Zero defects is a philosophy of Lean. It simply means that every process should be designed so that it is impossible to produce poor quality. The underlying premise, which is true in nearly every case, is that the cost of preventing problems is lower than the cost of fixing them.
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Zero defects is an unattainable goal. In practice, no company has ever achieved zero defects. Every company makes errors, and those errors contribute to the cost of poor quality.
The philosophy of zero defects, though, promotes the quest for perfection that keeps companies from stagnating. And that quest has resulted in the overall quality of companies getting higher, as well as the achievement of zero defects within individual processes.
Zero defects is sought through a variety of methods.
Using andons and line stops to prevent passing on poor quality.
Building mistake proofing (poka yoke devices) into processes.
The origin of the concepts of zero defects is open to debate. It is a key component of the teachings of many Lean experts, which suggests that it could be traced back to the early days of the Toyota Production System. There are also numerous reference to the early usage of the term in Philip Crosby’s 1979 book, Quality is Free.
Regardless of where the term originated, it is now in widespread use.
Several things contribute to poor quality, which undermines the goals of zero defects.
Treating zero defects as an absolute rule rather than a philosophy or mindset. That simply adds frustration when it is not achieved.
A focus on production rates. Focus instead on creating standard processes that are balanced to takt time. Standard Work leads to better quality.
Passing on poor quality. Closely related to number 2, when people are pressed to produce no matter what, they tend to be more willing to send poor quality downstream.
Sending mixed messages. When leaders compromise on quality to meet an important deadline, they undermine the concept of zero defects.
Zero quality sounds daunting, but keep in mind that no company has ever achieved it. If you think of it as an absolute throughout the company, you will feel frustrated by not achieving it. But if you try to achieve it whenever possible, and look for ways to make processes robust enough to prevent mistakes, you will find the philosophy of zero defects to be much more manageable. And you will find that striving for it, even if you fall short, will make your company, and your job, much better.
The purpose of promoting zero defects is to shift mindsets in your organization. Do not actually set your quality KPI to 100% good parts. Instead, change the way you think about quality. Make it clear that producing good parts is more important than hitting production targets.
Of course, you will need to solve the problems that hinder output, but when you get your team thinking in terms of preventing errors, quality will rise dramatically.
There is a point of diminishing returns in quality. Perfection is extremely costly. The inflection point, though, where the cost of prevention outweighs the cost of detection and correction, is probably far, far past where you think it is.
Finally, keep in mind that focusing on zero defects as a mentality in your organization will likely act as a short-term speed bump to production. There are up-front costs to becoming a quality-centric company. But the long-term gains will be substantial.
Zero defects is a mindset, not an absolute goal.
No company has ever achieved zero defects, but those that embrace the philosophy get much better.
Zero defects is possible on individual processes. Achieving it on many processes adds up to improved overall quality.