When defective products occur in a factory, are they simply dismissed as due to a lack of skill on the part of the employee in charge or a simple machine malfunction? If the problem is only dealt with superficially, it won't lead to a fundamental solution, and defective products may continue to occur in the future.

Proper quality control is essential to delivering high-quality products to customers. This time, we will explain in detail how to implement quality control using the 4Ms.

1. What are the 4Ms of the production site?

4M is a term commonly used in the manufacturing industry, referring to the four elements necessary for the smooth operation of a production line and for quality control. The 4Ms of quality control are an acronym for the following four words:

・Man: Human
・Machine：Machine
・Method: Method
・Material：Material

The above 4Ms are considered fundamental to daily quality control, and this is the basis of Machining / Processing production. However, reflecting the current trend of factories shifting to "high-mix, low-volume production," concepts such as 5M+1E and 6M have also emerged.

5M+1E adds Inspection and environment, and 6M adds Inspection and Management, but this time we will focus on the basic 4Ms.

2. Managing quality from a 4M perspective

In quality control, it is considered effective to continuously maintain and manage each of the 4Ms (Man, Machine, Material, Material). Let's take a closer look at why.

Maintenance and management

Establishing rules that must be followed and consistently enforcing them is called maintenance and management.

Relying on the experience and intuition of workers can lead to inconsistencies in daily operations and product quality. Therefore, creating rules and communicating them to workers is the first step in quality control.

In maintenance management utilizing the 4Ms, it is necessary to establish and confirm the rules required for each aspect to maintain quality.

Checkpoints necessary for maintenance and management

In maintenance management conducted from a 4M perspective, the following items will be defined and implemented:

・Man: Reporting rules for tardiness, absences, and early departures; work shift schedule; handover procedures for employees who are leaving the company.
• Method: Work manuals including methods for accurately communicating work instructions, determining equipment conditions for the work environment, and work sequences.
• Material: How to fill out invoices (item names and quantities of materials, etc.), how to maintain and organize tools, and rules for reporting work completion.
• Machine: Cleaning and maintenance rules and inspections standards

The above is just one example. Each factory should decide on rules focusing on items that are considered to have an impact on quality control and then maintain those rules.

3. 4M Change Point Management, Essential for Preventing Problems

Change point management involves identifying changes in the 4Ms (Man, Machine, Material, Method), predicting these changes in advance, and developing countermeasures beforehand.

For example, changes in a factory might include staff resignations or machinery breakdowns due to aging.

It is said that when a change occurs, problems that affect quality are likely to occur. Therefore, in order to maintain consistent quality, change point management that assumes the occurrence of problems is essential.

Changes can be divided into two types: predictable and unpredictable. Since the countermeasures differ depending on the type, let's look at each in detail in the following chapters.

4. Countermeasures for predictable points of change

The following measures are recommended for predictable points of change:

Create a manual in advance.

Changes in assigned tasks due to employee hiring and departures are one of the predictable points of change. In particular, a decrease in skilled workers due to departures can lead to a decline in the overall skill level and work speed of the factory, potentially having a significant impact on production.

In this case, creating a work manual is effective. Preparing a manual that even inexperienced employees can understand in advance can reduce variations in quality.

Prioritize the tasks to be addressed.

Consider the impact of each change on quality and prioritize the necessary actions.

Taking the machinery on a production line as an example, the number of machines used in manufacturing is not small, so it is not easy to manage them all in the same way. Therefore, the machines are ranked based on their importance to production, and the frequency of maintenance and management is determined accordingly.

This allows for smoother responses to changes such as malfunctions due to aging and fluctuations in the production line.

Record the data

It is also important to carefully record daily data such as machine operation figures, worker hours, and inventory levels.

By accumulating data, we can understand the normal values for each parameter and more easily notice points of change. If we can detect points of change early, we can take countermeasures quickly and minimize losses.

Ensure that everyone is fully aware of the rules.

When changing work procedures or rules, be sure to thoroughly communicate the changes to everyone.

Because workers are accustomed to their previous methods, even small changes can disrupt their work and lead to mistakes. To reduce human error, be sure to share the rules with all workers.

5. Countermeasures for unpredictable points of change

Next, let's look at countermeasures for unpredictable changes. The following countermeasures are effective for changes that cannot be predicted in advance.

Establish reporting rules

When unpredictable changes occur, the key is how quickly you can respond, so it's ideal to have a system in place that allows workers who notice a problem to quickly report it to their supervisor.

In the event of an unexpected problem, clearly define and communicate in advance "who" to report to and "what" to report.

Investigate the cause and develop measures to prevent recurrence.

Upon receiving the report, the supervisor categorizes the problem into 4Ms and investigates the causes of what changes led to the problem and why.

Accumulated data can be used to investigate the cause of problems. By identifying the cause from abnormal values and other indicators, developing preventative measures, and creating new manuals, future changes can be managed as predictable points. Let's build countermeasures to prevent similar problems from occurring in the future.

６．まとめ

In manufacturing, quality control methods using the 4Ms (Man, Machine, Method, Material) are considered fundamental. While continuous maintenance using the 4Ms is important, problems can still occur. Therefore, change point management, which involves predicting the points of change that may cause these problems and developing countermeasures, is also crucial.

Changes can be divided into predictable and unpredictable changes. For predictable changes, create a manual so that anyone can handle them, and for unpredictable changes, establish reporting rules. Clearly define how to deal with each type of change.