3D printable spring-loaded scope cap

This repository contains the 3D printable files for a spring-loaded scope cap for scopes, red-dots and magnifiers. The scope cap is designed to protect the lens of your scope from scratches, dust, and other debris when not in use.

The cap is fully parameterized, so you can make it fit to whatever optic you have.

I've included exported versions for the Holosun 503r and Holosun Magnifier HM3X (as pictured).

Requirements

Tools

• Calipers
• Wire cutters
• 3D printer

Materials

Spring

You will require some sort of torsion spring. This can be a hard part to source. The easiest and cheapest solution for me was to buy these miniature clothes pin at a craft store, take out the spring and bend it into shape.

All you need to do is bend one of the legs outwards. This is the required shape in the end:

Pin

You will also need a pin to hold the optic together.

I suggest using 1mm copper wire.

You can also use any other thick wire you have. Just set the `pindiameter` accordingly (see Customize).

Printing

Print the ring mount first. If it is too tight or too loose, edit the `diameter` (see Customize) and try again. Once it fits you can print the cap with the same diameter.

Print settings

I tried printing this in various different materials, but overall regular PLA works the best.

Recommended Settings:

• Material: PLA
• Layer height: 2mm
• Nozzle: 0.4mm
• Infill: 100%

Assembly

1. Insert the torsion spring into the ring mount.

2. Bring the parts together and push the pin wire through. Cut the pin flush. The pin will not need to be perfectly straight. If it is a little crooked it will even hold together better.

Customize

To get a custom cap for your particular optic, open `scope-cap.FCstd` with Freecad. Open the Spreadsheet from the sidebar.

The yellow fields are the fields you can change (the ones next to it are just for reference). The most important value is the inner diameter. Measure your optic with calipers and enter the value (using millimeters).

You can also edit the height of the mount. Depending on how much or how little space you have on your optic.

Depending on what kind of spring (see chapter Spring) you have you'll also have to set the parameters for it in the lower (wire) part of the spreadsheet. This can be a bit complicated, but again, calipers help here.

You can also set the diameter of your pin here (`pindiameter`).

After you've finished editing the parameters. Click on and export (`File->Export`) each of the two shapes. One is the cap and one is the ring mount.

Troubleshooting

It is too loose, too tight

Adjust the `diameter` accordingly.

It is too hard to open / It won't stay closed

Adjust the `outerslack` parameter. Increase the value slightly to loosen it and decrease the value to tighten it.