Hot end fan suddenly slow to spin up

Hi all,

My hot end fan takes 30-60 or so seconds to spin up to what is presumably full speed after the printer has been turned off for any length of time (like overnight). At first it doesn't spin at all, with only the occasional stepwise lurch forward. When helped along manually, it does a few steps under its own steam then stops again. It gradually picks up speed until it's constant after a minute or so. Almost as if its supply voltage wasn't up to the full 12V on turning the machine on but took some time to build up to that value. Once the fan is spinning, it stays so and 4-5 hour prints come out ok (to the extent that my prints can be called "ok", I'm still new to this and playing around with Slic3r settings).

It also used to be bloody loud until I gave the spindle a squirt of WD40. Incidentally, this is around the time that the spin-up issue started. Coincidence or correlation? Please don't shake my belief that if WD40 or duct tape don't fix it, then it can't be fixed.

Cheers,
Bart

If it's one of those cheap and nasty little fans, the bearings have probably gummed up or failed. I've got through about 3 or 4 so far.

Sometimes you can peel off the label and get at the bearing - put a tiny drop of thin OIL on it (about as much as you can get on the end of a length of wire is enough). Note I wrote OIL, as WD40 is a water dispersant (WD) not a lubricant. It might clean stuff away, but it won't make stuff run any better.

If you can't get at the bearings, then it's replacement time. In fact, it's worth ordering a new one as mine never lasted long after lubrication.

Hi David,

Thanks for that, back to eBay then, this time looking for fans. WD40 is also a lubricant though. A major component of it by volume is a volatile solvent which evaporates quickly but this then leaves behind a non-volatile coating of lubricant.

Cheers,
Bart

One other thing to check is whether the bolts holding the fan have warped its case, which can cause the fan blades to rub. My original fan had that issue and would not start unless I slackened the 2 mounting bolts a bit - but as they also hold the heatsink against the cold block I did not want to compromise the heat transfer by loosening too much and so bought another fan (MUCH quieter). I used RS part 758/8207 but there are plenty to choose from.

Dave

Quote
dmould
One other thing to check is whether the bolts holding the fan have warped its case, which can cause the fan blades to rub. My original fan had that issue and would not start unless I slackened the 2 mounting bolts a bit - but as they also hold the heatsink against the cold block I did not want to compromise the heat transfer by loosening too much and so bought another fan (MUCH quieter). I used RS part 758/8207 but there are plenty to choose from.

Dave

I drilled 2 extra holes in the heatsink, and I now use 4 screws to secure the fan and fan inlet duct, with nyloc nuts on the extra two.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Quote
bartdietrich
WD40 is also a lubricant though. A major component of it by volume is a volatile solvent which evaporates quickly but this then leaves behind a non-volatile coating of lubricant.

Bart,

I don't agree... but it's not worth one second of arguing!

If it works for you, all well and good - I'll stick with thin oil myself.

Good luck with your fan hunt (I recommend the ones with ball bearings, if you can find them).

Edited 1 time(s). Last edit at 05/06/2015 07:41AM by David J.

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David J
I don't agree... but it's not worth one second of arguing!

Nor does this guy, apparently [www.hardwareheaven.com]
.. or here [www.popularmechanics.com]

:-)

Dave

Fair enough, although that's not what WD40's own website says ("light lubricant"). May not be suitable for heavy duty use, but a 12V fan is hardly a heavy duty application. And once my fan gets going, it's so much more quiet than it used to be. :-)

Thanks dmould for the RS part number. I was placing a partially work-related order with RS anyway so just slipped that in. Saves me trawling through eBay listings to get the right dimensions etc and it'll be here tomorrow. :-)