Select Page

Some Lean Six Sigma Tools – Analyse, Improve and Control (#2 in the series Some Lean Six Sigma Tools)
By Samuel Okoro

The cost, speed and quality leaps of Lean Six Sigma are obtained through the application of appropriate tools. We conclude by reviewing some tools from the Analyse, Improve and Control phases of DMAIC.

The Analyse Phase

Purpose of Analyse: In implementing Lean Six Sigma this phase identifies and verifies the relationships between causes and their effects. It helps in the discovery of factors that affect key process inputs and outputs. The analyse phase seeks to find patterns in the data obtained during the measure phase in order to make sense of it all.

Tools for Analyse:

Scatter Plots: Two variables are plotted against each other on a graph. The resulting picture gives a visual indication of how well correlated the variables are.

Regression Analysis: This can be regarded as a mathematical equivalent of the scatter plot. Here an equation is derived to express the dependence of one of the variables on one or more others. The equation can then be used to predict values of the dependent variable for given values of the independent variables.

Fish bone diagram: large arrow is drawn with the effect whose causes are being analysed show on the right at the end of the arrow. Main categories of probable causes are shown on branches emanating from the main line. For each category, detailed causes are brainstormed and indicated against the corresponding branch. x-process

Time Trap Analysis and Capacity Constraint Identification: A time trap is a process activity that inserts delays into the process and may be due to capacity constraints or other operational inefficiencies. Whatever the source of the delays, it finally shows up as long lead times. A capacity constraint is a sub-process or activity whose output per unit time is less than that of the preceding and/or subsequent sub-process or activity.

Non Value-Added Analysis: From the as is value stream map, each process activity is examined to determine its contribution to customer requirements. Those which do not contribute to customer valued outcomes and are not necessary for other business reasons (e.g. regulatory requirements) are eliminated.

The Improve Phase

Purpose of Improve: In the previous phases, defects (variability outside the customer’s specifications) and wastes (non-value added activities and costs) have been identified, measured and their causes found through analysis. The purpose of the improve phase is to eliminate the defects and wastes.

Tools for Improve:

To Be Process Maps: A map of the desired process is created, in which identified non-value added activities have been eliminated

Setup reduction: From the capacity constraint and time trap analysis carried out in the Analyse phase, we can determine whether the major source of delay was due to long setup times. In that case, the following steps are applied.

• Document and classify setup procedures
• Improve organisation-Study work area layout and analyse required movements. Use 5S if necessary to remove inefficiencies. Brainstorm improvement opportunities in the setup steps.
• Where possible convert internal (setup activities that are done with the machine down) to external (setup activities that do not affect the running of the machine) procedures. In transactional situations, this means converting serial procedures to parallel.
• Improve the remaining internal setup procedures.

5S: This lean tool results in a clean and organised work area, with a place for everything and everything in its place. The steps of the methodology are:

• Sort
• Straighten
• Shine
• Standardise
• Sustain

Applying 5S eliminates inefficiencies resulting from lack of organisation by reducing the amount of unnecessary motion and transportation.

Total Productive Maintenance: Where downtime is a major cause of low process cycle efficiency, total productive maintenance, which aims to reduce the percentage of downtime, should be applied.

Mistake Proofing: By proper design of the processes and equipment, the possibility of errors (and with them the need for inspections) is eliminated. Examples are designing online forms that cannot be submitted if data is incompletely entered, or if the wrong type of data is entered. Similar to this are parts that can only be assembled in one way.

Design Of Experiments: This is the statistical design of experiments to enable you determine the impact of two or more variables on another variable of interest. This tool also accounts for interaction effects between variables.

Hypothesis Testing: This is a statistical tool for testing the validity of assumptions. In this case the assumptions might relate to the impact of causes on effects. For example, if performance is suspected to be operator dependent, tests might be carried out to verify whether observed differences in performance between two operators are statistically significant.

Solution Selection Matrix: Generally there will be more than one possible solution identified to the problems under consideration. The selection matrix compares them using a set of weighted criteria to determine the most appropriate.

Project Management: Actual implementation of agreed solutions will be in the form of a project, and will require use of the usual project management tools for planning, communication, risk assessment, and monitoring.

The Control Phase

Purpose of Control: The purpose of the control phase is to ensure that the gains from the improve phase become embedded in the organisation.

Tools for Control:

Standard Operating Procedures: The improved process design will certainly include new operating practices. These must be codified in an operating manual to which operators can refer. Having a standard operating manual helps prevent slippage into old inefficient practices.

Statistical Process Control: Control charts, reflecting the improved capabilities of the process must be constructed and used to monitor process performance over time.

Visual Management: The essence of visual management is captured in the idea that an employee should be able to walk through the work area and come away with 90% of the information. This is achieved through 5S organisation, illustrations of process steps placed close to the process, SIPOC diagrams and value stream maps, the use of shadow boards etc.

Conclusion

The list of tools considered in this article and the last are only a few of the several available. On any one project, only a few are likely to be used.

Samuel Okoro is the CEO of Leapfrog Alliance Ltd, a management training and consulting firm that helps organisations to reduce costs and improve quality through better business processes. His personal passion is to help move Third World business to world-class levels. For further details please visit http://leapfrogalliance.com or email sjokoro@leapfrogalliance.com.