Wanhao - Monoprice i3 V2.1 Cobra Cooler for Stock Fan

by Roll1990 Dec 19, 2016
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What software did you use to design it? :)


I really like this thing but still have issues with fit on my Maker Select V2.1. It doesn't fit the newer bearing block as printed, making clearance with a Dremel so it does fit puts the ducts too close to the hot end and it melts even with ABS. Any chance you could share the CAD file? Would love to be able to make one that will actually work on my printer.

What would be ideal is to use the fan_mount_v2.stl mount included in this thing. It fits perfectly.

WANHAO i3 Fan duct
by Thorped

Had a nightmare trying to get a good print of this cooler using ABS. Was printing it standing up as in the photos. It would do OK until it got over about 1 1/2 inches tall then it would fall apart. Layers not sticking, strings and holes in the walls. Could be because I do not have my printer enclosed which is something I need to do. Finally after 3 tries I decided to print it laying down, open ends of the duct down on the build plate. Turned out great, if you are having trouble printing this thing try printing it flat. I used support build plate only and 45 deg. It did put some support structure inside the duct but was easy to remove with a small pair of needle nose pliers.

Just made one with PLA using the recommended settings with the version of Cura that came with my Maker Select V2 bought direct from Monoprice just before Christmas. Turned out pretty bad with strings everywhere. Not faulting the design and am hoping installing this cooler will help with the strings. Think I should not have changed the support settings, supports were too thin do do any good and added to the string problem. My label just says V2, not sure what the difference is between it and what everyone is referring to the V2.1. Not sure if it's a V2 or a V2.1

Discovered my bearing mounts have a hump in the middle which doesn't allow it to be installed as designed. Needs to be hogged out for the hump on the bearing block in order to be able to get it in position so the screw will go in. I can make it fit and it should work well enough to see if better cooling will help with the string issue?

Version #1 is now installed and seems to be working great. Had to hog out clearance for the bump in my bearing blocks but a Dremel took care of that pretty quick. Wished I was good enough with 3D CAD to make the change in the print but that is beyond my expertise at this point.

Version #2 is being printed and is turning out much better with this cooler installed We have a winner and looking forward to what will be my final version using ABS.

Printed this a while ago and just now got it mounted to my makerselect v2. Fits almost perfectly.

Could you please make a version though that gives maybe 0.5-1.0mm more clearance with the build plate? One of the arms continually drags on my print as it passes over as it is the same height as the nozzle.

I tried on my MP Maker Select V2.1. It has black plastic bearings surrounded by a metal sheath and a black plastic holder. The Cobra does physically fit the two mount holes below the bottom bearings. But the bearing is being held onto the frame from the other side of these holes on the extruder form. Since these screw holes are filled from the other side they can't be used unless I used short screws that wouldn't go in very far.

And even if one could use the holes where the bearings mount, the round air output arms are touching the heat cartridge and would certainly melt. They are literally too long and even if trimmed will rest right on the heat cartridge. I tried trimming the arms down by about 3/8" so they no longer touch the heat cartridge but then don't really point correctly at the part surface

Also I noted only a little air output is detectable with the fan running on full. And yes I did clear the supports everywhere. Seems the larger chambers disperse the fan air so much that little comes out the arms.

And last, the Y Axis cabling and drag chain mounted on the bed heat plate to the rear frame catch on this fan shroud every time the X coordinates were at center and the Y coordinates were at about 185 or up with a low Z height. Also when the Z axis is low and the hot end is moving back and forth it drags the fan on the build plate because the bottom of this shroud is lower than the nozzle is.

I'm starting to see why a rear mounted parts fan for this printer is such a chore to find. It needs to clear the off-centered heat cartridge and be lower than the heat cartridge but higher than the nozzle and not impede the build volume while missing the drag chains it passes by/over/under while leaving a view of the nozzle while printing and guiding air toward the printed area. Easy right? Not so much...

So this mod didn't work for me and my Maker Select V2.1 unfortunately. I was told by a person at MP tech support that there are 8 different possible bearing mount situations depending on when the printer was made. So what works on one Maker Select V2.1 may not work on another.

Update 08-25-17: I downloaded a fan mod called T Rex that is shaped similar to the cobra but is a little more angles than the Cobras curves. It sits just a tad lower than the heat cartridge. I bypassed using that one before because it required replacing the 40mm square fan with a 50mm rotary fan. At the time I didn't want to buy new parts when I could already use the one I had. It had the opposite problem as the Cobra with the T-Rex in that it drug itself on the plate as it was about 1/16" lower than the nozzle. I guess its those darn mounts on the back of my bearings again being different somehow. But with my Cura Slicer I shrunk it 1/8" in the Z direction only. I then had to then more permanently attach a 50mm rotary fan (glued) to it as it's motor carriage was no longer quite deep enough. But that did the trick. With the 50mm rotary fan, its quite loud if run at 100% and way too much air. (At 100% I can feel the air 2 feet out from the bed.) So I had to go back to my stl files and redo the gcode files to run at 50% and that's now much quieter and just the right amount of air. I don't know much about editing in CAD or Mesh programs yet and probably could have edited this Cobra mod to fit but I didn't have that skill set yet and didn't want to wait till I did. It took me 3 weeks of hacking parts but I finally got the T-Rex right for my printer. So if you too have one of the 2.1 version printers with different bearing mounts and such try the T-Rex. Or if you have editing skills you could probably resize this one to not touch in the wrong places.

No problems here with Maker Select v2.1

The blower end is kind of close to my hotend but not touching. I printed one in HTPLA and ABS as a backup for the reason that I normally print PLA at much lower temps than the HTPLA and ABS. I would suggest printing in a higher temp filament if you can.

While I didn't run into any issues with the mounting holes, I've absolutely run into the issue with the arms touching the heat cartridge on my 2.1. It's a shame too, because I like the look of this fan upgrade the most over all the others I've seen.

i thought it would fit to my i3+. i printed it but it is not compatible i'm afraid, cnt find a place to mount it in :/ is there a version of the same model for i3+?

I'd like one too... I'm just about to print this for my plus. I know this is an old comment but hopefully can help others. https://www.thingiverse.com/thing:2271974

Fan Duct for Wanhao Duplicator i3 Plus

I wish you had a variant of this with the adapter block for v2.1 with a radial fan not the stock 40mm. That's what's keeping me with the cii cooler, but alas that east up the corners (I use clips for my glass).

Try the T-Rex fan on Thingiverse. You might still have to shrink or grow it a bit for your paticular bearing setup but it will use a 50mm rotary fan and with a bit of modifying clears all parts. As I mentioned in another comment, there are apparently several different types of bearings that MP uses on the 2.1 version of the printers and you will likely have to modify any design a bit to accomodate them. You will have to tell your slicer to not do more than 50-75% speed though with the 50mm rotary fan as it produces a lot more air than the 40mm square one.

Anyone have luck printing this in Slic3r? The model seems to have holes when I load it, but no issues in Cura. Was hoping to use Slic3r though

Slic3r is not a very good slicer. I would recommend Craftware or Cura

Slic3r is great. It's all I use with the exception of Monoprices version of Cura. I can't get Cura to work for crap on my Rostock Max v3 nut slic3r is flawless.

As much as I like it, it doesn't work for me cause when it moves back it hit the cable chain I printed for the Y-axis, maybe I can shorten the back of the fan duct. Maybe

I made one without using supports(accident) and it turned out great

Just made this in PLA (REC PLA). Works great!
I was kinda concerned about the heat - but no melting so far.
And it made the leveling much easier.

Man I need this with a 120 mm fan mount. I needs all the cool airs.

nice work! Printed without supports. The screw is slightly difficult to put in. Put in first from the other side to thread the hole.
Had to remove the cable rail for the heated bed wires because it would touch.

Where did you move the cable rail to? I'm having the same issue.

I removed the cable rail completely. However, I have since switched to the Thorped style fan on all my printers

Prints really well, but is too short to use for the Wanhao DI3 V1. . It sits a ways back from the hot end, so the front half of the prints don't get cooled as much as the back half.

Having issues with the vent touching the hot end on my MPMS v2.1. The vent on the "heat sink side" of the print head is touching the hot end. I don't imagine this will go well when it heats up. Anyone else have this issue?

4 x 16mm allen head screw

Does this mean an M4 x 16mm or the quantity 4?

Also, any issue with printing this at .2 instead of .1?

You need one M4 x 16mm allen head screw to attach it to the back of the bearing block. Printing at .2 should be fine, I did one that way.

What type of a M4 x 16mm screw.... M4-.07 x 16mm, or a M4-32 x 16mm, or ?
PS printed out well, sounds like I will have to sand down the end by the build plate from what others have posted?

Thank you for this great project and for answering my questions.

For the support type, do you recommend

  1. Touching buildplate
  2. Everywhere

These are my cura options.

10% support, touching build plate only, 55 degree overhang angle. You don't want support everywhere because you'll never get it out of the ducts!

Having issues with there being holes in the vents near the end when loading this up in Simplify 3D. I ran it through netfabb and tried the fixed version but have the same issue. If there was a way to add a picture here I would. Anyone else having this problem?

Comments deleted.

Hmm, just printed it and found out my front fan is 30mm, Think they had some parts left when making my v2.1

Weird, I bought mine from Amazon 2 weeks ago and it has the 40mm fan...

Bought it few days ago from a local store, maybe it was older than they said.

Printed in ABS worked out pretty well.

Looks good and good timing too! was getting very confused with all the variations and adapter blocks. Really like that you can use the stock fan and see the nozzle so you can see what's happening.
Going to try and print now in ABS. Any tips for getting the print to stick to the bed? had 2 failed attempts with other models....

I solved my ABS to PLA and back issues with a glass plate and PEI for ABS then back to BuildTak for PLA. This thing explains what I did to solve the problem of switching between a glass plate and the stock BuildTak surface on my Maker Select V2.

Glass plate spacers for X&Z
by BobInOK

Not sure about ABS, I used PLA. I did build it with a 5mm brim, maybe give that a shot.

are you not worried about the heat from the bed when printing possibly deforming it? I am still trying with ABS... onto the glue stick now. Still have a glass bed to try but trying to just use the standard bed for now. If all else fails, PLA it is lol

Not sure yet - I've done several PLA prints with this cooler attached, the ends of it are very close to the heat block, but no deformation. Haven't tried ABS yet. I think lots of people have made the original cooler out of PLA and still going strong. It might be able to withstand more heat than you think because there's plenty of cooling air traveling through it.

Not sure yet - I've done several PLA prints with this cooler attached, the ends of it are very close to the heat block, but no deformation. Haven't tried ABS yet. I think lots of people have made the original cooler out of PLA and still going strong. It might be able to withstand more heat than you think because there's plenty of cooling air traveling through it.

Yes, that's true although you don't use the fan when printing ABS and that would be my worry. Really nice design tho bud. Have got it printing in ABS now and it's looking good. Used a cheap prit stick type glue on the bed and its worked a treat. I will post a pic when its done.