is the Fan Speed Min setting ignored in CURA?

[peetersm 124]

I think I need some help figuring out how to ask Cura to only run the fan at 0% or 100% and nothing in between. (I'll explain later why)

I have set the Fan speed min (%) to 100 which I think should tell Cura that if ANY amount of cooling is needed then the fan should be turned on ala M106 255.

I set the Fan speed max(%) to 100, just for good measure.

But when I look at the gCode I am seeing places where the fans are being turned on at slower values such as:

;LAYER:1

M106 S84

(......)

;LAYER:2

M106 S168

 

Is there another setting I have over looked?

 

The reason why I want to do this is that I am running an UMO and I believe the PWM used for fan speeds<100% is causing major trouble with my temp sensor and causing failed prints. When the fan speed is anything other than 0% or 100% I am seeing immediate jumps of 5-10 degrees in the temp sensor. (see video)

 

 

and reading this thread lead me to test out the impact of fan speeds.

http://umforum.ultimaker.com/index.php?/topic/6327-weird-temperature-swings/

 

I have ruled out shorts in the wire (I am on my 2nd cables already) and testing fan speeds can duplicate this issue for me. I have tried twisting my fan cables and move them over 20mm from the temp wires, but still see this behavior.

 

 

[amedee 349]

The problem comes with the 'Fan full on at height' parameter which makes that the fan will go from zero to max gradually until this height is reached.

To achieve what you want, just disable the fan in the advanced tab, and use the TweakAtZ plugin to turn it on when you need it.

 

[nallath 1,120]

Did you check if the fanshroud is to high? The airflow needs to blow right below the nozzle. If it's directly on the nozzle, you get these temp changes.

 

[peetersm 124]

@nallath - looks like you missed the fact that the temp is fine when the fan is at 100% or zero. The temp only has issues when the fan is between these values.

@amedee - thanks, your suggestion did not work since diableing the fan seems to over ride tweak at height, but it got me on the right track!

What you need to do is set:

Fan full on at height (mm) = Initial layer thickness (mm) + Layer height (mm)