rolled throughput yield (rty) six sigma black belt presentation
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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?. - PowerPoint PPT PresentationTRANSCRIPT
Dave Dortman920-207-1648
Rolled Throughput Yield (RTY)Six Sigma Black Belt Presentation
Define Measure Analyze Improve Control
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
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Define Measure Analyze Improve Control
• 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.”
What is Rolled Throughput Yield?
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Define Measure Analyze Improve Control
The Hidden Factory AKA “Classic Yield”
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StartedScrappedStartedNumber
StartedNumber Shipped
NS Y is Yield Classic
Rework
Scrap
Operation InspectionN S
Rework “The Hidden
Factory”Classic Yield does not account for
rework
Define Measure Analyze Improve Control
Rolled Throughput Yield (RTY) Calculations
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Inspection
Rolled Throughput Yield, RTY:
Rework
N S
steps process ofnumber N free)(defect yieldpassfirst FPY
FPY FPY FPY FPY RTY N1
Scrap
Operation Inspection
Rework
Scrap
Operation
FPY includes no defects
Rework accounts for differences
between Classic Yield and RTY
Define Measure Analyze Improve Control
Rolled Throughput Yield (RTY)
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Receiving Inspection:First Pass Yield #1 = 0.955
Machining Operations: First Pass Yield #2 = 0.970
Finishing Operations:First Pass Yield #3 = 0.944
RTY = FPY1 x FPY2 x FPY3
RTY = 0.955 x 0.970 x 0.944 = 0.875PartsReceiving
For every 1,000 parts received, only 875
reach this point without rework
Dollars lost to rework and scrap
Define Measure Analyze Improve Control
• 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 ProcessAmount of Material Entering Process
• No! It is an overall yield of scrapped product, it ignores rework.
Why is RTY important?
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Define Measure Analyze Improve Control
Defective Units versus Defects per Unit
• If you can count the number of defective units after each process step, then you can calculate RTY as
RTY = 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 approximation
FPY = e-dpu
where dpu is the average defect per process step
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Define Measure Analyze Improve Control
Rationale for e-dpu
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.
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Mr. Poisson
Define Measure Analyze Improve Control
e-dpu provides a good approximation!
Yield DPU0.955 0.0450.97 0.030.944 0.0565
Total DPU 0.131RTY87.72%
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RTY = FPY1 x FPY2 x FPY3
RTY = 0.955 x 0.970 x 0.944 = 87.45%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.
Define Measure Analyze Improve Control
Braun is Batting .500 !!!
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• 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.
Define Measure Analyze Improve Control
Variation, Rework, and Scrap
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The goal of Six Sigma is to eliminate rework and
scrap by eliminating variation!