“Garbage in, garbage out.”
That’s the mantra commonly ascribed to computer scientists and software engineers to describe how low-quality data impacts the software development process.
The same concept applies to manufacturing in the context of layered process audit (LPA) questions. Layered process audits are a high-frequency audit strategy aimed at ensuring process inputs comply with work standards, as opposed to trying to identify defects after production.
When it comes to LPA questions, creating a generic plant-wide checklist and adopting a “set it and forget it” approach doesn’t deliver meaningful data. Instead, manufacturers must invest time in the process, collecting input from quality, engineering and plant leadership to ensure questions are relevant and provide real value.
In other words, the effort you put into writing LPA questions determines the quality of data they ultimately provide.
With that in mind, this post looks at 7 generic LPA questions that don’t work, and how to fix them for more meaningful results.
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Anatomy of a Good LPA Question
Before diving into the questions, it’s worth examining the elements of strong LPA questions. A good LPA question is:
- Specific: Questions should be specific to the process, clearly stating the criteria or specifications required for verification and avoiding subjective terms such as 'properly' that are open to interpretation or require additional knowledge.
- Objective: LPA questions should be easily answered with a yes or no based on the question and any additional supporting criteria provided.
- Clear: LPA auditors come from every area of the organization, making it essential to avoid jargon and abbreviations that someone unfamiliar with a specific area would not know.
Given these considerations, let’s take a look at some real-life examples of ineffective questions and how to fix them.
1. Is the operator following the job instruction?
This question doesn’t specify what the job instruction even is. Nor does it address the real issue behind it, which is whether the operator understands the job instruction.
Better versions of question could be:
- Can the operator explain or demonstrate each step in the job instruction?
- Is the operator following each step in the order outlined in the work instructions?
If using an electronic LPA platform, you could even link to the most up-to-date version of the document for the auditor to reference.
2. Are quality alerts posted?
LPAs involve auditors from every area of the organization. It’s unlikely non-experts from another department would even know where to look for quality alerts, which are critical for keeping focus issues front-and-center for operators.
To fix this question, auditors might instead ask the operator to show where quality alerts are posted, or demonstrate how their work relates to the quality alert.
3. Is the gauge calibrated?
Someone from another department might only conduct one LPA per month. That means the person is going to walk up to a machine that, to them, looks like a helicopter with 20 different gauges. This question should be more specific, clearly stating:
- Which gauge needs to be calibrated
- What the specifications are
- The tool used to calibrate the machine
4. Does the operator know the quality policy?
The real question here is not whether the operator can recite the quality policy, but whether he or she is applying it. Improved versions of this LPA question could include:
- Can the operator describe how the process affects quality?
- Can the operator describe how their work impacts the customer?
5. Are all materials at the work station?
This question isn’t specific and requires expert-level knowledge of which materials are required at the work station. To improve this question, it should include a list of the specific materials needed. Ideally, you would also attach photos of those materials so auditors can quickly see if anything is missing.
6. Is the operator wearing PPE?
An auditor from sales may have no idea that PPE stands for personal protective equipment. What’s more, the question doesn’t describe the specific type of PPE required.
At an electrical station, for example, a better question would be whether all operators are wearing dielectrical boots, safety goggles and hearing protection. If you’re using an automated LPA system, you could even attach photos of the required PPE for more clarity.
7. Is the first piece properly made?
This question is problematic due to its non-specific nature, and the fact that “properly” is a term subject to interpretation.
Instead, you might have auditors ask whether the first piece been measured to a specific dimension on the spec sheet using a specific caliper or other tool.
A Quick Recap
As you write your LPA questions, you want to make sure each one is specific, objective and clearly understandable by non-experts. The result will be highly relevant questions that look like the following:
- Does the part number on the routing ticket match the part number on the controller display?
- Is the operator loading parts using the nylon rollers, avoiding metal to metal contact?
- Does the temperature readout for the adhesive show a value between 101.9 and 107.5 Fahrenheit?
Regularly updating and refining questions is also key to getting good data, adding questions based on complaints, process failure mode and effects analysis (PFMEA) and corrective actions. Ultimately, a well-asked question is 80% answered because it’s so specific that only a small amount of information is necessary to verify process compliance. Achieving these objectives takes time—and an LPA system that makes it easy to make adjustments as you go.