Improve Phase - Identify the Solutions

Six Sigma - Levels of Root Cause Analysis

It may not be necessary to spend equal efforts for any type of problem/issues. The kind of investigation may vary depending on the issue frequency/impact/nature. This articles details out the multiple level of Root Cause Analysis (RCA) that can be approached deepening on the problem nature.

Six Sigma – Root Cause Analysis (RCA)

Introduction: Beneath every problem there is an underlying cause but we need to identify the root cause to prevent the recurrence. Many times the actions taken to address the issue reoccur again in the same place or in a different place. This symptom indicates that the root cause is not been identified/addressed. Root Cause Analysis (RCA) is a structured approach for identifying and eliminating the underlying root causes. It may not be feasible or necessary to conduct RCA for all the issues as it involves time and effort. RCA is an analytical tool to perform a comprehensive, system-based review of critical incidents. Primary objectives of RCA includes

·        The primary aim is to identify the root cause(s) and prevent that problem from ever recurring

·        Systematic way of approaching and resolving the problem

·        Prevent the recurrence at lowest cost in the simplest way

Steps:  

1. Define the problem
2. Gather the information
3. Plan for Root Cause Analysis
4. Conduct RCA
5. Develop the solutions and action plans
6. Manage the Action items

Six Sigma – Root Cause Analysis Techniques

Many techniques available in conducting Root Cause Analysis, each technique has its own advantages and suitable for a particular situation. Common, widely accepted and simple to use techniques includes

·        Cause & Effect diagram

·        5-Why Analysis

·        Brainstorming

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Cause & Effect Diagram: Also called as Fishbone diagram. This is a tool for identifying all the causes of an effect. The effect being examined is the problem/opportunity that has to be eliminated. C&E Diagram is a graphical representation of the causes and effect. Use this technique for

·        Multiple causes has to be grouped logically

·        Understand width and depth of the causes

·        Problem is repetitive

Steps:

·        Write down the effect to be investigated and draw the backbone arrow (as below)

Note: KB Article – Knowledge Base Article has to be selected by the engineer to resolve an issue reported by the customer. Selecting of wrong article either delays the resolution or unnecessary escalation to a next level as the issue is unresolved by the engineer. 

·     Brainstorm with the identified people considering all the broad areas/ groupings of the potential causes of the effect “Classified KB article is incorrect”. Rule of thumb consider the generic 4 categories i.e., Man, Method, Material and Environment. You can define your own categories and may use affinity diagram to group the cause.

·        Group the causes identified during the brainstorming into logical groupings to represent the Cause & Effect relationship.

·        Drill Down all the causes for further reasons and goon extending the branches till the root cause is identified (May use 5-Why technique as required)

Five – Why Analysis: 5-Why is a problem solving technique that allows us to reach the root cause by repeatedly asking the questions. Even though this technique is called “5-Why” we may reach the root cause with fewer or more than five questions. Use this technique

·        Repetitive issue without any supporting data

·        Simple and low risk problems that does not require significant analysis

·        Problem is very specific to a process/ system (Not spread to multiple processes)

Steps:

·        Define the problem

·        Gather the team and confirm the problem

·        Ask the first Question Why? Record all the answers on a whiteboard or flipchart

·        Ask few more successive “Why” until we reach no further causes

·        Confirm the root cause and proceed for next set of actions

Example: Customer complaints on the delay in Pizza delivery

·        Why there is a delay in the Pizza delivery?

o   Delivery boy not reached on time

·        Why the delivery boy not reached on time?

o   He could not find the address

·        Why he could not find the address?

o   Address given to him is incorrect

·        Why the address is incorrect?

o   Address is not available in the records

·        Why the address is not available in the records?

o   Customer is new, manually note down the address

·        Why the address is incorrect?

o   Incorrectly noted while taking orders

Solution: Incase of the first time users, confirm the address once again and provide the telephone numbers to the delivery boy to reach out to the customer in case of any issues.

Brainstorming: One of the very widely used and easy to use techniques for analyzing the problem to reach the root causes. Brainstorming generates ideas and later evaluated to finalize and confirm the causes.  

Steps:

·        Establish a clear objective, Re-phrase for confirmation

·        Create a list of questions

·        cover all potential causes in the following four areas People, Process, Environment, Tools

·        Document all the findings and agree on the same 

Six Sigma – Improvement Approaches

In Six Sigma program there are multiple approaches that can be applied or used depending on the opportunity/problem being addressed. Below approached are majorly used either in solo or in combination in the six sigma program.

·        Lean

·        PDCA

·        Six Sigma – DMAC

·        Six Sigma – DFSS

Below table shows the criteria that can be used as guidelines for selecting the approach

Below table shows the high level details about the approaches.

Differences between Lean and Six Sigma: There are many similarities between Lean and Six Sigma with respect to the approach/objectives. Below tables shows few differences between the two approaches and suggested technique is a blend of both again depending on the problem/opportunity in hand.

Analytics – Lead Time Prediction

Below approach can be used to predict the lead time of completing a project considering the variation and cycle time distribution from the past data. The results are interpreted considering the probability of interest.

Steps to predict the Lead Time:

• Collect the data from past related to cycle time and data may include the sub divisions i.e., cycle time may include the actual cycle time, hold time, cycle time of multiple steps etc.,

o   E.g., Project of setting up a new server may include purchase, installation steps. While gathering the data we can collect the data at the desired level to capture the uncertainty in each steps while predicting.

  

•        Understand the distribution of the data

•     Calculate the Lead cycle time for multiple probabilities considering the distribution data is following. For this example we are considering that the data is following Normal Distribution. We can use Excel Function NORM.INV (probability, mean, standard_dev) to calculate the Lead time (Predicted) for the project considering different probabilities

• Another way of predicting the lead cycle time is through simulation. Assuming normal distribution generate the normal variables

o   Cycle Time : Mean (31) and Standard deviation (17)

o   Hold Time : Mean (23) and Standard deviation (24)

o   Add up to get the Total Cycle time = Cycle Time + Hold Time

• From this you can interpret that 90% probability cycle time = 103 days
• Probability to complete the project in 60 days = 55%

Lean – Tool Box

Below list contains the list of tools used in Lean

·      Value Stream Maps (VSM)

o   Visually map the flow of production

o   Current and future state of processes highlighting opportunities of improvement.

o   Exposes waste in the current processes and provides a roadmap for future state

o   categorizes activities into three segments: value enabling, value adding and non-value adding

o   Value enabling activities, however, cannot be totally eliminated from a system

o   focus of this tool is on identifying and eliminating the non-value added activities in each process step

·        Takt time

o   Takt time is the rate at which a completed project needs to be finished in order to meet customer demand

o   This is the "heartbeat" of the customer

o   Takt = T/D    

§  Where T is Time available for product/service.

§  D is a demand for the number of units

§  T gives information on production pace or units per hours

·        5S

o   Used to organize the work area and eliminates the waste that results from poorly organized work area.

§  Sort – Eliminate that items that are needed

§  Set in order – Organize the items that are needed

§  Shine – clean the items

§  Standardize – defined standard operating procedures

§  Sustain – Regular compliance and improvement with respect to standards

·        Pull / Kanban

o   Regulating the flow of goods using the signal cards as needed

o   Eliminates inventory and overproduction

·        Spaghetti chart

o   Graphical technique used mostly in lean manufacturing

o   Used to display the actual flow/layout/material/machines and distances in a work process

o   Poorly laid out process work area that looks like a mass of cooked spaghetti

o   Used to track work item flow, material flow and people flow

·         

·        Poka – Yoke

o   Design the process to detect, fix and prevent the defects as and when it happens

o   Cost of fixing the defects increases exponentially as the work progresses and the defects found in later stages than where they got injected

o   Also called mistake proofing

·        SMED Single Minute Exchange of Die

o   Reduces the time to Set up

o   Converting the setup steps to external and simplifying the internal steps

o   Eliminating non-essential steps and standardizing the work instructions

·        Total Productive Maintenance

o   A holistic approach focuses on proactive and preventative

o   Empowering operators to help maintain their equipment.

o   Shared responsibility for equipment by plant floor workers

·        Heijunka

o   Production scheduling that purposely manufactures in much smaller batches

o   System of production designed to provide a more even and consistent flow of work

o   Reduces lead times and inventory

·        Gemba

o   It’s a philosophy that encourages to go to the work area and observe for any opportunities than sitting in the closed cabins

o   Promotes fist hand observations from the floor employees

·        Hoshin Kanri

o   Align strategy (Top management) to tactics (middle management) to Actions (employees)

o   Continuity towards goals by eliminating poor communication & improper direction

·        Jidoka

o   Design the equipment’s to automate some part of the manufacturing process i.e. partial automation is less costlier than full automation

o   Mainly focus on avoiding/detecting and fixing defects quickly

·        Just in time (JIT)

o   Pull the parts based on the customer demand instead of pushing the parts based on the projections

o   Reduced the inventory levels and reduces the space requirements

·        Kaizen

o   Regular and incremental improvements

o   Participation from all the employees