The cost, speed and quality leaps of Lean Six Sigma are obtained through the application of appropriate tools. Following the DMAIC improvement model of Lean Six Sigma, we will look at a number of tools from each phase.
The Define Phase
Purpose of Define: This phase of the Lean Six Sigma implementation identifies the improvement opportunities and customer deliverables and defines a scope. At the end of the define phase, we should have a project charter, clearly identified stakeholders, a project team, estimation of business implications, an evaluation of customer requirements, a high level process map and project management and communication plans.
Tools for Define:
Stakeholder Analysis: The various stakeholders (customers, shareholders, employees) are listed and the potential impact of the improvement project on each assessed as substantial, average, low or nil.
SIPOC diagram: Of the tools applied in this stage of the improvement project, perhaps the most commonly used is the SIPOC diagram. SIPOC stands for Suppliers, Inputs, Process, Outputs and Customers. The diagram provides a visual answer to the questions required to understand the process: who are the primary stakeholders of this process? What value does it create? Who is the owner of the process? What are the inputs and who provides them? What resources are consumed by the process? What process steps create the value?
The steps involved in creating the SIPOC diagram and the involvement of team members in brain storming and idea generating sessions are as important as the resulting diagram.
VOC – Voice of the Customer: Critical to a proper definition of the improvement project is the availability of data representing customer viewpoints and requirements. These are collected using VOC tools like interviews, surveys, focus groups, comment cards, suggestion/complaint boxes etc. The definition of customer here includes internal and external customers.
Using Kano analysis coverts raw quantitative and qualitative data obtained from the above into clearer expressions of the value customers place on various product and service features you offer.
Development of critical-to-quality requirements converts customer statements, which may be imprecise, to precise requirements (valued from the customer’s perspective) for your product or service.
The Measure Phase
Purpose of Measure: This phase quantifies the current state of the process with respect to cost, speed and quality and provides an idea of the gaps to be filled. At the end of this phase, we have a detailed map of the process, data on key input and output variables, an analysis of the capability of the process, refined project charter and plans where warranted by new information, and recommended actions to pick low hanging fruits.
Tools for Measure:
Operational definition – various measures are defined so that all team members apply the same definitions when gathering data for the improvement project.
Process map, value stream map, complexity value stream map: This produces a more detailed representation of the process than the SIPOC diagram and includes such information as wait times, processing times, resource consumptions, process operator etc.
Cause Effect Matrix: This tabulates causes against effects and calculates scores which are used to rank the causes. As a measure tool, this matrix is used to select which inputs to focus on because of their significant impact on the process outputs.
Preliminary FMEA (failure modes and effects analysis): This tool has a similar function to the cause and effect matrix. All possible failures in the inputs are considered, and then weighted according to probability of occurrence, severity of impact on outputs and difficulty of detection. This assessment also helps to determine what inputs the project team should focus on.
Data collection plan: This includes decisions as to what data (balanced between input and output) to collect, identification of stratification factors (these help determine patterns in the data), determination of sample size, identification of data sources, development of data collection sheets and assignment of data collection duties among team members.
Pareto charts: This is one more tool for focusing the team’s efforts on the most important problems. A Pareto chart is a bar chart where the horizontal axis represents categories. On the vertical axis we can plot in descending order, the frequency of occurrence, or cost, speed or quality impact of each category. Where a clear Pareto effect exists, only a few of the categories (typically 20% or less) are responsible for majority of the effects (80% or more).
Measurement systems analysis: The process of obtaining measurements is subjected to standard analyses to ensure reliability, repeatability and reproducibility. Other attributes of the measurement system are stability, bias and discrimination.
Control charts: A control chart is a run chart sequence of quantitative data with three horizontal lines showing a centred mean and upper and lower control limits. Control charts help to assess the nature of variation of the process. In-control processes are expected to yield data points randomly distributed around the mean but within the calculated control limits.
Process capability assessment: This tool measures of process capability assess the ability of a process to meet functional requirements. Several measures of capability exist. All of them are compare the process standard deviation to the allowable range of variation as specified by the customer.
Samuel Okoro is the CEO of Leapfrog Alliance Ltd, a management training and consulting firm that helps organisations located in the African region to improve quality and reduce costs through better business processes. His personal passion is to help move African business to world-class levels. For further details please visit http://leapfrogalliance.com.