Compound 40mm Fan Fume Extraction System

These parts can convert a collection of 40mm fans to a powerful ventilation system, capable of negatively pressurising a 3D printer enclosure, such that all the airflow through the various leaks in the enclosure will be only from the outside in, effectively eliminating printing fume releases while the printer is operating in a closed condition ('Heating Mode' on the H2 series).

 

This system is designed around 19mm (~¾") inner diameter vinyl hose. A larger hose would be more efficient, but this smaller diameter is very easy to work with, and to route anywhere you need.

 

• The stator vane sections between the fans function to convert the rotation imparted to the air stream into useful pressure
• The long input diffuser section reduces the pressure drop from slowing the air stream as it enters the larger area of the fan section
• The output nozzle does the reverse, but does not need to be as long to be efficient
• The intake bell/filter prevents debris from entering the fan (see below!), and efficiently couples the high velocity flow in the hose to the enclosure
• An optional coupler is added to permit easy pressure measurement via small diameter hose

To minimise the requirements of the fan, the chamber should be as well sealed as possible. In stock configuration, the biggest culprit is the poop chute. By using an enclosed poop bin with a decent internal volume (such as the excellent model here https://makerworld.com/en/models/1461546-enclosed-poop-bucket-for-h2d), the intake bell/filter can fit inside (I believe I used a 22mm drill bit to fit the hose, and a good seal can be achieved.

 

The fans that I had available, the Sanyo Denki 109P0412G3013, has a rated flow of 14.8 CFM, rated static pressure of 18 mmH2O (174 Pascals), and combining 8 of them in series with the highest theoretically possible pressure recovery efficiency would yield a static pressure of 1.4 kPa. Testing my combined configuration with a handheld digital pressure meter resulted in a static pressure of 1.3 kPa, which seems like a good result! This also gives a very good flow through a total of 5 metres of 19mm hose.

 

I have chosen to power each section of 4 fans (rated at 0.31A current draw at 12V) from a surplus 12V 2A generic power supply, with the DC barrel jack cut off. With just one fan section powered (about 0.7 kPa nominal total static pressure), the pressure is good enough for almost total elimination of fume leakage (the biggest remaining culprit seems to be the poorly sealed top vent). I would regard this as a good target minimum for the total static pressure of your fans. With both sections powered, the suction is very impressive, and the noise measures at 50 dBA from up close. The chamber can still comfortably reach 65 degrees while exhausting this flow rate, heating time may be improved slightly by engaging the fan only when the chamber has reached the target.

 

The default profile contains parts for 4 fans: 4x stator sections and 9x gaskets. Each fan section will require 4x M3x40mm SHCS plus M3 nuts (for 28mm long fan, adapt as needed for other length fans), and the inlet diffuser will attach with any shorter screw (about 10mm). The assembly should proceed in sections from the rear as illustrated, with the screws pointing rearwards, and then the inlet diffuser will finally attach at the front.

 

The stators are printed with brims and tree supports which will need manual removal, unless a separate interface material is used. ‘Support for PLA/PETG’ is best, but PLA may work here.

 

Boost MeIn theory the design is adaptable to fans of different diameters, and different hoses, but I haven't tried this yet. If there is demand for something, let me know! This is my first major 3D design project :)