Error Proofing to Implement Quality

An important concept in implementing a lean manufacturing Six Sigma program is consistent vigilance over quality levels. Typically, quality inspections concentrate on the end result of the production process. A proactive approach that assures quality before a product is complete can be a more effective means of decreasing waste and increasing quality. To this end, introducing error-proofing can be a viable option.

Error-proofing or Poka-Yoke is the process of implementing safeguards to prevent processes from producing defects in the first place. Poka-Yoke is based on the Japanese terms Poka, meaning inadvertent errors, and Yokeru, meaning to avoid. The underlying philosophy of error-proofing is that even a minute amount of defects is unacceptable. In order to reach this goal, defects must be prevented in the first place. To this end, inspection efforts are not limited to the completion end of the production line, rather quality is checked every step of the way. Such dedication to preserving quality and eliminating causes of waste is a major factor in developing a lean manufacturing Six Sigma organization.

A major feature of an error-proofing system is that it relies heavily upon employee empowerment and involvement. Effective error-proofing often arises from those who best understand a process, so anyone from management to an assembly-line worker can contribute a workable solution.

Forms of Error-Proofing

Error-proofing takes many forms depending upon the application and organization. In general, however, it may be broken down into three categories:

  • Warnings - In simplest form, error-proofing in the form of warnings provide feedback on a potential problem. Everyday examples include a tone sounding if car lights are left on, or a smoke alarm going off.
  • Shutdown - This form of error-proofing ensures a problem is corrected before production resumes. In this case, automatic safeguards halt a production line, for example, until the situation is rectified.
  • Autocorrection - This error-proofing system consists of an integrated test-feedback-repair loop. Spell checkers on word processing software is a common example of this category.

Applying Error-Proofing Techniques

In order to be most successful, error-proofing programs must include input from the workforce. This serves a dual purpose. On one hand, workers with the greatest familiarity with a process have the most accurate perspective on its shortcomings. They are positioned to make valuable contributions in error-proofing the manufacturing process. Secondly, employee involvement serves a psychological purpose. A workforce that feels empowered to contribute to the method of operation has an emotional investment in preserving quality and improving performance. This feeling of ownership over quality levels is critical for a lean manufacturing Six Sigma company.

To begin the error-proofing process, all possible errors must be identified. Failure Mode and Effects Analysis (FMEA) and Fishbone Charting are useful tools to identify these factors. From this point, the workforce should be involved in suggesting the introduction of possible Warning, Shutdown or Autocorrections to guard against defects.

Error-proofing is not complete at this point, rather it is an ongoing process. Employees and management alike should feel encouraged to continuously enact improvements in the production process as conditions change or waste becomes evident. This flexibility in enacting quality controls yields a successful, low-waste, lean manufacturing Six Sigma environment.