An Expensive Opinion

Over a year ago, I was involved in a project to solve a weld problem. This company performed thousands of spot welds every day and some (approx one in 300) just didn't take. The failure wasn't obvious unless you tugged at the weld and even that wasn't a reliable test. But a poor weld could be serious if it failed in the field so this had to be solved.

A department manager was convinced that a current monitor would take care of things. In his opinion, the weld fails when the current drops below some critical number. So when the current is too low, the operator discards that last welded part. My argument was that there are many things that could cause a weld to not take; part cleanliness, surface geometry, applied force, squeeze time and more factors that are part of the welding process. The project required much more effort and some data. But he was adamant and he told us that this was what they do in the automotive industry. So we backed off and accepted this as a problem nearly solved.

A year later, the process has a reject rate of one in 300.

Collecting evidence to learn about a root cause takes so little time. Solving a problem based on an opinion can set you back months.