work well together to achieve quick process improvements and greater product consistencies. This is true particularly if you subscribe to a top-level and often misunderstood and misaligned definition of each. Lean equals zero waste. Six Sigma equals zero variation. Certainly there’s some overlap here because lean includes variation elimination as well, but the point is, you really can’t separate the two when it comes to developing an overall improvement effort.
Lean encourages action along a broad front by empowering people at all levels to contribute. This allows organizations to welcome challenges and implement improvement initiatives. Of course, improvement starts by using the appropriate tools. We’re all familiar with the results of lean tools and practices such as process mapping, kanban, kaizen and 5S. Kaizen can help us standardize a process or eliminate waste, and often we see results within days. 5S can help us structure our environment so that problems can be identified more quickly.
Six Sigma brings the discipline of define, measure, analyze, improve and control, as well as the rigor of statistical analysis, to identify a root cause, sustain improvement and provide the solid measurements that create a balanced scorecard. Most of us know by experience that Six Sigma is a solid, scientific methodology for reducing process variability. Process variability affects quality because the more you reduce variation; the more likely it is that the process will produce a good product. It’s not just quality, though. Variation reduction also affects the entire value stream (a uniquely lean view) because reducing variation will provide more consistent yields, which means that you can predict what you will get out based on what you put in. Therefore, you can design your process to flow more continuously, with less just-in-case inventory and improved lead times. Very often this is an underappreciated benefit of reducing variation.
Imagine a board game for manufacturing engineers where all the game pieces are assembly machines, conveyors, parts feeders, robots and other types of equipment. The game takes place in a Tier 2 auto parts plant that has adopted lean production principles. The objective is to acquire the right type of assembly equipment while confronting management, operators and customers constantly chanting the lean manufacturing mantra of "waste elimination."
As lean initiatives become more popular, many engineers are playing that game every day. To thrive in that type of environment, engineers must break the age-old habit of always wanting to buy the fastest machine equipped with the latest bells and whistles. The trick is to challenge complexity and balance the right amount of automation to meet lean objectives and customer needs.
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