Some time ago we added ventilation pipe for a room we were remodeling. This is model is used to prevent water ingress and insects through the pipe while still letting enough air through.

Model is completely customizable and has great deal of flexibility. The following parameters can be configured:

1. debug: If set to true it will show angle of protection;
2. nozzle: Printer's nozzle diameter which is used to determine thickness of walls;
3. layer: Layer height used for grid;
4. include_fins: Whether to render fins;
5. include_grid: Whether to include grid (bug net);
6. angle: Angle for fins. Ideally should stay at 45° to provide optimum number of fins to coverage ratio. It can be customized with values ranging for 1° - 89°;
7. protect_angle: Angle from which the fins should appear to cover 100% of the object. Toggle debug to true to see expected elements direction;
8. overlap: Increase or reduce spacing between fins linearly with this parameter;
9. thickness: Total model height;
10. diameter: Outside diameter of the model;
11. outer_wall: Outer shell thickness;
12. inner_wall: Thickness of fin walls.

How to print grid: Set include_grid to true and export. Then in your slicer turn off top and bottom layers. This will cause for thin bottom wall to be treated as infill. Use infill settings to configure grid size to your liking.