A mid-sized manufacturer ran its production planning on the official ERP, on paper. In practice, the planning happened in a set of spreadsheets that one planner had built years earlier and everyone had come to depend on. The ERP held what was supposed to be true; the spreadsheets held what the floor actually did. Over time the spreadsheets won, and they became the system of record by default — undocumented, unbacked-up, and understood by a single person.
The risk was concentrated in one place. The formulas had grown subtle over the years, copy-paste errors crept in unnoticed, and a corrupted file or a planner’s resignation would have taken real operational knowledge with it. Leadership knew this and had asked, more than once, for people to stop. People did not stop, because nothing else did the job.
The challenges we had to solve
- The genuine logic lived inside spreadsheet formulas that had never been written down or reviewed.
- People relied on the spreadsheets precisely because they were faster and more forgiving than the ERP screens.
- Any replacement had to fit the floor’s pace, or it would be abandoned for yet another spreadsheet.
- The change touched one person’s territory, so trust mattered as much as the software.
How we approached it
The first job was archaeology. We worked through the spreadsheets with the planner who built them, recovering the rules they encoded and, just as important, the ones that were really mistakes the team had learned to live with. We were careful to keep what was deliberate and to flag what was accidental, rather than faithfully reproducing every quirk. Only then did we scope a focused application that did this one job well instead of trying to fold it into the wider ERP.
We built it in increments and let the planner keep the spreadsheets running beside the app until the numbers matched and the new screens felt quicker for the common tasks. Where the app needed real data from the ERP, we connected the two so figures were not keyed twice. Once it was trusted, we retired the spreadsheets deliberately, and we wrote down the planning rules so they were no longer locked in one file and one memory.
Where it stands
Planning now happens in something the company owns, can back up, and can hand to a new person without a week of nervous explanation. The rules are visible rather than buried in formulas, and a single corrupted file is no longer a serious business risk. The planner who built the original spreadsheets helped shape the replacement, which is part of why the floor accepted it.