What Does It Mean?
Defect density measures the number of defective units of a product produced against the total number of units made. The KPI tracks the quality of different products to compare with each other, as well as historic benchmarks.
Why Does it Matter?
Manufacturing profits require more than high quantities of a product. Defective products not only result in delays, but also cause costly recalls, diminished profitability, and permanently damage reputations. Moreover, products that are consistently defective can become a drain on long-term revenues.
Tracking defect density with your manufacturing analytics can help you understand which products are defective, and can indicate why and how often. More importantly, they can serve as an important metric of quality and standards over time, as they can highlight improvements or regressions in product defects.
How Do you Measure the KPI?
To measure defect density, you need to have the data on the number of defective units of a single product, as well as the total number of units produced. To find the density, divide the number of defective units by the total number of units produced.
What Sources Would You Use to Measure the KPI?
Tracking defect density requires you to examine your quality assurance and final production data. As such, you can monitor data that comes from end-stage production, sales, recalls, and quality assurance processes.
Give me an Example…
Imagine that your production line has been receiving complaints on and off about a particular item you have been producing for years. However, complaints seem isolated enough to be random and you ignore it. Over the next few months, complaints continue to increase, informing you that there is actually a problem somewhere in the process.
Tracking the defect density can give you a better idea of what is going on. By measuring the incidence of defective products, you can determine what the problem is, and when it began. In turn, you can rapidly identify the best solution, and ascertain if the problem is a one-off issue, if it falls within the acceptable range of defect density, or if it is simply no longer profitable to continue producing that item.
Furthermore, understanding each product’s defect density helps you make better decisions about which products to prioritize, which require a fix, and which you should stop producing.
What Benchmark/Indicators Should I Use?
Some useful indicators include: