🏗️ The Three Layers of Quality Work
Quality-related work in manufacturing can be organized into three distinct layers. Understanding this structure is the first step to understanding quality assurance correctly.
QA
Quality Assurance
Guarantees quality to the customer and market. An outward-facing activity.
QC
Quality Control
Manages and controls data within defined specifications and tolerances. An internal activity.
Inspection
Inspection
Daily inspection and measurement data collection. Raises the alarm when something changes.
These layers are not independent — each supports the one above it. Daily inspection data makes quality control possible. A functioning quality control system makes quality assurance possible.
🔍 Layer 1: Inspection
Inspection is the day-to-day work of checking products and processes. It includes post-process inspection (confirming products meet specifications), in-process inspection while lines are running, recording measurement data, and storing it as daily management records.
The most important role of inspection is not missing abnormalities. When a measurement shows early signs of change relative to the specification, detecting it early and escalating it to the quality control layer is the job.
⚙️ Layer 2: Quality Control (QC)
Quality Control means tracking how characteristics change over time against defined targets, and maintaining or correcting that state. On the manufacturing floor, control charts are commonly used to monitor how daily measurement data moves within the tolerance band. When a trend begins to strengthen, deciding what to do about it is the core of QC work.
| Item | Detail |
|---|---|
| Target | Characteristic values in the manufacturing process (dimensions, hardness, surface roughness, etc.) |
| Main tools | Control charts, statistical methods (SQC) |
| Criteria | Whether values remain within specification and tolerance |
| Action | Detect trend changes → investigate cause → take corrective action |
| Direction | Internal (process and product focused) |
From the floor
QC work is about stabilizing the present. The real skill is not just reacting when abnormalities appear, but catching early signs of change and getting ahead of them.
🛡️ Layer 3: Quality Assurance (QA)
Quality Assurance sits above Quality Control. It means setting a quality target for the products and services your company makes and sells — "this is the minimum level of quality we must achieve" — and then guaranteeing to the customer and market that this target is met.
Where QC manages the process of making, QA includes the judgment of whether what has been made satisfies customer requirements — and if not, whether to ship it.
Note: customer-dependent manufacturers
Companies that operate by receiving drawings from a customer and manufacturing to order (contract manufacturers) often stop at the QC layer. Because the customer defines the quality target, the manufacturer can operate without owning the QA domain. This is a common and legitimate structure — but it means QA responsibilities rest with the customer.
🏭 Mass Production Transition and QA
Quality assurance becomes especially critical at the transition from development to mass production.
🔎 QA's Role in Factory Audits
Once mass production begins, the customer's representatives may visit the factory for a quality audit. The audit verifies that the quality management system designed before production began is actually being operated as intended — that the methods established to meet the quality target are running correctly.
Audits can be demanding, and commercially difficult requests sometimes arise. But building a quality management system capable of passing a rigorous audit is one of the most meaningful differentiators a manufacturer can have.
The purpose of QC work — restated
Properly tracking and monitoring the data and phenomena surfaced through daily inspection — and stabilizing that state. When abnormalities occur, responding and restoring stability. This accumulation is the foundation that makes quality assurance possible.
🎯 The Core of QA: Defining Quality
The most important thing in quality assurance work is defining quality. This is not simply setting inspection criteria.
"Given the work we have taken on — what are we actually capable of?" Starting from that question, and from the company's overall purpose and reason for existing, you define what quality is necessary for the products and services you offer. Just because a customer says "I want this" does not mean you simply build it. You must determine — as an entire company — what needs to be achieved in the product in order to satisfy that requirement. That process is what "defining quality" means.
Example: the sports car
A customer specification arrives: "We want a sports car." Inside the company, the conversation begins — "this engine is non-negotiable," "we'll need a new powertrain," "it must remain controllable at high speed." In other words: what must the product achieve in terms of quality? Defining those requirements is where QA starts. The customer specification alone is not enough. What the product must satisfy in order to meet it must be worked out across the whole organization.
🏢 QA Within the Company as a System
A company is a system. Orders arrive. The company produces an appropriate output — a product or service — in response. The mechanisms by which this happens, operating within a defined structure, constitute the company.
Within that system, quality assurance must build both: the definition of quality, and the methods for verifying it. Defining quality alone does not finish the job. Once you decide what to build and how to build it, you must also define what the resulting state looks like — and create the means to confirm it.
🇯🇵 Japanese Manufacturing and the Future of QA
Japan developed as a nation through industry — at least through the Showa era. The modernization that began with the Meiji period drove economic growth through manufacturing. Industrial products became so widespread that manufacturing is now part of the infrastructure.
Today, the products circulating in Japan include a large proportion made overseas. The era in which Japan competed globally through manufactured goods has genuinely shifted. But the pressure is likely to increase from here.
There is a growing desire to see more companies with their own finished products — companies that own a brand and can sell it, or that have built their own supply chains and can bring new products to market. As more companies pursue their own products, the importance of quality assurance grows with them.
QA's role going forward
Developing new products requires engaging with quality assurance. "Defining quality" — and translating that into technical terms — is the key function quality assurance must perform. The more companies that want to own their own products, the more critical QA becomes.
Summary
- Quality work has three layers: inspection → quality control → quality assurance.
- Inspection is about early detection and recording of abnormalities.
- QC tracks process data (via control charts and similar tools) and stabilizes it.
- QA guarantees quality to the customer — it is an outward-facing activity.
- The starting point of QA is "defining quality" — translating requirements into technical specifications.
- Defining quality and designing the verification method must be done together.
- The complete form of QA is a loop: release → collect market feedback → feed back into design, development, and production.
- As more companies seek to own their own products, the importance of QA will only increase.