No doubt you’ve seen the video where Tom from Made with Layers drills holes into his P2S and installs an exhaust fan. I guess it would work but that requires additional electronics and manual control. Converting it to an ABS printing mode would also require removing the tape he added and adding tape to the exhaust hole.
There has got to be a better way.
For example - there are vent holes (covered with an extra piece) on the bottom left. An exhaust filter could be set up to exhaust out of there, through some filters. This will need an extra fan.
Or: the cold air intake fan could be made to pull air through the left bottom vent (and/or the poop chute) through ducting and some filters, to create a recirculating system - that way the intake and exit airflow are somewhat balanced. This would then no longer be a cold air intake but the air will still cool down from going through a duct outside of the printer. This method requires no additional electronics and no new control method.
So far not one of the reviews that I have seen have shown any evidence that the P2S filtration system does not work. It seems to me that in practice repeatedly passing the contaminated air through the carbon filter may well be better than the single pass scheme used on the P1S, at least for those that do not have external extraction.
Anyhow, I think we need to see proper test results first.
My guess is the solution to this is reversing the airflow through the printer so a filter can be used. Given your wonderful past filtration designs I would suspect you will be the best person to attempt this if you so choose.
No additional electronics, the main fan pulls from the unit below, which in turn, pulls from the duct on the bottom right. Airflow is balanced (there will still be some leaks but much less).
Heat exchanger is air-to-air and could be passive or with another fan, and cools the recirculating air.
I think the easiest way would be to reverse / mod the optional aux fan to blow through the unused vent at the bottom and place some kind of filter before it. The fan is plug and play, just need a new housing. Should be doable.
By the way, I asked Bambu support about the air filtration and got this answer:
Regarding Your Specific Request for Custom Filtration Scenarios:
We understand that some users, like yourself, may have specific requirements where external exhaust or forced filtration for certain materials would be desirable.Please be assured that we are actively evaluating secure and user-friendly methods to implement an active exhaust feature. Our goal is to eventually support our community by releasing detailed DIY guides or offering official modification kits. This will allow users to implement this functionality themselves while ensuring safety and performance are not compromised.
aux fan warping parts near the aux fan (so people install deflectors)
Recirculating mode air hits print bed and print due to its exit vent
Unfiltered air escaping the printer with PLA/PETG
replace the entire fan housing so that the air is always drawn through the filter. Then the air either exits back into the chamber but at the bottom OR exits out through the bottom right hand-hold. If the air is made to exit the printer, then cold air will be drawn through the MC board vent holes and poop chute.
The toggle could be manual and the motor could be disconnected or, with a bit of tinkering, automatic.
You’d lose the aux fan obviously but you could add one on the left if you really want one (I do not)
Found this on MW, passively filters air coming out of the poopie chute. I think installing this will just redirect the air through the MC board vent holes but the description says there will be a fan added.
Adding a filter to the cooling fan may not be impossible, but I see some potential issues.
There is little available space for a filter. The housing can already hit the front frame of the printer. So the filter must be quite small, maybe too small to be effective.
I question the ability of the small fan to pull very much air through a restriction, which may reduce heat sink cooling and affect prints…
Adding weight to the fast-moving head does not sound like a good idea.
I think it would be better to pursue a stationary solution that can be larger, with more filter material, and a stronger fan that will not affect printing.
Looks really promising, if the flap becomes operated by a motor, could even have an extraction sequence at the end of the print to filter out the remaining air.
But he used another fan. I would prefer the original aux fan so it connects to the motherboard plug & play.