I've chosen this size of ring so that it doesn't interfere with the fan of the E3D V6 hotend.
The ring snaps only at 3 places. Making it very easy to install/remove from the case.
BOM:
(x1) 80mm COB LED Light Ring. Outer Diameter 79.35mm, Inner Diameter 70.65mm
I think this one is the same: http://www.aliexpress.com/store/product/Free-Shipping-Super-Bright-COB-LED-Angel-Eyes-DRL-Halo-Ring-Light-White-80mm/1045972_1862287928.html
(x6) Magnets. Diameter 9mm, Height 2mm
To hold it you must use standard bolts. Stainless steel ones won't work.
I've used cyanoacrylate (superglue) to paste the magnets to the case.
80MM_LED_Ring.3dm | 734.7KB | |
80mm_LED_Ring.stl | 2.0MB |