Green Belt

Train up all the line engineers and supervisors at least Green Belt level is one of the Six Sigma program objective for the company I worked as Black Belt. Beside working on my own Black Belt project, giving training and technical support to my Green Belt candidate is one of my important responsibility.

In that company, GB are not required to master all the Six Sigma problem solving tools, they need not to worry about the application since Black Belt who mentor them will do all the job for them. What they need to know is basic understanding of DMAIC process flow, follow through action item given to them in each DMAIC phase and able to interpret graphical report generated by Minitab.

My personal opinion again….

Green Belt and Green Belt project is the most effective way for any process improvement in the Six Sigma program. The result could be more significant than the Black Belt project.

The reasons are;

1. Usually Green Belts are those process owners who know their process well. They have the control, therefore they can take immediate action to correct the process if any deficiency identified. Things could not be change so easily if same deficiency was identified in a Black Belt project.
2. A Black Belt can lead many Green Belts at one time. Total saving generated from Green Belt projects could be more than Black Belt project.

Do you believe that ? most of the saving from the company I worked for was generated by Green Belt project.

The Belts

People who involved in Six Sigma program should familiar with the terms GB (Green Belt), BB (Black Belt) and MBB (Master Black Belt).

It is also an important topic that I have to go through together with my trainees on the beginning of the training. Peoples attending the training (in my company) keen to know the differences and certification criteria, mainly because of the benefit entitlement after certification.

The Belt system has been a standard practice in most Six Sigma company. I don’t know since when and who initiated (either Motorola or GE) the system.

Certification criteria could be easily found in www.isixsigma.com Therefore I don’t want to repeat the same story in my post.

Personal opinion, a good Six Sigma company should have the following people trained;

GB : People who directly work in functional operation, such as Production Engineers, Quality Engineers, Process Engineers Supervisors, Technicians

BB : People who work as support function such as Functional Managers, Project Manager.

MBB : Only necessary for big company like Motorola, GE etc. Too expensive for small scale companies.

Well, I will talk about this topic in my coming post.

Ppk Estimation For Non Normal Distributed Data

Non normal data is the data that do not fit into the shape of normal distribution. In fact, we are facing this type of data most of the time in the actual process.

As an engineer or manager, we should understand our process well and know what kind of distribution a particular process should behave.

Process capability calculation for non normal data isn’t straight forward as what we did for normal distributed data.

In fact, I am not so sure how to estimate the Cpk value this type of distribution manually. I still rely on Minitab when dealing with this kind of data.

I tried to search through Minitab Help and here the formula I get.

The formula looks simple, but I still can’t get a correct answer by substituting the figure I have into the equation. How come? Anyway, I need not to worry so much as Minitab can do all the statistical analysis for me.

Here the problem I have, can anybody tell me how Minitab work out the PPL = 0.4?

Process Capability (Cpk) For Normal Data

Many of us may not aware that the formula that we used to apply for Cpk estimation ( as below ) is only applicable for data which is normally distributed.

In other word, the formula above cannot be use for Cpk estimation for data which is non normally distributed, such as Yield.

Why is it so ?

As I mentioned in my earlier post, the original Cpk equation can end up in

Because of this, Cpk equation we discussed above actually linked to the Standard Normal Distribution. That’s why we able to estimate the defective rate of a process based on the Cpk index given.

In order to apply the equation correctly, we have to ensure our data collected tested and complied to the following condition

1. The data have to be collected from a stable process.
2. The data have to be normally distributed.

Found this useful chart in Wikipedia while searching ref info for this article
Just to share…

Process Capability Index (Cpk)

A simple Cpk index really makes me busy for the past three week.

Actually, Cpk is not new to me, I have been using it for process capability benchmarking since long time ago.

Before that, I never question how the Cpk 1.33 was derived, to me, as long as the process Cpk close to 1.33, I am fine.

I started to flip through the web site discuss about the Cpk when a process I plan to release to production was rejected by the QA manager. Reason to me is simple, process Cpk

So, I can conclude that Z = 3 x Cpk

Now I can answer the different in term of Sigma level.

For Cpk = 1.14, Z = 3.42, estimated DPPM = 626

For Cpk = 1.33, Z = 3.99, estimated DPPM = 66

Hmmm… the different of DPPM is obvious.

Well, to me, I feel comfortable to release the process for mass production. This should be a good start for any new process release. Further process parameter optimization can easily make the Cpk value looks good.

Well…. Finally, I got the answer… now I realized, Z score is more meaningful for capability interpretation.

Six Sigma & Me

I started to get in touch with Six Sigma three years ago.

I was a project engineer before that. As a project engineer, my main objective is to get the product out within time line and budget. “Quality” to me is second priority. I don’t really appreciate quality management tools, and I hate the quality guys who like to introduce all kind of control plan to slow down my work.

Six Sigma – is another term that I dislike at that time. I hate the Green Belt and Black Belt who like to approach me, ask for data, DOE or trying to change the way I work.

I get my Black Belt certification a year a go. I am a project manager now, but I am still practicing Six Sigma approach in my project.

Anyway, I still do not believe “inspection” (usually a requirement in most of the Quality System) will help to assure the product quality.

Six Sigma In General

The Six Sigma has become a super star in today’s corporate world. The main reason it become so popular is because the amount of money saved by Motorola from this program has make the corporate leader believe Six Sigma is the solution to fight for rising operation cost.

Six Sigma was originated from Moto’s quality department, Moto use it to drive quality improvement by reducing process variation and reduce defective rate. But people today use it as a cost reduction tool instead of quality management tool. They try to apply Six Sigma methodology everywhere. From manufacturing sector to service sector like banking, call center etc. Theoretically, Six Sigma should work well as long as there are data available.

Many companies has invested million of dollar in the Six Sigma deployment, they pay high price in infrastructure set up, training and promotion. How many of them really achieved the original target set ? How many of the six sigma project completed has really impact the company financial figure ? How many of chop off the program from the business system ? Anyway, they information is really limited.

Just simply run through the forum in isixsigma.com, easily I can find number of discussion on the effectiveness of Six Sigma program.

Don’t get me wrong, I am not questioning the effectiveness of Six Sigma methodology. I was in a company adopted Six Sigma program for the past 3 year. The Six Sigma program in the company isn’t so successful. I involved in the Six Sigma activities, basically I know where went wrong.

Six Sigma DMAIC to me is a very powerful tool that I believe it works in solving most of the management problem. I will tell you more on my view in Six Sigma in my later post when I m free.

Nevertheless, if you wish to know anything about Six Sigma, you may write me a mail. I will reply your inquiry through e-mail.