Watching a 3D printer with Klipper and a cheap webcam
A print that fails at hour two and keeps extruding for five more is the most expensive way to make spaghetti. The fix is a camera and something that looks at it.
The camera is a discontinued 720p Logitech from a drawer. Mainsail's crowsnest handles it fine; the only setting worth changing is the resolution, because the Pi Zero 2 I run Klipper on cannot keep up with 1080p at any framerate.
The part that actually helps
Not the live view. A Home Assistant automation that takes a snapshot every 15 minutes while print_stats.state is printing and posts it to my phone. I glance at it, and if it looks wrong I pause from the notification.
I tried the automatic spaghetti detection projects. Two false positives cancelled good prints, and the one real failure got through. The 15-minute photo is dumber and better.
Also useful: a smart plug on the printer with a power monitor. When the heaters go idle for ten minutes after a print, it cuts power. The plug's history is also the closest thing I have to a print log.