This is a stand alone air filter, redesigned from the ground up but based on the original good ideas presented in "80mm/40mm Fan Carbon Filter v2", thing # 2172962.

This is meant to recirculate/filter the air within a printer's enclosure, not to exhaust it out of the enclosure, to help preserve the heat within the cabinet and to prevent pulling a cold draft of air across the heated build plate.

There are two versions of the filter top which mate to either an 80mm fan, or a 92mm fan. Anything less just doesn't seem to pull enough air to be functional as a filter. Both of those sizes are standard sized PC fans readily available in 12V and 24V.

I up-sized the space inside the box from its predecessor, creating a filter box that is taller and wider to accept more media. The interior is 90 x 90 x 40 (WxLxH), plus the headspace leading to the fan.

The filter box mates to the base via pegs/holes. I undersized the holes slightly, so that if you drill them out with a 9/64 bit the pegs should fit perfectly snug.

Update: I just printed one in PLA and 9/64 was not enough. 11/64 worked, plus a little superglue.

For assembly, the filter top and the filter base are a snug press fit, where the filter top goes around the outside of the filter box. The fan should be mounted to draw air from out of the box, blowing upwards.

Inside the box there's enough space that I was able to fit:

• 1 layer of A/C foam pre-filter, cut from a roll I got from Amazon.
• 1 corrugated fine particulate filter cut from a 3m purple allergen furnace filter
• 4 layers of carbon filter material fabric.

Or skip the prefilter and pack in more carbon sheets.

Airflow was good with an 80mm fan. 92 mm will be even better. Overall, either size fan manages to keep pace with the ABS fumes my printer produces. Sitting next to the printer during a long ABS print run, I can no longer smell the fumes or only rarely.

Here's a search phrase that might work to get you started on the filter media: "Universal Cut to Fit Carbon Pre-Filter Pad Roll"

Update 10/26/2019

Also, here are the original Fusion 3D Designs in case someone would like to fork/improve/mod this.

80mm Fan Mating: https://a360.co/32NUbec 92mm Fan Mating: https://a360.co/2BMxdIC Filter Box Base : https://a360.co/36a0Y3W Filter Box : https://a360.co/346gIDu

Printing Tip! for printing the tops of the filter boxes, turn them upside down by rotating along either the X or the Y axis by 180 degrees before you slice them.