When AQL Tables Don't Fit: Use Conditional Flows as a Workaround

This post covers the use of conditional flows to address out-of-the-norm cases in AQL inspection

Quality control in manufacturing often relies on standard procedures—but not every situation fits the mold. When exceptions occur, systems need to adapt. In this post, we explore how Conditional Flows can handle these cases with flexibility and precision.

Basic conditional logic can be implemented using simple expressions based on Material (lot) properties or attributes, addressing simple use cases, such as skipping specific Steps or determining the upcoming Flow.

For more complex scenarios, beyond the scope of expressions, Rule Sets can be used to execute advanced decision-making and control logic within the workflow.

Acceptance Quality Limit (AQL) Inspection is the process of checking a sample from a lot to evaluate the number of defects against a predefined acceptable limit (defined by the AQL standard). If the number of defects in the sample is within the acceptable limit, the entire lot passes; if it exceeds the limit, the lot is rejected.

Using the AQL inspection standards above, we can infer that for a lot with `73` units, for an Inspection Level I, the sample size code letter is `C`. Then, assuming an AQL of 1.0%, the final conclusion is that the sample size must be of 13.

🧩 Challenge: AQL relies on statistical sampling, where a portion of the lot is inspected to assess the overall quality of the entire lot. Occasionally, a lot may reach the AQL inspection stage with only one single board/wafer; either due to earlier production problems or because it comes from a very limited manufacturing run. In these cases, the standard AQL tables are not applicable for determining a valid sample size. How can the CM MES system address or work around this limitation?

The previous example shows just a glimpse of what Flow Items with conditions can achieve. These elements can operate on their own or work alongside other CM MES entities to create smarter, more flexible process control.

While the demonstrations focused on Material properties, the range of possibilities is much broader. Conditions can incorporate attributes and characteristics of materials, product and product family properties, or even specific process step data.

For more advanced needs, custom rules can be embedded directly into the flow logic. This allows the MES to route materials dynamically and apply targeted rules when lots enter or exit process steps, ensuring the right actions are taken in both standard and edge-case scenarios.

In conclusion, Conditional Flows bring the flexibility needed to handle AQL exceptions and other edge cases with ease. By adapting the process based on real-time conditions, they ensure quality control remains both efficient and intelligent.