Lean training courses discuss yield as a measure for the quality of a process. Six Sigma considers yield an important term. There are two types: first pass yield, or FPY, and rolled throughput yield (or RTY). Free Lean Six Sigma training discusses whether FPY is better than RTY. This article compares the rolled throughput yield and first pass yield. It also explains how to calculate each method using the Six Sigma approach.
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We will be looking at the following sections to learn more about Yield, also known first-pass yield metric in Lean Six Sigma.
Definition and meaning of yield
First-pass yield or Throughput yield
Illustration – FPY
RTY – Formula and Illustration (Method 1
RTY – Formula and Illustration (Method 2).
Definition of Yield in LEAN
Let’s discuss one of the key metrics for LEAN methodology. It is the concept yield. LEAN yield, also known as first pass yield or throughput yield, is simply the ratio between the number of units produced and the number of units that enter the process. This is a reminder of the concept of ‘unit’. A unit is any item being processed.
There are two types of yield
First-pass yield (FPY).
There are many ways to define yield. You can also refer to it as types. The first is the first-pass yield, also known as FPY. It is also known as the first-time yield, or throughput yield. It is a unit-based metric. The downside of the first-time yield is it does not account for scrap products with multiple defects. This is because the calculation takes place after an “inspection” to determine if a unit is safe or not.
Let’s take a look at an illustration of the first-time yield and throughput yield formula. We will be looking at the email response process of a BPO company that acts as a service provider for Utilities and Energy companies. We are looking at the total number of emails, i.e. A team of customer service representatives responded to the email at 550. All emails were quality checked before being sent to customers. 203 emails were found to have numerous errors or defects during the quality audit. Out of the 203 emails, 190 were reworked as part of the correction exercise and returned to the email queue. 13 emails were not received by the customer because they were not well-received.
This would give us the first yield or throughput yield formula. It would be 347 divided with 550. This gives us 0.630, or 63.09%. How did we get to 347? It is the sum of 550 (total amount of emails) and 203 (defects). To count the emails that were sent to customers, we subtract the number (13) from the total number.
Let’s now talk about the concept of rolled throughput yield. RTY is the acronym. What does RTY mean? RTY is a measure for the overall quality of a process. It is a summary of DPMO data for a product or process by multiplying each step’s DPMO. The preferred yield calculation method is the rolled-throughput yield, which is superior to the first-pass yield.
RTY is the lower yield of any one process. Each process step will always have a minimum or maximum yield. The RTY decreases exponentially as the number of steps increases.
Let’s take a look at RTY as an illustration. We’ll be discussing two formulae to calculate RTY. Let’s take a look at the second one.
Illustrations of RTY
First method to calculate RTY
In this example, there are 5 steps. Each step has its own input units and output units. Input units are those that enter each step of a process, while output units are the good units that each step produces. We can get the first pa with the help of a formula.