Rolled Throughput Yield The hidden “factory” Rolled Throughput Yield

What is Rolled Throughput Yield (RTY)? RTY is the probability (%) that a single unit can pass through a series of process steps free of defects It is used to assess the “true” yield of a given process, with additional consideration given to rework and scrap RTY exposes what is often called the “hidden” side of the factory that plagues so many organizations and (sadly) is sucking profit right off their financial statements It is one of the most powerful operational metrics an organization can use to monitor its performance

How is RTY different from First Pass Yield (FPY)? First Pass Yield (FPY) simply calculates the # of good units produced / by the # of total units going into a process step, or FPY = Good Units / Total Units Rolled Throughput Yield (RTY) adds the consideration of rework and scrap – and multiplies the yields from each process step, or RTY = (FPY1) (FPY2) (FPY3)…

A Manufacturing Example PROCESS #1 – 100 parts went through this process and 84 “good” parts left this process (16 were scrapped) First Pass Yield (FPY): 84% PROCESS #2 – With some WIP laying around, 110 parts went through this process with 82 “good” parts passing (10 were scrapped and 18 were reworked) First Pass Yield (FPY): 74.54% PROCESS #3 – With even more WIP laying around this process, 138 parts were produced with 126 parts passing (12 were scrapped) First Pass Yield (FPY): 91.30%

A Manufacturing Example (continued) Since the manufacturing manager only cares about “what goes out the door” the process they would be most concerned with… is the last one, or Process #3 Process #3 yielded over 91%, so they must have had a great day, right? NOT QUITE… There are some fundamental flaws with this technique. The most obvious is the fact that they are ignoring all the scrapped / reworked parts that Process #1 and Process #2 created. This is the “hidden” factory that RTY can uncover.

How to calculate Rolled Throughput Yield (RTY) LET’S RECAP: PROCESS #1 = 84 / 100 parts and FPY of 84% PROCESS #2 = 82 / 110 parts and FPY of 74.54% PROCESS #3 = 126 / 138 parts and FPY of 91.30% SO: RTY = (FPY1) (FPY2) (FPY3)… WHEN CALCULATED: RTY = (.84)(.7454)(.913) = 57.16%

Conclusion This value (57.16%) is a more accurate representation of how this production line is performing, and takes into account the rework and scrap from all process steps More importantly, this value is our opportunity as lean and six sigma practitioners to identify the true root causes of problems and fix them permanently We must not kid ourselves into believing we are performing better than we actually are By focusing on RTY, we can be sure we stay focused on the true pulse of the organization