We call this one-way valve "_respiratory_" because it was designed to be adaptale to the low cracking-pressure requiered by breahting-related application. This is because this one-way valve was designed to integrate with our open-source 3D-printed gaz mask : [distorsion/3D-printed-parametric-gaz-mask](https://git.deuxfleurs.fr/distorsion/3D-printed-parametric-gaz-mask)
In this repo we provide all the element of the valve (_as described bellow_), and the body of the valve (_either_ [3Dfiles/owv_input_body.stl](./3Dfiles/) _or_ [3Dfiles/owv_output_body.stl](./3Dfiles/) _depending on if you want a filter at the output/input or not_) that can be integrated into your project.
In the first design of one-way valve for ou gaz mask, we first used a very soft membrane made of thin silicone. In this design, the membrane is actually 3D printable, either out of "_normal_" material (_preferably PETG_) or out of flexible filament.
While this requieres a larger diameter to obtain the low cracking pressure, this allows the valve to automatically close without negatiev pressure, which is needed for breathing-related application as we aren't constantly breathing in an out, and there can be a second of hang durng which a softer membrane wouldn't close and would let air go the wrong way.
<imgsrc="https://git.deuxfleurs.fr/distorsion/3D-printed-parametric-respiratory-one-way-valve/media/branch/main/pictures/one_way_valve_membrane_insert.png?raw=true"alt="Image not available"height="250"/>
The valve insert shown above (_located at_ [3Dfiles/owv_membrane_insert.stl](./3Dfiles/)) is a thin membrane made out of "_normal_" 3D printing material, with the membrane being one part with the threaded insert that screw into the body of the valve.
<imgsrc="https://git.deuxfleurs.fr/distorsion/3D-printed-parametric-respiratory-one-way-valve/media/branch/main/pictures/one_way_valve_separate_membrane_and_insert.png?raw=true"alt="Image not available"height="250"/>
<imgsrc="https://git.deuxfleurs.fr/distorsion/3D-printed-parametric-respiratory-one-way-valve/media/branch/main/pictures/one_way_valve_separate_membrane.png?raw=true"alt="Image not available"height="250"/>
Here we see the second alternative which is a slightly thicker membrane (_located at_ [3Dfiles/owv_separate_membrane.stl](./3Dfiles/)) made out off flexible filament (_here shown in blue_), with a separate rigid insert (_located at_ [3Dfiles/owv_separate_membrane_insert.stl](./3Dfiles/)) that hold this membrane.
There is no large advantage from using a flexible filament, appart from a potentially lower cracking pressure obtainable from a smaller valve diameter.
<imgsrc="https://git.deuxfleurs.fr/distorsion/3D-printed-parametric-respiratory-one-way-valve/media/branch/main/pictures/one_way_valve_stopper.png?raw=true"alt="Image not available"height="300"/>
Once you have printed all the requiered pieces as described in the [_3D printing section_](#3-3d-printing), the assembly is simply done in three steps :
<imgsrc="https://git.deuxfleurs.fr/distorsion/3D-printed-parametric-respiratory-one-way-valve/media/branch/main/pictures/one_way_valve_step1.png?raw=true"alt="Image not available"height="300"/>
We first screw the base (_located at_ [3Dfiles/owv_base_cap.stl](./3Dfiles/)) into the valve body, with the smoothest part of the insert (_typically the part that was printed down_) pointing toward the exit of the valve (_where this face will interface with the membrane_).
<imgsrc="https://git.deuxfleurs.fr/distorsion/3D-printed-parametric-respiratory-one-way-valve/media/branch/main/pictures/one_way_valve_step2.png?raw=true"alt="Image not available"height="300"/>
We then screw the membrane (_either one of the options shown in the [membrane section](#1-a-membrane-design)_) so that it seals with the cap we just screwed in.
<imgsrc="https://git.deuxfleurs.fr/distorsion/3D-printed-parametric-respiratory-one-way-valve/media/branch/main/pictures/one_way_valve_step3.png?raw=true"alt="Image not available"height="300"/>
Finaly, if we want to have a filter we can now put it into the body and hold it by screwing in anther cap (_located at_ [3Dfiles/owv_base_cap.stl](./3Dfiles/)). This can also be done at the other hand of the valve, where then the cap and the base (_which are the same model_) will be stuck together with the flter material inbetween.
<imgsrc="https://git.deuxfleurs.fr/distorsion/3D-printed-parametric-respiratory-one-way-valve/media/branch/main/pictures/one_way_valve_separate_membrane_sliced.png?raw=true"alt="Image not available"height="400"/>
<imgsrc="https://git.deuxfleurs.fr/distorsion/3D-printed-parametric-respiratory-one-way-valve/media/branch/main/pictures/one_way_valve_sliced.png?raw=true"alt="Image not available"height="400"/>
_Coming soon !_
## 4 - Parameters
If you want to changes the parameters of this design, you can edit the _Freecad_ file [3Dfiles/one_way_valve.FCStd](./3Dfiles/), which is fully parametric, with parameters present in the **Spreadsheet**.
If you want/need to change parameters, we would suggest you play with them and try to understand the impact of each parameters. We will only explain a small selection of important parameters that you are most likely to have to edit.
We will only describe a few parameters that you are most likely to have to change.
### 4.a - Structural parameters
_**wall_thickness** :_ \[_default=2.7mm_\] The wall thickness accross the print (_except for the strap attachment point_). Can be tweeked to make the print either stronger or weaker but lighter and faster to print.
_**snap_fit_clearance** :_ \[_default=0.09mm_\] The clearance between two objects that would fit togeteher with difficulty. Also impact the clearance betwen threads.
