Yield metrics

There are several different yield metrics that you can use to describe the performance of your process, in terms of the percentage of good units coming out of a process.

Throughput Yield (Ytp)  

Number of good units produced divided by the total number of units going into each step of the process. Throughput Yield considers the amount of scrap and rework in a process.

For example, you have a 3-step process for producing labels. The labels are printed, laminated, then cut. You want to calculate the throughput yield at each step of the process.

1    Suppose you have 1000 labels that go into the printing process and 950 that come out acceptable. The throughput yield of the printing process is 95%.

2    The 950 labels then go to the laminating process, 800 come out acceptable. The throughput yield of the laminating process is 84%.

3    Finally, 800 labels go to the cutting process, 700 come out acceptable. The throughput yield of the cutting process is 88%.

Remember, in calculating this metric, only count what makes it through the process without rework or scrap.

Rolled Throughput Yield (Yrt)

Rolled Throughput Yield (Yrt) is the probability that a single unit can pass through the entire process free of defects. You can multiply the individual throughput yields at each process step to obtain the overall, rolled throughput yield.

Using the example above, Yrt = Ytp at step 1 * Ytp at step 2 * Ytp at step 3.

So the rolled throughput yield for the label process is 0.95 * 0.84 * 0.88 = 0.70. Overall, of the 1000 labels that entered the process, 700 labels came out as acceptable (700/1000 = 0.70).

Remember, in calculating this metric, only count what makes it through the process without rework or scrap.