Fan speed issue with Cura and UM2

[eldrick 65]

I have my Expert fan settings at min 20% and max 45%.

However, during the print, with the cooling fans not running, if I check the fan speed on the built-in display, it usually shows a small percentage of fan on - most often 1%, 3%, 6%, sometimes as high as 12%, but generally with the fans not running.

This is potentially destructive, as you can hear the fans straining to start, but not actually turning, and that means that current is going thru the driver board and the fans, heating both of them. If you turn the fan speed down, you can hear the noise drop, so this is not just a false reading.

I think that this needs correction in two ways: a) many fans will stall at less than 10% or so, so Cura should never try to run them that slowly, and b) when starting the fans, it should issue an initial "kick" of higher speed to get the fans running before settling back to a low value.

 

[Daid 306]

IMHO, it's the firmwares job to protect the fan and kickstart it.

The low percentages might be a bug? But be sure not to check during the first bunch of layers, as then the fan is slower.

 

[eldrick 65]

"IMHO, it's the firmwares job to protect the fan and kickstart it."

- The firmware cannot protect the fan from software that tries to run it at damagingly slow speeds,

- The vast majority of machines supported by Cura do not have any form of firmware that "kicks" the fan.

IMHO, a good slicer would never send values to a fan that would certainly stall it.

 

[Dim3nsioneer 557]

"IMHO, it's the firmwares job to protect the fan and kickstart it."

- The firmware cannot protect the fan from software that tries to run it at damagingly slow speeds,

- The vast majority of machines supported by Cura do not have any form of firmware that "kicks" the fan.

IMHO, a good slicer would never send values to a fan that would certainly stall it.

 

I agree on the fact that a good software takes care of as many dangers as possible.

However, I agree with Daid's sentence. It's the usual way to go (I co-worked on the firmware of a device with fans some time ago).

I strongly disagree with your first point. I don't see any reason why Marlin should not be able to achieve this protection. One would have to introduce a variable for minimum fan speed. The only allowed value below this threshold would be 0. The kickstart feature is already implemented in Marlin but disabled in the Ultimaker version. I could imagine that Daid would activate the feature for the next firmware version if he is asked nicely.

I'm not sure about your second point. A lot of these machines are Ultimakers today. Then there are a lot of RepRaps driven by Marlin...

 

[eldrick 65]

I don't see any reason why Marlin should not be able to achieve this protection.

My point is that current Ultimaker machines, and the Open-Source Cura users on non-Ultimachine hardware, have no such protection, and since many of them will never get a Marlin upgrade, they won't.

Cura does not currently include the trivial code that would protect these machines from potentially shortening the life of electronics and fans, for Ultimachine and other hardware. Sending an initial M106 to kickstart the fans and preventing duty cycles of less than perhaps 10-15% would pretty much fix the issue.

 

[Daid 306]

My point is that current Ultimaker machines, and the Open-Source Cura users on non-Ultimachine hardware, have no such protection, and since many of them will never get a Marlin upgrade, they won't.

 

Except for the BFB and Makerbot printers, all other supported printers run a form of Marlin or Sprinter, which can be upgraded. (If not, they are violating GPL, and you can sue the printer producer)

It's not Cura's task to protect the hardware. That's my stand on it. You can always fork if you think otherwise.

(It's also not trival code. As you need to kickstart for a certain amount of time. And, as the M106 is queued in the movement buffer timing is difficult)

 

[eldrick 65]

...since many of them will never get a Marlin upgrade,...

...because the users don't upgrade them, so their hardware will remain exposed to any slicer sending inappropriate too-slow speed settings to the fans,,,

Oh well...

 

[takei-naodar 0]

IMHO, it's the firmwares job to protect the fan and kickstart it.

The low percentages might be a bug? But be sure not to check during the first bunch of layers, as then the fan is slower.

 

Only Problem is though that the kickstart only is done on the second layer as far as i can see... or is way too underpowered/ not long enough.

 

[gr5 2,172]

I haven't looked at the new kickstart code in Marlin but will it kick on every increase? Even if increased from 10% to 25%? I hope so.

I don't see why you think running a fan at 10% duty cycle will damage it. Yes it will heat up. But not much - why do you think it will be damaged?

Many cheap fans are much too smart these days - they have circuitry and voltage regulators and tachometers and they won't turn on until around 60%. And they run no faster at 100% than they do at 60%. I don't know why they are designed this way. Many people change their fans to some fan they order online and there are many types out there and they all need the kick at different percentages and such and there are hundreds of different fan models out there. I don't think Cura should worry about this - this kind of thing should be built into Marlin - you should be able to configure each of your printers to have their own custom Marlin (pretty much this is done already), and each Marlin should know if the fan can withstand PWM mode or not.

 

[gr5 2,172]

One could easily write a plugin that does what Eldrick wants.