First check of the cooling performance

A project log for Extruder for Prusa i3 MK3S

Extruder with Mosquito hotend for the original Prusa i3 MK3S

CadmiumCadmium 09/20/2019 at 08:271 Comment

I made some quick measurements to check if the cooling of the hotend is working properly.

The measurements were made during a long print with PETG when the temperatures were in a steady state. The thermocouple for measuring the heatsink-temperature was attached close to the lower edge of the heatsink, where you can expect the highest temperature.   

First I made a measurement at room temperature, then I closed the heated housing of my printer and made measurements at elevated temperature.

Please note: Month ago I replaced the Noctua printer by a Sunon MF40100V1-G99-A for better cooling performance.

Ambient temperature [°C]Hotend temperature [°C]Heatsink Temperature [°C]
25240approx. 30
45240approx. 60


The thermal contact between the thermocouple and the heatsink is far away from perfect, thus the real temperature of the heatsink will be slightly higher than the measured temperature.

As expected, the cooling at room temperature works better than the cooling at high temperatures.

Because the extruderbody is made from PETG (continuous operating temperature ~65°C), I would not recommend to print large parts with hotend temperatures above 240°C with closed printer enclosure.


Deneteus wrote 09/20/2019 at 08:55 point

PETG's glass transition temperature is 67–81C depending on what additives are being used in it. So your results could be because of the filament you used. That's not counting the internal enclosure air temp. ABS would be a first choice considering its glass transition temperature is 105C and you don't have to cool it when printing to get your extruder body printed and out of the way. I would have ordered it printed with high temp engineering plastic from Shapeways or something like that if I was trying to be fancy with it. It would have better airflow.

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