Unnecessary travels along printed parts

[desconocido 0]

Hi, I'm using Cura 4.2.1 and I have issues with resulting print quality.

Cura generates an "extra circle" between outermost and innermost perimeter in addition to infill, which seems to be unnecessary. This extra circle has severe effect to the print quality, as it seems to drag plastic from nozzle - the outermost layers are suffering from underextrusion. The "other" slicer didn't generated any extra circles, the model looks pretty good.

I tried a lot of options: travel optimization, wall order optimization, different combing modes and retraction / z-hop settings, different temperatures, acceleration and speed values. Is it possible to eliminate this "extra circle"? I really like Cura, but sometimes it does really weird things and the resulting model looks bad 😞

The results (left 3 parts are sliced with Cura with different settings and the rightmost is other slicer, same plastic, model, speed and temperatures):

Attaching a model and other stuff, check at 25+ layer (0.2 layer height):

cura issues.zip

Edited September 11, 2019 by desconocido

[desconocido 0]

I checked a G-CODE, and it seems like Cura tries to extrude less plastic than my printer is capable to.

For example:

G1 X120.635 Y115.546 E641.66235
G1 X120.774 Y115.333 E641.66255
G1 X120.994 Y114.994 E641.66282
G1 X121.114 Y114.794 E641.66298
G1 X121.332 Y114.429 E641.66328

As for my printer, a single step extrudes 1/410 = 0.00294(mm) of filament, but the G-CODE in this "extra circle" attempts to extrude much less than even a single step. The extruder wheel stands still, but, due to plastic viscosity, it drags plastic out of nozzle. At the next, "normal" perimeter, it lacks plastic and there is an underextrusion. Am i correct? Is it possible to filter out such extrusion attempts? Thank you in advance!

[burtoogle 513]

Hello @desconocido, set the minimum wall flow to something like 30, set combing mode to no-skin, set max comb distance without retract to 10 or 20 or similar. Quality should improve. Hope this helps.

[desconocido 0]

1 hour ago, burtoogle said:

Hello @desconocido, set the minimum wall flow to something like 30, set combing mode to no-skin, set max comb distance without retract to 10 or 20 or similar. Quality should improve. Hope this helps.

Minimum Wall Flow is exactly what i needed - extra circles removed. Thanks, dude!

 

P.S. Wondering why this option isn't active if "Compensate Wall Overlaps" is unchecked?

Edited September 11, 2019 by desconocido

[burtoogle 513]

Just now, desconocido said:

P.S. Wondering why this option isn't active if "Compensate Wall Overlaps" is unchecked?

 

Because when the wall compensation isn't checked, all wall flows are 100%. It's the wall overlap compensation that reduces the wall flows.

[desconocido 0]

18 minutes ago, burtoogle said:

 

Because when the wall compensation isn't checked, all wall flows are 100%. It's the wall overlap compensation that reduces the wall flows.

If i disable compensation, i get an extra circle again. And this extra circle is far from 100% of flow, such low that I thought it is a travel 🤨 That's why i didn't even tried to change Minimum Wall Flow, i just disabled overlap compensation without any success. It is a bit counterintuitive to me:

- if it is Disabled, there will be an extra circle with extra low flow rate

- if it is Enabled (default value) and Minimum Wall Flow is set to 0 (default value), there will be an extra circle with extra low flow rate, same if it was Disabled

Is it a bug or a feature?

Edited September 11, 2019 by desconocido

[desconocido 0]

On 9/12/2019 at 2:19 AM, burtoogle said:

 

Because when the wall compensation isn't checked, all wall flows are 100%. It's the wall overlap compensation that reduces the wall flows.

I tried your development version of Cura, it seems to treat inner walls differently, a bit better, in my opinion. Although it generates "blobs" and seemingly random travels sometimes, it could be fixed by a some negative horizontal expansion value - 3-lines wide walls are printed in outer-to-inner order but this doesn't destroy overhangs on my other models, unlike swapping the order with a checkbox. Could you please tell me in what files/functions these changes are? Just for an educational purposes 🙂 Thank you

 

The "weird" travels:

After "horizontal expansion" adjustment:

Edited September 14, 2019 by desconocido

[burtoogle 513]

1 hour ago, desconocido said:

Could you please tell me in what files/functions these changes are? Just for an educational purposes 🙂 Thank you

 

I'm not sure which changes you are referring to. I've made so many changes to many parts of Cura. To see how they are different. Clone my CuraEngine repo and then compare the mb-master branch to the master branch and you will see all the stuff I have changed. I just did that and the diff contained 4845 lines!

[desconocido 0]

33 minutes ago, burtoogle said:

 

I'm not sure which changes you are referring to. I've made so many changes to many parts of Cura. To see how they are different. Clone my CuraEngine repo and then compare the mb-master branch to the master branch and you will see all the stuff I have changed. I just did that and the diff contained 4845 lines!

Thanks. I mean inner wall generation (yellow/green color, the path taken between outer walls).

Edited September 14, 2019 by desconocido