When to Use Lean Six Sigma Tools?
In many scenarios, new lean six sigma practitioners, uncertain about the methodology, tend to get confused on when to use the different lean six sigma tools. This article, the first of a two-part series, gives an overview on when to use different Lean Six Sigma/Change Management tools and in which phases of DMAIC (Define, Measure, Analyze, Improve and Control).
#1: Fish Bone Diagram (Ishikawa diagram) or Cause and Effect Diagram
To brainstorm the causes of variation (represented by bones of the fish) that lead to the effect (represented by the head of the fish! (6Ms – Man (and Woman!), Machine, Method, Mother Nature (Environment), Measurement System and Materials. Ensure that Man (or Woman) ONLY doesn’t get blamed as the cause of variation; don’t debate endlessly whether a particular cause is Method or Man etc - note down the causes first and then classify later
Which phase of DMAIC to use? Measure/Analyze
#2: Hypothesis tests
To test and prove or disprove a hypothesis (for example, to test whether the average production time of a shift 1 is greater than shift 2). Ensure you use the right hypothesis test. Also ensure the pre-requisites for each hypothesis test are met. Refer Minitab Statguide for detailed information.
Which phase of DMAIC to use? Measure/Analyze
#3: 5-Why Analysis
To get down to the root cause of a particular problem/issue. Ensure that God doesn’t get blamed for everything.
Which phase of DMAIC to use? Analyze
#4: Cause and Effect matrix (C&E matrix)
To rank each X against Primary Y, Secondary Y and the Counterbalance and prioritize Xs. Operational definition of rating (9-3-1-0) an X against a Y should be clear and agreed upfront.
Which phase of DMAIC to use? Measure/Analyze
#5: Kaizen event
When the problem/issue needs to be solved immediately and requires a focused effort (and time) from the team. Ensure the pre-work is planned thoroughly and completed prior to actual kaizen event; scope should be defined such that the problem/issue can be solved and solution implemented within 3 - 5 days (or atleast a pilot).
Which phase of DMAIC to use? Improve
#6: 5S
To sort, organize and perform housekeeping of files, products, service items, maintenance tools, clothes, etc. Helps with increasing productivty and employee morale
Which phase of DMAIC to use? Any Phase
#7: Poka Yoke
To mistake proof a solution/process/sub process. Physical prevention of an error is the best form of poka-yoke - strive for this.
#8: Value Stream map
To not only map out the flow of a process, but also get in-depth information about the process such as Customers, Suppliers, Downtime, Errors, Production time, Inventory, Value added time, Information flow, Material flow, People flow, Throughput rates, Incoming raw material rates, 8 wastes etc; to determine the bottlenecks in a process.
Don’t rely on existing process maps/SOPs to construct a VSM; observe and walk through the process (Gemba) 3 - 4 times to get a good understanding of the process before constructing a VSM.
Which phase of DMAIC to use? Measure
#9: Process Map
To visualize the flow of a process. Swim lane process map can be used to capture the steps of the process as well as the who executes those steps.
Which phase of DMAIC to use? Define/Measure
#10: Measurement Systems Analysis
To rule out the possibility that Measurement System is one of the causes of variation (one of the 6Ms)
Ensure that the MSA is conducted with full cooperation from the participants; Ensure all the rules of the MSA are followed (for example, minimum number of operators, parts etc). Refer Minitab Statguide for detailed information.
Which phase of DMAIC to use? Measure
#11: Design of Experiments
To experiment actively and determine the optimum levels of critical Xs to achieve the desired Y. There are many types of DOEs. Refer Minitab Statguide for detailed information.
Which phase of DMAIC to use? Analyze/Improve
#12: Regression
To establish an equation between critical Xs and Y and predict future values of Y. Always test whether the assumptions of the model are valid or not (for example, for least squares method, all residuals must be normally distributed, should show no pattern or in other words remain a mystery!). Refer Minitab Statguide for detailed information.
Which phase of DMAIC to use? Analyze/Improve
#13: Production Leveling (Heijunka)
To reduce unnecessary inventory and capital getting locked up as inventory in warehouses. Production Leveling helps with creating "flow" and getting the product/service on time/faster to the customer.
Which phase of DMAIC to use? Analyze/Improve
#14: SMED (Single Minute Exchange of Dies)
To reduce the changeover time on a machine, between systems etc. SMED helps with creating "flow" and reducing batch sizes.
Which phase of DMAIC to use? Analyze/Improve
#15: FMEA (Failure Modes and Effects Analysis)
To analyze how each (prioritized) X fails, what are the effects on Primary Y when X fails, Why each X fails, what are the current controls etc. In simple terms to drill down to the root cause of the problem/issue. Ensure the operational definitions of ratings for Severity, Occurences and Detection are agreed upon and the scale is customized if necessary. Ratings should be based on data.
Which phase of DMAIC to use? Analyze/Improve
#16: Control Charts
To determine whether the process is stable and has special or common cause variation. Use the appropriate control charts based on the type of data and pre-requisites. For example I-MR control chart cannot be used if the data is not normally distributed. Refer Minitab Statguide for detailed information.
Which phase of DMAIC to use? Measure/Improve/Control
#17: Capability Analysis
To compare customer's specification limits with process control limits (in simple terms to determine whether the process can meet customer's specifications or not). Ensure the specification limits actually come from the customer and not some hypothetical numbers. Refer Minitab Statguide for detailed information.
Which phase of DMAIC to use? Measure/Improve
#18: Brainstorming techniques (Reverse, Analogy, Six Thinking Hats etc.)
To brainstorm solutions for the root cause(s) or critical Xs. Six Thinking Hats requires the use of an experienced facilitator who is trained and certified in Six Thinking Hats.
Which phase of DMAIC to use? End of Analyze/Improve
#19: Pugh matrix
To select the best solution objectively from among a set of solutions. The Pugh matrix is a much better objective tool compared to other tools which tend to be subjective.
Which phase of DMAIC to use? Improve
#20: Kano model
To determine the needs, wants and desires of customers. Offers insights into the product attributes which are perceived to be important to customers. Supports product specification through better development of team understanding
Which phase of DMAIC to use? Pre-Define/Define
#21: VOC gathering techniques (Surveys, Customer complaints, secret shopper, Structured interviews, Gembas etc.)
To determine and understand the pain areas of a customer(s) and thereby make a case for change (whether a project is required or not). As far as possible, collect VOC by direct interaction with customers rather than surveys to get quality information. VOC is converted to CTQs (Critical to Quality Characteristics) i.e. objective measures which can determine if VOC is met or not.
Which phase of DMAIC to use? Pre-Define/Define
#22: Control Plans
To ensure the gains/improvements made through the project don’t slip back to the original state. Most of the projects fail due to incomplete or no control plans.
Which phase of DMAIC to use? Control
#23: Threat vs. Opportunity matrix
To create a sense of urgency (burning platform) for change. Focus on Threats if we DO make the change as well.
Which phase of DMAIC to use? Pre-Define/Define
#24: Stakeholder analysis/mapping
To determine areas of resistance and support. Ensure the stakeholder rating (such as ++ or --) is based on some data/previous experience with the stakeholders and not just based on heresay or person opinions.
