Ohno: Quality is the True Value of Improvement

To build products of good quality is a priority more than anything else for our manufacturing industry. No matter how many products you produce, if they are of poor quality, then customers will not buy them. Even if you reduce the production costs, if you cannot sell them, there will be a loss.

In the case of automobiles, safety is especially important. We would fail our social responsibility if we bring products to the market where we “cut corners” or made the excuse of “we had our hands full”, or “we made it cost less”. This can turn out to be fatal for a company.

In short, ensuring the quality is the first thing that must be considered. You are giving priority to a less important thing when you make little of it for some other reasons. Consider what kind of work does the term “quality assurance work” refers to.

Standard Work

Unlike in the past, when the intuition of the operator or the degree of skill played greater role, today each process is segmented, and less specialization of skills are needed. Standard work for each production process is part of quality assurance.

Standard work must be designed to ensure the required quality. If there is unevenness among the processes, checking process by visual observation or gauge must be incorporated into standard work as a single process.

If defects are still produced under these conditions, then it is either because the standard work is not followed, or because there is some defect in machinery, equipment, molds, or tools. Understand why people are not following standard work. 

Quality First

Sometimes people say things like, “When we tried reducing labor, defects increased” or

“We reduced too many people, which shows up in our product quality.”

As we explained earlier, looking at it from the concept of the TPS, this is putting the cart before the horse, and it should never happen.

Issues that occur

By looking at what kind of issues take place, they can be broadly divided into the two categories:  

(A) Omitting or forgetting some of the necessary procedures, under the impression that the work that must be completed in a shorter time. Rather than eliminating unnecessary activity, they end up cutting corners instead.

(B) Since we previously had surplus of time allotted; creating intermediate stock and rework were possible. The labor reductions have exposed our quality defects.

Stopping the line

The case of (A) is commonly encountered in assembly work done on conveyor lines. This mistake occurs because the line was not stopped to avoid delaying the production process.

In the labor reduction activities, people are well taught about the importance of stopping the line. The first thing to teach a new person is how to stop the line.

By stopping the line, we can find out about the imbalance between the amount of work assigned to each person and discover facts for the elimination of unnecessary activity. It is also possible to solve the fundamental cause of the delay. 

If people omit some work because there is not sufficient time allotted, it may be because they think the line must never be stopped. The supervisor is responsible to make sure that people understand that passing a complete product to the following process is more important, even if it requires stopping the line. 

Obsession with line speed

There is no need to obsess over line speed or Takt time. It is important to clarify that “Takt time and the number of people are unrelated.” The person is doing all that is required at their own pace, so a cycle of work is completed.

If they do not finish within the Takt time, the line may be stopped until it is completed. Making sure that work fits within the takt time requires completely different measures, and that is the job of managers, supervisors, and technicians.

For instance, if a person requires 70 seconds to finish from process one to process five, while takt is 60 seconds, they would exceed takt by 10 seconds. There should be no need to explain that we must never omit those 10 seconds. The people should do their work normally, and the line should stop for 10 second intervals every time to make products with good quality.

It is the job of the supervisors and the technicians to implement improvements to make sure that any person can finish the processes within 60 seconds working at a normal pace. By cutting down unnecessary activities or reducing the distance they walk, with improvement, there would be no need to stop (delay) the line.

If you try to eliminate the line stop without improving the working process, this will naturally result in a lower quality of products; this must be strictly avoided.

Rework versus solving the problem

In the case B, by reducing the number of people and inventory, we see that many defectives were produced frequently. These were reworked within the production process rather than solving the root cause.

A following process fixes the defect caused by a preceding process without giving feedback. For example, there is a mismatch with the tapped hole due to a design problem. You fix it with the correct screw holes in your process.

Because the problem is managed, the root cause remains unsolved. The additional labor and inventory for these makeshift repairs increase the cost. When these problems are made obvious because of labor reduction process, it is a chance to improve.

Return a defect to the one who made it

Supervisors and technicians must return the defective products to their respective departments. They should visit the preceding process to pursue the root causes behind these defects and solve them starting with understanding the root cause.

This can be compared to taking pain medication for chronic appendicitis, instead you decide to get surgery and fully recover.

This concept also applies to solving the defects caused by machines, equipment, molds, and jigs, which we have described earlier. If we find that the equipment is causing a defect, it is important that we stop the line immediately to identify and eliminate the root cause.

If we end up doing in-process readjustments on our own just because the maintenance department would not respond after we contact them, we may start to fix the problem within our own production process, and this imperceptibly becomes a part of the regular process.

We should not stop with a single written request or a single phone call. We must keep taking measures patiently until we get a product of perfect quality.

Learnings

1. Producing a quality defect is more expensive than making a good product.
2. Cutting corners or using excuses for non-quality can turn out to be fatal for a company
3. Standard work for each process step is a cornerstone to quality assurance
4. Who produces something should be able to guarantee its quality.
5. Who cannot guarantee that quality must be allowed and obliged to stop the line.
6. Detecting a quality-defect is an opportunity: is shows the weak spots in the process. By eliminating the root-cause the same defect should never occur twice.
7. Never fix somebody else's 'defect': bring it back to the 'owner' in order to give him the chance to improve.
8. Do not stop finding root-causes for quality defects until there no more defects.