Hey there! Planning your first lights-out cell is exciting but definitely comes with some hidden pitfalls that veteran engineers often discover through painful experience. Based on what I've gathered from manufacturing forums and industry insights, here are the most commonly overlooked failure points:

1. Chip and coolant management - This is the #1 killer of unmanned operations. Chips building up around fixtures, coolant levels dropping, and filtration systems clogging can bring everything to a halt overnight. Veteran engineers swear by oversized chip conveyors and redundant coolant monitoring.

2. Tool life management - Automated tool changers are great until you run out of tools. The hard lesson: you need tool life monitoring that accounts for actual wear, not just cycle counts, plus automatic tool offset adjustment and enough tool capacity to last through the entire unmanned shift.

3. Fixture and workholding failures - Parts coming loose or fixtures wearing out mid-run is catastrophic. Engineers learn to implement redundant clamping verification and regular fixture maintenance schedules that most people overlook.

4. Environmental factors - Temperature fluctuations, humidity changes, and even power quality issues that humans would notice immediately can cause subtle but accumulating problems over hours of unmanned operation.

5. Software and communication failures - Network drops, software crashes, or data corruption that would be a minor annoyance during manned hours can completely stop production when no one's there to restart systems.

The veterans' advice? Start with shorter unmanned runs (like overnight) and build up gradually. Document every failure meticulously - those 'minor' issues that happen once a month become critical when they happen at 3 AM. Good luck with your lights-out journey!