Originally Posted by
tomtomtom123
I don't think ferrules if made by FDM from plastic filament would be stable enough to resist repetitive braking. There are air gaps between layers and lines of extruded filaments. The gaps would eventually compress resulting in misalignment. If you're using shift cable housing that's a bundle of steel wires, if there's a wire longer than the others it may poke a hole through the ferrule.
It's possible, and I do have a jar of 500 brass ferrules for brakes, but scaled some for that purpose while I was at it. I print mostly with petg cf for functional parts and would be surprised if the ferrule even on a brake cable could fail in any way that would cause any danger. It seems like any failure mode would be more akin to gradual housing compression, candle stretch etc. but I could be wrong