Creality K1 back-fan filter using Anko filter

This is a filter for the back fan of the Creality K1, using a cheap Anko brand HEPA+Carbon filter.

The filters are “Replacement Filter Set Small”  from the Anko brand for their small tower purifier (sold by Kmart in Australia and probably elsewhere) .  They're 212x90mm, and a total of 25mm deep (plus foam all around).  The box has an additional 5mm pre-filter gap in the hope all the filter is used, not just the section in front of the fan.  

Press-fit the filters into the box.  Press-fit the box onto the K1.  The legs fit into the gaps surrounding the fan exit.  It seems very secure so far.

Attach the filter horizontally for the best fit.  Its current design overlaps the filament spool if vertical.

Design: I've included the OpenScad source, in case your filters are a different size or you want it mounted vertically (decrease the ‘offcentre’ for a more central hole).

Print in any filament.  Print box-down so support acne isn't visible, or for no supports, split into box-edges and the rest, and glue them together after.