How is Lean Different from Six Sigma? Lean is the elimination of waste. Six Sigma is about the elimination of variation. Pick the right tool for the right purpose.
The Goals of Lean and Six Sigma
The goal of Six Sigma is to produce output that is consistent and free of defects. Defective output requires re-work, and re-work is waste. Inconsistent output is the result of a flawed process. Six Sigma seeks to identify the flaws, determine their cause, and eliminate them.
Six Sigma DMAIC starts with the view that waste includes defective products. To remove waste, you find the root cause of defects (using statistical methods), then design an improvement (Design for Six Sigma) or replace a fault so that the defects no longer occur.
Using a manufacturing example again, let’s say you have a factory that produces widgets. The widgets should all be a certain size, shape, and weight. In your sample output, you discover that fifty out of 1,000 widgets are flawed (e.g., wrong size, shape, or weight). To correct this, you could use Six Sigma to determine what’s causing the variation/defects. Then, you could work to reduce them to a Six Sigma level.
The goal of Lean, on the other hand, must begin with the view that the product and process that creates it must add value to the customer. Anything that does not directly add value to the customer is a waste. It further defines the common wastes and how to eliminate them.
Lean vs. Six Sigma
While it may be desirable to use both Lean and Six Sigma, they are separate issues. An operation can be Lean and still have an unacceptable level of variation in the output. It can also have the variation under control and not be Lean. The two are complimentary, but neither is dependent on the other.
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How Lean, Six Sigma, and Design Can All Coexist
The Difference Between Lean and Six Sigma
While Lean encourages daily, general improvements, Six Sigma demands data-based, specific improvements for specific projects.
Lean doesn’t require a hierarchical structure of qualified “masters” to implement the changes. Every individual employee, regardless of their roles in the business, is encouraged to participate in actively improving the manufacturing process.
Six Sigma requires a hierarchical structure of various experts with various belts. These belts signify their level of experience and knowledge in the Six Sigma way.
With the Lean approach, you can walk into your factory today, instruct everyone on what to look for, and give them methods for applying changes they see fit.
With Six Sigma, you’ll have to hire a certified expert to assemble a team, identify a problem, and direct that team until the problem is solved.
In Lean, you let everyone test and experiment to see what works and what doesn’t – a bottom-up approach.
In Six Sigma, you let the qualified professional leading the team decide when you’ve completed the project – a top-down approach.
Which to do first? Lean or Six Sigma?
Undoubtedly, you should do Six Sigma before Lean.
Why, you ask? Because Lean is about creating an efficient process, and Six Sigma is about making the process deliver what the customer wants with little variation. You don’t want to do Lean first because you could make a perfectly-efficient process that delivers something that the customer doesn’t want. If something doesn’t need to be done in the first place, there is no point in doing it well.
If you do Six Sigma first, you’ll have a process that can reliably produce the output that the client wants. Then, use Lean to make that process very efficient and productive.
In other words, use Six Sigma when your process has a lot of variation or doesn’t always perform how the client wants it to. Use Lean when your process already delivers what the customer wants, but the process itself needs to be more efficient or more productive.
Both are tools, philosophies, and management systems, but they are geared toward different ends.
It is possible that both processes could use the same or similar tools and end up with the same improvements.
Note that in the real world, some management teams are more focused on efficiency and productivity than customer satisfaction, and in those cases, Lean is the best choice. Also, it is sometimes helpful to do quick Lean activities, so you can show improvements quickly (whether or not the customer cares about them) to build credibility to do the longer Six Sigma projects.
Integration of Design, Lean and Six Sigma
Six Sigma: Six Sigma is a data-driven approach for reducing process variation and defects. It uses the DMAIC (Define, Measure, Analyze, Improve, Control) methodology to identify, measure, analyze, improve, and control processes. Six Sigma reduces the variation in the process and builds repeatability by following a problem-solving approach using statistical tools. Reduction in variation increases quality, throughput, and overall outcome while cutting costs.
Lean: Lean eliminates waste, decreases wait time and creates value across all areas of business. It uses tools like Value Stream Mapping, 5S, and Just-In-Time to identify and eliminate non-value-added activities.
DFSS: Design for Six Sigma (DFSS) is a proactive approach that prioritizes the creation of products, processes, and services that align with customer needs and minimize defects. DFSS eliminates the need for costly trial and error in the design process, as it incorporates customer requirements directly into the initial product design phase.
Lean-Six Sigma Integration
Often organizations practice Lean Six Sigma, which combines Lean’s focus on efficiency with Six Sigma’s emphasis on quality. This integration aims to reduce waste while also improving process quality by using the DMAIC methodology.
Many organizations recognize that they have a combination of both sets of issues. The two methods complement each other working together to identify errors and waste more efficiently than using just one method. Lean Six Sigma helps organizations in any industry increase revenue, reduce cost, and improve collaboration in today’s competitive world.
Both Six Sigma and Lean coexist in any organization. Lean accelerates Six Sigma. Lean provides stability and repeatability, which helps Six Sigma collect the data more accurately. Therefore, many organizations implement both methodologies into an integrated system or improvement roadmap.
Problem identification, problem-solving tools, and techniques are common in both Six Sigma and Lean methodologies. Such as the Pareto chart, FMEA, Why-Why, Fishbone diagram, etc. The extensive set of these tools increases the speed and effectiveness of the process.
Although both Six Sigma and lean management are cutting-edge methodologies, each system places emphasis on specific aspects of organizational performance. Consequently, in a highly competitive environment, implementing either program in isolation may lead to diminishing returns.
Design Integration with Lean and Six Sigma
When designing new processes or products, organizations can integrate DFSS principles with Lean and Six Sigma. This ensures that from the outset, the process or product is designed to meet customer needs, minimize waste, and reduce defects. Tools like QFD and FMEA can be used to identify critical customer requirements and potential failure modes, while Lean principles can be employed to eliminate waste and streamline processes.
Tools Used by Both Six Sigma and Lean
In both cases, process mapping and value stream mapping are essential. If you cannot define your process, how can you possibly know what is wasteful or what is variation? Once you have defined your process via a process map you can use value stream analysis to determine where the waste is.
