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Since I heard UM was no longer doing the dual extrusion kit for UM2, I have been thinking about replacing the dual fan shroud for one that better suits using a single nozzle.

So I ended up downloading a few designs from youmagine and found Venkels design really improved my print quality. But since then I got the Olsson Heater Block upgrade which means the nozzle sits a bit lower.

So I redesigned Venkels Fan Shroud so sit at the new lower height. As I was doing this I noticed a few things with the design that didn't seem to be the best solution.

So I did a bit of research on axil fans and asked some experienced and very knowledgeable people on the subject and what they have found. Then I started designing my own shroud.

Originally I wanted to keep the same look of UM2's original shroud with the fans on 45deg angle etc.. but from what I had learnt I found this wasn't the best option.

I also would like to make one out of metal as printed ones just don't last so have kept the design in away it can be replicated in metal.

I calculated the area of the open area of the fan and the area of the exit orifice of the original fan shroud and found them to be the same. so I thought that was the best starting point.

Here is what I came up with

My Fan Shroud


I carried out Makers overhang and bridge tests using the default cura settings. I know they don't give the best quality but I'm just looking for comparisons.


Shroud comparison 1

Shroud Comparison 2

Overhang Test Comparrison 2

Overhang Test Comparrison 1

I also have noticed that people are designing shrouds and greatly reducing the exit orifices, this goes against everything I had recently learnt but thought I shroud test it anyway. I designed it so the orifice is more directed at the nozzle and reduced by just over half the area, here are my results

VMMR Bridge Back

VMMR Bridge

MMR Overhang (2)

MMR Overhang

I know there is always room for more improvement and I can carry on testing more things.

I will load the designs on youmagine for Olsson block and original heater block and nozzle.

But ultimately I want to get some made out of metal. so if there is any interest let me know as It will reduce costs if more then one is made.


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Hey, great tests, Thank you for sharing your insights :)

When I CPv9 for standard UM2 HotEnd's constructed:

I did not know it, but suspected it that fans can work more efficiently when they are aligned horizontally. Also, I already suspected that reduced air outlet openings are unlikely to improve results.

Rather, a 360 degree cooling should take place close to the nozzle tip (~3-5mm) and also take into account Surrounding (but more distant) freshly oviposited material. I think this is the most efficient way to reduce the warping of the material.

I am a bit sad that you have not tested my design as well, or have you done it before? No matter, because almost every available on Youmagine / Thingiverse variant is more powerful than the original UM2 fan shroud. And these sheet metal design should never be delivered with a single extruder head.



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HI Markus

I really like parts of your design and I tried to use some of your features in mine. I do have designs that have clip in fans etc..

The only reason I didn't just download your design and use it is because I wanted as much air blowing on the print as possible and I'm not really concerned about air blowing on the Teflon isolator.

If you would like me to try it so you can see how it compares I can (and probably will anyway)


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I haven't had time to load it yet but I will soon and ill post it here. It does require a lot of insulating against the heater block or it will deform. hence why I think a metal version is really the best way to go.


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Interesting thread, I'm looking at the fan duct too, I'm using Mnis' fan duct and noticed an improvement especially on the left ear of the Ultimaker robot, although I wasn't sure what all the little holes are for other than perhaps preventing over pressure. But I do like the way the ducts can swivel out of the way for access.

What's the recommendation on the angle of the fans? Horizontal or Angled?

I'm looking at getting the flow centred about the nozzle but not fighting each other's flow and I may experiment with a thin heat shield to protect the heater block.

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The many small holes are there to eliminate the heat accumulation above the Hotend so that the fan cages can not deform too much.

A slightly unfair comparison ...If you additionally cool the radiator of your fridge, then significantly less energy will certainly be necessary to maintain the preset temperature internally stable. The area above the UM2 printhead has no temperature control and the small rear fan blows with a maximum available power. I mean this little fan is undersized. And as far as I know still lacking any evidence regarding efficiency or inefficiency of a stronger cooling above the Hotend. However, the Ultimaker 2 will fail without cooling the ColdEnd after a short time, this is certainly widely known.

Of course, I will not force anyone to use my designs, that I certainly do not need. Sorry if someone sees it that way ;) It is more important to learn from each other to get a really good product. I saw your test results and was very pleased. This reminds me that I have so far not made any extensive testing with my designs. Unfortunately, I lack the time also, and I was hoping that someone can make more intensive tests, the more I would not say so...

I really like your design and want to test it when it has reached a nearly completed Status. it looks a bit like an ark of Noah, it suggests me feel safe and I like that very much :lol:

Anyway, a few suggestions from me:

- I think the nozzle tip looks out too far, maybe you'll get better results with a cooling closer to the object surface.

- To avoid in certain places a large heat storage, you can try to realize smaller air passages.

- Fast print speeds make it generally difficult to cool freshly oviposited material efficiently, therefore take some users large additional fans for an extensive object-cooling.

- If you are constructing it mainly for normal users, then it must be easy to implement. For example I see at my (really) big universal feeder a large negative effect that many optional components seem rather daunting. And that's really a shame, because the thing actually works many months without any problems extremely reliable.

- The cooling of the entire printhead plus a sufficient material cooling was my main Goal for CPv9. Remove heat directly where it arises, and to avoid mixing of air streams, I still see as very important. As a result, everything is kept very much cooler above the Hotend including the insulator-screw, and this gives the entire PTFE little more overall stability. More than that, my main CPv9-Design makes the third fan (...these annoying and sickly printhead cooler) totally unnecessary :mrgreen: Of course, me being aware that the critical transition zone from Hotend to ColdEnd can hardly be cooled efficiently enough. That would probably work well only if the ColdEnd would be made of any metal.

By the way, I also have a few test objects are printed with this head lift feature in Cura. For some special PLA varieties, a setting of up to 0.5mm works perfectly and there are no visible disadvantages for me. Thus, the nozzle tip does not go against warped material edges and causes less mechanical stress of objects with a small footprint.

Tip: Some old USB Harddrive enclosures for notebooks etc. have different thicknesses of sheet metal cages made of aluminum or copper for electrical shielding purposes that are sometimes coated on one side with glue. Often, these sheets can be reused for other purposes, simply cut to size with scissors they might pass as a heat shield for printed fan Cages.

I would very much like to be able to see and test many of the available fan cages when they were made entirely of metal. Maybe we should design the fan cages so that they can be folded out completely from a piece of sheet metal, just like the original.

I am looking forward to be able to see more details of your design.



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I'm currently printing off objects with different nozzle sizes and will post pictures here when done.

Fan angle doesn't really matter that much, I have experimented with a hole range of angles but settled with horizontal. what is important is giving the air room to pick up speed once it has passed through the fan. so if they are on an angle you would need to reduce your build volume to do this.

Yes it does look like a boat. personally I don't like it but it really comes down to performance

I did not think you were forcing me to try your design and yes sharing ideas is best.

I actually printed the fan shroud with slotted holes so I could raise it up and down. the height you can see it there is the same height as the original. I found this to be a good height. it allows enough room for the air to escape without slowing down. I have done smoke tests to watch where the air travels but its to hard to see in the video, I was able to watch in person.

I originally was just going to fold up something like this

Screenshot (1)

But instead decided not to. I have already started designing the folded out version of mine to try. I might just end up making one myself. will be cheaper than getting it made. I just have to make some free time and overhaul our old folder at work. Its in a bad state at the moment.


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Original shroud with fans mounted at widest point measured to be 99.6mm. My shroud is 100mm wide, .2mm either side is nothing to worry about.

I didn't have any issues with the old one hitting the sides or my new one.


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Hi Labern

I'm interesred too in your project. I'm awaiting delivery of an Olsson block. The present fan system is suboptimal for printing small parts (if you print only one small part like the famous "Marvin"). When Ultimaker decided to stop dual extrusion for the UM2, they should have offered at least an optimal single hotend (which I would even pay for). At the moment it looks, like UM2 product development goes towards customers (I remember the statement of Sander van Geelen; of course he didn't say this in my words ;-D ). But "tinkerers" can be quite innovative and successful.

When a satisfactory shroud will be made of metal I'll order one too.

Kind regards from Paul

PS. When a lately removed the shroud, it gave me a hard time, since it was "glued" to the nozzle by ca. 1-2 cm3 of leaked (?!, I have no clear idea why / how it got there) brownish plastic mass. I had to remove it with the aid of a soldering iron.


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Well today my replacement fan arrived for the main head.

I orderd and recieved the Sunon MC25060V2-A99 of of ebay from it-tronics.de.

So what's the difference I hear you say?

Well I can actually hear you , initially the lead was a bit short so also having a raspberry Pi and loads of stuff to play with I extended the wires and then added the connector.

I got them from www.proto-pic.co.uk, both the housing and the pins.

Connected it up and turned it on!, bugger can't hear it had to check it was spinning and it was wahoo one happy bunny,

Before I took the old one out I checked the airflow with a windoo skywatch 3 and got about 2.7 to 3.1 m/s and a dB of 67, I SAID 67.

With the replacement fan in place the air flow was again between 2.8 and 3.2 and the dB was only 45dB I done a few test runs this afternoon and so far everything is running fine.

Now it's a lot quieter sitting next to the UM2 as its printing, well worth the £15 ish for all the bits, would have been a bit better if the leads on the fan were just 4cm longer

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Yes I replaced that one a while ago. Its a nice upgrade. Now I want silent stepper drivers, Then it would be awesome.

I found it easy to de-solder the wires from the old fan and solder them on the new one.

Printing a slightly refined shroud now. If it turns out good ill post it on youmagine.


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At the moment I'm not sure if I would ever buy another Ultimaker machine :roll: I think it was in the past, too many avoidable problems :huh: Rather, I want to try it yourself to design a machine, and as many parts as possible then I produce with my UM2 :lol: Hopefully it does not remain just a dream :D


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This may seem like a silly question, but why do designers of fan ducts for the UM2 connect the left- and right-side ducts across the middle in front of and below the hot-end?

Wouldn't it be easier to have two pieces - a left- and a right-side duct? Seems like this would alleviate issues as to heat from the hot-end.

If airflow needs to be directed away from the hot-end, connect the two pieces across the bottom with a thin piece of metal, like the piece of beer-can Venkel used as a heat-shield on his version.


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