Ormerod Fan Direction

I've assembled my Ormerod as per the instructions, specifically with the label on the fan facing the heatsink and the rotating part facing outwards. The result is that air is drawn in near the hot end, and expelled towards the y-axis motor.

Is this correct? I don't see anything in the Ormerod information that indicates which way the fan should blow. From what I've read about 3d printing in general shouldn't the air be blowing onto the extruded filament to cool it?

I think you will find that air is being blown out of the vents near the nozzle. However, there is a large amount of backwash from the fan, which makes it feel as if it is blowing the wrong way. You can eliminate the backwash by fitting a device such as this: [www.thingiverse.com].

Edited 1 time(s). Last edit at 11/04/2014 05:49AM by dc42.

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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].

The fan is blowing in the correct direction, ie onto the heatsink, so long as the fan label is facing it. The fan won't move at all if it's wired the wrong way around, so can't inadvertently blow the wrong way. You can undo the fan and hold it while you power on the printer, to check which way it's blowing, if you wish. The reason you can feel air coming back out of the fan, as if it were blowing the wrong way, is due to fan 'backwash'. This is caused because the fan is too powerful, and there isn't actually very good flow of air through the fan duct, so some air comes straight back out.

We have recently done away with the heatsink duct and fan duct printed parts, replacing it with a laser cut spacer (see [reprappro.com] ) with a mounting point for a more useful, controllable extra fan (to be released soon), as we feel the printed parts are rather ineffectual. You can achieve that same effect by removing the fan duct, but leaving the heatsink duct in place, as it holds the wiring. Less air will come out the back of the fan, but will escape out of the larger opening of the heatsink duct, to the side.

The Ormerod community has come up with a number of 'air reducers', grills and ducts that slow the air flow into the fan, or distribute it better. See: [reprap.org]
My personal favourite is the Cthulhu, but I haven't tried printing it yet!

Ian
RepRapPro tech support

Thanks both for the advice. As I could easily feel this backwash from the fan I hadn't chanced a wet finger near the hot end to see if there was any airflow there too! I'll try some of the mods, probably starting with dc42's backwash eliminator.

I must admit I did wonder about the design when I was assembling the hot end; the outlets are so much smaller than the inlet, and little CPU fans can't maintain much pressure difference.

I think my Ormerod deserves a new fan, its been working on the supplied fan since i got it in January. The bearings are all a bit wobbly now, and quite noisy.

Is there a upgraded fan i can get at reasonable money inc postage?

Quote
PaulHam
I think my Ormerod deserves a new fan, its been working on the supplied fan since i got it in January. The bearings are all a bit wobbly now, and quite noisy.

Is there a upgraded fan i can get at reasonable money inc postage?

Here's a couple of links,

data of the original fan:
[forums.reprap.org]

Tread with link to alt. fan
[forums.reprap.org]

Erik

I replaced mine with RS758-8207 Has worked fine for nearly a year and many reels of filament, and is practically silent.

Dave