Poka-Yoke improves quality and regents products defects. Poka-Yoke helps build quality into manufacturing process.

Product quality is key to successful business. Manufacturing process, machinery, human errors and many other small and big factors contribute to product defects. It might be frustrating, that customers demand and expect zero defects. Quality is not free.

Manufacturing companies around the world strive to compete in product quality, reliability and cost. It is costly to inspect and sort parts after they have been manufactured. Error-proof (poka-yoke) devices must be incorporated into the manufacturing process to prevent defects pass the operation and go to the next step.

Majority of product defects are caused by human error. Here are some examples of human errors: Omitted processing, incorrect processing, missing parts, wrong parts, mislabeled parts. In many cases operators are not aware that they produce defects. It happens, when machinery is set-up incorrectly, measuring tool is off or not properly calibrated, missing tools to perform the task, broken tool. Operators must be trained for the operation they perform and effectiveness of training must be verified by supervisor or the engineer.

Poka-Yoke or error proofing is a technique to prevent product defects caused by human error. Here are examples of Poka-Yoke (error proof). Defects exist in two states: it is about to happen (perdition) or it is already happened (detection).
 

Here are some samples on Poka-Yoke:
1. Identify parts by their characteristics: weight, dimensions, shape, color. Establish a standard item (good sample) to compare process parts to this good sample. Implement weight station, limited switches, stop switches or pins, color recognition switches.
2. Detect deviation from procedures, omitted steps. Use process sequence method.
3. Detect deviation from fixed values. Use counter, critical condition detection ( pressure, current, temperature, dimensions)

Everyone must work together to achieve the goal of zero defects. The quality of the products starts from the products design and must be built into the manufacturing process. Each step of manufacturing process must be evaluated by manufacturing and/or quality engineer for potential human errors. Error proofing (Poka-Yoke) must be implemented to prevent human errors.

Statistical Process Control (SPC), if implemented, assumes that 100% inspection is unnecessary and it is time consuming task. SPC is a quality control tool, not an error prevention tool. It describes the process capability to produce good parts, but does not eliminate the source of defects.



What is Poka-Yoke? The Japanese manufacturing engineer, Shiego Shingo has incorporated error proof techniques into a formidable tool to achieve zero defects. Poka-Yoke stands for "mistake-proof" or "fool-proof". The idea was very simple - to respect the intelligence of production workers. Poka-yoke (permanent error-proof) can benefit Operators involved in repetitious tasks  that depends on vigilance, concentration and memory by allowing them to concentrate on other value added manufacturing tasks. Having error proof in place permanently will free operator's mind and time. Poka-yoke is a concept of elimination any defects (even small number) to pass through the process to the next step. To compete with the world class manufacturing companies, you must adopt a philosophy and practice of producing zero defects.

If you have been involved in a quality improvement of the existing (old) manufacturing processes -- there are plenty of opportunity to implement error proofing. You will become a "shining star" by implementing simple cost effective error proofing at no time. Every station and manufacturing process must be evaluated for the potential human errors. Start with review of customer's complaints, operators complaints, online rejects, review quality check sheets and operator's instruction sheets. Watch the operator to do the task at every station --you will be surprised how many "opportunities" for error you will discover. The best part of implementing an error proofing - it is never over. Continuous improvement is essential to catch new "opportunities for error proofing".

Building the poka-yoke (error proof) into the new manufacturing process and equipment must be a priority for every machine design team and manufacturing / quality engineer. Knowledge of error proofing available and their role in preventing defects are essential to build quality into the manufacturing process.