iSixSigma

First Time Yield (FTY)

Definition of First Time Yield (FTY):

The purchasing department manager left another message, informing the planning department that they once again sent over a request for a quote that didn’t contain all the information needed to place the order. 

It’s a problem that seems to keep repeating, but is it truly that impactful an issue? To better understand the situation, the true frequency of the problem must be quantified, and that’s where first time yield is used. 

An overview: What is first time yield?

First time yield, also known as first pass yield, is the percentage of the time that a product or service passes through a process step without any defects on the first attempt.

The formula is straightforward, being the number of products that pass through a step of the process without error on the first attempt, divided by the total number of products being tested. Be sure to recognize that the total number of products is different than the total number of tests run, since a single product may be tested multiple times if rework is involved.

First Time Yield = [Number of product without error / Total number of products]

For example, the planning department creates 20 quote request documents. These documents are required by the purchasing department as they contain key information needed to reach out to the suppliers and acquire a quote. 

It turns out that four of the requests contain incorrect data, requiring the purchasing department to return the documents back to the planning department for rework. Sixteen quote request documents have correct information the first time they pass through the step. Using the formula, we take the 16 documents that passed the first time and divide this number by 20, the total amount of requests, arriving at an 80% first time yield.

3 benefits of attending to first time yield

Having the data regarding first pass yield will help you understand where your process stands on the issue of quality.  It helps you understand where you are and quickly puts a spotlight on issues that need to be addressed to get to the next level of quality.

Great measure of efficiency

First time yield is a very easy metric for all members of the team to recognize. If a product doesn’t pass, there is an issue tied to why it didn’t pass. This data is easy to communicate and is often used as part of overall efficiency calculations, such as OEE (overall equipment efficiency).

Identifying areas of improvement

Yield information in general is how we hunt down inefficiencies due to quality. First time yield, along with throughput yield, are key metrics used to determine where the quality issues are occurring, and their impact to the system. 

Looking at the lowest first time yields within a larger process will point you in the right direction on where the largest opportunity for improvement can be found. Identify and analyze these steps first, utilize a pareto chart to identify the largest contributors to the lower than desired first pass yield, and work hard on eliminating or minimizing these issues.

Allows for rapid identification of issues

It is typically easier to measure first time yield than other metrics. Metrics that are easier to measure can also be easier to identify more quickly, allowing for a faster reaction. Automatic data collection systems are common and may even be capable of collecting lower-level data that can point towards key impacts.  

3 best practices for first pass yield

  • Remember that even if a single first time yield appears high, when you take the multiple steps that have yields and calculate the throughput yield, the overall process may have a poor rolled throughput yield. Always strive to get your first time yield as high as possible.
  • Be wary of automated data collection systems. These systems can be a great source of yield information, assuming data fidelity, but many do not collect the level of data that will be useful to help determine the root cause of the yield issues. Even with this data at your fingertips, be sure to visit the area where the work is performed. Watch the process and discuss known issues with the personnel performing the work on a daily basis.
  • Be sure to frequently revisit first time yield, as well as your other yield metrics. Great measurements can turn into poor measurements very quickly, and the time it takes to identify and address the impact on yield is time that will cost you in time, money, and possibly your reputation with your customers.

Frequently Asked Questions (FAQ) about first time yield

Is first time yield all I need to help determine my rework costs?

First time yield is a good way to detect possible issues, but by itself, it does a poor job of identifying if a product is requiring multiple rework cycles, is repaired the first time, or is repaired multiple times. Utilize test yields, which factors in the number of times a test is performed per group of products with your first time yield percentage — this will help you get a clearer picture as to the total rework costs.

What is the difference between first time yield and throughput yield?

First time yield measures the ability for a product or service to pass a step of a process on the first attempt, while throughput yield measures the ability of a product or service to pass an entire string of steps that make up the process on the first attempt. It is possible to have high first time yields at most or all individual steps, yet have a much lower throughput yield for the entirety of the process.

How often do I need to check my first time yield data?

This is difficult to answer since different systems have different levels or required quality, but as a rule, first pass yield should be checked as often as your systems allow. The point of the metric is to help you identify quality issues as quickly as possible, so that you can address them as quickly as possible. There are some systems where a dip of 5% to 10% in yield can lead to wasted money, affect on-time delivery, and result in unhappy customers. Other systems may not feel the pinch of the poor quality for weeks or months. It is only to your advantage to check your yield information regularly — daily whenever possible.

First time yield is a great metric to identify the health of the steps in a process

First time yield is an easy metric to calculate and communicate to your team, allowing for quick response time to quality issues. When used in conjunction with other yield metrics, it is useful in gaining a clearer picture of the overall efficiency of your operation.

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