DIY Mini Air Purifier (Corsi-Rosenthal Box) - UPDATED

prusaprinters

Update, Nov 2023I've added two new versionsThe first is a version 2 of the split design.  The locking tabs were made separate so incase they break you can just print more tabs instead of a whole new base piece.  The base was also made thicker so the cord fits completely inside of it.  This helps keep the cord in place better.  I also improved the locking tabs so they hold better.The second is for those with a large format printer.  I took the V2 design and merged it into a solid piece.  This makes the whole unit much more rigid, however it makes assembly and disassembly more challenging.  I would only use this option if you plan to leave it assembled.  When assembling start with the fan first then the filters in the top piece then the bottom.________________________________________________________________________________________________________________BackgroundIncluded are files for 8 bracket pieces that print without supports and connect without fasteners or glue.  Along with a fan and 4 furnace filters they can be used to create a mini Corsi-Rosenthal Box. (Standard C-R Boxes use a 20 inch box fan and 20 inch filters.) This C-R box can be used to filter the air in a small to medium size room, removing contaminates such as smoke, virus carrying particles, wood dust, etc. depending on the type of filter media used.Typically Corsi-Rosenthal boxes are constructed using tape to connect the filters to the fans and base.  Inspired by Heath Haussamen's tweet, I thought it would be fun to make some 3D printable brackets to construct a similar mini version.  I wanted to make my version easy assemble and disassemble and allow use of the fan by itself when filtering was not needed.  It also makes changing filters very straight forward.Using four US standard 12x24x1 inch filters you can create a tall version, 12x20x1 for a medium version, and 12x12x1 creates a little cube.ResultsIt turned out better than I expected, and has some nice airflow for its size while being very quite.  Also, the fit with the 3M filters is good enough that I'm not sure I even need to tape the sides of the filters together.BOMI used four 12x24x1 inch MERV 13 3M Filtrete MPR1900 filters for my tall version but this should fit other brands.  It is recommended to use MERV13 or higher for virus carrying particles.   Walmart also has a good deal on a 4 Pack of the same filters HERE.The fan is a Black & Decker 9in Mini Box Fan, Model BFB09W.CostAt the time of writing this the total cost is the same for each of the 3 versions as the different sized filters are all priced the same.  I went with the larger filters as I plan to put this on the floor of our bedroom.  I don't think the larger size will filter more air per minute, but the filters should last longer and it should be quitter.  The 12x12x1 version is great for portability.Fan: $17.503M Filtrete MPR1900 MERV13 Filter 2-Pack: $38, Qty2: $76PETG Filament: $12 @ $20/KgTOTAL COST: $105Similar sized air purifiers run anywhere from $150 to $300 so this seems like a reasonable DIY project.  Also, I'm using higher cost filters.  You can buy MERV13 filters for about half the cost if you look around, so closer to $70-$75.Referenceshttps://www.texairfilters.com/a-mini-corsi-rosenthal-box-air-cleaner/PrintingI recommend using PETG or ABS for these brackets as they need to flex.  When the fan is inserted it bends the inner walls of the upper brackets to create a good seal and make the dimensions work so the filters create a perfect square.Recommended Printing ParametersMaterial: PETGNozzle Size: 0.6mmLayer Height: 0.3mmSupports: NoneAssemblyBaseSlide the two quarters base pieces together guiding the two tabs through the first slots, over the retaining nubs, and under the second slots.  Once in place these are a little tricky to remove so take your time and assemble on a flat surface.   Make sure the side tab is on the correct side of the mating piece as well.  Do this again with the remaining two quarters to create the second half.  Slide the two halves together similar to the previous steps to create the base.FiltersInsert the four filters into the base similar to the image below with the air flow arrows pointing inward.Top FramePlace the corner pieces on top of the filters so that the chamfer running around the inside is continuous, see image below.  Ensure all four locking tabs are properly engaged.  The chamfer is at an angle because of the unique geometry of the fan.FanInsert the cord through the hole in the bottom of the base.Align the fan so the outer rim will sit on the chamfer and the fan blade and housing will point vertically.  The fan feet fit into the notches seen below.  You may need to pull some of the upper frame pieces apart to get it started.  Once the fan is seated you can push them all back together.Run the cord through the two notches in the base piece to help hold it in place.  Depending on the surface you place it on you may need to trim a small part of the filter cardboard to make room for the cord. EncouragementIf you like what I'm doing consider buying me a coffee:Buy me a coffee