biqu_bx_fan_silencing.md

BIQU BX FAN SILENCING MOD

So you have a BX but the fans are a bit too loud for you. Well I have some good news and some bad news.

The good news. There are ways to make the fans more quiet and in fact you can make them completely silent by turning them off when they are not needed. The bad news is that when the fans are needed you cannot avoid at least some noise.

Making the fans more quiet

Most of the noise from a fan is generated by rushing air and vibrations against the chassis of the machine. We will deal with the rushing air in the next part but for now let's talk about vibrations.

In the image below you can see the primary guilty party, the 5020 blower fan within the electronics enclosure. It is used to cool the 400MHz CPU as well as the TMC drivers. You want it on when the machine is doing serious number crunching and driving the steppers but you don't want it to vibrate against the enclosure and amplify the noise. A common trick is to simply place a rubber washer in between the enclosure and the fan which dampens the vibrations. As you can see in the picture you will be able to access the one screw from above but the other will require you to drop the electronics enclosure out from below. Pop the washers in and your fan will be a lot more quiet.

Turning the fans off when they are not needed

Once a print is done, all of the complex number crunching and motor driving that generate heat stop. There is therefore no need to be cooling the internal electronics and the fans can be turned off. Once another print starts or when the motors start to move again, you will need the fans back on.

This modification makes the fans behave in that exact manner and it is really easy to do. Simply unplug the internal fans from the two connectors that are circled in red in the picture below. The top connector belongs to the blower fan and the bottom connector (white one hiding behind the black wire) belongs to the front fan with the super bright blue LED. There may be some glue on the connectors so you'll have to pull that off first. Some people have mentioned that they are difficult to get to and that is a valid point. I simply used tweezers to grip the plugs on either side and pull them out (obviously with the power off).

Once the connectors are off you need to connect them to the new plugs on the PCB identified in the picture below. Connect the blower fan to the plug on the left and the front case fan to the plug on the right.

Once the fans are in place they will now be controllable by the software. Install the software located at the following link which will control them. The blower fan will come on whenever the motors are moving and the front case fan will come on whenever the part cooling fan is on during a print.

https://github.com/looxonline/Marlin

Hi Luke! Thanks for all the mods and for the firmware!
I've got an issue: I have updated my SKR SE-BX V2.0 with your firmware, then dismantled it to make some holes in the metal hoping to connect a quieter 92mm fan to the 2 headers you mention in this Gist, but somehow, my part cooling fan is now always on...
Changing the part cooling fan speed has no impact on any of the 3 headers. I've tried moving them, and If I connect any of the case fans to one of the DCOT header, I get no fan control for the part cooling at all... Any clues?

Hi Luke! Thanks for all the mods and for the firmware! I've got an issue: I have updated my SKR SE-BX V2.0 with your firmware, then dismantled it to make some holes in the metal hoping to connect a quieter 92mm fan to the 2 headers you mention in this Gist, but somehow, my part cooling fan is now always on... Changing the part cooling fan speed has no impact on any of the 3 headers. I've tried moving them, and If I connect any of the case fans to one of the DCOT header, I get no fan control for the part cooling at all... Any clues?

If you've connected everything correctly and it is still on then you may have blown the FET and will need to replace it.

If you've connected everything correctly and it is still on then you may have blown the FET and will need to replace it.

That's what I was fearing. I was very careful not to bridge anything as I dismantled it, and I waited a fair amount of time before doing so. Then again, it happened to me on a SKR Mini E3 before...
Oddly engouh, If i connect the case fan to the topmost original mobo fan header (DCOT closest to the E0 connection, the part cooling fan is completely off and cannot be turned on.
Anyawys, I'll order a new mobo!
Thanks again Luke!

Hi Luke, the same thing is happening to me with the part cooling fan. I thought it was because I botched the original one so I ordered a replacement. However it is acting the same way as before, it's always on and can't be controlled. Thought it might have been firmware but that didn't change anything. Do you have any ideas what it might be?

@rak500 did it fix you issue to buy a new one or do you still have the same issue?

Thanks for anyhelp I can get!

I ordered a new one in the end. I was told that it was a fairly common occurence on BTT mainboards by the reseller. He apparently broke one the exact same way.

Did you get a working one right away or did you get a replacement for the replacement? Feels pretty bad if it's a hit or miss when ordering a replacement. Might be the reason Biqu/BTT don't sell the mainboard on their own website.

Hi,
I have the same kind of problem, the part fan is working all the time at full speed. Where did you get replacement ? The full main board or just the FET ?

Hi, I have the same kind of problem, the part fan is working all the time at full speed. Where did you get replacement ? The full main board or just the FET ?

This is very strange to have so many FETs going. I would assume that it is likely a firmware issue on these boards and perhaps your board version is not the same as the version I compiled the firmware for.