After some time of using the printer I can say a few more words on this long topic of fans.
1. Fans on extruders are not needed.
I don't use fans on extruders, in my opinion they're not necessary and consume unnecessary energy.
Each time I switch them off anyway.
And finally I disassembled them, switching them off was still a nuisance.
I will use the released leads for other purposes. I have an interesting idea in this area. I'm sure he'll write something about it later.
2. The fan on the printhead block is a very important element in the construction of this printer model.
It prevents blockages at the end of the teflon tube. And although it has to work continuously, there is no need for it to work at full power.
So in order to explore this topic I made an interesting experience.
It was possible after some hardware modification. Thanks to my solution I have the possibility to measure the temperature in an additional place.
Of course, I owe it to the wide functionality of the controller board.
My modification was to add one more thermistor and connect it to an unused, third extruder connector. Luckily, the firmware provides its support.
For the new thermistor I have foreseen a special place. This is the highest point of the head block. After all, the heat always moves upwards.
I prepared a holder made of copper sheet and placed the whole under the existing screw between the handles of the bowden tube. Everything fits perfectly together.
Thanks to the new hardware functionality, in the slicer program that I use, I have an insight into the temperature readings at a new point.
The experience consisted in switching on the heating of the printhead and observing the readings of the new thermistor.
I was very curious to what extent the head block would heat up when its small fan was switched off.
The temperature for the hot end element I set at 255°C. Only 5° higher than usual, during printing. For the results I did not have to wait long. The temperature rose quite quickly.
At selected intervals I was performing readings. You can see the results on the pictures.
The read temperature is presented in the log at the bottom. The values read from the new thermistor contain parameter T2.
In the final result you can see that the temperature has reached the value at which the filament starts to be plastic, which causes blockages and problems with dosing the material.
When the fan is switched on, the temperature drops quickly, even when the fan is not operating at full power. Practically, a 50-70% setting is sufficient. The fan performs its function when the power is limited.
It should be remembered that if you decide to limit the power of the fan, it is worth checking the temperature readings at random.
At this point I will also draw your attention to some interesting functionality, which could be introduced.
Well, it is quite easy to get the mechanism of autonomous cooling of the head block. Such functionality is possible thanks to Gcode M106 command with additional T & H parameters.
M106: Fan On
Hnn:nn:nn... Select heaters monitored when in thermostatic modeRnnn Restore fan speed to the value it has when the print was paused
Tnnn Set thermostatic mode trigger temperature
M106 P1 I1 S87
M106 P1 T45 H1:2
M106 P2 B0.1 L0.05
The first example turns on the default cooling fan at half speed. The second one inverts the cooling fan signal of the second fan and sets its value to 1/3 of its maximum. The third one sets the second fan to a thermostatic fan for heaters 1 and 2 (e.g. the extruder heaters in a dual-nozzle machine) such that the fan will be on when either hot end is at or above 45°C.