Parametric Scope/Binocular/Camera Lens Cover

Binocular covers are easily lost. Scope covers are expensive. 3D printed covers are usually bulky, fragile, and complicated affairs, with lots of easily broken moving parts. They also are difficult to properly size to your needs. 

TPU covers exist, but with temperature changes, the living hinge will harden so the cover tries to stay closed or will be too floppy and get in the way.

To fix these issues, I’ve designed a simple TPU cover that relies on geometry to stay open and to stay closed, regardless of temperature. The bottom shape on the cover is made up of arcs and lines that together have the same perimeter as the circumference of the cap. When it is placed on the scope, the TPU is flexed into a circle. This circle overlaps where the cap is. This overlap acts as a catch to keep the cover opened or closed. To open, simply pop the cap past the ring, and it will stay open. To close, pop it past the ring again and the cap will stay closed. 

To properly size, use a set of calipers to measure the outside diameter of whatever scope/binocular/camera lens you are making this for. Then open the .f3d file in Autodesk Fusion 360. Select the “Modify” drop down menu. Select the “Change Parameters” option from the bottom of the menu. In the window that pops up, input your measured diameter. It is preset in inches, but if you use a different unit simply specify with the measurement (for example, type 50mm). The model will automatically adjust to your inputted measurement and you can export it as STL or 3MF and print it. 

If you do not have access to Fusion 360, comment your measured diameter with the units used and I’ll upload one that size.

To 3D print, use TPU and 100% infill. Ensure the “avoid crossing walls” or your slicer’s equivalent is selected. Orient the file flat and do not use supports. Prints quickly with no waste.