MK3 air filter with customisable 3D printing files

This unit has been sitting in my bedroom for a while now. It's extremely quiet and just gradually moves the room air through the cheap disposable paper filter on an ongoing basis 24/7.

This new version has a simpler mounting with separate top plate with a small section of anti-turbulence fins. It still uses a cheap eBay illuminated 120mm fan as a good compromise between function and noise. The smaller fans tend to be a bit high pitched and noisy.
For an area where noise is less critical a stronger fan could be used.

The hole pattern is less efficient than the original square matrix, but looks much more stylish. Especially with the fan's illumination. I may look at combining the two designs to put the square hole matrix onto the round platen.

For those new to the project it's based on a conventional air purifier that draws the room air through a particulate filter. Unlike the commercial units, this one has a cheap and easy to source filter material in the form of paper towel or toilet paper. Both of those materials are based on a high density random lay of wood fibre that results in a filter medium that can potentially filter out particles in the region of one micron and up. That includes most dust and spores.
Best of all, the filter can be changed as often as you like, as it's cheap and easily available.

Do not use paper as a fan filter on a computer. They require coarse high airflow filters to keep things like fluff and hair out.

The 3D openscad scripts are below. There are four separate scripts.

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Here are the 3D printing files. You will need to copy and paste them into openscad so you can adjust the variables if you like, and then build the final model and save it as an STL file.

The first script is for the base/fan-adaptor. You can adjust the height and screw hole sizes.

//MKII adaptor for 120mm fan
$fn=100;
//You can adjust the two variables below
depth=40; //depth of air chamber (40)
hole=4; //fan screw holes (4)
difference(){
union(){
//baseplate
hull() {
for (i=[0:90:330])rotate([0, 0, i]){
translate([74,0,0])
cylinder(h=1.5, d1=15, d2=15);
}
}
//Main outer cylinder
cylinder(h=depth, d1=120, d2=120);
}
//internal cylinder
translate([0,0,-1])
cylinder(h=depth+2,d1=118,d2=118);
//screw holes
for (i=[0:90:330])rotate([0, 0, i]){
translate([74.5,0,-1])
cylinder(h=4, d1=hole, d2=hole);
}
}
The second script is for the top platen for the filter paper.

//MK3 platen for filter paper on 120mm fan
$fn=100;
//You can adjust the variables below
depth=10; //depth of lip and fins (10)
platen=1.5; //thickness of platen (1.5)
//don't adjust anything below here
hole=platen+2;
difference(){
union(){
//platen
cylinder(h=platen, d1=140, d2=140);
//Main outer cylinder
cylinder(h=depth+platen, d1=118, d2=118);
}
//internal cylinder
translate([0,0,platen])
cylinder(h=depth+platen,d1=116,d2=116);
//filter hole pattern
for (i=[0:45:330])rotate([0, 0, i]){
translate([35,0,-1])
cylinder(h=hole, d1=20, d2=20);
translate([16,0,-1])
cylinder(h=hole, d1=10, d2=10);
}
for (i=[22.5:45:350])rotate([0, 0, i]){
translate([24,0,-1])
cylinder(h=hole, d1=10, d2=10);
translate([41,0,-1])
cylinder(h=hole, d1=10, d2=10);
translate([32.5,0,-1])
cylinder(h=hole, d1=5, d2=5);
}
translate([0,0,-1])
cylinder(h=hole, d1=20, d2=20);
}
//anti turbulence fins
difference(){
for (i=[0:45:330])rotate([0, 0, i]){
translate([46,-0.5,0])
cube([12,1,depth+platen]);
}
}
The third script is for the feet. You will need to print four of them.

//MKII leg for 120mm fan
$fn=100;
//You can adjust the two variables below
depth=50; //height of leg
hole=4; //screw holes
difference(){
union(){
//Main outer cylinder
cylinder(h=depth, d1=12, d2=12);
}
//internal cylinder
translate([0,0,2])
cylinder(h=depth+2,d1=10,d2=8);
translate([0,0,-1])
cylinder(h=4,d1=hole,d2=hole);
translate([0,0,depth-1])
cylinder(h=2,d1=10,d2=10);
}


The last script is for the weighted paper ring if desired.

//Weighted ring for paper
$fn=100;
//The variables below can be adjusted if desired
depth=2; //depth (weight) of ring
inner=100; //inner hole diameter of ring
outer=140; //outer diameter of ring
difference(){
union(){
//main disk
cylinder(h=depth, d1=outer, d2=outer);
}
//hole in middle
translate([0,0,-1])
cylinder(h=depth+2,d1=inner,d2=inner);
}

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