Recap: The Lean Toolkit

The lean toolkit is comprised of a set of tools that are used in support of the six sigma DMAIC process, which is an acronym for Define, Measure, Analyze, Improve, and Control. While this toolkit is not all inclusive, the set of tools that have been discussed over the last few columns will allow an organization to move through each of the DMAIC functions and facilitate implementation of any lean initiative. In the last column, we discussed the Improve function of the DMAIC process, so let’s now finish with the Control function.

Control

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The word control often has a negative connotation surrounding it, which in some usages is well deserved. However, in the context of lean, control simply means putting things in place to monitor and maintain the improvements that have been gained from the Define, Measure, Analyze, and Improve functions of the DMAIC process. Although this is the final step in the process, it bears repeating that the overall DMAIC process is an iterative, never-ending journey, if executed properly.

Control Charts

Control charts are a graphical representation of the current state of a process and should be implemented at the operator level to maximize effectiveness. A control chart’s true function is to provide real-time feedback to control and improve a process, which means that the data displayed on the charts must help front-line operators make better process decisions. All control charts have three basic components: 1) A process center, or mean, 2) An upper and lower control limit, and 3) An upper and lower specification limit. In a stable process, data will be randomly centered on the process mean and contained within the control limits. Data between the control limits and the specification limits signal that a process adjustment is needed. Data exceeding the specification limits would be considered out of acceptable limits and defective. The most common form of control charts are the X-Bar and R chart. X-Bar refers to the average of the data in each sample and plotted in the top half of the chart, and R stands for the range of the data in each sample and is plotted in the bottom half of the chart (Figure 1).

Cpk Analysis

Every product has an optimum value, and because every process has variation, it also has a tolerance. This is defined as specification limits, with both an upper and lower spec limit (USL, LSL) surrounding the optimum value. Simply stated, when a product or process is outside of either of these spec limits, bad product is produced. How well the process variation is centered and contained within these spec limits is called process capability. The relationship of this variation to the mean and spec limits is the process capability, or Cpk. The less variation in a process, and the closer the variation is to the mean, the higher the Cpk number. With all the statistical tools available, the formula is not important for this purpose, but what is important is recognizing what this number means. It is generally accepted that a Cpk of less than 1.33 would indicate a process that is not capable of consistently meeting customer requirements, and a Cpk of 2.0 would represent a six sigma level. Calculating process Cpk levels is not a one time occurrence, it must be performed on a regular basis (quarterly is usually sufficient).

Audits

Developing a robust internal auditing system provides a methodology for monitoring and maintaining process improvements and sustaining the momentum created by a lean initiative. The audit program should include all lean process specific functions as well as areas such as training and quality system compliance. It is also a key tool for minimizing (or eliminating) undesirable findings during an external customer or quality system audit. With a solid program and skilled staff, an internal audit system will assure the success of lean efforts and operational excellence.

Management by Walking Around

Tom Peters, author of the “Excellence” series of books and one of my favorite management consultants, coined the phase MBWA (Management by Walking Around). This is another of those concepts that seem so obvious, but how many of us actually do this? This is a rhetorical question, but really, how often do we go out on the shop floor and just observe what is going on? I don’t mean tracking down orders and making sure people are working, but how does the facility look? Do the workers look happy? Are we working smart or overcompensating by working hard? What would I think if I were the customer? You can’t answer these questions sitting in your office!

Do Something Now!

As we close out this series on the DMAIC process, my advice would be to do something now! Waiting for a plan to be perfect will only ensure that it never begins. Doing something now is always better than doing something later, and hopefully, this series has given you a roadmap for beginning this journey.