In the early stages of lean rollout, predominately across the industrial sector, not everyone fully embraced the methodology. In many situations, teams—in their hurry to cut ‘waste’ and reduce costs—implemented changes which resulted in lower quality escaping into the hands of the customer.

When hearing of lean efforts, many quality professionals came to realize it was a matter of time before warranty claims would likely come flooding in! Thankfully, those days have mostly been left behind. It took time and effort, but proponents of lean and Six Sigma methodologies as well as other quality professionals have worked hard to achieve a marriage of convenience. For the most part this has fared fairly well.

While lean manufacturing improvement methods and Six Sigma’s variation reduction and defect prevention methods of quality improvement are mutually exclusive, they have been found to be complementary. Both look at eliminating muda which is a lean manufacturing term in reference to waste or non-value-added activities that impede efficiency and profitability.

Afterall, just as customers aren’t willing to accept lower levels of quality, they don’t want to pay for a company’s inefficiencies. Where there is a competitive environment for similar types of products and services, the prices normally reflect the cost of production and profit.

When waste is eliminated from all aspects of delivering the product to the customer, the low-cost producer can maximize profit and achieve greater margins compared to competitors. However, many organizations and innumerable consultants have often focused on one or the other in either defect reduction or lean manufacturing.

When the focus is on quality alone, there’s a narrower definition of waste which focuses mainly on nonconformance, namely scrap, rework, and repair. Companies become more focused on point improvement. In other words, companies work on a specific element of the process or product to create a specific improvement in a characteristic or activity. Six Sigma activities often have decent examples of this narrow focus on specific elements.

Quality has evolved over the decades from inspection to quality management and onto longer term improvement. But the basic concepts have not changed since the original work of Dr. Walter A. Shewhart, who many refer to as the father of statistical quality control. His work fostered other quality giants like Drs. Joseph M. Juran and W. Edwards Deming to create a legacy of modern quality strategies and techniques.

The purpose of quality has always been to focus on the process and identification of the sources of variation, control them, and then add value to produce, as efficiently and effectively as possible, the product the customer wants and deems worthy of purchasing.

Because the amount of effort required to uncover all sources of variation in a process or activity can be very involved and time consuming, the underlying ideas of statistical process control are often lost or even ignored. The emphasis then becomes one of product acceptance instead of variation reduction.

Similarly, lean activities focus on the elimination of variation, a form of waste, in a process that has intense scrutiny on cycle or takt times (not exactly the same) and total movement of the product or process. Lean improvements, or blitz kaizens, performed in a vacuum (without focusing on the product conformance) can result in a highly effective generator of nonconforming product (scrap, rework, or repair).

How should quality and lean be linked together in product and process redesign and improvement?

Undoubtedly, the lean methodology can eliminate or expose many areas that can create nonconformance. Indeed, the fewer steps and handoffs can reduce variation and limit potential areas for problems. However, it’s extremely important not to lose sight of the end game which is to deliver a quality product to the customer.

The process of establishing a lean manufacturing cell or workstation can highlight many areas in which variation can be introduced to create a nonconforming product. But variation cannot be overlooked in the total lean activity or just pushed aside in the effort to get quick results of cycle or takt time improvements.

As an example, consider the early rollout of a lean event at an industrial facility in which a manufacturing cell was created for a family of parts. Cycle times were significantly reduced through improved layouts, combining operations, installing 5S philosophies and improved workflow management. At the end of the process, a traditional inspection, specified by the customer, determined whether the product was acceptable in accordance with its requirements. The results were less than satisfactory!

With the focus solely on lean, the team failed to integrate the determination of acceptance at each step in the process. Quality control methods to drive out variation were not put in place; therefore, the process was not optimized to eliminate waste. Ultimately, the waste was not detected until the end when inspection and acceptance activity was performed.

But how should quality and lean be linked together in product and process redesign and improvement? The answer is not always simple nor straightforward. This will be discussed in next month’s column.