If you have a Voron, and you want to somehow filter volatile organic compounds released when printing some materials, everyone will point you towards the Nevermore Micro, which fits below the print bed. Unfortunately, the volume of the carbon filter material is limited by the gap between the print bed and the bottom, and the bed fans mod requires sufficient space for the air to circulate under the bed, so I needed a better design. Also, the full-size Nevermore is way too large (and would block the view from the top of the printer).
So, as any good maker would do, I made my own. The general goal is to provide a sufficiently long path through the filter media to maximize the amount of VOCs filtered out. The material provides resistance to flow, and so the allowable path length is limited by the desired flow rate, and increased by the maximum static pressure of the fan. We could calculate it, but its easier to just build the thing and measure it afterwards.
We’ve shown the exteriors of the first and second versions above, and you can see that it is in two parts, a head containing fans in black and a removable cartridge in red. The removable cartridge has this internal geometry, shown with the expected airflow pattern below. The fans are positioned in the middle of the head drawing air in from the cartridge and out into the printer. This was chosen so that the pressure in the cartridge is lower than ambient, which prevents air from leaking out around where the cartridge meets the body. (We avoid the complexity of needing some kind of rubber seal between the parts.)
The trade-off in this sort of design is that the fans extend past the rear wall of the printer. They don’t extend all that much into the body, as pictured here. Since we’re attaching these to the back of the printer, and the maximum thickness of the assembly is limited by the height of the roller brackets, this design was the best compromise on the geometry. It is high up enough that it does not interfere with the rear of the Z-assembly.
Here is the first version printed and installed on my printer. It is much more printable – the cartridge prints as a single piece (instead of having a screw-on panel), and the internal geometry of the head is parallel to the print orientation so it can be printed with bridging instead of internal supports.
The second version doesn’t have an inlet for the filament yet – once that is figured out, I’ll install it on my printer, take pretty pictures, and submit it to the Voron mods directory.