How to set speed from the top fan?

Vertex 3D Printer Vertex - Printer software (repetier, slicer, ...)
1

Hi,

Can i set the speed of the top fan?
When i slide the fan bar i only set the speed of the little fan not the top fan.

I notice a massive temperature drop when the fan kicks in.

temperature%20drop.gif1024×675

When i cover the fan ‘intake’ bij 30% the temp rises again a little

2

I would like to give two comments:

  1. in my K8400 the both fans on the printhead are driven with the same line, so I cannot control them separately (has this changed in between?)

  2. the temperature drop has two mechanisms:

  • first of all you need more heating power when the fan is running. As you see on the bottom graph, the heater power setting is 100%. So if you’re cooling so effectively that the heater cannot compensate, the temperature will drop.
  • secondly this is not the only mechanism. The thermal link between the heating block and the temperature sensor is not good and can vary from assembly to assembly due to tolerances of the parts. Furthermore the temperature sensor and the cables are exposed to the air flow quite effectively. When cooling the temperature sensor you will see a temperature drop too. But this means, that the temperature control will heating up as soon as possible, driving the heater to the maximum power.
    This is a critical condition, because the real temperature at the nozzle can increase unregulated, which can lead to a melting of the isolator.

I personally faced only a few conditions where I needed the fan. However, the fan power can be set by a GCODE: M106 Sxxx with x between 0 (fan off) and 255 (maximum fan power). Normally your Slicer should care about this.

3

[quote=“hoh61”]the fan power can be set by a GCODE: M106 Sxxx with x between 0 (fan off) and 255 (maximum fan power)[/quote]Actually I’ve set mine to :
M106 S100 ; Turn on fan

And I’ve moved the small fan more horizontally so it doesn’t blow directly on the heater bloc.

4

[quote=“hoh61”]I would like to give two comments:

  1. in my K8400 the both fans on the printhead are driven with the same line, so I cannot control them separately (has this changed in between?)
    [/quote]

I tested in lowering the fan speed, but not far enough.
Yes both fans are on the same control.

I had to drop it as far as 20% (-80%) in order to get the temp back to normal.

temperature%20drop%20fan%2023.gif1024×576

I’ll keep monitoring the heatblock temp on the next prints to make sure it don’t overheat.

5

Have you checked the thermistor for proper mounting?
What is the temp of your room?