Poka-Yoke Tool: How VKS Can Mistake-Proof Your Factory

What if you could ensure your factory never made an error ever again?

It’s not a pipe dream – outside of things like unexpected downtime or external factors that cause delays, mistake-proofing your manufacturing plant can actually be done. The trick is to ensure you have the right tools and that they are implemented correctly.

Let’s go over how to mistake-proof your factory so that you can have the highest quality output and see the maximum returns on your product.

3 Types of Poka-Yoke

The “magic” not-so-secret secret to mistake-proofing is a concept from lean manufacturing called poka-yoke, a Japanese term that translates to “idiot-proofing” (later modified to mistake-proofing).

A poka-yoke tool is one that adds a constraint to a process such that any errors must be rectified before the process can develop any further. If you're setting up processes, do make sure to learn how to write good work instructions in 10 easy steps.

Shigeo Shingo coined the term “poka-yoke” in the 1960s when he developed TPS (Toyota Production System). It was inspired by a common error he caught: assembly workers would occasionally forget to place a small spring underneath a button, and the product would fail to operate as intended. Shingo corrected this problem by adding an extra step — a poka-yoke — where the worker would have to first place the springs in a special holder before assembling.

With one quick glance at the special holder, a worker can instantly double-check that they had installed the finicky screws. Discover the origins of such systems in The Origins of Lean: The Deming System of Profound Knowledge.

There are three types of poka-yoke you can use:

1. The Contact Method tests values by using physical attributes or constraints
2. The Fixed-Value Method tests that a specific number of actions are performed
3. The Sequence Method verifies that actions are performed in the correct sequence

Together, each of these 3 poka-yoke tools ensures that nothing is forgotten, incorrect, or out of order, leading to error-free output in a lean factory. With our work instruction software, you can cover each of these categories for the ultimate confidence in a lean production process.

Poka-Yoke #1: Contact

The first type of poka-yoke tool is the contact method, which involves physical contact needed to trigger a next step. A great example of this in manufacturing is using a special jig in an assembly process. If one step of assembly hasn’t been performed correctly, it won’t lock into place and trigger the jig to move the product along the line. Another example might be when a panel or part is unlocked only after a certain button is pressed.

It is common to see the contact poka-yoke method used in combination with digital tools such as IoT devices like sensors. This setup includes third-party devices that can validate measurements along a pass/fail scale, and an operator can only move forward in the process if the test has been passed. The physical motion required (either to move forward in instructions or to meet other physical requirements throughout assembly) is validated digitally, allowing further action on the shop floor.

Let’s go into more detail with a further example from VKS DataConnect. With DataConnect, information is directly sent from a test bench or jig to the VKS software.

After completing an action (such as placing a part in the correct place), the operator activates the appropriate inspection tool via the VKS user interface. This triggers a camera inspection, which confirms proper placement of the part. VKS DataConnect sends a stored procedure to an SQL database monitored by a PLC. Upon detecting the new data, the PLC transmits the inspection program number to the camera. The camera validates that the part is in the correct position, and the action receives a “pass”, allowing further action. The operator can now proceed to the next step in the production process.

The contact method of poka-yoke is a great option for manufacturing scenarios like validating that labels have been placed on packaging before items are passed on to shipping, or confirming proper application and logging of serial numbers before further processing can be done during production.

Poka-Yoke #2: Fixed-Value

The second type of poka-yoke tool is the fixed-value method, which essentially counts that the correct number of components are present or that actions have been performed to the correct measurements.

A great example of this is VKS ToolConnect, which allows the VKS software to directly communicate with IoT tools like torque wrenches.

First, an operator would see in the work instruction that they must attach 6 screws to the product in a specified placement. The operator activates the tool, performing the action, and the VKS software receives exact torque values for the 6 screws. This guarantees all of the screws are properly inserted, and this step of the process receives a “pass”, allowing further work to be done. By implementing this fixed-value poka-yoke with ToolConnect, you save time on manual inspections and also ensure that processes are followed exactly to the smallest detail.

For example, if there was a machine failure and only 5 screws had been installed, VKS would not move to the next assembly action until corrective action is taken, thereby mistake-proofing production using connected tools.

Poka-Yoke #3: Sequence

The best example of this style of mistake-proofing is using VKS work instructions to guide production processes. At each workstation, VKS software provides an interactive, visual how-to guide that shows workers exactly how to perform actions. Workers must go step by step through the instructions, input values when prompted, and cannot skip ahead until required actions are performed.

VKS also allows further implementation of fixed-value poka-yoke with automated forms that prompt the operator for specific input values, essentially building quality control into the production process.

VKS As Your Comprehensive Poka-Yoke Tool

VKS fluidly connects with your other manufacturing tools and processes to guarantee work is done correctly every time regardless of the worker or product iteration. Don’t try to squeeze quality checks in at the last minute – they won’t be as effective as building quality into your processes from the start with proper poka-yoke methods that fully mistake-proof your operations.