This paper outlines the NAX problem solving approach developed by a group of problem solving experts at a large Danish Producer of medical equipment. The company, “Medicmeter” is one of Denmark’s leading companies when it comes to lean and it has developed a strong problem solving culture. The main steps of the approach are to extensively gather direct detailed process knowledge at the actual process, assemble a team that systematically builds on each other ideas, apply team thinking in a structured way to get a rapid and very deep understanding of the problem, and conducting a structured deselection of hypothetical causes to uncover the true root causes. What sets this approach apart from other is that it contains a guide of how to facilitate these steps. A case study was performed in a production department at Medicmeter to demonstrate its effectiveness and reproducibility. It resulted in a close to 60% reduction of the issue concerned.