Roof Rack Rail Endcaps

My son managed to get a pair of OE roof racks from a salvage yard for his 2003 VW Jetta, but they didn't have the endcaps. He asked me to design a set for him that could be 3D-printed, so this is what I came up with. These also make use of <a href=https://www.amazon.ca/dp/B0CZL686L9>a set of lock cylinders that I found on Amazon</a>. I've never had the OE endcaps to go off of, so I designed these from scratch strictly with the rails available at my disposal.

Here's a quick video that shows the cap being slid on and use of the keyed cylinder to lock it in place: https://youtu.be/gNnbCHxs3no

I printed a prototype using PLA, but for production, you'd probably want to use something like ABS. I don't have a set-up to allow me to do that, so I'll see if a friend can do that for us. I'd recommend getting close to 100% infill just to give it rigidity -- at that density, each endcap assembly will use up around 90g of filament (so assuming you print a set of 4, that's around 400g).

I found that printing the "lower" portion was best done with it up on end, with a wide brim for bed adhesion, and supports (using Tree Supports worked well for me). The guide bar and the "upper" portion can just be printed as provided, with no supports. I aimed for 0.12mm layer heights to "smooth out" the arcs as much as possible, but you can use whatever layer height makes sense to you. The guide bar is meant to just fit into the upper part and be secured by friction. Using a mallet to get the parts to mate permanently gave me great results. The lower and upper parts can be glued together if you wish, although I found it wasn't totally necessary.

Standard FDM printing settings:
- Layer height: 0.2mm
- Infill: 70%
- Supports: As needed