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Lean vs Six Sigma: What are the Differences for Manufacturers?

May 28, 2021

 by David Collins III

three people working and discussing a machine

If you have spent any time in manufacturing, you have heard the words “Lean” and “Six Sigma”. Often they are used interchangeably or together, which may cause some confusion. Have you been in this industry too long and are afraid to ask what the difference between the two is? Don’t fret. It is a common misconception that even experienced individuals often misunderstand.

The most crucial difference to understand is that Lean is a way of thinking and that Six Sigma is a set of techniques and tools for process improvement. Put another way, lean is a way of life, and Six Sigma is a way of doing things. 

Both are focused on eliminating waste, though lean primarily focuses on eliminating waste through tools that target organizational efficiencies while integrating a performance improvement system (continuous improvement, etc.) whilst, Six Sigma focuses on eliminating defects and reducing variation.

Lean Manufacturing

Lean thinking encourages continuous improvements, as organizations are trying to look for opportunities to improve operations and eliminate waste. The origin of the lean is the Toyota Production System. We could write dozens or hundreds of blogs on the Toyota Production system (we already have written a few such as here and there). The system focused on building an organizational culture that reduced or eliminated waste in all its forms. Reduce wasted time, material, and movement through every step of the production process.

It seeks to design out overburden (Muri), inconsistency (Mura), and eliminate waste (Muda). To do that, the systems are meant to be as easy as possible, as regular as possible, and use as few resources as possible. While this system sounds robotic with its emphasis on efficiency, it is nothing of the sort. Lean is human-focused and aims at empowering operators to determine the root causes of problems and find solutions. Everyone in the company is expected to find solutions and reduce waste.

You may ask yourself, this sounds great; why doesn’t everyone do it? Remember that lean is a “way of life”, meaning that it’s a culture that must be ingrained amongst all employees. Changing and mending the way of thinking is not an easy change to make. An American automaker tried to implement lean techniques in the 1970s and 1980s but was not successful since they imported the methods but not the mindset. 

Six Sigma

Six Sigma is most often identified with General Electric but was pioneered by Motorola. The sigma of Six Sigma is from the abbreviation of the lower-case Greek sigma (σ) used to represent Standard Deviation. Six sigma means six times the standard deviation within the specification limits, meaning 3.4 defects per million opportunities. A process to the Six Sigma level has a 99.99966% chance of being error-free. Six Sigma uses statistical process control and other tools to improve processes. The primary methodology is DMAIC (Define, Measure, Analyze, Improve, Control). CMC uses a version of this methodology in all its projects. 

Six Sigma is more project-based than Lean. The project-based nature has its advantages since running a project is more manageable than changing company culture. It is top-down and led more often than not by experts (ranked on colored belts), both of which mean initial implementation is more effortless. 

However, Six Sigma’s top-down approach can also run into some problems. Operators will change only marginally to appease and satisfy their supervisors. Top-down solutions often have less buy-in from the employees since they are not part of it. Lean stresses improvements made at the lowest possible level, creating greater buy-in but does not have a rapid turnaround. 

Which method should you use? We believe that Lean is more valuable, though Six Sigma offers a lot to improve manufacturing operations.

What do you think? Has your company had success implementing these programs?   


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Topics: Lean Manufacturing, Manufacturing Consulting, Manufacturing In China

David Collins III

David Collins III

David was a Senior Strategy Consultant for Deloitte, served in Iraq as a Special Operations Civil Affairs soldier, and as a Governance Advisor to the Afghan Government with the Department of State. At CMC, David advises clients on strategy and investments.

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