Understanding and Calculating Rolled Throughput Yield

When it comes to manufacturing, efficiency and productivity are key. One of the metrics used to measure these factors is Rolled Throughput Yield (RTY). RTY is a statistical tool that provides insight into the overall yield of a process or a series of processes. It is especially useful in situations where rework is involved. In this piece, we will delve into the concept of RTY, how it is calculated, and its significance in a manufacturing context.

Concept of Rolled Throughput Yield

The Rolled Throughput Yield (RTY) is a measure of the probability that a single unit can pass through a series of processes without defects. It is a crucial metric in Six Sigma methodologies and is used to assess the effectiveness of a process or a series of processes. The RTY takes into account not only the yield at each step of the process but also the possibility of rework.

Unlike traditional yield measurements, which only consider the yield at each individual step, RTY provides a more comprehensive view of the process. It takes into account the cumulative effect of inefficiencies in each step of the process, thus providing a more accurate measure of the overall process efficiency.

Significance of Rolled Throughput Yield in Manufacturing

In the manufacturing industry, the Rolled Throughput Yield is a critical measure of process efficiency. It helps identify areas of the process that are causing defects or inefficiencies, thus providing opportunities for improvement. By improving the RTY, manufacturers can increase their overall productivity and reduce waste.

Moreover, the RTY is particularly useful in situations where rework is involved. Rework is a common occurrence in manufacturing, where defective products are corrected or repaired to meet the required standards. The RTY takes into account the possibility of rework, thus providing a more accurate measure of the overall yield.

How to Calculate Rolled Throughput Yield

The calculation of Rolled Throughput Yield involves multiplying the yield at each step of the process. The throughput yield at each step is the ratio of the number of units that pass the step without defects to the total number of units that entered the step. The formula for RTY is as follows:

RTY = Π (throughput yield at each step)

Where Π represents the product of the throughput yields at each step.

Example of Rolled Throughput Yield Calculation

Let's consider a manufacturing process that involves three steps. In the first step, 95 out of 100 units pass without defects but with 5 due to rework. Thus the throughput yield is 0.90 (90/100). Recall that throughput yield excludes reworked units.

There are now 95 units that enter the second step. In this step, 74 units pass on the first attempt with 10 more units being reworked. Therefore 74 out of 95 units pass without defects first time round, thus the throughput yield is ~0.78.

In the final step we have 84 units entering the process. If 62 units pass on the first attempt with 15 units being reworked, then the yield is ~0.74.

Using the formula for RTY, we get:

RTY = (90/100) (74/95) (62/84) = 0.51744

This means that the overall yield of the process, taking into account the possibility of rework, is approximately 51.74%.

Improving Rolled Throughput Yield

Improving the Rolled Throughput Yield involves identifying and addressing the sources of defects or inefficiencies in the process. This can be done through various methods such as process mapping, root cause analysis, and process improvement techniques.

Moreover, the use of Six Sigma methodologies can be particularly effective in improving the RTY. Six Sigma provides a structured approach to process improvement, with a focus on reducing variability and eliminating defects.

Conclusion

The Rolled Throughput Yield is a powerful tool for assessing the efficiency of a process or a series of processes in manufacturing. By taking into account the yield at each step and the possibility of rework, it provides a more accurate measure of the overall yield. Understanding and calculating the RTY can help manufacturers identify areas for improvement, increase productivity, and reduce waste.