"Spriya" - High Efficiency Anet A8 Fan Duct

by lokster, published

"Spriya" - High Efficiency Anet A8 Fan Duct by lokster Feb 24, 2017


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If you use this fan duct & think it makes your prints look better, don't forget to TIP! ;)

The story

I designed this fan duct as a 100% free & open source alternative to another one which was very good, but unfortunately it's license was preventing me from modifying it the way I see fit & share it freely.
So I started Blender, and made my own from scratch in a couple of days. One that I can share freely with the community, so anyone can use it, remix it or trash it - in any order ;)
The fan duct works very good for me, but I give you no warranty that it will work for you.

Highlights of this fan duct:

  • The most important: it's more effective compared to the semi-circular design, and A LOT more effective than the stock Anet A8 fan duct.
  • it's quieter, compared to the stock & the semi circular design
  • it does not block the view, and you can see your nozzle tip
  • it uses my own attachment design, and once it's inserted onto the fan, it's impossible to fall off. Forget about the tape or glue for securing your "always falling" fan duct.
  • it blows more air, compared to the other duct designs I tested. Instead of concentrating "on the tip of the nozzle", the air flow is wider, and separated at 2 flows at approximately 90 degrees. This way it cools wider area, even if the nozzle moves away from the "point of interest".
  • when mounted & tuned properly using PID Auto Tune (described below), it does not cool the heat block, and the temperature is very stable - plus/minus 0.5C.
  • VERY lightweight - just 3 grams, compared most of the other fan ducts which weigh 4-6 grams or more! So even if you find out it's trash, you've lost the material for just 1/6 3D Benchie or one calibration cube :)
  • open source design, made with open source software - I am releasing the original design in .blend format, which you can load in Blender and make modifications. You are then completely free to release any remixed designs you made! In fact, it will be great!
  • the mesh is relatively low-poly, so it's easy to edit in blender if you want to make your own adjustments.


I used the Marvin Key Chain as a test object - http://www.thingiverse.com/thing:215703.
The print settings were as follows:

  • layer height 0.2mm
  • shell width 1.2mm
  • temperature 190C (PLA)
  • print speed 30mm/s outer shell, 60mm/s inner shell, 100mm/s travel
  • no infill
  • print acceleration 800mm/s^2, travel acceleration 1600mm/s^2
  • the objects "back" side was facing to the back of the printer (towards Y MIN), so it was prone to "sagging" on the lower layers (true for any spherical object).

Test Results

  • the stock fan duct - a lot of sagging on the back, and left/right sides of the model (terrible)
  • the "Semi-Circular" fan duct - some sagging on the back, and just 1-2 layers on one of the sides
  • "Spriya" design (this fan duct) - (almost) no sagging at all, with just two tiny irregularities - two "dots" on the back side of the model.
    Check out the photos to see a comparison.
    I have also tested with 3D Benchy - placed so the bow of the ship is facing to the right. The results were consistent, and in fact even better: sagging on bow with the stock fan duct (and some layer irregularities); just a little sagging with the semi-circular design; and absolutely no sagging or defects with "Spriya".

Tuning your heater using PID Auto Tune

This step is very important, so don't blame the fan duct if you have not performed it and you are getting bad results :)
Every time you install a new fan duct, it's highly recommended to perform the so-called "PID Auto Tune" procedure on your heat block. It's performed very easily - when your printer is cold, connect it to your PC, and start your preferred program that allows you to send GCODE commands directly to your printer. You can use Pronterface (http://www.pronterface.com/) or whatever you prefer (some slicers have this function built in).
Next, decide what's your preferred print temperature - in my case it's 190C.
You will also have to turn the fan ON.
Execute the following GCODE command to turn it on:

M106 S255 

Now run the PID auto tune GCODE command (replace "190" with whatever temperature you use):

M303 E0 S190 C8

It will respond with
Info:PID Autotune start

Your printer will go through 8 cycles of heating / cooling, so it will take a couple of minutes.
In the end, you will get a response, that looks something like this:

bias: 164 d: 90 min: 188.73 max: 191.76
Ku: 37.70 Tu: 20.50
Classic PID
Kp: 22.62
Ki: 2.21
Kd: 57.96
Info:PID Autotune finished ! Place the Kp, Ki and Kd constants in the Configuration.h or EEPROM

Copy this response somewhere, otherwise it will quickly get lost in the idle "wait" messages.
Now go to your printer's Configuration -> Extruder menu, and set the control type to PID. Next, set the P value to match the Kp, I to match Ki, and D to match Kd.
Finally, save your settings to the EEPROM.
This is how it's done with the Repetier firmware. It should be almost the same with the stock Anet firmware, and similar with Skynet3D (Marlin)
When you have tuned your heater properly, the temperature will fluctuate by just plus/minus 0.5 - 1C and will be very stable.


  • Actually try it before starting to philosophize whether it's effective or not :)
  • Read below to find out the recommended print settings
  • To mount the fan duct, you have to loosen the screws of your fan a bit, insert the duct, and tighten them again.
  • The name "Spriya" is a Bulgarian dialect word, and means "strong wind", "vortex", "blizzard" etc ;) It's a joke.
  • Check out some of my other open source stuff at http://lokspace.eu
  • If you have problems slicing / printing the normal version, try the "thick walls" version - "Spriya - Anet A8 Fan Duct - Thick Walls.stl" found in the archive (it has 1.2mm walls, but it's still lightweight).

    Don't forget to post "I made one" photos! Your input is welcome!

Print Settings


Anet A8










I used Cura 2.4 to print this.
Check the pictures to see how you should lay the model down when printing (rotate it 90 degrees along the X axis, and allow supports - as shown on the fifth picture. Only the attachment part needs a bit of support, so you can set the "Support Overhang Angle" to something high like 80.
You also need to set the support placement to "everywhere", and support type to "concentric".
Support density of 15% works OK. Be careful when removing the supports afterwards!
Without support, the upper part of the attachment might sag a bit, but it will still work.

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This fan duct is great. It appeals to the eye, fits almost perfectly, and was easy to print! Nice work! The duct works so well that I am going to have to redo the Auto-PID tune! Thanks! YOU ARE AMAZING!

Is it possible to use this Fan on the Anet A6?

No, i tried. Doesn't fit standard A6 fan.

HY, the blower fan got to be running at 100% before start the PID?

worked great! so much quieter than the provided whistle that comes with the anet!!!

Hi lokster, firstly thank you so much for the amount of detail and help you have provided for this print!
I've used the "Spriya" Fan Duct for 2 days now, however, I'm noticing that the temperature for the first few laters is between 5-10 degrees lower than it should. After a while, the temperature seems to stabilize and is much more accurate.
Is this expected behaviour?

What I've done so far:

  • I have done the PID calibration twice to make sure
  • Moved my extruder so that the duct isn't blowing on the hot block.
    Please see the attached screenshot from OctoPrint that illustrates this temperature fluctuations.

Any help would be highly appreciated!

I've had the same problem. What I do is essentially (I would normally print at 200) just bump the temperature up 5 degrees (205 for me) the small increase doesn't seem to affect my prints at all.

Hi Deiago, I've got the same problem as you have. Did you find a solution?

Best regards

Printed it. Turned out okay, but it's lower than my noozle therefore it would hit my prints. I changed back to the original fan duct. Anybody had a similar expierence?

Just lower your nozzle and re level your bed


The semi-circular one from the same author works great for me but this hangs too low

Pic of both to illustrate

Hi body, can u make a improvement? My fan duct is touching in the block because i have the block in a posicion that the wires r in the back.

Then rotate the extruder. The model works fine as is.

Wow, this fan duct is so much quieter than the stock one! I couldn't stand the noise and was going to replace the fan, but now I'm all set. Very impressive, lokster! Thanks

Olá amigo, o melhor duto que eu encontrei para a minha anet a8, mas eu preciso aumentar o encaixe no cooler em 25mm, e não sei usar o blender, é muito abuso da minha parte pedir isso? tenho 0 experiencia com o programa.
Ficaria muito agradecido pela ajuda, até mais!

Hi. I just printed it without any difficulties. I just would like to know where should be placed the extruder where you performe the autotune PID. I noticed that if you are very near the bed, it cools much more the nozzle.
Thanks for your help.

Forgive my noobism, but with printing this with 100% infill and supports enabled, it's also filling in the inside, which will block the air. How can you print this with supports (as advised on the detail page) and still having air openings.

don't do infill do supports and try to move it using fusion 360 so its sitting down. (:

You can just change all that in Cura... what even is fusion 360?

In the 3rd pic, what is the second orange piece going along the bottom of the extruder/fan and the 2 pieces under the heads of the fan screws?

Its not related to the fan duct - it's a simple mount for my laser engraver module / pen holder - http://lokspace.eu/anet-a8-3d-printer-laser-engraver-mod/

Hi so I printed the thin version and I found a major problem that this had for my A8.

My bed is perfectly leveled at 0.2mm on all 4 corners including the middle (using the paper method) but when I use this duct, it would keep hitting the print.(I know I mounted it correctly on the fan plus made sure it is high as it physically can be, while getting the notch right)

Should the corners of the duct be so close? I feel if they are raised by a small bit, it wouldn't keep hitting the prints?

Try lowering the extruder nozzle. :)

i printed it using the recommended settings on my stock ANET A8 with skynet 2.3.2 and it worked out fine.
the supports where a little tricky to get them out, but it was not that difficult.
used the pronsole.exe to send commands and tuned it at 210 degrees. no need to copy the output as it stays there fine.
then in skynet3D 2.3.2 go to control>temperature and scroll down to PID-P and change setting.
then goto store memory or type in console: m500
now lets see how this works out..

With great difficulty I finally succeeded in make the PID adjustments
Thanks a lot for the knowledge

Made this and now all my prints look very clean and awesome on one side and then like total crap on the other, anyone know how I can fix this? I did the PID process and everything but I am still running into the problem.

Any recommendations of an x-carriage or mount for the radial fan? I can't mount the radial fan on my carriage, no place for it.

Did you make an "inside" version, something like this... https://www.thingiverse.com/thing:2322182

Semi-Circular Anet A8 Fan Duct for Don1337's carriage
by Murkser

some tips for pid tune? because every day it shows me another numbers :/

It's normal :) All of them should work fine. Just make sure your heatbreak (throat) is not inserted too deep and you are not cooling the heat block.

and what position of z axes during pid tune? 0 or somewhere far from bed? :)

somewhere 0 should be fine

I find that the wall where the slot is cracks very easily. If that were at least 50% thicker, I think that would help keep that in one piece. I've cracked my 2nd one and going to glue it.

It's the usual thing with fans. People forget that with the A8, the height of the nozzle will depend on how much you screwed it in during your build. And since the instructions don't tell you how much to screw it in, each printer is likely to be different. I personally screwed my second hot end in further, to make inserting the filament easier.

So, height of duct to fan nozzle will always vary. It's just one of those things, because of a printer you build yourself from a kit. Just remember the money you saved doing it!

It would be good if you showed a photo of the duct from the side, so we can see the height it should be, compared to the nozzle. Thanks.

This air blower made a huge difference on the quality of my parts. The pid calibration is also very useful. Thank you.

Printed it this week and it is great. The only problem is the thermal runaway i get, when the fan works with more than 30%. The bottom from this duct is just 0,2mm above the nozzle. So my heatblock should not be cooled :/
Pid Tuning was also done after printing this.

You're not the only one, with my fan set at 25% when I set my PLA temp to 195 I'm running between 183-188. My first print with it about 20 in I walked away, somehow didn't even look at the nozzle temp and came back to find that a few layers of PLA came out without sticking at all, and then the PLA stopped flowing at all and my nozzle temp was at 142*. Like yours mine is very close to my nozzle height- I have my threaded tube screwed all the way in putting the heat block up quite high and the arms on my cooler look like they're going to touch the print but haven't yet

I'm going to have to play with the PID tuning, but honestly, the fan is so silent at 25% that I'm tempted to just set that as my default fan speed.

I'm not sure if this has been discussed but, is there a way to print this without the supports or helpers covering the nozzles? I was able to peel off the ones from the front easily, but I cracked the part that mounts to the blower trying to get the ones on the top inside....

I printed the thin wall version without supports. Flip it 90 degrees so that the ducts are vertical, I had a few minor stringing issues but the result was good and fan noise has been eliminated. Thanks for sharing this!

what speed did you do it with for the one without supports? seems a bit impossible. Also this is my first fan print so that means the filament gets no cooling at all since the one that came with the printer is defective

I can't remember what speed it was but it was one of the first prints that I made so I wasn't changing any settings apart from temperature. You could print a different (basic) fan duct and then use that to print this duct. I'll see if I can dig up the file if I still have it

Just checked steeings
Print speed 60mm/s
Print temp 210
Bed temp 50
Hope that helps

I can't slice this with Cura 2.5 - laid on the side as suggested the top of the fan insert part does not get sliced by cura, it's plain left open.
Repetier 2.01 with Slic3r Prusa Edition renders it OK but generates horrible support structures which leave out a major part of the fan insert 'roof' thus making it a challenge to print that section.
I was able to print a usable version only with repetier/slic3r, but cura definitely generates better support structures...

Could you share your complete set of cura parameters for a successful print ?

Use the new Cura. It works great.

Seems to work really well but this does blow more air on the hotend which causes a big temp drop. (mine was running 20c below spec) make sure you recalibrate as descibed after attaching this duct once you do you will be very happy with the results

I was able to print with no supports. Just had to rotate 90 degrees so the flat back piece was pointing down

I can't get my PID autotune to complete it never gets up to tmp. What were your PID values? I am thinking if I can put something in similar to the final value then PID Autotune can run properly. Also are you running your fat at 100% (255/255)? Thanks!

Most likely your heat block is too low and the fan duct cools it. Some people have this problem. Make sure the duct does not blow on the heat block.

Thick one with 0.2mm cut off bottom object in Cura will make its first layer correctly stick to the base, finally I got it.

I managed to print it with only a few minor support issues due to Repetier/Cura setting it up to attach the supports too strongly to the duct. Worked good enough the first time that it only needed a little sanding because of the mentioned support issues but this thing solved a major problem where I was having curling on the rear of my prints due to the basic one-direction fan duct that came with the Anet A8 that I received not cooling the back of my prints and it having difficulty printing any of the circular ducts.

To summarize: This thing is awesome, but make sure you print with supports!

This thing is virtually impossible to print - not sure how everybody is printing this but it's so uneven off the bed my supports are getting all screwed up.

Thank for sharing this, it's the best fan duct for the A8. My remix for an E3d V6 setup: http://www.thingiverse.com/thing:2305596

Spriya for E3D

Saw a mod for the extruder fan to change it to an 80mm computer fan, I would be great if I could still use this duct with that. Only problem is the mounting system here will not work with that because it needs to be like the original mounting system.

Would it be possible to have a thick-wall version with the original mounting style in case I did use the fan conversion? That particular fan is very loud and annoying.

could anyone provide me with proper settings to print it in S3D?
I don't seem to get it done right, my last print just broke while I tried to remove the support.
The support was everywhere in the inside and it was impossible to remove it without breaking the wall of the print itself :/

turn it 90 degrees and manually set support inside the part that attaches to the fan. that is the only part wich needs some support. or you could try to print at default angle and set support at only touching buildplate.

why with this fan duct the temperature of the hotend drops 10C when fan turn on?

did you do the pid autotune? also maybe try turning it on 1 mm into the print to prevent air circulating to the block.

A couple of possible reasons

  • you need to do PID tune
  • maybe your dimensions are different. Some people seem to have longer nozzle throats (or maybe not screwed enough)
  • the fan is mounted a bit differently, which results in fan duct cooling the hotend.
    On my setup, the tip of the fan duct is ~4mm above the tip of the nozzle, and it works flawlessly - the temperature is very stable - plus/minus 0.5-0.8C after the PID tune, which is perfect.

i dont understand how to use the pid tune..

thanks for reply

do you have your hot end on a separate mosfet? I read that the standard board mosfet isnt strong enough to keep the hotend on stable temps.

Comments deleted.

I printed this fan duct, but is not compatible for Anet A6, somebody has adapted this design??

My printer has no Config->extruder settings.
I can use gcode to set pid. Which gcode should I use: m301 for extruder or m304 for bed? Also, how to get current values via gcode and how will I know if it worked?

What do you suggest for support structure now that concentric is no longer available in Cura?

in Cura I only see support types lines and Grid, not concentric.
which should I use?

in case anyone was wondering line worked better

I've tried all ducts, and this one is by far my most favorite and most reliable. Also, having a Bulgarian name is an added bonus, given that I grew up in Bulgaria :) Thanks for sharing!

Thank you, this was the first thing I printed after my test print when I got my new Anet A8. It printed with minimal sagging and has been very effective.

Is there any chance you could publish a version with custom supports added inside the body so that no others are needed? I think most people could print it without further support if the bridging over the main chamber was supported.

Doesnt print fails everytime

I suspect some people's printers/slicers have problem with the thin walls, because you are not the first with this problem. Would you be interested to test it again if I upload a version with thicker walls so I can confirm this is the cause and update the description?

I printed the this version and it worked, but there was a tiny hole near the end of the duct. I would like to try the thicker version

I'm trying to slice in Slic3r and I always end up with small gaps near the tops of the fan ducts. I'd be willing to give a thicker-walled version a try.

You can see the gaps here:

I have just uploaded "Spriya - Anet A8 Fan Duct - Thick Walls.stl". It has 1.2mm walls, and should be easier to slice / print.

Thanks for the design, I will print this since the big circle one (work) but scrapped one of my print because the circle is to near the layer, when a little glitch append it can touch the fan duck and ruin the print lol

Comments deleted.

may I ask what your cura settings are I just got a new anet a8 and every time I print the print is messed up and I'm super confused because it took me many hours to build

I've tried printing this twice now but it always seems to get messed up on the right duct half way through. Have you heard of this issue from anyone else, and if so was there a solution? Picture is linked below.


print it as the model loads. dont rotate it. I printed with grid support and a 10 line Brim that worked for me at least.

The print turned out just fine (no supports at all since I couldn't figure out where to adjust those specific support configurations you mentioned in your description) and I did the PID Auto Tune but it seems to me that the air coming out is pointed too high?! I already adjusted the Hotend to be higher and spinning it any higher would resolve in the ducts being at a lower position then the hotend itself.
I'm printing at 200°C (PLA) and didn't have any temperature issues before but now it seems that this temperature can't be reached anymore. Apparently it goes to ~198° and constantly stays there though in octopi I can see that my target Temp is 200°C.

Apart from that the print results are very good. Though I don't have any exact comparison to the 360° Fan Duct I was using before

Just send me a photo from the left side of the hotend, so I can see how it looks compared to mine, and I will make you a custom version ;)

Just printed one because you can never have enough fan-ducts. ;-)
First observations:
-Supports were also printed at both ends of the duct tubes, i.e. also internally.
-Also the supposedly open slot in the side was printed shut on both sides.
Note that this could be due to my inexperience but I followed the print setting guidance to the letter.
-The wall thickness is insufficient which results in a rather fragile piece.

Not sure if I'm actually going to use it.
I'm currently using a similar one from Leo_N and I have no complaints.

From the photo of your "make", it looks like you printed it without orienting it correctly (this is mentioned in the description). The model MUST be rotated -90 degrees along the X axis in your slicer (as shown on the fifth photo), otherwise it won't print well.

remixed to be 5mm lower so it would work with my machine. The threaded rod between my hot end and my X-Carraige is 5cm longer than the original. http://www.thingiverse.com/thing:2159432

Thank you for putting this design out there for us to tweak.

Spriya Remix, 5mm lower than original for longer extruder feed screws (heat break)

what program did you use to remix? I have a modified e3d hotend and thus the hotend middle position relative to the fan is different...

The support density is listed as 100% in the built in data and 15% in the paragraph you typed. It seems like 15% is the correct answer but I figured I would check before I printed this. Looks like a great design. Thanks for creating and posting it.

You have mistaken. The infill density is 100%, and the SUPPORT density is 15%.

First of all - just by putting my finger below the nozzle this fan feels much stronger than any other I tried.

Just 1 thing to add to the PID instructions - after you get the success response, you should copy it.
I did this with octoprint, got the finished message, went to configuration -> extruder -> control and changed it to PID and the console already had too many other incoming messages that the results were gone and I had to run it again.

Great job with this design!

Yes, you are right - it's best to copy the final response with the PID values, otherwise it might get lost in the idle "wait" messages in the log.
I will update the description, thanks!

with octopi you can just turn autoscroll off to stop it from being overwhelmed

hey i was wondering that pid test, t runs it withought activating the fan, so technically why would it matter if the fan is different?

You are correct, I missed that in the guide. Updated.
You MUST turn the fan on before the PID auto tune, otherwise the auto tune is pointless :)

If I put this on it hits my hothead.

It works on my stock Anet A8. Maybe your dimensions are different? Can you upload a photo somewhere so I can see the problem?

How far above tip of the nozzle can this fan be to be effective? I initially had it level with the nozzle but in some cases it would scrape.
I then screwed down the nozzle a bit so this is sitting maybe 1-2mm above. Occasionally stray strands (usually from support structures) get caught and dragged along. Doesn't usually compromise the print.
I'm still new to printing and I'm not exactly sure where these should be blowing. I see from above they shouldn't be blowing on the heat block (I assume that is the square metal block above the nozzle). But should they be blowing ON the nozzle, right below the nozzle, etc.

Are we trying to cool the nozzle, or the plastic that has just been deposited from it?

So, how much higher can the bottom of the ducts be above the tip of the nozzle to still be effective.