WARNING

I have had a lot of user feedback in the last few weeks and it appears that the tape mounting method works for some people and doesn't work for others - and I think it's because the back panel of the machines vary in flatness. Some back panels don't sit flat on the machine - I think it's the foam gasket inside that pushes the back panel out unevenly - and the mounting method is only really suitable for attaching 2 flat things together, otherwise the tape lifts off after some time. An additional bracket will stop the filter from falling off but it will not stop the tape lifting off. I will need to figure out another method of attaching it while retaining a relatively good seal. I will come back to this to design a better mounting method. Sorry for the wait!

Purpose

The ideal fume extraction setup should capture all fumes and either completely filter it clean or send it outside through ducts. Even though the P1S and X1C are enclosed, the enclosure has many holes and gaps, the entire printer should be enclosed in a cabinet or zip-up tent with ducting and an additional fan to push the air outside. The fan should provide enough flowrate to ensure the electronics do not get too hot and that, if printing PLA, the chamber doesn't get too hot to cause extruder jams through heat creep. However, depending on your situation, such a setup may be undesirable or unachievable for several reasons.

• Perhaps you can't put your printer next to your window and you don't want to run ducting across the room.
• Perhaps it's too difficult to seal the window gaps after routing a duct through it. If you live in a hot/cold/noisy area, window sealing could be important.
• Perhaps you consider such an ideal setup is overkill for the occasional hobby use.
• Perhaps your mom will yell at you.

The NTK Filter is adds a simple VOC and particulate filter behind your P1S or X1C to provide some additional filtration without taking much space or additional electronics. It also has an additional benefit of reducing the sound level of the fan, especially in the more annoying higher frequencies. This is a part of a larger project (Noise and Thermal Kit) but can be used independently.

Performance

Before assessing the performance, let's consider some physics:

• A bigger filter creates less head loss (or “back-pressure”). Not only is there more “vent area” for air to pass through, air will move slower across the filter. Typically for an object moving through air, drag is proportional to the square of the air velocity. This means that doubling the filter size will more than halve the head loss.
• Slower air movement through a filter increases efficiency of a filter for very fine particles and VOCs. The slower air gives very fine particles and VOCs more time to collide with the filter media through Brownian motion (ultra fine particles are captured through static charge, not by mechanical means).
• The total head loss in a system is largely determined by the most restrictive element/s.
• Putting a HEPA filter before the VOC filter increases the life of the VOC filter as particulates don't clog the pores of the VOC filter media.

These are some considerations of the P1S and X1C machines:

• There is no built-in HEPA filter.
• The OEM carbon filter is small and very restrictive but the chamber fan still works sufficiently as it is designed for the filter.
• For printing PLA, if you don't want to open the door/lid due to the smell and/or noise, air flowrate is important to keep the chamber temperature down, as noted in this Bambu Lab Wiki Article.
• The printers have a lot of gaps and holes where chamber air can escape before being filtered.

With these in mind, the following changes are made to the filtration system to try to increase filtration performance.

• The OEM carbon filter (VOC filter) is replaced with a refillable carbon filter cartridge approximately 3.5x the size with a similar thickness for lower head loss and increased filter efficiency.
• A HEPA filter stage is added to capture particulates. This is also very large to minimise head loss introduced by this stage.
• The HEPA filter is placed before the carbon filter to increase longevity of the carbon filter.

From a couple of days of testing, I have noted the following results.

• Can adequate flowrate be maintained to keep a cool chamber temperature when printing PLA for a long time without special build-plates (such as Supertack)?
  • Yes (with ambient room temperature ~20 deg. C, further testing to be done in summer)
• Can the VOC filter efficiency be improved from the OEM setup?
  • ABS Print: YES - significant improvement when printing ABS with 20% chamber fan according to my sniff-o-meter. However, the ABS smell is still easily noticeable.
  • PLA Print: YES - completely unnoticeable (this is a big deal to me as my wife and I usually find the smell super annoying!)

 I do not have an air quality meter currently. Testing is ongoing.

Here is a simple airflow test video to illustrate the extraction performance:

Limitations

While the NTK Filter improves on the stock filtration system, it is definitely not perfect. VOCs and particulates may still leak out through gaps and holes, you may open the chamber door while printing or the carbon filter stage can lose efficiency. If you are printing some of the nastier materials, you should do as many of these things as you can:

• Install a recirculating chamber air filter to supplement the filtration (I'm working on something for this, see below!),
• Keep the room well ventilated during (and for some time after) printing
• Use a room air filter
• Stay out of the printer room during (and for some time after) printing
• Print in a room with an extraction fan (perhaps your laundry or an unused bathroom)

Print Material and Settings

Use PETG or a material with better thermal properties with the included print profile. The profile is tuned for Bambu PETG HF and you may need to change the filament profile. PLA is likely to be perfectly fine but I have not tested it.

Clean the plate and use glue!

The built-in support can be broken off then cleaned up with the Bambu scraper or a sharp knife. Any white stress marks from the cutting can be removed using a heat gun or a lighter.

Feel free to add your own print profiles (and keep the profile points!) but please add a good description to help people choose. I've uploaded the STL file of an un-pre-supported main body in case you want to try to support the large overhang in a different way.

Other Materials Required

• 3x HEPA filters - These are the same filters as on some iLife vacuum robots (~80mmx40mmx15mm) as well as the popular “BentoBox” mod. They are available on Amazon (example from Amazon.de) and Aliexpress as well as many other stores.
• Approximately 250mL of activated carbon pellets or granules designed for purifying air (the weight will vary depending on pellet shape and size). They are available on Amazon as well as many other stores. They do not need to be “acid free” as this is not a recirculating air filter - however, do consider getting carbon that's not “acid washed” so you can use the same filter media for a recirculating filter. I bought ones that look like chips/shards but the cylindrical pellet ones will introduce less air resistance.
  • The carbon I bought was not the Nevermore branded carbon but had these 3 lines in the description which were promising: "Highly effective and exclusively water vapor-activated coal. Not impregnated. Not washed", "The entire production takes place without chemical additives. Not treated with acid, therefore no oxidation", "Preferably also used as a recirculation cleaner in 3D printer housings. With pH value of 9-11, no more rust on bare metal surface". I'll add a link to it once I verify that it's OK for internal recirculating filter use.
• 1mm thick VHB tape ("nano tape" and “mounting tape” are good search terms) . They are clear acrylic tapes and can be re-positioned and removed cleanly. There are many cheap unbranded options available on Amazon (example from Amazon.de)
• 2x M3x12 machine screws (can be M3x16 but these take longer to screw in)
• 2x M3 plain hex nuts

Optional, for attaching to NTK Side Panels

• 3x M3x10 machine screws
• 3x M3 plain hex nuts

Installation

Note: if you use an AMS Hub, you will need to reposition it a little upwards as it is very close to the exhaust grille in its default position.

1. Remove the OEM carbon filter. If this is fairly new, you can cut this open and use the pellets in the new filter. If it's old, throw it away.

2. Attach the VHB/nano tape to the manifold body in a rectangular pattern as shown in the photo. Ensure that the tape is continuous around the rectangle to get a good seal and do not cover the small hole as these give access to the case screws.

   

3. Remove the tape backing, align it the best you can and press firmly.
4. Install the 2x M3 nuts into the nut pockets.
5. Install the HEPA filters.
6. Fill the carbon cartridge with carbon media. Fill as much as you can without having the lid bulge out.
7. Close the carbon cartridge lid and ensure that the holes line up.
8. Attach the carbon cartridge to the manifold using the 2x M3x12 screws.
9. Attach a cardboard flap to the poop chute and tape over some of the large holes and gaps to make it easier to maintain negative pressure in the print chamber.
10. Adjust your filament start g-code as appropriate to ensure that the chamber fan turns on automatically. This is an example of my ABS-GF filament start g-code: M106 P3 S51 ; S51 = 20%

Frequently Asked Questions

• I saw a video where someone said HEPA filters are marketing gimmicks and MERV 14 filters are the best! Why HEPA?
  • For recirculating filters such as room air filtration, a less restrictive (not High Efficiency) filters are often better because a given fan can generate a higher flowrate and filter faster. Many off-the-shelf room filters use HEPA filters and this is a poor filter choice and definitely a marketing trick. People that are sensitive to air particulates often make their own filters using MERV 14 filter panels used in the HVAC industry. This is not the case for a single-pass filter such as this one - we don't need a huge flowrate and very little of the exhausted air will come back through the filter after getting into your room so HEPA is the correct choice in this case.
  • In in-chamber recirculating filters (such as the popular BentoBox), even though HEPA may not be the best choice technically due to the lower flowrate, lower resistance filters may not be available in the form factor suitable for inside a 3D printer. Having a filter you can source easily in many countries is a good design choice.
• I'll be adding more to this as I continue to get feedback and questions!

Support

If this model helped you, please leave a thumbs up and a boost. If you would like to donate or sell these commercially, please join a membership!

And stay tuned for “AUX Pro” - an auxiliary fan duct with a filter module option to turn it into a slicer/app controlled high flow chamber filter without any added electronics.