Rolled Throughput Yield (RTY) Six Sigma Black Belt Presentation

1. Rolled Throughput Yield (RTY)Six Sigma Black Belt Presentation

2. What do we need to know about RTY? • What is RTY and why is it important? • The “Hidden Factory” • How to calculate RTY • How to estimate RTY using e-dpu

3. What is Rolled Throughput Yield? • Rolled Throughput Yield (RTY) is the product of the observed yields from each step in a process. It is the probability of a unit passing through all steps of a process and incurring no defects. • RTY shows the effect of variation on both rework and scrap. • Rework is known as the “Hidden Factory.”

4. The Hidden Factory aka “Classic Yield” Operation Inspection N S Rework “The Hidden Factory” Rework Classic Yield does not account for rework Scrap

5. Rolled Throughput Yield (RTY) Calculations Operation Inspection Operation Inspection S N Rework Rework FPY includes no defects Scrap Scrap Rolled Throughput Yield, RTY: Rework accounts for differences between Classic Yield and RTY

6. Rolled Throughput Yield (RTY) RTY = FPY1 x FPY2 x FPY3 RTY = 0.955 x 0.970 x 0.944 = 0.875 Parts Receiving Receiving Inspection: First Pass Yield #1 = 0.955 Machining Operations: First Pass Yield #2 = 0.970 Finishing Operations: First Pass Yield #3 = 0.944 Dollars lost to rework and scrap For every 1,000 parts received, only 875 reach this point without rework

7. Why is RTY important? • Measures the percent of product that goes through the process without being scraped or reworked. • Reworks within an operation have no value and comprise what is termed “The Hidden Factory!” • Is the yield calculated below a RTY? Yield = Amount of Material Exiting Process Amount of Material Entering Process • No! It is an overall yield of scrapped product, it ignores rework.

8. Defective Units versus Defects per Unit • If you can count the number of defective units after each process step, then you can calculate RTY asRTY = FPY1 x FPY2 x FPYNN = number of process steps • If you can only count the number of defects after each step, then you must estimate the Frist Pass Yield using the Poisson approximationFPY = e-dpuwhere dpu is the average defect per process step

9. Rationale for e-dpu Mr. Poisson Based on the Poisson distribution Y = e–dpu “e” is a constant 2.718281828…The natural log (ln) of this constant is 1. If the number of defects per unit is known, RTY can be calculated.

10. e-dpuprovides a good approximation! Y = e–dpu Y = Yielde = 2.718281828…dpu = defect per unit In Microsoft Excel, the EXP function returns e raised to the nth power, where e = 2.71828183. RTY = FPY1 x FPY2 x FPY3 RTY = 0.955 x 0.970 x 0.944 = 87.45%

11. Braun is Batting .500 !!! • If Braun is batting .500 what does that mean? • What would a RTY of 50% indicate? • Answer: 50% of product made it through the process without being scrapped or reworked. • If RTY = 50%, how much product would be scrapped versus reworked? • Answer: We don’t know just from the single RTY number.

12. Questions ???

13. Variation, Rework, and Scrap The goal of Six Sigma is to eliminate rework and scrap by eliminating variation!