Build in Quality with Error-Proofing and Autonomation

Using Error-Proofing

Poke Yoke is a Japanese term for “error proofing”.  The idea is to build in quality by providing constraints to prevent incorrect use, making it close to impossible to make a mistake.

An example of this would be a USB cable – you can only plug a USB cable into a USB port – nothing else will fit.  It’s mistake proof!  This is Poka-Yoke.  Another example would be the fact that many cars are unable to start if they are already in gear, or a form with specific drop-down menus so the user choice is limited, avoiding errors.

The question we ask ourselves for Poka-Yoke is:

• How do we provide constraints to prevent incorrect use in this product or process?

Figure 22:  An example of error proofing, where plugs around the home or workplace can only fit into the socket they are meant for.

Using Autonomation

Autonomation or “Jidoka” in Japanese, means providing both team-mates and machines with the ability to detect when something is wrong and immediately stop work so they are not passing on defects to the customer.

Doing this also highlights any problems in a process, because work stops when a problem first occurs.  By stopping when a problem first occurs, we can get a consensus on the root cause of the problem (3.3) before we try and solve it.  Then we can put a quick fix in place at first to keep the process moving, and work on a long term fix directly afterwards.

Using an Andon, which is a light that shows the status of a process or operation (such as green for go, red for stop) is one way to use Jidoka.

The questions we ask ourselves for Autonomation or Jidoka are:

• How do we know when something is wrong?
• What is the visual signal we would like to see when this happens?

This step is an extremely important part of our ability to make problems visible (4.1) at the Gemba – Jidoka must be a part of each step in our process so defects are never passed through.

It is also one of the main principles of Lean that we “solve problems close in person, place and time”, as they happen.  To give you an example, let’s think back to the Net Promoter Score in (1.3).  If our customer gives us a six out of ten or lower, and we arrange to get this information straight away, we might call them to sort out any problem they might have right then and there, instead of letting it get lost in the system or losing valuable information from the source.

Implementing Jidoka with a Zero Tolerance for Rework

Jidoka is not just about stopping when we have a defect.  At its core it is also about having a zero tolerance for defects and rework.

Before you implement Jidoka in your workplace, an easy way to begin is to have your team-mates set aside any item that comes to them requiring rework, and not work on it at all.  Then, at the end of the shift, collect all the unfinished items and note down the different “defect” types.  You can do a Pareto Analysis (3.2) to see which defect types are the most common, find out why they occur with root cause analysis (3.3), make errors visible if possible (4.1) and stop work if they ever happen again so you can fix them close to the source.  This is Jidoka.

Add any Poke Yoke or Jidoka ideas that fit with your space to your current state Value Stream Map, as a Kaizen burst (2.5).

Check out these selected chapters from the teachings within Five Minute Lean:

• Five Minute Lean – Introduction

• Five Minute Lean – Put it Together With Design for Ease of Use
• Five Minute Lean – Work Towards One-Piece-Flow (and Reducing Silos or Batching)
• Five Minute Lean – Eliminate the Eight Wastes to Improve Flow
• Five Minute Lean – Create a Pull System with FIFO, Kanban Triggers and Visual Management
• Five Minute Lean – Map the Value Stream to Reveal Opportunities
• Five Minute Lean – Present and Manage Your Change Using an A3 and LCA
• Five Minute Lean Summary
• Five Minute Lean – Introduction
• Five Minute Lean – Help Your Process Flow with Line Balancing
• Five Minute Lean – Create a New Standard Procedure and Checklist for Quality Control

Selected chapters from the story within Five minute Lean:

• Lean Parable – Where Lisa Makes a Change
• Lean Parable – Where Lisa Discovers a New Way
• Lean Parable – Where Lisa Performs a Balancing Act