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How to reduce accumulated nonconforming material

Updated: Mar 21, 2021

Defects happen. Usually, the part gets tagged and set aside to deal with later. Eventually there is a pile of parts, covered in dust, with a tag indicating that the part has had a birthday. The problem is that nonconforming material accumulation is tying up cash and could lead to running out of parts. Patterns of defects go missed, so mistakes occur repeatedly.


Creating a cycle time metric is a simple way to reduce the accumulation of defective parts. When people are measured to a target, they prioritize their time to meet the goal. To create a cycle time metric, map the process. How does your team manage nonconforming material, from the time it is identified to the time the parts are scrapped, or determined useful? Here is a sample process for internally manufactured parts:

Each step of the process is potentially conducted by a different person in the organization, so each step should have its cycle time measured. Having an IT system with timestamps makes measuring the process much easier. Be sure to set an aggressive target to rally the team around improvement.

In the event your organization does not have an IT system to manage nonconforming material, a visual management system is an option. Create time buckets and use either colors or locations can be used to define the age of the part. The part metric can be computed by counting the parts in each age bucket on a weekly basis. Be sure to include a weekly Gemba walk to the nonconforming material area with the team to stay focused on accumulation reduction.

Finally, the last approach to reducing nonconforming material accumulation is through a continuous improvement program. The failure mode and the root cause of the defective part should be captured in a manner that can be analyzed later. Of course an IT system makes this easy, but an Excel spreadsheet can be used as well. After data is accumulated, a simple pareto chart can be used to prioritize continuous improvement projects. Be sure to include the workforce in the projects, as they often have great insights about the defects. Solutions should be robust if possible, rather than relying on communication and training.

Good luck with your journey to reduce nonconforming material build up. It's sure to help improve cost of quality and create a good quality culture.

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