Case study: Poka-yoke ensures error-proof supply of fluid applicators to end-of-arm tooling

If your organization uses Lean manufacturing or Six Sigma tools in its operations, you’ve probably used the methodology of poka-yoke, which means “mistake-proofing” or “avoiding inadvertent errors.” There are actually two types of poka-yokes – a poka-yoke that prevents a mistake (sometimes referred to as a “control” poka-yoke) and a poka-yoke that raises an alert if a mistake is made (sometimes referred to as a “warning” poka-yoke).

The concept of poka-yoke – and the term – were developed in Japan in the 1960s by Shigeo Shingo, an industrial engineer and expert on the Toyota Production System (TPS). Poka-yoke is a fundamental tool of both Lean manufacturing and Six Sigma, and while it’s typically applied in manufacturing facilities, it can be used in virtually any process.

What does poka-yoke have to do with fluid applicators?

The process of fluid application involves more than just applying fluid to a substrate – it includes multiple steps that take place before and after the fluid is applied, such as wetting out the applicator before use and replacing an applicator after the fluid is dispensed. Each step presents a point where an error could be made – even with a fully automated application system. But implementing poka-yoke principles and methods can eliminate these potential errors.

Here’s an example of how Designetics used the poka-yoke methodology to ensure that your fluid application system is error-proof.

 

Mistake-proofing with the applicator track

In Designetics’ automated fluid application systems, fluid applicators are supplied to a robot’s end-of-arm tool by an applicator track. When a new applicator is needed, the robot ejects the used applicator over a waste receptacle and procures a new applicator from the applicator track.

Although this sounds like a simple process, it presents several opportunities for error that could result in scrap, rework, and downtime. But the poka-yoke design of our applicator track prevents these potential errors from occurring, ensuring your fluid application system operates at maximum productivity with no quality defects. Here’s how…

The poka-yoke design of our applicator track ensures that applicator change-out on a robot’s end-of-arm tool is a smooth, error-free process.

 

The first poka-yoke design feature of the applicator track is a type of warning poka-yoke, which alerts an operator when an error occurs so that corrective action can be taken before a mistake is made in the manufacturing process.

The applicator track is a gravity-fed unit that is loaded with a specified number of Designetics fluid applicators. The force produced by this “train” of applicators pushes the leading applicator into the correct, pre-programmed location for the robot’s end-of-arm tool to locate it and pick it up. This means that if the applicator track is low on applicators, the leading applicator may not be in the correct position, and the end-of-arm tool could experience a collision when it tries to pick up an applicator.

To avoid this potential error – and the downtime and cost that would result – the applicator track has been designed with two sensors – a “low applicator” sensor and an “in-position” sensor. These sensors are wired to the robot’s controller, so if either condition occurs, the robot can halt movement – or take other pre-programmed corrective action – to avoid a collision.

The second poka-yoke design feature is a type of control poka-yoke, which prevents an error from being made.

When the robot is programmed to acquire a fluid applicator from the applicator track, the applicator’s orientation is precisely defined. Then, for proper fluid application to occur, every applicator the robot acquires must be in that precise orientation. For example, if the applicator’s position varies even by a few degrees from the specified orientation, the width or path of fluid application would be incorrect.

That’s why Designetics applicator tracks are designed to ensure that fluid applicators can only be loaded into the track in the correct orientation. If an operator attempts to load applicators into the track incorrectly, the track’s design prevents them from being loaded, preventing possible re-work and scrap due to incorrect fluid application.

Designetics’ applicator track ensures applicators can only be loaded in the correct orientation. It also features a docking station to rest the applicator between dispensing cycles and a tamping station for removing excess fluid after initial wet-out of the applicator.

 

Error-free fluid application is your goal – and ours

No process is inherently error-proof. That’s why Lean manufacturing and Six Sigma tools have been adopted by manufacturers of all sizes and in every industry around the world. By incorporating the foundational principles of Lean and Six Sigma – such as poka-yoke – into the design of our fluid applicators and automated fluid application systems, Designetics helps you improve quality, reduce scrap and rework, and increase productivity. To discuss how we can help you make your fluid application process error-free, give us a call.

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