Why High Yield Doesn't Always Mean Profit
Some plants report a 99% final yield and still struggle to make money. Final yield only counts units that ended up good. It makes no distinction between a unit that passed the first time and one that was touched two or three times. The metric that exposes the difference is First Pass Yield (FPY).
If four processes each run at 95% FPY, the cumulative figure is 0.95 multiplied four times, or about 81.5%. Even with a reported final yield of 99%, roughly 18 out of every 100 units were handled again at least once somewhere on the line. That gap is often called the "hidden factory."
Designing Routing That Treats Rework as a Process
The starting point is to put rework into the MES routing as a formal operation rather than an exception.
Disposition paths after a defect
When a unit is rejected, define four dispositions, each with its own next step.
Linking work orders and limiting rework
Issue a dedicated rework order that references the original work order as its parent. The original order's results stay clean, and the labor and material spent on rework are collected separately. Add two rules on top of that.
What to Record
The more fields you ask for, the more the shop floor avoids entering them. These are the essentials.
Once lot- and serial-level history is tied to shipment records, you can see immediately which customer received units that went through a given rework, and when.
For scrap, timing is what matters. If parts have been physically discarded but remain in inventory, counts will not reconcile. If scrap is posted in bulk at month end, the loss lands in a different period from the one in which it occurred. Design the flow so that inventory deduction and loss posting happen at the moment scrap is approved.
Using the Data to Reduce Rework
As records accumulate, the location of the loss becomes visible.
Rollout Sequence and the POLYGLOTSOFT Approach
Applying this to every operation at once tends to provoke resistance on the floor. We recommend the following order.
POLYGLOTSOFT MES provides defect registration, disposition branching, rework orders, and lot traceability as its foundation. Routing rules and approval flows that match your process, along with ERP and accounting integration, are delivered through custom development. If you want to see the rework cost hiding behind your yield figure, contact POLYGLOTSOFT. We will work with you from shop-floor assessment through pilot deployment.