Fan duct for RepRapPro Mendel

by ambrop7, published

Fan duct for RepRapPro Mendel by ambrop7 Apr 11, 2013
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BSD License
Fan duct for RepRapPro Mendel by ambrop7 is licensed under the BSD License license.

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This piece is a fan mount/duct/nozzle for the RepRapPro Mendel with the updated x-carriage design. It mounts to a head slot next to a print head whose nozzle is to be cooled. The nozzle directs the air flow just below the extrusion point.

UPDATE: added a version which mounts opposide to the head, as opposed to next to it.


The fan mount is to be screwed the same way as a print head, though you should first put nuts into the hexagonal nut slots. Screw the fan directly into the plastic; because the holes are not very deep, you may have to cut the screws or add washers on top of the fan.

Print this in ABS, not PLA. If PLA is used, the nozzle will suffer from melting due to the proximity to the resistor wire, heater block and the heated bed.

I was having problems printing this using Slic3r; the bridges on the bottom (top) are not anchored properly and fall down. With Cura generated g-code the result is very nice; the part in the picture was printed at layer height 0.25mm with 0.5mm nozzle.

You may have to reduce the Y range of your printer, such that at Y=0 the bottom of the duct doesn't bump into the clips holding the bed together.

Make sure that the part is not too high, or it will rub into your print bed. The distance to consider here is from the top of the bed (when head is lowered to Z=0) to the bottom of the plastic where the fan mount will be screwed. This distance should be strictly more than the total height of the part. In the precompiled STL, this is 27.5mm. If you need to make the part lower, in the openscad source, adjust the total_height. You will also need to move the nozzle appropriately; to do that, adjust the Z (third) coordinate of tube_start and tube_end by the same amount in the opposite direction (since these two are negative, this means to adjust their absolute value in the same direction).

The tube_start and tube_end parameters define the starting position and the direction of the nozzle. The tube_end will ideally be a few millimeters below the extrusion point (so as not to cool the heater block too much). Note that tube_end only controls the direction of the nozzle, its length is defined by tube_length.

NOTE: Due to the use of a minkowski sum the recompilation will be very long (~30 minutes). You can greatly reduce that by changing the resolution of the sphere in the sum to something lesser than 12, though that will make the width of the duct walls more incorrect.

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This works very well! I used the same fan, although it is a bit loud. I reduced the overall height by 2mm to make sure the bottom cleared prints. Now able to finally print more complex shapes.

What is white thing on nozzle (material)?

A few questions:

  • What size fan are you using for this ?
  • Do you also know what the CFM of the fan is ?
  • Any before/after print images?

I printed a different Mendel fan Mount design (http://www.thingiverse.com/thing:75078)http://www.thingiverse.com/thi... and have tried it with 40x40x10 (?? CFM) and 40x40x20 (10.2 CFM) and neither one solved the problem so I currently have a oscillating table fan (http://www.amazon.com/Holmes-HAOF90-UC-Blizzard-Oscillating-Table/dp/B00005CDPQ/ref=sr_1_1?ie=UTF8&qid=1368066119&sr=8-1&keywords=blizzard+holmes)http://www.amazon.com/Holmes-H... sitting in front of my Mendel, which is obviously not optimal.

The 40x40x20 fan did help a bit, but not quite enough. I've got a 40x40x28 fan on order as well that has the highest CFM rating I could find on a 40x40 fan.

I'm also curious what print settings you're using for PLA with that fan setup (bed temperature/hot end temperature/layer height/etc).

RepRapPro Tricolor Mendel Fan Mount
by hlx_mr

I think the efficiency of the fan could be improved by putting a cone on top to stop excess air from blowing out the sides, but that hypothesis is yet to be tested :)

I bought these 24CFM fans specifically for this purpose: http://www.ebay.com/itm/Delta-FFB0412SHN-40mm-x-28mm-Extreme-Speed-Ball-Bearing-Fan-FFB0412SHN-FOO-/370609498971http://www.ebay.com/itm/Delta-... .

I don't have images available right now, but the little pulley being printed in the picture came out nice, and it was melted without a fan. For PLA I'm mostly using 0.3mm layer height, fan speed min 15%, max 40%, bridges 40%, enable fan below 20s layer time, slow down below at 10s layer time, min speed 10mm/s. I've never found I needed to run the fan above 40%, as it's a very powerful fan (even though it's blowing through a tiny fan).

Your with-cooling picture seems okay. You can check if there's an overheating problem by poking the top of the print with a screwdriver while it's in progress and seeing if it bends.

I'll try to post some pictures with/without fan, but it'll take some time because I'm currently in the progress of upgrading to dual extruders and I need to fix this part so it can be mounted on the other side of the head (as opposed to being next to it).