The beautiful enclosure of the Prusa Core One is not as airtight as it could be and if you have LEDs installed inside air and light will vanish through the corner gaps where the steel profiles come together.
Others have addressed this already but I wanted to design the caps so that they match the optic of the Core One Enclosure with as less material as possible. No chunky pyramids on top of each corner. 

I designed small caps or brackets that close these gaps in the corners by adding only minimal material to the enclosure. They snap on with little hooks at the end of each arm. Thus PETG is recommended to use as filament with some flexibility. PLA or PC may be too brittle for this. 

For better visibility the prototype is printed in orange. If printed in black PETG these corner caps blend well with the silhouette of the Prusa Core One enclosure and are close to invisible.

Because of the complex geometry of these caps supports are inevitable to print them. I tested a lot of orientations on the build plate to print the caps in a way they look nice and get the necessary sturdiness for the purpose. The orientation of the layer lines is crucial to avoid breaking the caps when flex stress is applied if installing them. This upright orientation together with organic supports worked best for me.

To install the caps just put them on the referring corner with one arm’s hook in the corresponding gap and press onto the center of the triangular cap until the other two hooks snap into place and the cap sits firmly on the corner.

As tolerances for this model are low and in case the cap does not snap into place as intended or if you want better sealing you may use some glue to fix the caps. I recommend 7mm black hot glue sticks (that’s what I used) because they seal very good and can be removed without residues if you want to deinstall the caps. 

The temperatures of the metal parts of the frame are not above 70°C even if printing Polycarbonates. So hot glue is safe to use here. Otherwise you would not be able to touch the surface of the enclosure when printing high temperature materials. :-)
 

Please show me your printing results and send me fotos of your makes. I like to see how you use this model. If you have ideas for improvement don’t hesitate to send them to me in the comments.   I will try to incorporate your suggestions and will modify the model for special needs if you ask me to do so. 

And of course a like ♥ or a rating ⭐ of the design are always welcome. 

happy printing, 
clamikra