I made a duct for the 25mm extruder fan. Use freely! There are two versions, wide and narrow exhausts. I have not printed the wide version yet.
thingiverse.com/thing:618656
Looking good ronkeli! 
I’ll try that out asap. Maybe it will also enable my hotend to heat a little faster…
I’m not sure how significant the 25mm fan really is as it seems rather underpowered at least comparing to the main fan on the top. If one could guide the flow of the main fan closer to print, now that would make a difference. However one thing to considers is that how important it is to cool also the insulator guide with the air flow? Would it cause problems if there was no additional air flow for it?
I guess the small fan is really only to cool the filament when it gets out of the nozzle. For that purpose I think it is more than adequate. But only a guess…
Nice thing. I’m already printing it :).
Thanks ronkeli.
This modification can lead to problems with curling plastic or filament that gets stuck inside the PEEK piece. Use with caution.
[quote=“raby”]Nice thing. I’m already printing it :).
Thanks ronkeli.[/quote]
No problem!
Is it because this might cool down the filament too quickly and cause it to get stuck in the nozzle?
Would it be better to divert the air flow away from the nozzle or let it spread over a wider area?
Anyway USE WITH CAUTION as adviced by VEL327!
I too like to know if that 25mm fan is only to cool the filament as I just created a modification myself too.
This mod attempts to point the airflow more or less directly towards the nozzle, hoping that this will cool the filament right after it has left the nozzle.
I have printed the part tonight but maybe I’ll wait mounting it until I get some more insights on the exact function of the 25mm fan.
Thanks
Erik
Erik - Nice mod. My understanding is that it is to cool down the filament as you describe. I have to my K8200 printed this nozzle http://www.thingiverse.com/thing:174247, and after done that I got excellent prints. It cools down the filament without cooling the heatbed.
Regards Eero
Erik, thats a very nice duct too! Let us know how it performs!
I have had my “high velocity duct” mounted for several hours now and have been able to print very small parts without cooling issues.
Also no filament has got stuck in the nozzle yet…
Cheers!
-Ari
@ronkeli: What kind of filament are you using ? PLA …
I think PLA at 190 is not a problem for the peek isolator guide but could be a problem with ABS and XT ( 240 ).
The peek isolator need to be refreshing. My isolator guide runs with a temperature of 60 with the original fan. It is already too much as with an E3D head it is 50.
Anyway it is a nice MOD and I already printed it but I will probably add a Fan before mounting it.
I still have some doubts if I will install it…
Although the original 25mm fan position is probably not positioned at the most efficiënt place to cool the filament, it’s there for a reason? If it’s meant to help cool the Peek isolator, I don’t want to stop that of course.
Maybe it is possible to add this mod with a second 25mm fan connected to the same screw terminals?
That way I can try to cool the filament without disturbing the original cooling design.
Erik
At the moment I’m using PLA but will move to ABS as soon as everything is as should be.
What comes to the isolator, I have a strong feeling that the cooling power of the 25mm fan is minor compared to the 50x50mm centrifugal fan on top, which exhausts directly behind the isolator and has significant air flow. But I’m not sure of course…
I just found another 25mm fan in a store nearby so I’ll add that to be safe ;).
Better safe than sorry! 
Well… I just found out that short-circuiting is not the best thing for your printer…
I tried to connect the new fan to existing terminals and probably short circuited the board.
Smelled some burned plastic, noticed some smoke too ;).
I hope I’m still ‘lucky’ as all the functions except the fans still work.
I measure 15V on the main board connectors, end of the loom and even on the terminals on the Extruder Board.
When I connect the fans to a separate power supply they run normally too.
But, when I connect the fans to the Extruder Board, they won’t run.
Time to enjoy the rest of the weekend, kindly asking Velleman if I can buy a replacement Extruder board…
Too bad … How did you do to short circuit the extruder board ?
Manually pushed the wires from the new fan onto the screw terminal that belongs to the original 25mm fan, just to see if they would both run at the same time.
The moment I touched the terminal with both wires, the fans stopped running and within a second or so I saw some smoke and it was already too late.
I’m not an electrical engineer, but I thought I connected Red/Black wires correctly…
The only option I currently have left is to connect both fans to a separate 12V power supply and use that while printing.
If that doesn’t work, I have to wait for new parts to arrive.
Arg, I experimented someting similar on another board (smoothie). Fortunatly the board survive without any damages but my conclusion was to turn off the board before connecting a Fan. I don’t know why, I m not an electrical engineer too.