HEPA air cleaner - the video

I love this project! I thought that a single 120mm fan might be a bit weak, so I adapted the script to fit two fans: //120mm fan adaptor HEPA filter $fn=100; //You can adjust these four variables //Primarily the filter hole diameter screwhole=4.8; //fan screw hole diameter (5) filterhole=112; //HEPA filter hole diameter thickness=1.5; //Thickness of plastic layer (1.5) insert=10; //Length of insert into filter (10) //Do not adjust anything below here cone=(120-filterhole)/1.5; wall=thickness*2; difference() { union() { //base cube([145.8,120,thickness]); // front translate([0,thickness/2,0]) rotate([270,0,0]) linear_extrude(height = thickness, center = true, convexity = 0, twist = 0) polygon(points=[[0,0],[145,0],[104,112],[42,112]]); // back translate([0,120-(thickness/2),0]) rotate([270,0,0]) linear_extrude(height = thickness, center = true, convexity = 10, twist = 0) polygon(points=[[0,0],[145,0],[104,112],[42,112]]); //left side rotate([0,70,0]) difference() { cube([120,120,thickness]); translate([7.5,7.5,0]) rotate([0,0,0]) cylinder(h=thickness+4,d=screwhole); translate([7.5,112.5,0]) rotate([0,0,0]) cylinder(h=thickness+4,d=screwhole); translate([112.5,7.5,0]) rotate([0,0,0]) cylinder(h=thickness+4,d=screwhole); translate([112.5,112.5,0]) rotate([0,0,0]) cylinder(h=thickness+4,d=screwhole); translate([60,60,0]) cylinder(h=thickness+4,d=120); } //right side translate([145,0,thickness]) rotate([0,110,0]) difference() { cube([120,120,thickness]); translate([7.5,7.5,0]) rotate([0,0,0]) cylinder(h=thickness+4,d=screwhole); translate([7.5,112.5,0]) rotate([0,0,0]) cylinder(h=thickness+4,d=screwhole); translate([112.5,7.5,0]) rotate([0,0,0]) cylinder(h=thickness+4,d=screwhole); translate([112.5,112.5,0]) rotate([0,0,0]) cylinder(h=thickness+4,d=screwhole); translate([60,60,0]) cylinder(h=thickness+4,d=120); } //top translate([41, 0, -112.8]) cube([64.2,120,thickness]); //taper to filter insert //filter insert translate([72.9,60,0]) cylinder(h=insert,d=filterhole); translate([72.9,60,0]) cylinder(h=thickness,d=filterhole+(20)); } //taper to filter insert //filter insert translate([72.9,60,0]) cylinder(h=insert,d=filterhole-wall); //fan attachment holes }

This fan runs on 12V. I used a standard plug-in 12V 1A adaptor.

Big Clive

Where are you taking your 24V Power Supply from please? Other than my rather large portable bench unit, I don't know where else I'll get that amount of power from.

Andrew Donaldson

This is something I will build. I paid around £65 for a commercial air filter and apart from a fancy touch screen, this is all that’s in mine. A different brand I bought had an ioniser model just before the fan intake. Genuine replacement filters cost £20. Unbranded cost £15. Some say activated charcoal with no black inner lining (I called a manufacturer out on this point in an Amazon re and they offered me cash to take the review down). Some clones have the inner black layer, but it’s just plastic, so it’s worth checking if it is a piece of carbon impregnated sponge. You can buy sheets of the carbon filter as it’s used in fish pond pumps, so if you want to get rid of smells, you can “double up”.

Simon York

I have a Holmes model purifier that does a decent job. I got it pre-pandemic for ~50$US mostly for wildfire smoke. The true HEPA filters are around $27. That said, I've seen the purifiers go for $100+ at local stores.

Bryan Humphreys

Well you didn't need to worry about wind noise in your mics - it seemed almost completely silent.

Jon Knight

I use a specific password for Thingiverse, so it's a low risk unless they post rogue 3D printables on my page. I'd guess Thingiverse isn't a super-high profit organisation, so hopefully they don't get fined by the self appointed information security police. Sometimes it takes an event like this to make them tighten security.

Big Clive

I looked at a variety of those including the boy-racer air intake filters (possibly too coarse). I also had a hunt on eBay to see if I could find a common generic cabin filter that was easy to find at a mass produced price.

Big Clive

It takes about 2 hours with a 1.5mm thick plastic wall. The time will vary between printers.

Big Clive

I considered the rectangular filters, but it requires quite a big print-bed to make such large frames.

Big Clive

There'll be some standard brand that uses similar filters. There are at least two units in the UK that are more or less identical, but branded differently. They seem to use the same filter.

Big Clive

Where do people get the filters? When I search eBay, it's mostly the folded ones for Kärcher and similar vacuum cleaners.

Rasmus

The Ikea air purifier filter is another option for just £5 and it's rectangle in shape (40x26cm), so could handle a 2x3 array of 120mm case fans. It's only EPA E12 rated however (>99.5% 0.3um retention).

Seán Byrne

Every laptop cpu fan is horizontal so yes it is an old wives tale.

Your new filter design is much better looking than my 'Shoe box' design :-)

Zeedijk Mike

BC - You mentioned Thingieverse. Did you hear the news last week that they had a major password/account leak. Something like 28.000 passwords up for grabs. Thingieverse have NOT informed their uses (Bastards) I heard it via Makers Muse channel (3D-Printing) and got it confirmed on HackerSpace website. So if you (or any of your audience) have an account -> Change your password

Zeedijk Mike

I wonder whether car (auto) air filters would be a viable option too?

Ymir the Frost Giant

I got Dua Lipa - same difference

Ymir the Frost Giant

DIY HEPA wants to read as diarrhea to me. Anyone else?

Michael Gilchrest

How long does it take to print one for a 120mm fan as shown in the video? I'm pondering going to my local library to book some time for printing... they do four hour sessions so I'd have to make sure it's realistic to cram a print into that amount of time. This video is incredibly well timed, Clive - I'm doing a home remodel and a bunch of these distributed through the house will do wonders at pulling all of the drywall and other dust out of the air once we move back in!

Mike O'Keefe

Whoever said you can’t use these fans horizontally is talking nonsense. They are used horizontally on CPU coolers all the time. I can also think of other applications that use the fan horizontally. including air purifiers e.g. Osram AirZing Mini, RRP £40 GBP.

Gadgetman

The one I'm using at the moment is an FLsun Q5 which has been fine. There are lots of options though.

Big Clive

I have my doubts about that too. Even the simple sleeve bearing fans should accommodate horizontal use. It might be Internet folklore.

Big Clive

Nice and simple, I like it.

Matt Tester

I need a 3D printer! Any recommendations?

I have my doubts about the fan orientation concern. PC fans are oriented both ways (top mounted and back/side) in nearly all computers. The CPU heatsink fan and the case fans are almost always perpendicular to one another. Cases are designed to stand or lay down in many instances. Also, modern gaming computers having fans mounted to the top of a standing tower is routine. My experience with fan failure is more likely cause by dust and grit getting under the impeller rotor and gumming up the stator. (My experience = IT person for a bit. YMMV)

I toyed with other designs, but went with minimum airflow obstruction.

Big Clive

The fan grill should be in the shape of your logo instead of the traditional spiderweb shape.

Mark Trombley