Cura: Buggy fan speed interpolation

[lwbsbde]

Hallo
I have Cura 3.6.0
And I have a problem with the fan speed.
My settings:
regular speed 30%
Max speed 100%
fan speed threshold 13s
minimum layer time 5s

the fan speed increases abruptly from 40 to over 70% without intermediate steps. from 70 to 100 with intermediate steps.

why no steps between 40 to 70 % ??

[rburema]

Hi @lwbsbde ,
Could you attach the project file for which this happens? (File > Save... then rename to zip to circumvent githubs' restrictions.)

[Ghostkeeper]

Possibly this is because the model abruptly goes from a large layer to a medium-sized layer?

[lwbsbde]

I have slice an Easter egg Model with different settings.

1. regular speed 30 , max 100, fan speed threshold 13s and minimum layer time 2s
2. the same but minimum layer time 4s
3. minimum layer time 8s

Layer longer than 13 s ,it is always 30 %
Layer shorter than 13 s , it is
Setting 1: at least 50% speed
Setting 2: at least 63% speed
Setting 3: at least 80% speed

If the minimum layer time 0s , then the speed is regulated correctly between 30-100 % .
If the minimum layer time 2s, then the speed is regulated between 50 - 100 %
If the minimum layer time 4s, then the speed is regulated between 63 - 100 %
If the minimum layer time 8s, then the speed is regulated between 80 - 100 %

The minimum layer time causes the speed jump

[lwbsbde]

Possibly this is because the model abruptly goes from a large layer to a medium-sized layer?

No , the layer time changes slowly.

[lwbsbde]

Hi @lwbsbde ,
Could you attach the project file for which this happens? (File > Save... then rename to zip to circumvent githubs' restrictions.)
PATTERN_-_KRAKEN.zip

that happens with all objects

[lwbsbde]

With Cura 4.0.0 beta , I have the same problem

[Ghostkeeper]

It's a bit easier to see with just a tetrahedron. With your settings, I see the result that you're wondering about. It seems that when the preliminary estimate becomes less than Regular/Maximum Fan Speed Threshold, it makes a jump from 30% to 77.6%. And then interpolates between 77.6% and 100% depending on how close it comes to the minimum layer time.

I don't know why that happens though, because in the code it seems to interpolate normally between regular and maximum fan speed:

https://github.com/Ultimaker/CuraEngine/blob/99ee78237b8d356ccc6096a2575fa4d73e15d166/src/LayerPlan.cpp#L1280-L1284

[lwbsbde]

It's a bit easier to see with just a tetrahedron. With your settings, I see the result that you're wondering about. It seems that when the preliminary estimate becomes less than Regular/Maximum Fan Speed Threshold, it makes a jump from 30% to 77.6%. And then interpolates between 77.6% and 100% depending on how close it comes to the minimum layer time.
I don't know why that happens though, because in the code it seems to interpolate normally between regular and maximum fan speed:
https://github.com/Ultimaker/CuraEngine/blob/99ee78237b8d356ccc6096a2575fa4d73e15d166/src/LayerPlan.cpp#L1280-L1284

1282 : what is "fan_speed_layer_time_settings.cool_min_layer_time_fan_speed_max" ?
is it the threshold time ?
I think "fan_speed_layer_time_settings.cool_min_layer_time_fan_speed_MIN" is better in the place !!
See line 1256

[lwbsbde]

I mean the error lies in the calculation of the layer time difference

[lwbsbde]

Star_big_0075_Spike_10x.stl.zip
A tetrahedron project file.
Layer 4-281 Fan speed 30 %

Layer 282 Fan speed jump to 63%

[Ghostkeeper]

1282 : what is "fan_speed_layer_time_settings.cool_min_layer_time_fan_speed_max" ?
is it the threshold time ?

Yes, that's the setting "Regular/Maximum Fan Speed Threshold" for the currently active extruder.

I think "fan_speed_layer_time_settings.cool_min_layer_time_fan_speed_MIN" is better in the place !!
See line 1256

cool_min_layer_time_fan_speed_MIN doesn't exist. The ASCII art is a bit unclear. In time, it's interpolating between cool_min_layer_time_fan_speed_max and cool_min_layer_time.

[lwbsbde]

does it work with you when you slice an object with minimum Layer time?
does it only work for me not ?
in which cura file on my Computer is this formula ?

[Ghostkeeper]

Once it's below the minimum layer time it works fine for me. It's between that and the Regular/Maximum Fan Speed Threshold that it seems to make a mistake on my end.

These calculations are in CuraEngine.exe on your computer (if you're using Windows; otherwise just CuraEngine). You can't easily edit them unless you know how to compile CuraEngine.

[lwbsbde]

I could not translate your answer clearly.
Can you confirm the mistake as he does me ?
Is it a bug in the Programm?
I have already reinstalled it several times. without success.

If Cura divides into line 1283 instead of layer_time_diff through cool_min_layer_time_fan_speed_max, I get a similarly wrong result. Maybe he does not subtract in line 1282 .

Can I preview the layer time and fan speed in the preview of cura? I would find that very useful.

[Ghostkeeper]

I'll keep it simple for your translation tool then :yum:

Can you confirm the mistake as he does me ?

Yes.

Is it a bug in the Programm?

Yes.

Maybe he does not subtract in line 1282 .

Maybe. I don't know.

Can I preview the layer time and fan speed in the preview of cura?

No. You can preview the printing speed (feedrate). That should allow you to see the minimum layer time, but not the fan speed.

[userosos]

Hi! This problem actual for Cura 4.0.
The pyramid for tests.

CalibrationPyramid.zip
Need scale to ~40 mm the sizes.
regular/maximum fan speed threshold - the parametr not work.

[rburema]

@Devs: Do we have a ticket for this yet?

[Ghostkeeper]

@rburema Yes, CURA-6410.

[lwbsbde]

did you find the error in the program?

[Ghostkeeper]

Not yet. It's slowly crawling towards the top of our todo list though.

[lwbsbde]

did you now find it

[Ghostkeeper]

Not yet. It's still in our bug backlog.

[BarsMonster]

I also face this issue at the moment in 4.4.1

[clfaye]

I have this same issue printing a small pyramid:
regular fan speed = 20%
maximum fan speed = 32%
Regular/Maximum Speed Threshold = 1
Regular Fan Speed at Layer = 15
Minimum Layer time = 5

Cura ignores the regular fan speed. The fan speed increases from 0 to 32% at layer 15. Layer 15 takes 5 seconds, so the fans should only be at 20%

[lwbsbde]

Hallo ...
could anyone kill the bug
PLEACE