Lean Six Sigma In Production Thinking - Yamazumi Chart Tools

Lean production was the famous “machine that changed the world” and Six Sigma has also delivered powerful and sustainable improvements in quality in recent decade. As a long time Six Sigma Black Belt, I was not surprised when I first saw these two powerful concepts combined in the term “Lean Sigma”. The elided phrase has even been registered as a trademark by TBM Consulting Group. It’s a natural marriage – on the one hand the relentless focus on flow and cycle time of a lean system; on the other the concept of repeatable excellence in quality.

We are taught from school to think of quality, cost and time as trade-offs: a so-called “iron triangle” that ineluctably leads to success in one element at the cost of another. Lean sigma forces us to revisit these assumptions. The concern with statistical process control and the elimination of variation in process performance is the same as ever – the added ingredient is simply speed. Lean is concerned, indeed obsessed, with the ruthless elimination of waste and speeding up of cycle time.

Lean sigma utilizes insights such as process analysis and Eli Goldratt’s Theory of Constraints to identify bottlenecks in a process. It first seeks to regulate all flow up to the level of the bottleneck, to prevent any build-up of waste. Then the bottleneck itself is “elevated”, or raised so the entire process can speed up. Lean tools are focused on the elimination of waste and rework – the same “hidden factory” that many Black Belts will remember from their basic training. It turns out that the cost of poor quality in terms of unnecessary rework due to statistical non-conformity is one of the primary sources of waste that lean production seeks to eliminate.

Lean tools and six sigma are therefore merely two sides of the same coin. Both focus relentlessly on inputs to drive outputs. Both seek to eliminate waste – Six Sigma in terms of delivering statistically accurate, centered and repeatable processes, and lean in terms of redesigning the entire value chain. Both need consistent support from senior management and a culture of immersion in quality principles to succeed. Both are obsessed with metrics and targets while paradoxically realizing that the truly high quality organisation needs to move beyond them. The humbling words of Deming still resonate in my ears every time a new quality initiative is launched – “Eliminate slogans, exhortations and targets for the workforce asking for zero defects and new levels of productivity”. Until that nirvana of deeply ingrained quality arrives, we must work with the tools we have.

Lean thinking acts as Six Sigma continuous improvement on steroids by delivering a core focus on cycle time and total value chain performance. It forces more strategic thinking through value chain mapping and requires challenge to every aspect of what a business process does. The Yamazumi chart is an ideal visual tool to test these basic assumptions and reconsider the fundamentals – what needs doing and why? Six Sigma can turn a poorly performing business process into a consistently accurate one. Lean sigma goes a step further and asks – should we be doing the process at all? Now that truly is a quality revolution.

Lean manufacturing was a concept built around the elimination of waste. Originally there were seven types of waste: transportation, inventory, motion, waiting, overproduction, over-processing and defects. Radical redesign of the flow of the production line can reduce most of these. For example, automotive supplier parks are located next to lean production factories to eliminate transit costs. Just-in-time production means that such factories only produce parts when they are given the signal to do so by the auto production line. Inventories and storage requirements are therefore minimized, although of course this does leave the entire supply chain vulnerable to disruption in the event of an external event. Meanwhile "pull" systems built around the kanban principle of visual indicators changed the layout of factories. And of course Yamazumi Boards were introduced to graphically map entire processes and identify bottlenecks for elimination.

Many of the innovative manufacturing features that formed part of the Toyota Production System are now mainstream in Western workplaces. The fusion of Eastern lean thinking and Western six sigma represents a new opportunity to combine the best of both disciplines and raise the productivity of global industry one notch further.

The scope for applying lean tools and six sigma in office and non-industrial environments remains enormous. Simple Pareto analysis will make dramatic discoveries and reveal inefficiency in everyday work processes. Six Sigma Yellow Belt material can be distributed amongst line operatives and key personnel in any organization. Every workplace has a "hidden factory" of unnecessary process re-work and lean six sigma will help you eliminate it.

All text (c) WestOcean 2010