusion, print slower, hotter, and with thinner layers. Hotter because the filament is less viscous.

Typical speeds for me (I like to get close to the limit):

100mm/sec 240C .2mm layer

150mm/sec 210C .1mm layer

Or for a part that needs to look beautiful:

50mm/sec 200C .2mm layer

100mm/sec 200C .1mm layer

(these last two print at the exact same volume per second)

 

[Nicolinux 288]

Very nice. I followed your advice and printed one of my favorite models (Cuddling Owls) very very slowly:

The big ones at 40mm/s with 190° and the little buggers at 20mm/s with 185°. They came out beautifully!