My shop is dusty. It probably has something to do with using a Shop-Vac as dust collection but I’m addressing that by buying a dust collector. Even so, I don’t expect it to collect everything so I’m waging a war on dust on two fronts. I made a cheap (under $100 for the housing, fan, and filters) air filter box and thought I’d share. It’s not particularly powerful but does a decent enough job and is quiet enough.
I made this more as an exercise to learn OnShape rather than to build a high performance filter - I’m a SketchUp refugee and I’m mad I didn’t discover OnShape before. I’m really liking it so much better. It feels like what SketchUp could have become if they worked on features instead of monetization.
The fan I picked is rated at 1040 CFM, but that’s Amazon CFM so real-world is probably like 700-800? (Is there a free/cheap way to measure that?) It’s still within range of the low end systems on Rockler for $300-$400. The two filters used are standard 20x20x2 (actual 19.5x19.5x1.75) - I picked an 8 MERV outer filter and a 13 MERV inner filter.
I cut the 6 pieces on the CNC table - note that 1/8” bit corner overcuts are already baked into the drawing via the magic of CNC Corner Joint extension in OnShape. It uses less than one 4x8 sheet of OSB. I used the scraps leftover from cutting out the table it’s sitting on in the pictures. Once cut, I’m pretty sure it will only go together one way and the L/R and T/B pieces are mirrors. Glue it up and throw in a few brad nails until it drys. Caulk around the inner seams if you have some on hand but this is probably optional with enough wood glue (I didn’t bother). Cut the silly in-line controller off the fan cord and drill a hole in the box to pass the cord thru on whichever side you want to to exit. The fan just screws into the front using wood screws and it’s flanged as well, so a bead of caulk there if you have the tube out. Wire to the 120v source of your liking. The filters just press-fit into the back. I left a half inch of overhang with the idea I could print or cut a holder if they were loose but that turned out to be unnecessary. It’s a nice snug fit. If you wanted to go for more filter space there’s a variable in the CAD that will move the filter stop in and out. You could reasonably put in at least (2) 4” filters before you start bonking the fan motor.
I’m going to screw in 4 eye bolts and suspend it above my primary woodworking area and wire it to the lights so it’s always on if anyone is in the shop.
I used 2 extensions here - CNC Corner Joint and Auto Layout. The mortise and tenons are all automatically generated, and Auto Layout gives you an idea of how to lay out your DXF optimally.
Very nice build! I built something similar a few years ago using an old squirrel cage fan that has been working great! Its time to change the filters on it now lol
Make a cube out of QTY5 1” MERV 11 filters and a box fan for the top. Works even better than dedicated air purifiers because air flow goes up by the square of filter area, and QTY5 20x20” pleated filters is a hell of a lot of area! MERV is rated based on % of fine particles removed per pass thru the filter, so MERV 11 with a ton of air flow gives you lots of passes, and therefore lots of nasties filtered out of the air. I can watch cat hair float up my stairwell when I crank the box fan to max lol.
I have one in my house and one in the garage. for the garage one I cut out the cardboard scaffolding of the filter so now I can vacuum off the wood dust, so the filters last a long time too. It is a huge difference in air quality, especially noticeable in wildfire smoke!
Also get the filters on Amazon…as much as it pains me to say that, but it’s like half the price or better than Lowe’s/HD lol.
I confess I have a “bought” one - a JET version from around the turn of the millennium, when it was cheaper for me to buy than to make.
Not to hijack this thread, but to inform, if you can deal with the loss of heat or cooling in your shed, while the filter is great you can improve air quality even more by directly exhausting the dust-filled air - I have two 8" inline fans which are each capable of more than meeting industry standards for air turnover in the space.
The one pictured has a printed duct (was originally made of 3mm mdf) which exits via two 150mm louvred openings. The other goes straight out a window which I open just enough to let it work without recirculating.
In my case, I leave the door to my wife’s sewing area open, to provide a bit of negative pressure in the house, and that truly keeps outside the workshop dust free.
8" duct fans for under US$100 work great. Made a big difference in my setup compared to my previous fan in a window setup. Plus I can now control the exhaust fan with FluidNC.
That’s what I use in the house. Big ole 4” filter and a $20 fan and some duct tape. We did spring for the fancy white duct tape to match the fan though. We fancy.
I’ve read all about C-R boxes before, mostly from the covid times, and originally thought about doing that for this design. To be honest, that’s why I ordered 4 filters was to use them all. Then I did some of the “math” and figured without a much more powerful fan, I’m CFM limited and not filter. Plus I wanted to design something to force me to use some OnShape but I’m also inherently lazy and designing a box for 4 sides of filters seemed like work.
