Lens hood with hinged cap for Sigma 10-20mm F3.5 EX DC HSM

This lens hood with spring-loaded hinged cap has two advantages over usual snap-on lens caps:
- opening and closing is super fast
- no need to worry about what to do with the cap while taking pictures.

This model is for Sigma 10-20mm F3.5 EX DC HSM wide-angle lens. The hood shape is is a copy of the original hood and it mounts using the same bayonet system, either with the cap opening up, or down. I choose the latter because it avoids having the shadow of the cap in the picture, when shooting with the sun in the back.

Instructions

The assembly requires:
- two M2 screws for the hinge (the other end of the arm is glued on the cap)
- a helical spring (I cannot provided sourcing information as I used what I had at hand). Its approximate dimensions are:
- outer diameter: 6mm
- loops inner diameter: 5mm
- length: 25 mm between loops center when the cap is closed (so the spring should be shorter to ensure that there is some tension to keep it closed)

I printed it in ABS, with 3 perimeters, and supports for the hood and arm, but I thing PETG would be stronger due to it's better layer adhesion. PLA works too, but may cause higher wear on the bayonet system. The tolerances on radii are very important for a good fit, you may need to adjust some values depending on printer / print settings.