The plant ran on spreadsheets, printed sheets, and a whiteboard on the production floor. Orders moved by hand and by conversation, and the general manager walked the length of the building several times a day to find out where anything stood.

I built the system that replaced all of it: order intake, planning with batch approval, a five-stage production pipeline — assembly, welding, cleaning, painting, warehouse — inventory that separates committed stock from free stock, and dispatch by customer order rather than by batch.

The part worth touching is the operator app. Shop floor staff don't have email, so login is a four-digit PIN against the personnel table, and each station gets one screen instead of a menu.

It also holds the design decision I'm most sure about. Originally a station couldn't register pieces the previous station hadn't passed forward — clean data, clean sequence. Then welding logged 5 while the cleaning operator had already cleaned 6, and the app told her the piece on her table didn't exist. I took the lock out. What replaced it: a queue tab for batches that haven't formally arrived, the ability to claim a batch forward if you physically have it, and a soft confirmation instead of a hard block, so the gap stays visible rather than punishing the faster station. One rule survives untouched — never more than the batch total.

The link below is a working recreation of the operator screen. PIN is 1234. Company, operators and data are fictional; the real system belongs to a client. Only the cleaning station is enabled.

https://claude.ai/code/artifact/129b1eb1-33cb-4637-a66f-9c0a79c49ea0?via=auto_preview