OSMO Action 6 Lens Cap

It is designed to be printed from flexible filament such as TPU/TPE with an optional hard insert (PETG) to make the cap harder.

The design contains a few different versions:

1. Simple flat: one piece with flat internal cap surface (TPU/TPE). This is similar to what you get from ebay/aliexpress/amazon/etc.
2. Simple stepped: one piece with stepped internal cap surface (TPU/TPE). The step theoretically should reduce chances the filament to touch lens in the middle. However, as the filament is flexible it still will be touching the lens.
3. Compound: flexible cup (TPU/TPE) and hard flat insert (PETG). The hard part could be just inserted or glued in with Super glue. The lens cap will not be as flexible as the "Simple flat" version.
4. Compound: flexible cup (TPU/TPE) and hard stepped insert (PETG). The hard part could be just inserted or glued in with Super glue. The step theoretically should reduce chances the filament touchs the lens in the middle. As the lens cap with hard insert is less flexible it is less prone to bending so less chances to touch the lens in the middle.

I personally use the last option (on photos): flexible cap made of TPU printed without ironing + hard stepped insert made of PETG printed with ironing and the insert is glued into the cap.

My recommendations:

• Use fuzzy skin for outer cap: looks good and not too slippery;
• Use concentric pattern for top/bottom layers: looks better;
• For cap without inserts and inserts use ironing for top layers: the surface that is touching lens will be smooth;
• Inserts should be printed with all layer height 0.2mm;
• Line width: ~0.4mm

You can check settings I used in uploaded Orca Slicer 3mf project files.