Noctua A4x20 to 5020 Blower Mod by Crazyates

Last crawled date: 3 years ago

This is a mod to convert a Noctua A4x20 to a 5020 Blower fan. Be warned: this does require cutting up and irreversibly destroying your A4x20 in this process. This might work for other 4020 axial fans, but I'm not sure about the motor hub size.
Concerning the fan blades: I popped the fan blades off the motor, and started cutting them off with the snippers that came with my Ender 3. You know the ones. I found that there's actually an inner hub and outer hub. I cut the outer hub off, and smoothed out the inner hub as best I could. This actually gives us a pretty good foundation for attaching the squirrel cage. Just pop it on. It's a tight fit, but you want it to be. Also, don't press too hard, as the frame is brittle and the fan blades could snap off the printed hub. Ask me how I know.
Concerning the A4x20 Frame: You need to chop it up, and remove a little over a 1/4 of the frame. It's almost more like 3/8. Be very sure of the orientation! My housing is made for the motor wires to exit in a certain location. You could cut off any of the 4 corners, just be sure to accommodate the motor wires coming out the back. I just started using the same clippers, but also be warned that the frame is very brittle. The tiniest snip can cause cracks to shoot through the whole frame. I had intended to keep all 3 of the motor mounts intact, but accidentally broke one of them. If 2 of them were to break off, I don't think I would trust using it. I don't remember the exact measurements of what you need to cut off, but I can measure and update later.
Concerning the Adapter Frame: This needs a frame to channel the airflow into the fins, redirect airflow into the exit chute, and physically mate up to a 5020 blower slot. The resulting dimensions end up being 50x40x25. The mounting holes line up with a 5020 blower, so in that sense it's easy to mount. The difficulty comes in the form of the extra width. Most mounts will need to either be adjust for the extra 2.5mm on the back, or the adapter needs to be designed to work around whatever mount you're using. I designed this to fit a Hero Me Gen 5 5020 blower duct. My adapter only blocks off about 2/3 of the back side of the fan, and the Hero Me duct blocks the other ~1/3. It works pretty well, but if you're using a different duct, I've included the STEP file as well.