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Using a fan to print aggressively acute angles.

by MaikaiGuy, published

Using a fan to print aggressively acute angles. by MaikaiGuy Nov 11, 2012
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This is a simple fan guard so I won't harm my fingers while holding a small fan.

Why am I holding a small fan you ask?

I've been working on something and needed to print overhangs with aggressively acute angles without using supports. I noticed I can get angles down to about 15 degrees and still have a quality print if I blew on the hot ABS as it is printing. So I ran down to Radio Shack and bought a small fan.

The picture is of 5x5x10mm cube with a 1x1x10mm arm coming off at a 15 degree angle to horizontal. The cube and arm on the left have no air flow. The cube and arm on the right do.

Please keep in mind this is a layer height of .27mm and a feed rate of 80mm/s. The slices at this layer height do not have much to grab onto. It's kind of a torture test for the problem I'm trying to solve.


This is a simple fan guard to save my fingers. The real purpose of this Thingiverse Thing is to share a technique for achieving aggressive overhangs and still have a quality print.

I looked at some of the fan ducts for extruder fans, but they all seemed to reduce the build area... unacceptable.

Getting great prints with aggressive angles is easy using a fan with a separate power supply (wall wart), but requires your attention. Since my Makerbot is still relatively new to me and I'm usually watching it print, this is not a problem. ;-)

While I was at Radio Shack, I also bought a wall wart to power the fan and a female plug for the fan wires to accept the wall wart's plug.

You'll need a soldering iron.

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Why does this require your attention?  Is there a downside to having the fan on all the time?  I have often wondered about whether using a fan for "normal" prints would decrease the adhesion between layers or cause some other problem.  Also wondering how much the fan helps you with bridging.  Sorry for all the questions!

Hey hassebert,
For what I'm trying to do I need to move the fan from side to side as the slopes are printed.  If I just leave the fan sitting on the platform blowing from one side, only that side prints well.

I'm working on a vented duct for the business end of the fan, to better direct the air.  I want most of the air deflected away, but have a small tube of air I can direct precisely on the print location.

I think having the whole fan blowing on the print would have negative consequences for larger prints.  I already have an issue with warping and corners pulling up from the bed on larger prints.  My Replicator is enclosed and that helped, but now I need it open to apply this cooling air stream.

It's a "damned if you do and damned if you don't" scenario.

I've never had an adhesion issue between layers.  

The fan helps A LOT for bridging.  You can bridge longer distances and there will be less sagging when bridging the same distances.

 So you're going for a more precise version of this?


40MM Fan duct for MendelMax & Prusa V2

That's nice, but I have two issues with the several solutions I've seen similar to that:
1) You can't put something like that on a Replicator Dual without reducing build volume.  I routinely build large enclosures and mounting plates for electronics projects and will not (can not) give up build volume.2) Too much air is directed at the printed piece.   For small jobs, I'm sure this is fine, but I already have an issue with warping and pulling off the bed when printing large jobs.  I have enclosed the printer and this helps a lot, but still the issue persists.  I need something precise.