In a nutshell, Six Sigma is a culture or philosophy of quality control which permeates the entire organisation. It is a data driven approach which aims to reduce and control defects; resulting in improved process or product efficiency. Six Sigma is the level at which there are lesser than 3.4 defects per million opportunities/ transactions.
The key question is: How do we go about implementing Six Sigma?
In order to implement the philosophy of dmaic model six sigma, we need a framework /roadmap which will help us to actually put our ideas to work. This roadmap is called DMAIC (Define, Measure, Analyse, Improve, Control) methodology. This framework converts the problem into something tangible that can be measured, so that a solution can be arrived at. This method can be used most effectively when any process or product does not meet customer expectations.
Let’s take a simple example to discuss how DMAIC can be used to implement Six Sigma, explaining each step in detail.
The Problem of the Late School Bus:
Here is a problem faced by ABC Public School. There is a lot of confusion in the school. The class teachers have scheduled a meeting with the transport department to discuss an urgent problem.
Teachers: “Hello, Transport Department! For about 6 months now, we have been noticing that the children travelling by school bus falling under Route 22 arrive late to class in the morning, after the school bell rings. Many children miss a part of the first period.”
Transport department head: “We will look into the matter and revert with a solution.”
Route 22 is an important route covered by this school bus.
Teachers: “Fine. Let us inform the school principal as well. We can ask her for the solution.”
After listening to this problem, the principal decides to implement Six Sigma methodology to the current transport process. A Six Sigma Green Belt has been appointed to tackle this problem.
The eager Green Belt has decided adopt the DMAIC methodology. She has a team of Champions to assist her in the task.pixabay.com
The Define Phase:
The Define phase is the first phase of the DMAIC roadmap. It is the base on which DMAIC rests. First, the goal has to be identified. Then, the Six Sigma Green Belt needs to determine the stakeholders for the process.
There are many Six Sigma tools that can be employed to help in this phase. The most popular ones are:
- Project charter
- Process flowchart
- SIPOC diagram (Suppliers, Inputs, Process, Outputs and Customers)
We’ve used the SIPOC diagram in our example. Let’s revisit our bus problem.
The team members have been identified: three school staff previously trained as Six Sigma Champions. The customers have been identified: the class teachers, children and the parents. The entire current process of ‘School bus pick up’ is mapped. It starts from the driver coming to the bus depot and ends with the children entering the classroom.
The important elements in this process are known as CTQs or Critical to Quality elements. What are the elements that make for a quality bus drive?
After a considerable amount of brainstorming with the customers, the six sigma team has identified the following factors:
- The children must be safe.
- The bus should reach on time.
- There should be no bullying on the bus.
- The ride should be smooth.
- There should be no over speeding.
Among the above quality factors, the team has zeroed in on the second one, i.e., the bus should reach on time, because the other factors do not pose any problems currently.
This process is now the CTQ (Critical to Quality) element.
A SIPOC diagram showing the Suppliers, Inputs, Process, Outputs and Customers will make the process very clear.
|School||Bus||Driver comes to bus depot||Children reach school||Children|
|Bus suppliers||Driver||Takes charge of allotted bus||Driver and monitor go home||Parents|
|Bus Monitor||Picks up monitor from school||Teachers|
|Children||Picks up the children from various stops.|
|Drops them at school|
|Children walk to class from drop off point|
Now, the time analysis is done. Random samples are taken on 10 days during the month and the delays are recorded.
Average delay = 60 minutes
Standard deviation = 35 minutes
The Measure Phase:
In this phase we attempt to answer these questions: Now that I know what the problem is, how do I actually measure it? Is the current system adequate for measuring the problem?
So let us quantify the problem, determine the method of data collection and measure current performance. Many dmaic model tools can be used in this phase; the common ones being:
- The Process Flowchart
- Data Collection plan
The keywords to be defined presently are Defect, Opportunity, and Unit. The Metrics will have to be arrived at.
In our study, the following definitions apply:
Defect: Any bus student delayed in reaching the class.
Opportunity: Each bus ride to school.
Unit: Bus students’ arrival times
Throughout the process, there can be many points for data collection. The current system allows for data collection as follows:
The driver records his arrival to take charge of his allotted bus from the bus stand by scanning his card. The time is recorded at this stage. There is no data collection till the last step. In the last step, the children scan their school card to enter the school.
This method is quite inadequate as the Six Sigma team is not able to collect data at each point of the process. Hence, the measurement is not complete. They have asked the school authorities to revise the data collection points by requesting for a few changes in the system.
When the changes are implemented, the team can determine the time when the driver takes charge of the bus. After which the driver notes down the time the monitor is picked up. After that, the parents note down the time of the bus arrival and departure from their bus stop. Lastly, the children punch their entry cards.
So now the data is collected at each step. The data collection plan has been validated by a few random samples as well.
The Analyse Phase:
The Analyse phase consists of statistical measurement of the collected data. The correlation between the variables and the defect is established and the significant contributors (also known as KPIV s which are Key Process Input Variables) are isolated. At the end of the stage, the function Y=f(x) relationship is ascertained.
There are various dmaic model tools that can be used like the Pareto diagram and Regression analysis. In our case, the Six Sigma team has decided to use the Root Cause Analysis tool.
The data is analysed to identify the root cause of the delay. Each minute process is recorded in detail. The non-value added activities are eliminated. A detailed study of the process flow would bring to light these activities.
Root Cause Analysis:
|Process||Person involved||Time (minutes)|
|1||Driver punches his card||Driver||5|
|2||Supervisor allots the bus||Supervisor||5|
|3||Security gets the key||Security||5|
|4||Driver drives the bus to school||Driver||10|
|5||Picks up monitor||Monitor||5|
|6||Drive to stop A||Driver||20|
|7||Wait for children and pick them up||Children||10|
|8||Drive to Stop B||Driver||15|
|9||Wait for children and pick them up||Children||10|
|10||Reach the school||Driver||20|
|11||Children punch card and enter school||Children||5|
So the total time taken to reach school is 110 minutes. The highlighted parts are the “non-value added” activities. These activities need to be eliminated or streamlined to reduce the total travel time.
Some of the possible process improvements are:
- The keys to the bus can be readily available with the supervisor instead of the security guard wasting time getting it.
- The monitor can arrive at the bus depot directly instead of waiting at the school. That saves 10 minutes.
- In Step number 9, the driver waits for 15 minutes instead of 5 minutes at the stop. They can aim to reduce that time by 10 minutes.
- Another potential improvement could be in Step 8 (travel from Stop A to B) and Step 10 (travel from Stop B to school). An analysis of the causes of delays between these stops reveals areas of improvement that can be worked upon.
- Step 8: Travel between Stop A and Stop B: There is a 10 minute traffic jam in 80% of the cases.
- Step 10: Travel between Stop B and school- One particular traffic light delays the travel by 5 minutes in 75% of the cases.
The Improve Phase:
In the Improve phase, the actual KPIVs and the relationship with the defects is identified. The improvement ideas are finalised and actually implemented. At this stage, the stakeholders should be willing to put the new plan into action.
Our school bus project has entered a critical stage now. After a brainstorming session, it has been decided that the following steps can be taken to improve the process.
- The supervisor has been given charge of the keys as well. This effectively saves 5 minutes of the driver’s time in taking charge of his bus.
- The Bus Monitor has been instructed to board the bus in the depot itself. This saves 10 minutes of the driver’s time in driving between the bus depot and the school.
- The drive from Stop A to Stop B is delayed due to a traffic jam on the main highway. This occurs in 80% of the time. The driver was instructed to find a solution and he has located an alternative by-lane to avoid the traffic jam. This saves another 10 minutes of the journey.
- While travelling from Stop B to the school, there is a signal which usually delays the bus by a further time of 5 minutes. Surprisingly no action needed to be taken. This is because the driver discovered that the additional time that he got by applying the above measures meant that the traffic signal no longer troubled him. It was Green all the way! This was a bonus advantage by applying above measures.
- It was found that there was a delay of 5 minutes almost every day in Stop B due to one particular child arriving late. The teacher sent a message to the child’s parents. The driver was also instructed to wait at both stops only for a couple of minutes and leave thereafter.
The school management has approved the implementation of these ideas with immediate effect.
The Control Phase:
Once the ideas have been implemented, they are built into the system as a requirement. This involves putting a system in place to ensure that the performance is controlled as well as measured. Standards and variances are defined and measured as part of a regular process.
The Six Sigma methodology has now become part and parcel of the company’s philosophy.
The job of the Six Sigma Green Belt is nearly complete as she hands over the project to the new Process Owner (in our case, the Transport Department). These can be documented as part of good management practice.
The bus transport system works very efficiently now. The performance is monitored from time to time using Six Sigma.
There is another meeting in the school after the new process has been established.
Teachers: “We are very happy to report that the children are now coming to class on time. I am able to concentrate on my teaching and the kids are happy.”
Transport department: “We are very thankful to the dmaic model in Six Sigma team for making our department very efficient.”
It is time to reward all the people involved in the project with a party and a bonus! That was yet another Six Sigma story with a happy ending.
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