rolled throughput yield (rty) six sigma black belt presentation

Dave Dortman920-207-1648

[email protected]

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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• 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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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


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


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


• 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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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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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


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.


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.

Dave Dortman920-207-1648

[email protected]

Questions ???


Variation, Rework, and Scrap

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The goal of Six Sigma is to eliminate rework and

scrap by eliminating variation!

rolled throughput yield (rty) six sigma black belt presentation

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