#1 린 식스시그마란? - 정의(Defining)
Introducing Lean Thinking
Since Henry Ford's first production line, Lean thinking has evolved through several sources and over many years. Still, much of the development has been led by Toyota through the Toyota Production System(TPS).
Toyota built on Ford's production ideas, from high volume, low variety, wide variety, low volume.
During a tour to General Motors and Ford, Kiichiro Toyoda and Taiichi Ohno visited Piggly Wiggly, an American supermarket, and noticed Just in Time and Kanban being applied.
Lean isn't a recipe for your organization to slash its costs, although it will likely lead to reduced costs and better value for the customer.
John Krafcik(who is joining Google to provide advice on the driverless car) commented:
"It needs less of everything to create a given amount of value, so let's call it Lean."
Bringing based on Lean
Toyota's Taiichi Ohno describes the TPS approach very effectively:
"All we are doing is looking at a timeline from the moment the customer gives us an order to the point when we collect the cash. And we are reducing that timeline by reducing the non-value-added wastes."
Toyota chairperson "Fujio Cho" provides a clue as to what's also needed:
"The key to the Toyota way is not any individual elements but all the elements together as a system. I must practice it every day in a very consistent manner- not in spurts. We place the highest value on taking action and implementation".
▶Heijunka provides the foundation. It encompasses the idea of smoothing processing and production by considering leveling, sequencing, and standardizing.
- Leveling involves smoothing the production volume to reduce variation, that is, the ups and downs and peaks and troughs that can make planning difficult.
- Sequencing may well involve mixing the types of work processed.
- Standardizing seeks to reduce variation in the way work is carried out, highlighting the importance of standard work of following a standard process and procedure.
*Remember, however, that you need to standardize your process before you can improve them. Once they're standardized, you can stabilize them, and now you fully understand how the process works, you can improve them, creating a 'one best way' of doing them.
▶Jidoka has two main elements, and both seek to prevent work from continuing when something goes wrong:
- Autonomation allows machines to operate autonomously by shutting down if something goes wrong. An early example hails from 1902, when Sakichi Toyoda, the founder of the Toyota group, invented an automated loom that stopped whenever a thread broke.
- Stop at every abnormality is the second element of Jidoka. At Toyota, every employee is empowered to stop the line.
▶Just in Time(JIT) involves providing the customer with what's needed, at the right time, in the right location, and the right quantity.
- Single piece flow means each person an operation and makes a quick quality check before moving his output to the next person in the following process.
- Pull production takes what it needs from the preceding process only when it needs it and in the exact quantity. Pull production reduces the need for potentially costly storage space.
- Takt time tells you how quickly action to things, given the volume of customer demand. Takt is German for a precise interval of time, such as a musical meter.
Sussing Six Sigma
Jack Welch, the former General Electric CEO, introduced Six Sigma; he said: "We are going to shift the paradigm from fixing product to fixing and developing processes, so they produce nothing but perfection or close to it."
In the 1980s, Motorola CEO Bob Galvin struggled to compete with foreign manufacturers. Quality Engineer Bill Smith coined the name of the improvement measurements: Six Sigma.
In Lean Six Sigma speak, a customer requirement is called a CTQ- Critical To Quality.
In the above example, the CTQ is five days or less, but the above histogram's average performance is four days. People might say that the average performance is still in CTQ; however, remember that this is only the average; your customers experience the whole range of your performance.
If you make an error but correct it before the order goes to the customer, you still count the defect because the rework activity costs you time and effort.
▶Key terms of sigma
- Unit: The item produced or processed
- Defect: Any event that does not meet the specification of a CTQ.
- Defect opportunity: Any event that provides a chance of not meeting a customer CTQ. The number of defect opportunities will equal the number of CTQs.
- Defective: A unit with one or more defects
You can work out your process sigma performance against CTQs as shown in the above [Calculating process sigma values]. We have a sample of 500 processed units. The customer has three CTQs, so we have three defect opportunities. The CTQs are related to speed, accuracy, and completeness. We found 57 defects. With the [Abridged process sigma conversion table], you can find the sigma value that's closest to your DPMO(Defect Per Million Opportunities) number of 38000. As you can see, this is 3.3.
Clarifying the major points of Six Sigma
The five principles of Six Sigma are:
- Understand the CTQs of your customers and stakeholders
- Understand your organization's processes and ensure they reflect your customers' CTQs
- Manage by fact and reduce variation
- Involve and equip the people in the process
- Undertake improvement activity in a systematic way
※ 참조: 본문은 책, "Dummy들을 위한 린 식스시그마(Lean Six Sigma)"와 The Toyota way를 정리한 내용을 기반으로 제 경험들을 조미한 글입니다. 현재는 원서 기반으로 내용을 정리하고 있는 중이며, 정리가 완료되면 한글로 번역을 추가할 예정입니다.