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Digital poka-yoke :

The secret to 0 defects in manufacturing



Defects are a common occurrence in manufacturing and can be minimized but not completely avoided. However, it is imperative for manufacturers to catch these defects as early as possible in the manufacturing process to prevent catastrophic problems down the road. For example, for an automotive OEM preventing defects or catching defects early in the car assembly process can potentially prevent the recalls of millions of vehicles that can cost the company hundreds of millions of dollars in warranty and repair costs. In the worst case recalls can cost an auto company to go bankrupt. Poka-yoke is one of the most effective ways of avoiding defects in manufacturing.

The Japanese term poka-yoke means “mistake proofing” or “error prevention”. It is the use of any automatic device or method that either makes it impossible for an error to occur or makes the error immediately obvious once it has occurred. It is a common process analysis tool in manufacturing. Poka-yoke is important because it helps manufacturers avoid production defects or catch them quickly to prevent potential catastrophic issues down the road. While current poka-yoke systems are effective, they are unable to capture all errors (resulting in more potential defects in the final product).Digital poka-yoke systems are much better at capturing a larger number of assembly errors so they can be corrected in real time, resulting in a more cost effective process in the long run.

Current poka-yoke implementation strategies

Poka-yoke is implemented in a variety of ways but one of the most effective ways is through mechanical design. Mechanical parts are designed by engineers in a way that can only be installed in a certain orientation and/or can only be installed using certain equipment. For example, many auto manufacturers design underbody car panels in a way that it can only be attached to a car using certain bolts and screws. If the bolt/screw deviates from the specification, an assembler would be unable to install it onto the car underbody. Using this method, mistakes are avoided in the assembly process since it becomes nearly impossible for the wrong panel to be installed on a vehicle which prevents car recalls in the future.

Mechanical poka-yoke systems can’t capture all defects

The major challenge with mechanical poka-yoke systems is that it can become tough to make sure that all assembly errors are caught since there can be various different ways for an operator to make an error. These errors are usually discovered in the pre-production phases at which time it becomes very expensive to change the mechanical design.
This is because changes during the pre-production stage result in redesign and requalification of the parts, which in the context of mechanical parts is very expensive. Only the highest priority errors can be prioritized due to budgetary constraints which leaves multiple other assembly errors unaddressed via mechanical design. These unaddressed errors can potentially lead to safety issues or costly recalls down the road.

Why digital poka-yoke systems are superior

Digital poka-yoke systems such as i-5O’s vision system can track all sorts of assembly processes and alert end users as soon as a deviation is observed so that they can take action immediately. Since the system is purely digital the cost of adding/updating processes is extremely low while the feedback is immediate which makes it better than the existing mechanical poka-yoke systems. While digital systems are not always perfect, implementation of this sort of a system at our clients has resulted in 0 false positives i.e. every single defective part was successfully recognized as being defective.For one of our large automotive OEM clients our vision system accurately classified when a bolt wasn't installed on a car underbody panel with greater than 95% accuracy whereas a mechanical poka-yoke system couldn't detect this at all.

i-5O’s vision system captures most assembly errors

i-5O has taken a unique approach to implementing poka-yoke by capturing the actions an assembler is performing and validating that the action is performed according to the specification in the standard work instruction. Essentially the system keeps track of all the steps in an assembly operation and alerts the workers and/or the supervisor when a deviation is observed to alert them of the possibility of a defect. The supervisor/worker can then decide whether the defect is worth correcting or if it’s within the specification.

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