DIY Mini Air Purifier (Corsi-Rosenthal Box)

prusaprinters

<h4>Background</h4><p>Included are files for 8 bracket pieces that print without supports and connect without fasteners or glue. &nbsp;Along with a fan and 4 furnace filters they can be used to create a mini <a href="https://en.wikipedia.org/wiki/Corsi%E2%80%93Rosenthal_Box">Corsi-Rosenthal Box</a>. (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.</p><p>Typically Corsi-Rosenthal boxes are constructed using tape to connect the filters to the fans and base. &nbsp;Inspired by <a href="https://twitter.com/haussamen/status/1488163457933344772?s=20&amp;t=TUB-MSJ4TaSZlcoKAEHjjw">Heath Haussamen's tweet</a>, I thought it would be fun to make some 3D printable brackets to construct a similar mini version. &nbsp;I wanted to make my version easy assemble and disassemble and allow use of the fan by itself when filtering was not needed. &nbsp;It also makes changing filters very straight forward.</p><p>Using four US standard 12x24x1 inch filters you can create a tall version, 12x20x1 for a medium version, and 12x12x1 creates a little cube.</p><h4>Results</h4><p>It turned out better than I expected, and has some nice airflow for its size while being very quite. &nbsp;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.</p><h4>BOM</h4><p>I used four 12x24x1 inch MERV 13 <a href="https://www.amazon.com/Filtrete-Ultimate-Reduction-Microscopic-Particles/dp/B00TUDHMGS?ref_=ast_sto_dp&amp;amp;th=1&amp;amp;psc=1&amp;_encoding=UTF8&amp;tag=robagon3d-20&amp;linkCode=ur2&amp;linkId=36a0b5825773d2edf8304d64516c8cc9&amp;camp=1789&amp;creative=9325">3M Filtrete MPR1900 filters</a>* for my tall version but this should fit other brands. &nbsp;It is recommended to use MERV13 or higher for virus carrying particles.&nbsp;</p><p>The fan is a <a href="https://www.amazon.com/gp/product/B06WP6CY4G/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&amp;amp;th=1&amp;_encoding=UTF8&amp;tag=robagon3d-20&amp;linkCode=ur2&amp;linkId=6e53cf74dd7078fe12baabdc412f3fe2&amp;camp=1789&amp;creative=9325">Black &amp; Decker 9in Mini Box Fan, Model BFB09W</a>*.</p><h4>Cost</h4><p>At 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. &nbsp;I went with the larger filters as I plan to put this on the floor of our bedroom. &nbsp;I don't think the larger size will filter more air per minute, but the filters should last longer and it should be quitter. &nbsp;The 12x12x1 version is great for portability.</p><ul><li>Fan: $17.50</li><li>3M Filtrete MPR1900 MERV13 Filter 2-Pack: $38, Qty2: $76</li><li>PETG Filament: $12 @ $20/Kg</li><li><strong>TOTAL COST: $105</strong></li></ul><p>Similar sized air purifiers run anywhere from $150 to $300 so this seems like a reasonable DIY project. &nbsp;Also, I'm using higher cost filters. &nbsp;You can buy MERV13 filters for about half the cost if you look around, so closer to $70-$75.</p><h4>References</h4><p>https://www.texairfilters.com/a-mini-corsi-rosenthal-box-air-cleaner/</p><h4>Printing</h4><p>I recommend using PETG or ABS for these brackets as they need to flex. &nbsp;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.</p><h5>Recommended Printing Parameters</h5><ul><li>Material: PETG</li><li>Nozzle Size: 0.6mm</li><li>Layer Height: 0.3mm</li><li>Supports: None</li></ul><h4>Assembly</h4><h5>Base</h5><p>Slide the two quarters base pieces together guiding the two tabs through the first slots, over the retaining nubs, and under the second slots. &nbsp;Once in place these are a little tricky to remove so take your time and assemble on a flat surface. &nbsp; Make sure the side tab is on the correct side of the mating piece as well. &nbsp;Do this again with the remaining two quarters to create the second half. &nbsp;Slide the two halves together similar to the previous steps to create the base.</p><figure class="image image_resized" style="width:67.18%;"><img src="https://media.prusaprinters.org/media/prints/131142/rich_content/57af4791-dcf9-4a05-a696-57497c65409e/image.png#%7B%22uuid%22%3A%228d56339a-361d-4bdc-8814-188b5e45b981%22%2C%22w%22%3A1319%2C%22h%22%3A658%7D"></figure><figure class="image image_resized" style="width:62.27%;"><img src="https://media.prusaprinters.org/media/prints/131142/rich_content/45f6af80-5d67-4b22-bb0f-1af8a57ac334/image.png#%7B%22uuid%22%3A%225408a08c-1ebc-4de7-a8b8-3d387a3573c1%22%2C%22w%22%3A1229%2C%22h%22%3A645%7D"></figure><figure class="image image_resized" style="width:66.36%;"><img src="https://media.prusaprinters.org/media/prints/131142/rich_content/5b230c38-5af9-4d46-904e-cbda1117a59c/image.png#%7B%22uuid%22%3A%2211a0c3ff-02dc-44c1-a587-d277acab5928%22%2C%22w%22%3A1200%2C%22h%22%3A803%7D"></figure><figure class="image image_resized" style="width:53.48%;"><img src="https://media.prusaprinters.org/media/prints/131142/rich_content/3581b351-80e2-491a-95be-0f8a56542576/image.png#%7B%22uuid%22%3A%226c929981-2ed4-4f9d-b3e9-0293bdd212fa%22%2C%22w%22%3A876%2C%22h%22%3A861%7D"></figure><h5>Filters</h5><p>Insert the four filters into the base similar to the image below with the air flow arrows pointing inward.</p><figure class="image image_resized" style="width:58.02%;"><img src="https://media.prusaprinters.org/media/prints/131142/rich_content/745b18cf-61d3-42c2-80a5-467f4fdbe9cc/image.png#%7B%22uuid%22%3A%22a8effdbe-6aa8-43b4-9041-d32cc6d033e8%22%2C%22w%22%3A789%2C%22h%22%3A1144%7D"></figure><h5>Top Frame</h5><p>Place the corner pieces on top of the filters so that the chamfer running around the inside is continuous, see image below. &nbsp;Ensure all four locking tabs are properly engaged. &nbsp;The chamfer is at an angle because of the unique geometry of the fan.</p><figure class="image"><img src="https://media.prusaprinters.org/media/prints/131142/rich_content/ae3874ed-7e66-4c0a-9a6a-79411b7a587d/image.png#%7B%22uuid%22%3A%225dc8decf-6ea6-4c19-bbdb-f3b120d62266%22%2C%22w%22%3A1329%2C%22h%22%3A580%7D"></figure><h5>Fan</h5><p>Insert the cord through the hole in the bottom of the base.</p><figure class="image image_resized" style="width:68.96%;"><img src="https://media.prusaprinters.org/media/prints/131142/rich_content/cb55b019-4282-4509-808d-4b7454e49f41/image.png#%7B%22uuid%22%3A%226c7d1b92-ca61-48f0-af05-b399203beb46%22%2C%22w%22%3A1196%2C%22h%22%3A827%7D"></figure><p>Align the fan so the outer rim will sit on the chamfer and the fan blade and housing will point vertically. &nbsp;The fan feet fit into the notches seen below. &nbsp;You may need to pull some of the upper frame pieces apart to get it started. &nbsp;Once the fan is seated you can push them all back together.</p><figure class="image image_resized" style="width:76.69%;"><img src="https://media.prusaprinters.org/media/prints/131142/rich_content/b5adb672-781d-4389-b1f8-44874698e8d4/image.png#%7B%22uuid%22%3A%22722da419-9946-442b-bb37-f2ecdb26a229%22%2C%22w%22%3A1446%2C%22h%22%3A878%7D"></figure><p>Run the cord through the two notches in the base piece to help hold it in place. &nbsp;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.</p><figure class="image image_resized" style="width:76.25%;"><img src="https://media.prusaprinters.org/media/prints/131142/rich_content/54cfd6f3-cd13-4932-9483-bc791349dad9/image.png#%7B%22uuid%22%3A%22e8aea1ea-9c23-460c-8eb8-2354fde3d845%22%2C%22w%22%3A1027%2C%22h%22%3A649%7D"></figure><h3>&nbsp;</h3><h3>Encouragement</h3><p>If you like what I'm doing consider buying me a coffee:</p><p><img src="https://cdn.buymeacoffee.com/buttons/bmc-new-btn-logo.svg" alt="Buy me a coffee"><a href="https://www.buymeacoffee.com/sj5pEfMZq">Buy me a coffee</a></p><p>*Affiliate links help support my designs</p>