What is zero defect thinking?
Zero Defects thinking is a philosophy or mindset within an organization where all employees strive to have zero defect. Zero defect thinking is their north star. Meaning that it will probably never achieved, just like the north star will probably never reached, but they use this idea of zero defect thinking as an orientation point for their behavior. Just as the real north star was used to find direction when navigating the sea in the past. In other words we can say that zero defect thinking is striving to perfection, while at the same time we understand that perfection will never be reached.
What is zero defect thinking not?
Zero defect thinking should not be used just as a slogan. Defects will not reduce by just stating a slogan. Defects reduce when using structure problem solving methods such as the PDCA cycle or DMAIC cycle. Without these methods and the corresponding statistical tools, you should not expect any reduction in defects. Therefore if you launch a zero defect thinking campaign, you have to make certain that there is a focus on the corresponding methods and tools.
What is a defect?
When we want to talk about zero defect, we have to define what a defect is. A verry narrow definition would be that a defect is a damaged part. But we could also look at it in a broader way. In this case a defect is everything what is not according to requirement. If we require the product to last for 10 years, a failure of the product after 9 years would be a defect. I we require that the food we serve at our restaurant is available at the table 15 minutes after the order has taken. A defect would be if the food is only served after 16 minutes, even if the customer has no complaints about the food.
Furthermore we have to understand that not all defects are equal. Having a flat tire on your car has less impact than the engine catching fire. Therefore it is important to rank the defects. Often we do not have unlimited resources to tackle all problems at once. Therefore the problems with the highest priority should be tackled first. Zero defect thinking does not mean that we have to tackle all problems at once. It means that we continuously have to reduce them. Preventing them for happening ever again. Making this type of defect, a zero defect.
It also not mean that we should not look at the defects which are on the bottom of the list. It just means that we should not look at them right now if we do not have the resources to look at them. Once the top priority defects have been solved, the less important defects will move up the list automatically and become more important to tack. As discussed before just using the slogan "zero defect thinking" make no sense. You have to have a structured way to tackle your defects one by one.
zero defect thinking and the cost of poor quality
The total quality cost consists out of two main components. The failure cost at one hand and the prevention cost at the other hand. The failure cost is the cost linked to the failure of the product or service, with the defect directly in other words. scrap cost, rework cost, fines, ... are all examples of failure costs. Prevention cost are cost associated with the preventing the defect from occurring. Training cost, inspection cost, machine updates, ... are all examples of prevention costs. There is a clear relationship between failure costs, prevention costs and quality level. if we do not have much prevention in place the prevention cost will be low, but is will result is a low quality level and therefore high failure cost. At the other hand, if we have a lot of prevention in place the prevention cost will be high. This will result is a high quality level and therefore low failure cost. As we can see in the graph below there is an optimum level for the total quality costs. This optimal level depends from company to company but it is clear that this is not at zero defects. So why then introducing zero defect thinking.
Again Zero defect thinking does not mean that we have to go blindly for zero defect. It means that we have to reduce defects in a structured and smart way. This means that we also have to accept that there is such a thing as acceptable defects. What an acceptable defect is depends on the product or service you are offering, the type of defect and what the impact is of this defect.
We have to make certain that a defect is not too quickly categorized as an acceptable defect. We have first to explore all possible solutions to prevent the defect in the future. Only when the cost of none of these solutions is acceptable we can categorize it as an acceptable solution. A lack of resources to find the root cause and solve the problem causing the defect should never be a reason to classify a defect an acceptable defect.
Please note that maybe today there is no acceptable solution available, but this does not means that there will be no acceptable solution available tomorrow. The acceptable defects should be reviewed on a regular bases just like the low priority defects.
zero defect thinking mindset vs continuous improvement mindset.
so far we have seen that zero defect thinking should be more then just a slogan. if you want to reduce your defects you will have to put a program behind it. This program should be built around tools to identify, prioritize and solve the problems which are casing the defect. These tools used are the same tool used for structural problems solving which can be find in any continuous improvement program. Another way of looking at it is that zero defect thinking is a subset of the continuous improvement mindset where there is a strong focus on quality.
Does it make then sense to launch a zero defect thinking campaign? the answer is, it depends on what your company needs at the moment. Do you see an increase in the different types of defects in your company? then it would make sense to launch it or put quality back on the radar. On the other hand if you want to launch a global cost reduction program, you should not only focus on quality and launch a broad continuous improvement program.
Since zero defect thinking focus only on quality and the slogan "zero defect thinking" gives the false impression that the goal should be really zero defects, which is an unrealistic expectation, many companies prefer to speak about continuous improvement and continuous improvement within quality rather then "zero defect thinking".
When we shop online we expect that the product we buy have zero defects. If not we will be very dissatisfied. At the other hand, often when we have a small defect rate in our production process we accept this as normal. This is also referred at as dual attitude. We behave different depending if we are the customer or the supplier. As a customer zero defect thinking is not an ideal, but a requirement.
DFSS and zero defect thinking
until now we have spoken about continuous improvement to reduce defects. But it would be even better to have no defects to begin with. This means that we have to design our product or service so that no defects can occur. Also here a structural approach exist: Design for six sigma our shortly DFSS. When applying DFSS we make certain that the variation within our product or services is small and well within the requirements.
it is wise to include DFSS in your zero defect thinking campaign if you are also responsible for the design of the product.