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additional fan for Ultimaker Original+

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Hi people of the Ultimaker community,

I recently got my UMO+ to actually start printing. The prints look great and the printer is really fast. Although the overhang quality was kind of a disappointment.


I experimented with the temperature of the nozzle and the fan speed a bit but still no nice quality.


As I read online, adding a fan improves the quality of overhang printing. So I want to add a fan. I have two super silent 30mm 12v fans laying around which I want to use for this setup.

After taking the stock fan off I noticed it was a 24v one and not 12v as I read everywhere online.


Is it safe/useful to use these 12v fans?

I don’t really have much knowledge and experience with wiring and electronics, can anyone explain me if and how this works?


Happy to join the community,



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Thanks, I wasn't sure if the difference in amps would be an issue.

Won't the second fan have less power due to resistance of the first fan?

Or is the difference not even noticeable?

It's voltage what defines this. And that's why you need to hook them up like that. The board supplies 24V. And the fans are 12V. So putting them in series will give both 12V


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You need good static pressure and airflow. You will also want a reliable bearing. I went with this one when placing my failed fan http://www.digikey.com/product-detail/en/ME40101V1-000U-A99/259-1566-ND/2757791%20.%20It%20has%20a%20

It turned out to be smaller than the original fan (OD was 40 mm instead of 40 mm screw hole spacing), but it still provides plenty of airflow. I use one of them with the aforementioned Tapir Shroud ( just printed a small size adapter plate ). Would probably be perfect for a dual fan setup ( smaller and lighter than original fan.)

The main caveat to this fan is that it doesn't like unfiltered PWM. This is easily solved with a RC low pass filter. I used a 40 ohm 1 Watt resistor and 10 uF ceramic capacitor. That also brought the max voltage closer to my fan's specs. For dual fan, you would want to use a smaller resistor and larger capacitor. My arrangement should have a cut off in the KHz range, which is probably way lower than needed (I would guess the PWM is at least in the 100's of KHz.) A 1 ohm resistor and 10 uF cap would would probably do the trick just fine.

Edit: Just noticed that marlin's PWM frequency may be far lower than I would have assumed. Some people are posting that it is only 7 Hz in software mode. Not sure if UM is using hardware or software mode. I am sort of surprised that the RC filter I used would have much effect at that frequency.

Ok, looks like the PWM frequency is about 30 KHz (Measured a period of 6.5 div* 5 uS/div = 32.5 uS), so 1/RC should be less than 10,000/s.

BTW, I have seen some posts that say the UM is not grounded, but I can say with good confidence that it is at least ground relative to my oscilloscope BNC ground.


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