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What You Need to Know About Quality Control and Quality Assurance

Let’s pretend you’re working at your desk on a sunny Tuesday morning. You’re in the middle of an important meeting, and all of the sudden, the desk falls apart. The legs slide out and your laptop, notes, and coffee cup go flying. It’s a mess.

That’s not how you expected to start your Tuesday, right?

The desk wasn’t built to quality standards, and as a result, it completely ruined your Tuesday. Quality is a very important part of manufacturing, and if the manufacturer had adhered to quality standards, you wouldn’t be cleaning up spilled coffee muttering expletives under your breath.

In this blog, we’ll talk about quality.

  • What is quality and why is it important in manufacturing?
  • What is the difference between quality assurance and quality control in manufacturing?
  • How do you measure quality? What are important quality KPIs?
  • What are best practices for maintaining quality?

As we learned in your disaster of a Tuesday morning, quality control in manufacturing is important. When products are made to quality standards, they are safe, efficient, and reliable.

What is Quality and Why is it Important?

Quality often means different things to different people. Google the definition of quality and you’ll get many, many different answers. For simplicity purposes, we will define quality as:

Quality: Meeting or exceeding customer expectations

If the desk you bought to do your job doesn’t fall apart during a Tuesday meeting and causes your coffee to spill all over the floor, then the desk is meeting quality standards and meets or exceeds your customer expectations, right? Correct.

In manufacturing, there are certain quality standards that need to be met.

Quality Assurance vs. Quality Control in Manufacturing

Quality assurance and quality control are often used interchangeably in manufacturing, but they are not the same. Quality control (QC) is a part of the larger ecosystem of quality assurance (QA). QC and QA are a part of the entire quality control system.

Here is how the American Society for Quality defines quality assurance and quality control:

Quality Assurance is defined as quality management focused on providing confidence that quality requirements will be fulfilled.” The confidence provided by quality assurance is twofold—internally to management and externally to customers, government agencies, regulators, certifiers, and third parties. An alternate definition is “all the planned and systematic activities implemented within the quality system that can be demonstrated to provide confidence that a product or service will fulfill requirements for quality.”

Quality Control is defined as “part of quality management focused on fulfilling quality requirements.” While quality assurance relates to how a process is performed or how a product is made, quality control is more the inspection aspect of quality management. An alternate definition is “the operational techniques and activities used to fulfill requirements for quality.”

Quality assurance is the ecosystem for maintaining quality whereas quality control is a subset, the reactive component at the end of production that ensures products are meeting standards during the final quality inspection.

Quality assurance = quality management, processes, standards, and the training of employees.

Quality control = maintaining those processes and evaluating if products are up to standard.

Using Quality Assurance and Quality Control to Improve the Plant

It’s important to understand how objectives in manufacturing — like improved quality— can be engineered through better data. This all starts by understanding the best manufacturing quality metrics and being able to discern which levers are responsible for moving the needle on this goal. This is where quality assurance comes into play.

Quality is an essential part of OEE; which gets talked about a lot. The truth is that quality is just like availability and performance. It is all relative to the manufacturer and the goals that the particular manufacturer wants to achieve.

For some, it is clearly a more meaningful factor than others. What’s more, some may even sacrifice aspects of their quality to improve things like performance and availability. But, the truth is that it is impossible to make these decisions without accurate data or a solid understanding of the metrics that matter most to quality in manufacturing.

Manufacturing Quality Metrics that Matter

So, what are the three metrics that matter most to manufacturing quality?

Well, beyond being the most important, let’s think about which metrics might be the most helpful to understand in the context of your plant floor.

1. Manufacturing Yield

Manufacturing yield is the percentage of something that is manufactured according to the manufacturer’s predetermined specifications in the original manufacturing process (looking at you, quality control)— without producing any scrap.

This is important for understanding the percentage of time things are produced exactly how they are drawn up on the whiteboard.

Think about food manufacturing. How many boxes of cereal are lost in between? Or, if you’re filling bottles, how many bottles make it from the beginning of the line to actually packaged in a case? Are there breakage or other quality issues that happen along the way?

It’s important to have a real yield number that is consistent. Quality is an easy metric to improve. By objectively understanding yield and scrap rates, manufacturers can identify real improvements.

1.5 First Pass Yield

It may seem odd to list first pass yield as 1.5, but bear with us for just a moment. Really, first pass yield is a subset of manufacturing yield.

“First-pass yield (also known as throughput yield) is defined as the number of units coming out of a process divided by the number of units going into that process over a specific period of time. Only good units with no rework or repairs are counted as coming out of an individual process.”

To put that definition in laments terms, how many parts have to run through the system before I get a good one?

Sometimes, after a changeover, you may have to run for 5-1o minutes, producing bad parts, before the machine is fully up and running and able to produce the good parts.

2. Customer Returns

This is essentially the metric for understanding the percentage of products that the customer returns or rejects.

This could be because the product is outside of specifications, defective, or damaged.

This connects well with yield because if you’re a manufacturer with a really high positive manufacturing yield, but an abnormally high customer return rate, there is obviously some kind of disconnect with room for improvement. Better quality control standards need to be implemented and maintained.

Truthfully, the most important factor in comparing these two metrics is ensuring that the metrics are accurate to life; meaning that you are actually seeing the real numbers.

Often, the numbers will get fudged to achieve an industry-acceptable number. However, as things are looked at retroactively, it becomes clear there is a problem.

3. Supplier Quality

This is really the last variable in the equation.

Supplier quality looks at the number of goods coming from the supplier that reaches the manufacturer with an acceptable measure of quality. This means that these materials can be used effectively to produce the products.

Examples of measuring supplier quality specifically apply to metal manufacturers who use heat-treating or powder coating. Typically, you send that product out for heat treating. Does it come back with 100% quality or does it have issues?

Or, if you’re ordering components from suppliers around the globe, what percentage of those parts ordered is good?

This is the supplier quality rate.

Manufacturing Metrics Line Up

It’s very easy to see how all of these metrics are essential to get a 3-D picture of manufacturing quality.

If your data is accurate, these metrics will paint a picture of where things may be breaking down in the chain. For example, if everything is presumably good until the customer receives the products, then the rejection rate jumps up you could begin to investigate that part of the chain.

Honestly, as we discussed above, the most important factor in all of these manufacturing metrics is understanding that the source of truth of this information is accurate.

Furthermore, it’s essential that this info is reviewed regularly or in real-time. This way, manufacturers don’t miss out on the opportunity to affect these issues before they become multi-month, systemic problems. In many cases, issues in this area will persist for years and years (and are known by those on the factory floor, but never raised to management).

If you’re not leveraging a manufacturing analytics application, it can be hard to understand all of these elements properly.

If you’d be interested in giving Mingo a closer look, you can do it here.

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Bryan Sapot
Bryan Sapot
Bryan Sapot is a lifelong entrepreneur, speaker, CEO, and founder of Mingo. With more than 24 years of experience in manufacturing technology, Bryan is known for his deep manufacturing industry insights. Throughout his career, he’s built products and started companies that leveraged technology to solve problems to make the lives of manufacturers easier. Follow Bryan on LinkedIn here.