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Rolled Throughput Yield (RTY) Six Sigma Black Belt Presentation

Rolled Throughput Yield (RTY) Six Sigma Black Belt Presentation. 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. What is Rolled Throughput Yield?.

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Rolled Throughput Yield (RTY) Six Sigma Black Belt Presentation

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  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!

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