UM2-RearFan-Automatic (The UM2 silence, and I in my little living room.)

[mnis 11]

You can solve with little knowledge in electronics, this problem yourself. If they feel the constant fan noise very disturbing, then there is at least one effective solution:

There are bimetallic temperature switches for various applications and in various designs, which are available at a predetermined temperature ranges.

For the rear UM2-fan, is ideal a TLRS-9700 @ 40 degrees "NO" (-NORMAL OPEN (...This compact thermal switch closes an electrical circuit when it reaches the specified temperature.)).

The price for such a part is far below 1 euro / dollar. The time required for the successful implementation is very low. Ask a friend if you do not trust yourself to do this work.

The switch can be integrated without additional electronics in one of the two fan-lines. It needs a little soldering knowledge and in addition some heat shrink tubing for proper insulation.

Warning, avoid short circuits:

The metal housing of the thermal switch is electrically connected to one of its leads, so an integration in the ground line of the fan must be done. Otherwise, the housing of the thermal switch can be completely packed into heat shrink tubing, in order to obtain a good electrical insulation.

The temperature switch fits easily into the UM2-print-head housing, and should be mounted horizontally on the top aluminum plate. There are on the aluminum plate an unused hole with M3 thread, this could be used for the mounting of the switch.

How it works:

The required 40 degrees to the thermal switch can be achieved in the upper print-head range with much delay, as there is to be considered a passive cooling. As soon as the nozzle temperature continuously exceeds 70 degrees, the passive cooling is no longer sufficient and the rear fan starts its work. In the recommended mounting of the thermal switch, the temperature difference is as about 30 degrees. Measured from the start of heating from 25 to 210 degrees, a fan-on-delay of less than 2.5 minutes is the result. If the nozzle temperature below 70 degrees again, then the rear fan is inactive.

Negative side effects?

I would say NO ...

I'm no expert, so I can therefore only report on the more than 100 hours of usage experience since this small modification: The PTFE ColdEnd does not seem to suffer from the cooling delay, the Ultimaker 2 continues to run smoothly.

 

A mounting example:

Even if later there will be an official upgrade for a second Hotend, then there is sufficient space within the housing for this temperature Switch.

Markus