First-pass yield and rolled throughput yield, worked by station
Calculate first-pass yield, final good units and rolled throughput yield across three stations, and see why rework hides losses that station yield shows.
First-pass yield (FPY) is the share of units that pass a station the first time, with no rework. Total station yield also counts units that pass after rework. The gap between the two is the hidden factory: effort spent fixing units that should have been right.
How do you calculate first-pass yield?
For a fictional assembly station that starts 500 units, 460 pass the first test and 30 pass after rework:
| Item | Formula | Result |
|---|---|---|
| FPY | =IF(B11<=0,"",C11/B11) |
92.0% |
| Final good units | =C11+D11 |
490 |
| Scrap units | =B11-F11 |
10 |
| Total station yield | =IF(B11<=0,"",F11/B11) |
98.0% |
A report quoting 98 percent yield is correct and still conceals that 8 percent of units needed rework.
What is rolled throughput yield?
Rolled throughput yield (RTY) multiplies the FPY of each station in sequence. It is the share of units that run the whole route without any rework.
| Station | Started | Passed first time | FPY |
|---|---|---|---|
| 10 Assembly | 500 | 460 | 92.0% |
| 20 Soldering | 490 | 465 | 94.9% |
| 30 Final test | 485 | 470 | 96.9% |
RTY is 0.920 * 0.949 * 0.969, about 84.6 percent. Each station looks healthy, yet roughly 15 of every 100 units needed rework somewhere along the route.
How should the stations be linked?
Each downstream start count should equal the upstream good count, or you must account for the difference. Here station 20 started 490 units, matching station 10's good units. The first-pass yield workbook treats each row independently, so keep the chain consistent yourself.
What to do with the numbers?
Station 10 has the lowest FPY and the most rework, so start there. Rank the causes with a Pareto analysis of defects; what a Pareto chart is explains the ranking. For equipment losses rather than product losses, use the OEE calculator.