Preventing Defects with Ishikawa Diagram

Apr 18, 2018


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When sourcing products from a factory in Asia, maximizing your control over product quality is essential. There are several ways to do it.

First and foremost, you need to choose the right supplier, and this step will determine all the following steps until shipment. Once you’ve selected your supplier, and even with the right supplier, defects might still happen and the best way to avoid them is to anticipate them.

With years of experience with clients importing goods from China in various industries, I’ve used a good number of tools to identify and anticipate defects before production, and I’ve come to the conclusion that Ishikawa diagram is the simplest yet most brilliant tools to be used in quality control.

Ishikawa diagram is also called cause and effect diagram or Fishbone diagram. It is a visualization tool that helps you categorize the potential causes of non-conformities and identify actions you need to implement to avoid them.

Ishikawa is not new at all, it’s a classic! Developed in the 60s by Japanese Quality control guru Kaoru Ishikawa, its basic concept is believed to have been developed in 1920! So we’re talking about a 100-year-old tool which is still relevant today! I first found out about the Ishikawa diagram when I worked in the automotive industry (no surprise when you know Mazda was one of the most famous users of the diagram, with their MX5 sports car).

I’ve used it in different industries and one of the best illustrative examples is a project I ran with a French gift and premium importer. I worked with them on a first order from a famous chocolate brand for 150K chocolate boxes; it was an important order and we were under tremendous pressure. The box was quite complex as it had different layers and types of printed material including metallic parts on the outside. The challenge was to get it right from the first batch (which seemed like “mission impossible” considering the complexity), and the client could not afford catching defects at the end of the production, for cost and timing considerations.

Our initial idea was to work closely with the factory and our client to draft fine-grained specifications to be used with the production team to finalize the processes to implement for producing these nearly goldsmith products. Ishikawa provided the perfect framework to understand the factors of potential defects, and it helped us conduct a comprehensive screening of the production, covering aspects such as workers skills, glue type and product assembly methods. It allowed us to anticipate and address issues with the factory ahead of the production, to help them control the risks during the production.

By diligently implementing the tool, we successfully passed the inspection from the first round, allowing our client to ship defect-free products in a timely manner, in other words, “mission accomplished” from our end.

Ishikawa diagram can be used to brainstorm with your team at the start of a project to screen all potential root causes that can create one or several defects that might occur. Those root causes are summarized around 6 categories of actors: Measurements, Material, Personnel, Environment, Methods, and Machines.

Measurements: Defects might appear because measurements of the product specifications linked to this defect were not performed properly to detect the non-conformity.

Material: Raw material is an essential part of your product and might be a direct source of issues when not properly sourced and selected.

Manpower/People: Skills to manufacture and control your products are very important, and can be an important factor of a defect.

Mother Nature/Environment: Aspects such as temperature, humidity, storage and transportation conditions are also a source of problems when not well controlled.

Methods: The way you manufacture and control your products is key to producing the level of quality you need. Wrong or insufficient methods can ruin a manufacturing project even if all other aspects (Material, Measurements, Personnel) are under control.

Machines: Machines and equipment used to manufacture your products can be also a source of the problem if they are not relevant or well maintained. It is important to note that Machines cover mostly production equipment, and not measurement equipment that can be classified both in Methods and Measurement.

When you start your project, you often design an audit scope to audit your supplier or write your product specifications for the supplier, an important step which aims to address the customer need, and which consists in writing a description of the product (color, dimensions, material, etc.). However, I would add another step, to get further into the details with a more thorough and accurate description of what you want and don’t want. I would recommend brainstorming with your team around the Ishikawa diagram to include clear instructions that will help you avoid all the defects factors.

Here are a few common examples of using Ishikawa for environment and methods:

Environment: When importing garments from Bangladesh, you might want to consider that humidity and temperature can be very high, especially during monsoon season. To protect your garments from damage, you may want to add clear instructions in your specifications about adding desiccant in each unit, package, master cartons and even in the container itself.

Methods: If you are importing a large set of small parts that need to assemble with very tight tolerances, you need to consider the risk of assembly in a case out of tolerance dimensions are not detected. This might be due to faulty measurement equipment, as the right methods to control such equipment are not in place. In your specifications you can for example insert requirements on the calibration of caliper and thickness meters or you can request R&R (Repeatability and Reproducibility) records.

Those are just a few examples of how Ishikawa can help you be more precise in your specifications to avoid defects once the production starts. Getting involved in controlling the quality of your products is a no brainer when you are dealing with factories in Asia. Pre-production steps like customized audit and specifications design are often overlooked when in reality they are much more efficient than basic pre- shipment inspection in avoiding quality issues. Ishikawa diagram is very useful to help you identify the areas of risk when preparing your audit scope or product specifications and I strongly recommend using it systematically.

I’m conscious that Ishikawa is not the only tool, it’s one among many… Which one do you use? And do you see value in getting involved at the first stages of pre-production to avoid defects?

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