This is an oxygen flow limiting device as part of the Helpful Hackathon. A 3D printable oxygen metering device that would allow the care-giver to set the pressure on the bottle of oxygen and know how much oxygen they are getting.
The concept is similar to an orifice flow metering device, where if you have an orifice that the flow moves through of a set diameter and you know what the pressure drop is across that diameter you can infer the flow rate.
To prove the concept we started with a flow rate of 10 litres per minute and pressure drop across the orifice of 1 bar. So if the flow regulator is set to 1 bar you should get 10 liters per minute of oxygen. These variables are used in a set of equations to give an orifice diameter.
This concept is in the testing phase after which the exact dimensions may change.
Currently the devices have been printed in PETG on a Prusa Mini using a 0.25 mm nozzle and then using a pin vise the orifice is drilled out to 0.8 mm in diameter.
An image showing the internal flow path of the oxygen regulator
A printed version of the most up to date the oxygen regulator