Prusa XL 5015 fan upgrade - Project Mastodon

UPDATED:  No drilling of the gantry cover is required if you print the revised front left Core XY mount.

NOTE: This is a full replacement of the stock part cooling fan and stock part cooling duct.


I just want to start by saying that I love my Prusa XL 5 tool head; but it's a love/hate relationship. If you don't want to read the back story, just scroll down to the instructions.

The designers at Prusa made some seriously flawed decisions when they designed the tool heads. The most outstanding being the decision to use a 4010 radial fan for the part cooling and the decision to make the supply voltage for the part cooling and heat break fans 5V when 24V was already available on the Dwarf board.

As a result, the part cooling is very poor because the poor little 4010 has the static air ability and air volume moving capacity of an emphysema patient. The issue is further exacerbated when the printer is located in a hot environment or fully/partially enclosed.

I live in ‘The Land Down Under’, where room temps generally exceed 32°C and get as high as 42°C. I have found that there is a significant drop away in cooling performance once the room temp climbs past 26°C.

As my base to work from, I have a Prusa MK3S in a custom enclosure and print all the time with door closed. The chamber temp sits ~46-50°C from passive heating, but with the stock 5015 part cooling fan and the brilliant fan shroud from RH_Dreambox; I can print any material, at any speed the printer is capable of, with overhangs in excess of 70°, and achieve consistent, flawless results.

https://www.thingiverse.com/thing:4124587

It was extremely frustrating when I came to the realisation, after many kilos of filament and over two hundred hours of testing; that my expensive, and long-awaited, XL couldn’t hold a candle to what I could produce on my MK3S. Even slowing the XL down to speeds below 40mm/s and reducing print temps on PETG to 225°C made little or no difference. Overhangs of 45° or greater were completed to a poor standard or just outright failed.

It was around this time that the 3D printing community, also experiencing the same issues, started releasing their own cooling shrouds for the XL. I tried all of them and all yielded the same, or in many cases, worse results. Many caused the fan self-test to fail as they restricted the airflow so much that the fan could not achieve the required max RPM.

In fact, the stock fan shroud will cause the same issue and Prusa Support regularly have customers remove the shroud to get it past the fan self-test stage. This is all the confirmation I needed that the stock fan and shroud combo are an epic failure. They rapidly released a ‘user pays’ upgrade for the MK4, which suffered the same deficiency. Surprise, surprise, it's effectively the same cooling solution as used on the MK3S, albeit with a slightly bigger 5020 fan instead of a 5015. Prusa went on to make it part of the standard build for the MK4S, which closely followed, and it's also the basis for the CORE One's part cooling.

Unfortunately, due to the clearances on the XL, they have painted themselves into a corner. In my honest opinion, this is why they have not released a solution/upgrade to resolve it in the 2+ years since the XL's initial release.

So, Project ‘Mastodon’ was born and I set about carefully measuring the clearances on the tool heads, etc. There are a lot of moving parts to take into consideration and clearances are tight! Life was made significantly more difficult than it needed to be thanks to Prusa’s increasing move away from Open Source by way of them still not releasing 3D models of the XL, schematics of the Dwarf board, etc.

I contacted Prusa Support to see if I could get a 3D model of the Nextruder. All I wanted was a cutaway of the actual heat block so I could use it in CAD for working out clearances. I didn't need any details of the Nextruder itself. I was happy to sign any required NDA, etc; but that was a ”No”.

Given that dead end, I reached out to the community to see if someone could do a high resolution 3D scan of an XL tool head. 

While I was hoping and waiting for someone to do the scan, I spent a significant amount of time trying to source the highest output 5V 5015 available that also had an operating RPM range that would match the stock XL 4010 so that there would be no errors or failed self-tests. This ended up being harder than expected. There are tons of awesome 12V and 24V 5015 fans available, but almost no high RPM 5V ones. I ended up building an Arduino based test rig to test fans and bought a laser tacho to verify tacho readings. In the end, there was only one on the market that met the criteria from a company called MX Research.



And yes, for those wondering; I experimented with a DC buck converter to step the voltage up to 24V and a MOSFET to translate the PWM for the 24V side.

Grant at 3D Musketeers came to the party with the 3D scan of the Nextruder about 6 months later – thanks dude! 😊

Had it not been for the lack of files and support from Prusa and the delay in getting someone that could provide me with a 3D scan of the Nextruder, this project would have been completed around a year ago.

Finally, I was able to start working on the problem, and oh boy was it more involved than first anticipated!

I had a working prototype by the start of October 2024. Initially I ran into issues with the clearances off the left side gantry. A 5015 fan is 5mm wider than a 5010 and I quickly found I didn’t even have half of that to play with. Weight was also a major consideration.

I took inspiration from the Voron StealthBurner hotend and removed the outer cover from the 5015 to reduce the overall thickness and reduce weight. The mount for the fan becomes the outer cover. Also, a key design consideration was to not modify the printer in a way that was not easily reversible, whilst also being achievable by any user with tools they already own.

Next was the challenge of the shroud/duct itself. This is extremely difficult due to the fan outlet being offset from the centre of the Nextruder, how close it is mounted to the bottom of the hotend, the clearances for docking/undocking and the need to clear the spring loaded ooze stopper on the dock.

After MANY, MANY revisions, hundreds of hours in Fusion 360, hundreds of hours of testing and many kilos of filament; I have the current design and it has been running on my machine for 3 months now with hundreds of hours of production printing. I have been able to print many parts that were previously unachievable on my XL.

The final package is only 3g heavier than the stock setup. I highly recommend upgrading to the awesome “Skelettonized” tool head parts from Kevin248 as they reduce the overall tool head weight by 14-16g.

https://www.printables.com/@Kevin248_103670/models

The cooling is still not quite as good as my MK3S, but it’s close. I believe this is down to a combination the RH_Dreambox shroud being refined using CFD and my design being the result of some very limited CFD (4 runs), a lot of eye-balling and ‘feel’ as well as water bowl testing; but ultimately it is just the major limitations of the area it mounts and the clearances I had to work with. I’m sure with full access to CFD, it could be tweaked to be better.

Anyway, that’s the abridged version of the journey. It’s been long and emotional with an enormous amount of time and effort and money going into it. Just this write-up and the following instructions took ~6 hours.

With that out of the way, on to the instructions! :)

This is not designed for the single tool head XL. I do not have access to one, so cannot guarantee it will fit. If it does, please let me know.

Some of the parts you print will look slightly different to those in the images below. The photo series was taken during disassembly/assembly with early prototype parts.

BOM:

• 2 x M3x20 BHCS bolts. https://www.aliexpress.com/item/1005006466180946.html
• 1 x M3x10 BHCS bolt. Use the same link as above.
• 3 x M3x10 FHCS bolts. You can get away with longer ones - I had M3x15 on hand. https://www.aliexpress.com/item/1005002400036568.html
• 1 x M3 washer. Preferably a large diameter/overside one. https://www.aliexpress.com/item/1005002367963082.html
• 5V 5015 blower fan from MX Research - quantity determined by how many tool heads you have. 
  https://www.mxind.com/en/products/accessories/prusa-clone/bearmini/5015-cooling-fan-5v6500rpm/?v=8bcc25c96aa5 
• Molex ClickMate 15135-0303 3 pin connectors. You can do 2 fans with each cable as both ends are female.
  https://au.mouser.com/ProductDetail/538-15135-0303
  Alternately, you could cut the plugs off the stock fans and use them.
• Some really small heat shrink. I used 1.5/0.75mm.
• 2 x M3 heat sets (Optional) Size doesn't matter too much, just use whatever you have.
• 1.5 or 2mm drill bit, a 3.5mm drill bit and a drill     Only required if you chose to drill the gantry cover instead of printing the new Core XY mount.

Printing:

PC or or ASA should be used for the fan mount and duct due to the heat the parts are exposed to. PCCF or ASA-CF is recommended for the duct due to the large suspended section of one of the outlets.

I highly recommend the Silicone Carbide Nextruder nozzles from Phaetus. They're cheaper than the stock brass nozzles and you can kit out a 5TH XL for less than one Diamondback nozzle. 

https://www.aliexpress.com/item/1005007877919205.html

I have provided pre-sliced, pre-supported models for printing on the XL. You may need to adjust the filament settings, etc, to suit your printer.

For the fan mount, a 0.25mm nozzle is recommended due to how thin sections of the walls are. You will probably get away with a 0.4mm and Arachne, but the resulting print may not be as pretty and may have some holes in it.

If you really want to ‘go it alone’ on your settings, load the pre-sliced version as a guide.

I recommend printing the new Core XY Mount in PCCF or similar. Use a 0.4 or 0.6 nozzle, 6-8 perimeters, 10 top and bottom layers with 20-30% infill. You can also install M3 heat sets instead of the two square nuts.

The spacers can be printed in PETG or whatever you like. I would never recommend PLA.

You don't need to be print the ‘Front Spacer’ or ‘Drill Guide’ if you print the new Core XY mount instead.

NOTE: You only need one set of the spacers.  That means you Alex! ;)

Preparation:
 

Printed parts and fan

1. Remove the brim and supports from the printed parts. Be sure to deburr and remove any elephant's foot, etc. This is essential for seamless assembly.
   
   Use an Allen key or similar to clean out the hole in the fan mount as it has a sacrificial bridge. 
   
      
    
2. The front cover needs to be removed from the new 5015 fan. Just use a small flat blade screwdriver to pry the clips.
   
   
    
3. The remaining tabs on the fan then need to be flush cut or sanded off.
   
   
    
4. On the outlet of the fan, the outside corner needs to be sanded back a few millimetres at about a 45° angle. If you don't do this, it will not locate properly in the new fan mount.
   
      
    
5. Trim the cable on the fan to length. ~120mm is plenty. Just eyeball it on the tool head - just remember, you can always cut a bit more off, but you can't cut a bit more back on. ;) Cut the ClickMate cable in half - you can trim it a bit shorter if you want. If you chose not to get them, then cut the plugs of your stock part cooling fans.
   
   
    
6. Solder the ClickMate cable to the fan cable. Pay close attention to the pinout based on the connector orientation. Don't forget to put your heat shrink on before you solder! ;)
   
   

Gantry cover

Unfortunately, despite all the design work, we still end up ~1.8mm too wide overall to allow the printer to successfully home the X axis. The new fan mount will now contact the sheet metal cover on the left gantry before the tool head hits the end stop on the X axis. This results in a crash during homing operations. I wasn't kidding when I said the clearances were a major problem.

To get around this, we need to space out the left side gantry cover.

1. Remove the 5 bolts retaining the left side gantry cover.
   
    
2. Carefully slide the cover off.
    
   There are two options from here. ‘Walk’ an existing hole in the cover or replace the front core XY mount.
   
   Steps 3-6 are the recommended path and don't require drilling the gantry cover.
    
3. Completely undo the tensioning bolt in the front of the front left side Core XY mount and remove the pulley carrier.
   
4. Remove the bolt that holds the mount to the frame and remove the mount.
   
5. You will need to install M3 square nuts into the new Core XY mount (indicated by the red arrows) which you can probably retrieve from the mount you just removed. The preferred method is to install M3 heat sets in the locations indicated by the red circles. 
   
6. Reverse the process to install the new Core XY mount.
    
7. Steps 7-10 are only necessary if you don't want to print the new Core XY mount. You can also skip doing the following steps if you don't want to make this very minor modification to your frame cover, however, you will lose some rigidity in the frame if the top front fastener is not put back in. You could try without doing it and then ‘walk’ the hole at a later date. Even if you do ‘walk’ the hole, it will not stop you from returning the printer to stock form at a later date.
   
   Put a 1.5 or 2mm drill bit in a drill. Using the drill template that you printed, place it on the front right corner of the gantry cover you removed. It will locate on the corner and in the counter sink of the existing hole.
8.      
    
9. Drill a pilot hole, remove the template, change over to a 3.5mm drill bit and drill the hole out to 3.5mm. Then, carefully ‘walk’ the hole over the the existing hole.
      
   
    
10. Drill out the hole in the drill template as this will not be reused in the final assembly. You will likely need to walk the hole a little as well, but you can do that at the end.

Tool Head Disassembly:

The print heads don't need to be removed from the printer. Lay a sheet of cardboard or a towel on the build sheet to protect it and then just manually undock the tool. You can completely remove the tool if you like. It's just 2 bolts on the flexible plastic support strip for the cable loom, unplug the cable look and disconnect the Bowden tube.

1. Open the cover on the Dwarf board and disconnect the part fan header. The end of an Allen key make this easy.
   
   
    
2. Remove the retaining bolts from the stock part fan and shroud.
   
    
3. Unfortunately, a poor decision (seeing a pattern?) in the assembly of the Nextruder means removing the stock part cooling fan is WAY more painful then it needs to be. The heat break has to be partially disassembled to get the fan's cable out. :(
   
   
   
   You have to remove the two bolts retaining the heat break fan and swing it out of the way. Pay close attention to which bolts come out of which hole!
   
   
   
   Then remove the two bolts holding the heat break onto the tool head main frame.
   
   
   
   This will make most of the assembly partially loose. Loose enough that you can VERY carefully manipulate the stock fan cabling out.
    
4. You can now put the heat break and heat break fan back together. Pay close attention to make sure the nozzle is square before tightening the bolts on the heat break.
   
   Temporarily reinstalling this bolt for the heat break fan will help ensure correct alignment. Just remember to remove it again once the other two bolts are tensioned or else you won't be able to get the fan back in.
   
   

Tool Head Assembly:
 

1. Push the fan into the new fan mount. It's a tight fit - just take your time, be gentle and make sure you are pushing it in square. The more out of square it is, the more pressure you will need to apply and you will risk breaking something.
   
     
    
2. Plug the fan into the header on the Dwarf board and carefully route around the back of the fan mount and across the top of it. Be sure not to crush/pinch the cable. This path is how the stock pan should have been routed.
   
     
    
3. Install the fan using the original fan mounting bolt.
    
4. Position the duct and loose assemble it with the 2 x M3x20 BHCS bolts. Holding it in position firmly with one hand to ensure there are no gaps, carefully tighten the two bolts and don't overtighten them. If you have gaps, you may not have cleaned the edges enough in the Preparation phase.
   
   
    
5. Loosen the hot end retaining bolt enough to allow you to align the heat block evenly with the duct outlets.
   
   
    
6. Put the tool head back in its dock and rinse and repeat for any additional tool heads.
    

Gantry Cover Reinstallation
 

1. Place the spacers on the sides of the CoreXY pulley mounts. Rubbing a piece of electrical tape on the back side of the spacers will transfer a little bit of glue which will help to make them stay in place for reassembly. You only need the front spacer (shown on the right in the images below) if you are not using the new Corey XY mount.
   
     
    
2. Reinstall the sheet metal cover and install the 3 x M3x10 FHCS bolts in the side.
    
3. Ignore this step if you used the new Corey XY mount or didn't drill the hole earlier. Place the drill template on the top front left corner and then lightly press the cover into place. Fasten it using the M3x10 BHCS bolt and M3 washer. 
   
   This is where you may need to walk the hole in the drill template to align with the hole in the front Core XY mount. Yes, it will chew out part or all of the ‘cone’ that was used to locate it for drilling. This is also why I recommend an oversize M3 washer.
   
   This bolt doesn't need to be very tight. If you start to deflect the plastic drill template, it's too tight.
   
   It is important that the sheet metal be pushed into position properly as the 'overhangs on the drill template set the spacing.
   
   
    
4. The top rear bolt is no-longer used and makes no tangible difference to rigidity.

All done!

Now you just need to run a belt tension calibration

https://help.prusa3d.com/article/adjusting-belt-tension-xl_401793

Phase Stepping calibration

https://help.prusa3d.com/article/phase-stepping-xl_681760

and an Input Shaping calibration to account for the weight changes and you're away.

Prusa don't have an article for Input Shaper, but the routine is found in Setting > Input Shaper > Calibration

You can also run a fan self test to confirm all the fan runs and pass the test. Control > Calibration & Tests > Fan Test

As I said, this was a massive project and it was all done for free. I make no money out of it and there are no affiliate links in any of my designs. If you do do this mod, please be sure to give me a review and post your make. This will help me get some Prusameters and collecting them is the only thing I get back for this.

Happy printing and be sure to check out my other XL mods.

https://www.printables.com/@IPIND3D/models