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I'm having really bad luck - hotend fan replacement.


anon4321
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Posted · I'm having really bad luck - hotend fan replacement.

So I broke my fan that is on the hotend (don't ask but lets just say that if you are leveling the bed and the fan is on from an aborted print, make sure you don't poke the hex driver into the running fan thinking you are clear of it while attempting to get to the bed screw!)

Previously, someone tried to add a second fan and blew the transistor on the shield. During that discussion, it became apparent that the fan is running at 19v which is MUCH higher than most 12v fans specify as the maximum voltage which is usually 13.8.

Has anyone replaced their fan with a different 12v fan?

Do you have any problems?

What make of fan did you use?

 

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    Posted · I'm having really bad luck - hotend fan replacement.

    I added a second fan to my UM1 quite early on, it has been on there for at least a year, probably closer to two without any issues at all. The fan is a 12V Fractal Design FD-FAN-50. It's hooked up in parallel with the original.

     

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    Posted · I'm having really bad luck - hotend fan replacement.

    I purchased a replacement fan and some 1w resistors and zeners to drop the voltage to the current level if needed. Actually, I got two fans in case I burn one and even a replacement transistor for the shield in case I smoke that too.

    We'll see how it goes....

     

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    Posted · I'm having really bad luck - hotend fan replacement.

    I purchased a replacement fan and some 1w resistors and zeners to drop the voltage to the current level if needed. Actually, I got two fans in case I burn one and even a replacement transistor for the shield in case I smoke that too.

    We'll see how it goes....

     

    Your chances not to burn a fan are actually higher if you combine the two identical fans instead of two different types. If you do the latter you might get an unhealthy current oscillation between the two due to the different inductance and resistance.

     

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    Posted · I'm having really bad luck - hotend fan replacement.

    So I can definitely report that not all 12v fans are happy with 19v even when the fan speed is lower than 255 like 100.

    A new fan instantly went up in smoke at 100 on the ulticontroller fan setting!

    I brought two of these.

    http://www.newark.com/nmb-technologies/2004kl-04w-b50-b00/axial-fan-50mm-12vdc-100ma/dp/58K7816?ost=58K7816

    Little more expensive than most but they are 11 blade fans and my theory is this will help them generate better static pressure.

    Well one is toast now but that is why I brought two.

    To save the other one, I'm using a 67ohm 3/4 watt resistor in line. The datasheet for the fan at newark says it draws 100ma which is what I based my calculations on but the fan is labeled 140ma so I'm not sure the resistor can handle the power dissipation

    Anyway, At 100ma, that 67 ohm resistor will drop 6.7V from the 19V (my supply is actually 19.5v). So the fan will see about 12.3 volts or 12.7 volts for my supply.

    At 100ma, the power dissipation is 100ma * 6.7 or 670mw so the 750mw resistor should be OK.

    If the fan is running at 140ma, that is a 9.4 v drop so the fan is seeing something like 9.6 or 10.5 for my supply. The worst case power dissipation for the resistor is 140ma * 9.4v or 1316mw which is way above the resistor's spec so we will see if it goes up in smoke...

    BTW, the original fan model is 5010S but I don't know the manufacturers logo...

    Appears to be these: http://www.amazon.com/Brushless-Cooling-50x50x10mm-Sleeve-bearing-Skywalking/dp/B00BJCA5AI

     

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    Posted · I'm having really bad luck - hotend fan replacement.

    These fans don't draw a constant current. They quickly oscillate between drawing more current, then less. So the fan *will* see the full 19V even if only briefly several times per second. You can average the voltage spikes out with a capacitor across the fan if you want. I would just go for it though - your plan seems reasonable. If you blow up a second fan then just get another I guess.

     

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    Posted · I'm having really bad luck - hotend fan replacement.

    So far the resistor solution is working.

    One downside to that particular model fan is it seems to regulate it's RPM. So much so within a few increments of the fan control value, the fan goes from off to barely running to full on. Like at 230 it is off, 233 it spins slowly by 237 its full on and doesn't seem to increase in speed as you go all the way to 255.

    So not a good model if you want to vary the air flow.

    Which is a shame because when it is "on" it moves quite a bit off air.

    All in all, I think I'm going to replace it with the model UM uses which I linked to above.

     

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    Posted · I'm having really bad luck - hotend fan replacement.

    anon4321,

    I also accidentally slipped a screw driver tip into the moving fan and broke a blade off of the fan. I am trying a new design with blower fans and I am in the process of printing the mounts now. These two blowers fans I found on Amazon, they are inexpensive and so far they seem to be holding up good to the voltage of the UM. They are from the same manufacturer as the original fan with nearly identical power ratings. If my mount design works I will post it. Here is the link to the fans.

    http://www.amazon.com/gp/product/B00BKE27V0/ref=oh_details_o05_s00_i00?ie=UTF8&psc=1

     

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    Posted · I'm having really bad luck - hotend fan replacement.

    So I tried the fan on the UM and it fits nicely and seems to handle the power well.

    New Blower Mount On Ultimaker

    Trial Fit.

     

    Axis Blocks Clearance

    Axis Clearance.

     

    12vDC Blower Fan In New Mount

    Fan Make and Model and a view of how the nozzle fits into the duct .

    I just need to make a Y cable and connect both fans now and print the mount and duct for the left side fan. I also need to source some m3 20mm or 22mm screws and nuts.

     

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    Posted · I'm having really bad luck - hotend fan replacement.

    Cool (no pun intended). Just be aware that I believe the blower on the electronics is actually a 24V version.

    However, as long as the the 12V versions are working on the head, you should get a LOT of air!

    Also be aware that I believe adding weight to the head may lower the print quality or max speed. If you get "ringing", try reducing acceleration (which also reduces deceleration).

    This is an example of ringing: http://www.mijnalbum.nl/Foto-THFGNNSA.jpg

    Seems to be a detailed discussion here: http://umforum.ultimaker.com/index.php?/topic/2532-prevent-ringing-wobbly-surface-after-sharp-corners/

     

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