First pass yield

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First pass yield(FPY), also known as throughput yield(TPY), is defined as the number of units coming out of a process divided by the number of units going into that process over a specified period of time. [1] Only good units with no rework or scrap are counted as coming out of an individual process.

Also related, "first time yield" (FTY) is simply the number of good units produced divided by the number of total units going into the process. First time yield considers only what went into a process step and what went out, while FPY adds the consideration of rework.

Consider the following:

You have a process that is divided into four sub-processes: A, B, C and D. Assume that you have 100 units entering process A. To calculate first time yield (FTY) you would:

  1. Calculate the yield (number out of step/number into step) of each step.
  2. Multiply these together.

For Example:

(# units leaving the process as good parts) / (# units put into the process) = FTY

The total first time yield is equal to FTYofA * FTYofB * FTYofC * FTYofD or 0.9000 * 0.8889 * 0.9375 * 0.9333 = 0.7000.

You can also get the total process yield for the entire process by simply dividing the number of good units produced by the number going into the start of the process. In this case, 70/100 = 0.70 or 70% yield.

The same example using first pass yield (FPY) would take into account rework:

(# units leaving process A as good parts with no rework) / (# units put into the process)

First pass yield is only used for an individual sub-process. Multiplying the set of processes would give you Rolling throughput yield (RTY). RTY is equal to FPYofA * FPYofB * FPYofC * FPYofD = 0.8500 * 0.8889 * 0.8125 * 0.8267 = 0.5075

Notice that the number of units going into each next process does not change from the original example, as that number of good units did, indeed, enter the next process. Yet the number of FPY units of each process counts only those that made it through the process as good parts that needed no rework to be good parts. The calculation of RTY, rolling throughput yield, shows how good the overall set of processes is at producing good overall output without having to rework units.

See also

A business process or business method is a collection of related, structured activities or tasks by people or equipment which in a specific sequence produce a service or product for a particular customer or customers. Business processes occur at all organizational levels and may or may not be visible to the customers. A business process may often be visualized (modeled) as a flowchart of a sequence of activities with interleaving decision points or as a process matrix of a sequence of activities with relevance rules based on data in the process. The benefits of using business processes include improved customer satisfaction and improved agility for reacting to rapid market change. Process-oriented organizations break down the barriers of structural departments and try to avoid functional silos.

Design for Six Sigma (DFSS) is a business process management method related to traditional Six Sigma. It is used in many industries, like finance, marketing, basic engineering, process industries, waste management, and electronics. It is based on the use of statistical tools like linear regression and enables empirical research similar to that performed in other fields, such as social science. While the tools and order used in Six Sigma require a process to be in place and functioning, DFSS has the objective of determining the needs of customers and the business, and driving those needs into the product solution so created. DFSS is relevant for relatively simple items / systems. It is used for product or process design in contrast with process improvement. Measurement is the most important part of most Six Sigma or DFSS tools, but whereas in Six Sigma measurements are made from an existing process, DFSS focuses on gaining a deep insight into customer needs and using these to inform every design decision and trade-off.

Rolled throughput yield (RTY) is the probability that a process with more than one step will produce a defect free unit. It is the product of yields for each process step of the entire process.

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References

  1. "Throughput Yield, TPY". six-sigma-material.com. Retrieved 2014-02-18.