In 1961, a Japanese manufacturing engineer named Shigeo Shingo working at Masushita Electric developed the idea into a formal tool for achieving zero defects and eventually eliminating quality control inspections. The term "poka-yoke" generally translates as "mistake proofing" or as "to avoid inadvertent errors."
The idea is to respect the intelligence of workers by taking over repetitive tasks or actions that depend on vigilance or memory, and free a worker's time and mind to pursue more creative and value-adding activities.1 A poka-yoke device is any mechanism that either prevents a mistake from being made or makes the mistake obvious at a glance.2
The concept is widely used in everyday examples but you may not have noticed:
The value proposition to implement Poka Yoke into Medical Device Manufacturing is and increase in product product yields and a reduction in rework and scrap. The great thing about poka-yoke is that implementation can be very simple and very effective.
What about the bottom line?
As more products are provided in the home care setting, the need to implement this methodology is even more important. Imagine you have an insulin pump and require a 0.5 mg bolus; would you happy to know that you could give yourself 5.0 mg instead?
Poka yoke is the most effective when a company's attitude is that it's better to have one million one-dollar improvements than one million-dollar improvement. If the company culture asks everyone to identify at least one improvement per week, this can quickly accumulate to a large cost savings.
Mistake-proofing can be implemented into the manufacturing process but it is certainly the most effective when it is incorporated into the design of the product. If the parts can only be assembled one way, then you've eliminated errors (and assembly time) within the production area. If it can't be implemented into the design, the tooling or manufacturing aids may be another area for implementation. If it can't be integrated into the tooling then other items like sensors, limit switches or counters can be very effective.
Poka Yoke is most effective when it falls into two major categories: prevention and detection. In a prevention approach, the design makes it impossible to commit a mistake at all. A classic example of a prevention design is the USB plug design. The connection is carefully engineered to be slightly asymmetrical so that it will not fit into the mating connection in any orientation other than the correct one. Prevention designs remove the need to correct a mistake, since the user cannot make the mistake in the first place.
A detection design signals the user when a mistake has been made, so that the user can quickly correct the problem. Line clearance methods that verify the number of components used equal the total number of finished devices completed. As an example, the number of pouches are counted to equal the lot quantity to be shipped. When the last device is sealed in the pouch, the worker should not have any pouches left. If there are too many or not enough, this alerts the worker that something was forgotten. Detection devices typically warn the user of a problem but they do not enforce the correction.
"Poka-Yoke, Improving Product Quality by Preventing Defects" also known as "the Big Red Book" (Productivity Press), is one of my favorites. The book is full of practical examples and diagrams of great ideas, showing preventative error examples as well as the Poka Yoke functions (shutdown, control and warning). Sometimes, these concepts are best explained with pictures and examples.
The idea of poka yoke is that the workers don't go to work thinking that they are going to make a mistake. "Mistakes are inevitable; people are human and cannot be expected to concentrate all the time on the work in front of them or to understand completely the instructions they are given. Defects result from allowing a mistake to reach the customer, and defects are entirely avoidable.1"
As described in the "Big Red Book," there are five examples for detecting or avoiding defects caused by human error:
The Poka Yoke method is something that improves your daily life; why not use it to make your product better, as well? The best solutions are simple, quick to implement and 100 times more effective than a 100-percent final inspection.
Jim Shore is a Product and Process Improvement Leader at Dynisco, Franklin, MA. Jim's role is to lead the manufacturing and cultural changes towards the Lean principle.
Jim holds a Bachelor of Science BS in Industrial Technology from University of Lowell in Institute, an MS in Management from Lesley College and is currently working on graduate studies for Regulatory Affairs at Regis College. He is a member of the American Society for Quality (ASQ), the Regulatory Affairs Professional Society (RAPS), the American Welding Society (AWS) and Biomedical ASQ Division (NEDG).
Jim is a Desert Storm Veteran (1991), having served his country in the United States Marine Corps for over 15 years and was Honorably Discharged at the rank of Gunnery Sergeant (E-7).