The Error Proofing component of the Change Management Toolset

Error Proofing is a process improvement that aims to prevent a specific defect from occurring in a production line. Effective error proofing involves detection of the error by the operator, feedback to stop the process, so that the error can be put right and problem solving by the improvement team to take corrective and preventative action.

Error proofing reduces the risk of:
• Operator injury
• Faulty products
• Machine damage and
• Defective product being produced or passed to the next process

The change agent's challenge is to change the culture within an organization so that the new mantra becomes:

Don't accept a defect
Don't make a defect and
Don't pass a defect on (to the customer)

Lean Six Sigma is a currently popular change management methodology in which the term for error proofing is Poka Yoke. The number one objective of poka yoke is to achieve zero defects.
Error proofing enforces procedures which are set in stone ensuring quality and almost entirely eliminating defects. As such, it:

• Eliminates the cost of product inspections since none will be necessary
• Makes waste costs insignificant
• Frees up operator time for the task at hand rather than problem solving and
• Promotes an attitude of continuous improvement.

A defect is a product that fails to meet set specifications whereas an error is any deviation from set process. In the error proofing process, inspection of the product occurs after each process is complete, so that errors can be detected close to their causative source. Once the causative process has been identified, the team then brainstorms all possible errors that might have resulted in the relevant defect. Quantitative data is recorded and special note of potential causes that occur on an ongoing basis is noted. Finally, the root cause is identified by testing out, often by a questioning technique called 5-Why which seeks to determine the root cause by repeatedly drilling down through asking the question why.

With knowledge of the cause of the error, the team can them conduct a solution finding exercise in order to develop an effective manual or automated, integrated error proofing system. Such a system might include limit or touch switches, photo-electric sensors or proximity switches. In all cases the triggering of the error proofing system will set off an alarm and/or halt the production process so that the error can be rectified.

Low cost error proofing devices which are inexpensive to replace make good economic sense. The ideal situation is to design a product that cannot be assembled incorrectly, so at best, devices should prevent the ability to make a defect. However, if the defect cannot be prevented, the device should prevent it from being passed to the next production process.

It is also imperative that the device provides prompt identification of defect location, allowing for quick troubleshooting. Error proofing deployment needs to be a rapid process since minimal disruption of the system means limited loss of income to the organization. Initial investigations to device implementations should certainly span, no more than a month for minimal process disruption.
Dividing the error proofing procedure into small steps each assigned to a named operator has proven a particularly effective approach when it comes to getting quick results. It has also been proven beneficial to run daily review sessions and to address issues raised promptly.

Assessment of the impact of changes made needs to be frequent. Further, as the system becomes more active in error detection, it will become possible to detect errors at an earlier stage so that new error proofing solutions should continue to be sought on an ongoing basis.

Peter Peterka is the President of Six Sigma us. For information on Six Sigma, Six Sigma Black Belt Training or Master Black Belt programs contact Peter Peterka.