Internal active air filter

My goal was to create an effective filter based on currently available and cheap cartridges.
I chose the following parts:
 

• A quiet and effective fan - first choice was Noctua NF-P12 redux-1700 PWM

https://www.amazon.co.uk/gp/product/B07CG2PGY6/ref=ppx_yo_dt_b_asin_title_o02_s01?ie=UTF8&psc=1

• Activated carbon filters - there are so many on the market, but I found ones that fit the design and most importantly, will last a long time with the minimal loss after trimming (because they are made to measure).

https://www.amazon.co.uk/gp/product/B07K9MN4QZ/ref=ppx_yo_dt_b_asin_title_o02_s01?ie=UTF8&psc=1

• HEPA filters - You have a lot of choices here. Maybe you will find cheaper ones in your store because homemade robots are becoming very popular and that's a good direction for us.
  They must be standard "iRobot Roomba 800".

https://www.amazon.co.uk/gp/product/B07JLKSNFL/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1

Installation begins with mounting brass threaded inserts M3x5x5 or M3x5x6 to the blower holes.
This is the critical point in the assembly of the whole. The entire housing rests on these inserts on both sides.
Follow the order in the photos.

When it comes to printing, there are no special requirements. Do it according to your favourite settings.
I used 15% infill, 0.2mm layer, 3 walls and 80mm/s speed as standard on my "Kossel on steroids" project.

The front air intake is not essential, but at least partially forms the incoming air. Due to the resistance of the filters, part of the air bounces off the fan and circulates in front of the intake. I used this ring to increase the efficiency of the filter by a few %.

I still had room for it, and you do as you see fit.
The same applies to the spiral glued to the blower fan. This is probably a memory from my youth when I saw passenger plane engines with such paints ... Hahaha ...

One final note - I was taking subjective measurements. After putting the filter on, I don't smell any ABS, TPU, Wood, ASA or PLA odours. Nothing, but in 100% run.

This already shows something. In my opinion, it is best to check the effectiveness when you return to the room with the printer after some time.
Therefore, 1,700 rpm is standard in this configuration. The windmill is then slightly humming.

You can also add a retarder that gives Noctua as add-on plug (BTW this is only a 100 Ohm resistor in serial conn.) to silence the fan to around 1400 rp/m. Most of the time it working really enough for me.

But then the filter efficiency drops to 90%. And the noise to the level "I can hardly hear anything".

Have a nice printing;)

Update - To increase efficiency you can use only carbon filters. I checked and they also work great and of course the filter has greater suction power.