iSixSigma

Ali Askari

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  • #73704

    Ali Askari
    Participant

    Cp and Cpk Calculation:
    Hi Syed,
    Try Reference: Juran’s Quality Control Handbook – Ch. 16, P. 19-35
    Useful pts – to get you going.
    Cp =  (USL – LSL)/6s
    To determine whether a process, given its natural short-term variation, has the potential capability to meet established customer requirements or specifications. Cp is a ratio of the tolerance width to the short-term spread of the process. Cp does not consider the center of the process. It estimates the “instantaneous capability” of the process.
    Cp = 1: The process barely meets specifications. There is a probability that at least 0.3% defects will be produced and even more if the process is not centered.
    Cp > 1: The process output falls within specifications, but, defects might be produced if the process is not centered on the target value.
    Cp = 2: Represents the short-term objective for process capability. Since Zst = 3 x Cp, we achieve 6s when Cp = 2.
    Cpk

    Cp = Cpk = process mean is on traget or process is centred.
                  Cpk = min (Cpl, Cpu)
    Cpk considers process centering. Cpk is a ratio of the distance measured between the process mean and the closest specification limit to half of the total process spread.
    Therefore, Cp against specific limits, then
    Cpl =  (mean – LSL)/3s
    Cpu =  (USL – mean)/3s
    Cpk = 0: The process mean falls on one of the specification limits, therefore, 50% of the process output falls beyond the specification limits.
    Cpk < -1: The process mean is completely out of the specification limits, therefore, 100% of the process output is out of specification limits.
    Therefore, now you can utlises your own process sample mean and then real specification limits both USL and LSL, to calculate your Cp and Cpk.
    Hope this helps.
    Ali Askari
     
     

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    #73469

    Ali Askari
    Participant

    I found this article useful, within that there is a summary on
    Implementation of Six Sigma      https://www.isixsigma.com/library/content/c011029a.asp
    check it out.
    Ali Askari

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    #73254

    Ali Askari
    Participant

    Bobby and Neynes Ladha, what your email – post it in the forum ? – So I can despatch one page summary.
    regards
    AA

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    #73220

    Ali Askari
    Participant

    Fahim,
    Here are few useful sites on “Lean”
    http://www.lean.org/
    https://www.isixsigma.com/library/content/c020225a.asp
    https://www.isixsigma.com/me/lean_manufacturing/
    https://www.isixsigma.com/library/content/c020204a.asp
    https://www.isixsigma.com/offsite.asp
    A=Fr&Url=http://www.autofieldguide.com/articles/109907.html
    http://web.mit.edu/manuf-sys/www/amb.summary.html
    This set will make a good reading and give you few ideas, for improvement in your paint manufacture. Plus, have you considered Lean vs Six Sigam.
    Ali Askari

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    #73131

    Ali Askari
    Participant

    Drop me an email, I have excellent slides on Kazien, Lean and Six Sigma  and few articles on above topics.
    regards
    Ali Askari

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    #73112

    Ali Askari
    Participant

    Fahim, Either you are new to Improvement or Quality process – or looking for few quick examples, to get few quick hits at work. Each process and industry is different, one need to learn to apply the improvement technique and skills – as required. Whatever, there is no short cuts! Few tips
    1. Do some research on the topic
    2. Buy few books.
    3. Get some reading under your belt
    4. Then contact few consultant with expertise in “Lean” manufacturing.

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    #73111

    Ali Askari
    Participant

    Barik,
    What are you after here – explain!

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    #73109

    Ali Askari
    Participant

    C.VASANTHARAYALU,
    Here are my comments on Project Selection and Six Sigma. have a read.
     
    https://www.isixsigma.com/forum/showmessage.asp?messageID=10737
    Ali Askari

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    #73108

    Ali Askari
    Participant

    Ibrahim
    The name of the game – if I can call it is “Improvement”. Not going on BB training and then obtaining certification. Project identification and selection (Project Y) – is key for a successful introduction of SS program in initial phase.
    Some time needs to be spend on this analysis, discussion, benefit vs risk, VOC, people committment and buying into the project Y and improvement. I find beside SS skill, one needs to have project management and soft skills.
    In SS, we asking people or organisation to change the way there have been doing their jobs or running their businesses, in past. This isn’t easy, to communicate and get it right each time. One needs to work at it and win partners and create new partnership and Alliance. Here are few pointers:
    Then, as one rolls out the prog, to wider group of staff within in the organisation – the focus should be
    (a) What are defects we can improve upon or reduce, or remove/eliminate.
    (b) VOC – listen to people and talk to shop floor and operating team (if you are manufacturing organisation) – if not “non-manufacturing” organisation, investigative the Customer Complaint Log/database, suggestion boxes, feedback forum or profroma – whatever is your company format in reporting problem, defects, hassle, complaint, etc.
    (c) Project id and selection – must have a bottom line impact and reduce waste or remove non-value adding processes with your organisation. Few examples:
    For internal features of business: Free Time, Revenue, Capital
    For external feature: Increase Customer Business Volume and/or Satisfaction scale.
    (d) Then you need to consider Type of Project – I usually ref. to them as GB or BB – because the impact and improvement need to be on a scale. In our organisation anything over $150K in term of delivering this benefit is a BB. GB’s project in initial days did not have an financial benefit – but we say today, there should delivery atl east $30K to the bottom. As you may realise – initial we did not focus GB to delivery benefit as the requirement was to get number of GB with in the workplace with SS skills – while undergoing training their were allow to target “low hanging fruits”. “Soft benefit”. But know – the low hanging fruit are not there, as we have mop up them all. Now we need “hard benefit” in GB projects, too.
    (e) You may also need to consider the X’s vital one.
    Finally, have a word with your QA or Improvement Managers, he/she may have the projects, line up. A Good QA or Improvement Managers, has been using these approaches (both improvement philophies and statistical methodologies for process and business improvement programs), however today we package it differently and call it SS and use Minitab or Jump. Great, makes improvement an agenda item on board level.
    This should be sufficient to get started, if you need any more drop me any email or post your reply and email here. Will response!
    regards
    Ali Askari
     
     

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    #73088

    Ali Askari
    Participant

    Ralf, end of the day, you have the choice,
    JUMP, MINITAB, STATISTIC, SPC XL (never make across)
    Up to Mid 97 SAS – we used, but discontinued !! on price issues.
    Our company used MINITAB for SS and it is also popular choice. It is used across the SS community Champ, MBB, BB and GB. In our company – other software are ultised, but mainly by statistician. Though, who have used Minitab for few year, have seen progress update and change, this shows the Minitab as a company is learn to users. I find Minitab is user friendly.
    Ali Askari
     

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    #72926

    Ali Askari
    Participant

    Craig Sherwood,
    Six Sigma is highly suitable to manufacturing process improvement. But equally can be applied in any sector of business eg Government department, non maufacturing serivce industries, eg maybe a grocery industry or banks, Call Centers, Railways, etc.
    Basic requirement is, to have Process and Continuous or Discrete Data Sets.
    With regards to: how and where and what. A simplfied approach will be – to explain the point:
    Define a process – here you need to understand the customers, inputs and outputs, Cost of poor quality (COPQ),  Few questions 1. What is “Crtical to Process (CTP), 2. What is “Critical to Quality” (CTQ). 3.What is “Critical to Cost” (CTC). 4. What is “Critical to Delivery” (CTD). 5. What is Critical to Satisfaction (CTS). Produce Process Map where the defects are.
    Iam of the school of “DMAIC” – therefore, as in the Ist point, one needs to define the process, understood the dis-satisfaction, cost of poor quality etc – this list is given above.
    Measure, Analysis, Improve and Control.
    You will definetely need to listen to your both internal and external customer (VOC). Leadership is important. Low hang fruit improvement, can get the organisation believe what Six Sigma can do, for them and business.
    Now you are doing in essence a six sigma approach to process improvement.
    Six Sigma can not be explain in one feedback reply. Therefore, if you need any help contact to discuss options – will be able to guide you. Good Luck
    Ali

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    #72925

    Ali Askari
    Participant

    Suresh,
    Al’s comments are priceise. Drop me a email on personal email: [email protected]. I can help to Design and Experitment (DOE – in six sigma terms).
    If you’re UK based business and as live in UK – this can useful to provide regular guidance in person. 
     
     

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    #72924

    Ali Askari
    Participant

    Juanita,
    You’ll not get any better explaination then that provide by RR Kunes – a summary. With regards to the “Risk Management” in finance terms – it will be better to work with a qualified or certified MBB or BB in this area. And at the same time – you need to consider to be trained in this discipline.
    If SS is to work for your organisation and add value – the staff and workforce need to buy into, it. Like any improvement prog. – it is team effort. To sustain the improvement.
    Good luck.
    Ali

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    #72922

    Ali Askari
    Participant

    Shahan Nadu-Vajpayee
    Excellent, I love the sense of humor.
    Ali

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    #72920

    Ali Askari
    Participant

    Hi, Wei
    Sharing few fundamental ponits, hope these will be of some help.
    As a standard procedure, best to carry out a “Descriptive Statistics” on each data set.
    1. “Descriptive Statistics
    (1a) Anderson-Darling Normality Test.
    (1b) P  value (higher then 0.05 is normal).
    (1c) mean, sd and many more data output post analysis.
    (1d) Boxplot
    (1e) 95% CI for Mu and 95% CI for median
    Via this approach – a snap shot of your each data set is obtained. Then this should allow you to plan next steps, what further tests are suitable. Mike, comments on Normality is cover with this approach and also comments made by othe contributors.
     2. Type of T-tests.
    (2a) Paired T-test: I have successful applied these when comparing old vs new equipment during the capital prog of puchase. For example, same sample two different equipment.
    (2b) Two Sample T-test: I have successfully applied these – raw material vs supplier’s. For example same raw material vs different supplier’s.
    3 “Test for Equal Variance”.
    This will give F-test (simple terms comparing sd) and Leavene’s test – these are for normal distribution and not normal distribution, respectively. P value is given.
    4. ANOVA – this also available. But, I usually go for ANOVA for data set more then 2.
    5. Have you considered the Gage and R&R, to enusre the data variability is understood – repeatability or reproducibility . What is part-to-part varition?
    Finally, if your data sets is comparison of two – then T-test and Test for Equal Variance will be valuable. However, without fully understanding the data type and n (no of data points) – hence a generic comments. 
    If you need further comments, contact via my email.
    Ali 

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