20 Inch Box Fan Air Filter – modified

thingiverse

20 Inch Box Fan Air Filter – modified still a work in progress, but prints very well. just check its fit for your fan. Big thanks to AtomicFix at https://www.thingiverse.com/thing:968923 This attachment for 20 inch box fans is perfect for workshops! I can keep it running and pick up stray dust as I cut wood (this does NOT replace a dust collector!). His style clips onto the box fan, but my box fan has tapered edges instead of square corners. The clipped style won't hook onto my fan without assistance. So, I modified his design by cutting down the sides and adding couple wings to allow better screw holding (1/2 inch screws are adequate, sheet metal). They don't hit the fan blade. The bottom is designed to support the filter itself. I mounted them about 1/2 inch above floor level so they won't get banged against the ground. You can put top and bottom into slicer, rotate them so they're flat (second slicer image), and then mirror them for the other side of fan. For the bottom, there is space below it in one section. I added a small wing to the outer edge so it hits the printbed. This eliminated the need for supports for me. This modification should be helpful to others.