Why the print speed and fan speed variation?

[Abom]

I've noticed with both V1.6.3 and Alpha 0.9.9 That prints will slow down dramatically during overhangs when I don't see anything in the profile to cause it. Also, the part cooling fan varies by about 40 percent in certain areas, which is causing trouble for me. I'll include the gcode for a fan duct that has slim arms for mounting. I'm print fairly hot, and when it gets to those arms the unrequested lower fan speed is causing problems with print quality.

Can anyone explain why this happens and if anything can be done about it?

Thanks.

Blower Fan Duct.rar

(508 KiB) Downloaded 269 times

[pjr]

If a path is not fully supported by the previous layer, then the path will slow and the fan will increase depending on 2 settings:

Settings/Matl - in the Fan/Cool section, the "Cool" setting will increase the fan speed if the value is higher than the "Loops" value (assuming the printing of a loop/perimeter)
Settings/Matl - in the Flow Adjust section, "Cool [mm^3/s]" is the maximum volumetric flow for an unsupported path

Note that both these settings are implemented proportionally - the more a path is supported, the less effect these settings have.

Peter

[Abom]

thanks Peter.