Two pallet cells run the third shift on their own. There is one person in the building, and he is not a machinist. We pulled the log for one Tuesday night to see what the cell actually did between the last operator leaving at 22:40 and the first arriving at 06:10.
The numbers
- Parts finished: 31, across four part numbers
- Pallet changes: 34
- Tool changes: 212
- Sister-tool swaps after wear alarms: 3
- Probe cycles: 62 (one before and one after every part)
- Alarms that stopped the cell: 1
The alarm
At 03:14 the probe found a bore 0.012 mm undersize on a stainless flange. The programme’s tolerance for an automatic offset correction is 0.010 mm, so the cell did what it is told to do outside that band: it parked the pallet in the reject station, logged the reading and started the next pallet. Nobody was woken up. In the morning the part was measured on the CMM, the tool was found to have chipped, and the flange was finished in one manual cycle.
Lights-out is not about running without people. It is about deciding in advance what the machine may fix on its own and what it must leave for a person.
What the operator does in the morning
Reads the log. Checks the reject station. Loads the day’s castings onto the pallets. Runs first articles for the two part numbers that change over at 08:00. The cell runs the same programmes it ran at 03:00; the difference is who is watching.
