Cpk is commonly used as an overall indicator of a factory’s manufacturing process capability. However, it can also be applied across different industries to measure the ability to meet a target. A popular analogy is how well you can hit the bullseye when shooting arrows at a target.
Of course, the higher the Cpk value, the better. But Cpk is actually made up of two components: Cp and Ck.
Many of you might already know what a fishbone diagram is. But do you know how to actually draw one? And what should you watch out for when creating one?
As the name suggests, the diagram looks like the skeleton of a fish—that’s where it gets its nickname. Its formal name is Cause-and-Effect Analysis Diagram, because it’s used to trace a problem (effect) back to its possible causes.
In the previous article, Workingbear mentioned a serious DOA (Dead on Arrival) customer complaint involving one of the company’s products. Most of the defective units had unresponsive keypads—specifically the 3, 6, and 9 buttons—and it was eventually traced back to oil contamination. At the time, the company formed a special task force to investigate the issue, and even sent engineers to the contract manufacturer’s factory to track down the root cause.
To be fair, the factory was quite cooperative and had already done some internal troubleshooting to rule out several possibilities.
This article shares a real case from Workingbear’s past experience dealing with an urgent customer complaint. One day, Workingbear was suddenly assigned to fly to a factory in China to “hunt for oil.” My manager even warned, “If you don’t find the source of the oil, don’t bother coming back!” So, with a heavy heart, Workingbear set off—didn’t even dare to book a return ticket.
The reason for this emergency was a serious DOA (Dead On Arrival) complaint. The product completely failed right out of the carton box when it reached the customer.
Environmental Stress Screening (ESS) is a method used to apply certain environmental and operational stresses—such as power on/off cycles, bias voltage, pressure, thermal cycling, and vibration—to new or repaired products (usually electronics or components). The idea is to expose hidden early-failure issues that normal testing might miss. This helps weed out defective units and ensures better product quality.
