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Question on 1.5 sigma shift

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  • #51901

    chhabra
    Participant

    We always tell that ST sigma is greater than LT sigma by 1.5
    I would like to know why it is 1.5 in statistical terms and also in laymans language. It would be great if anybody can provide the example as well.
     
    Thanks

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    #181628

    Mikel
    Member

    It is just an idea, it is not valid.

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    #181629

    chhabra
    Participant

    It is not an idea. It definately has some statistical explanation behind the difference of 1.5

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    #181630

    luke skywalker
    Participant

    Back before the rebellion was crushed, as Darth was rising to power, his mentor, the grand wizard Mikel, made a proclamation to the masses: “Behold. Green Belt wannabes, only for as long as you shall hold dearly to your control plans will your little processes operate at nearly th esigma level you have claimed. Without your intense micromanagement, the variation creeping into your process could degrade your results by….TWICE AS MUCH!”
    Mikel held for an inordinately long dramatic pause and watched the eyes of the disbelievers. Sensing he may have stretched it wee bit too much, he shrugged his shoulders and muttered, “Well, maybe not THAT much, it might only be about 1.5 times.” And then in his very best Tony Soprano, he glared at the little Green Belt candidates and said, “You gotta problem wid dat?”
    Those very GBs grew up to be consultants/prophets who have spread the wisdom of the 1.5 shift ever since.
    And congratulations, you are now the 1,000,000th to have asked about the legend of the 1.5. You get a bright yellow picket protector.Please allow 4-6 weeks for delivery.

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    #181632

    Robert Butler
    Participant

      The post below may be of some help. To the best of my knowledge nothing has changed since.  There is one additional paper by Box which I haven’t read but which I understand mirrors the Bothe paper. 
    https://www.isixsigma.com/forum/showmessage.asp?messageID=39663

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    #181633

    Gary Cone
    Participant

    There is no statistical explanation. It is not valid.

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    #181635

    Darth
    Participant

    About as good an explanation as any other that has appeared on this site.

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    #181638

    GB
    Participant

    Luke,
    That was really, really good!
    -HB

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    #181641

    Taylor
    Participant

    http://www.pyzdek.com/PDF/2001-05.pdf
     
    Interesting Read, but hog wash non the less……………..
     

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    #181651

    On Behalf of The Devil
    Participant

    Playing Devil’s Advocate to the naysayers:
    As has been brought up recently, and even in the article mentioned  in this thread:  No model is perfect, but some models are useful.
    Isn’t the sigma calculation just a model of your process in a “Perfect” world – with normal distributions (or perfect other-than-normal), perfect measurements, zero friction/wear, etc.?  Much of this “Perfectness” may appear to be correct in a myopic observation or measurement.  But measuring in greater detail, or over longer periods of the process, gaining more data for your model, you find things ain’t so perfect.
    How often do you see what appears to be a perfect circle from a “distance”?  The closer you get, the more precise you measure, the more imperfect the circle gets – whether it is pixels on the screen, variations in the ink/lead, defects in the paper . . . 
    So to put a little reality back into the mix of your “Perfect” model of the sigma of your process – add the shift!
    Isn’t that in essence what Einstein did when adding constants to his equations to make them “look right” i.e. match the observations?
    Now whether or not 1.5 is the correct constant to use can be another knock-down drag-out discussion.
    That’s just my opinion, I could be all wet.
    mrmhead

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    #181657

    Taylor
    Participant

    MrMHead
    I think it comes down to you have real data in front of you. Why throw in an unknown constant for the sake of the model? At the end of the day real data for the Process is the true model.
    Now of course you can do all that other stuff you talked about, but why? What have you gained from this understanding? A realization of ………………? Nothing that I would react to, or put stock into making changes in my process.
    Just my Opinion

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    #181666

    Craig
    Participant

    If I take a purely statistical stance, I think of it this way.
    What is the probability of any given value in a normal distribution? Well, that would be zero. What is the probability of exactly a 1.5 sigma shift? Likewise, that would be zero. (OK..I am stretching this)
    Zero is the amount of credibility I have in the 1.5 sigma shift.  Please accept the fact that it is a fudge factor that allows one to approach six sigma quality.
    w/o the fudge factor, you need to achieve 2 PPB. With the fudge factor, you get sneak by at 3.4 PPM with some creative opportunity counting.

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    #181668

    Anand
    Participant

    This is fantastic ! Simply great response! Hats off, Luke!
    This was an unanswered question so far. But now I think you have answered it.
     

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    #181671

    Severino
    Participant

    Even if I told my management we were operating at 3.4 ppm (which we aren’t) they would just make next years goal 1.4 ppm.  No point in adding a fudge factor to just make it harder on myself.

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    #181672

    Gary Cone
    Participant

    Luke,I think that is as good of explanation as I have heard, but Green Belts
    were just a dream when the shift was first proposed. I think it was
    really the execs at Motorola that were treated to the display you
    described.And a minor point also, the 1.5 shift is the equivalent of the variation
    inflating by 1.333, not 1.5. Do the math.

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    #181675

    Tuguchi
    Member

    According to Stan the 1.5 Sigma Shift is a great crap!
    It has no practical meaning and I agree with that 

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    #181679

    Darth
    Participant

    I can’t believe we are going through this crap again. Harry explained his derivation behind the 1.46 shift as it applied to a very narrow application in design and manufacturing. The extrapolation to a universal truth about all processes is where the concept loses credibility. If you want the details get the transcript from the Great Debate which took place in Arizona a number of years ago between Stan and Mikel.

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    #181680

    DeJu Vu
    Participant

    Darth
    Is that the same debate where Stan did his best Ron White impression and told Mikel FU (Florida University) :0

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    #181687

    Mario Perez-Wilson
    Participant

    Amit,Read this post about the plus or minus 1.5 sigma shift.
    https://www.isixsigma.com/forum/showmessage.asp?messageID=149809
    A more important subject is how to reduce the sigma or standard deviation in a process that is not six sigma.
    Mario Perez-Wilson (http://www.mpcps.com)

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    #181688

    Darth
    Participant

    Given your credibility and reputation, your post should put this topic to bed once and for all. Thanks for clarifying what must of us already knew.

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    #181690

    Sankar
    Participant

    I strongly feel this 1.5 sigma shift was a goofie to pitch sig-sigma sale stronger by Motorla as it need not be verified by any Scientific panel like in publication of papers. In the case of Walter Shewarts Control chart it is very clear, the control limits are matchable to specifications to 3 Sigma on both sides of the mean and any process can temporarily shift even after removing the assignable causes by 1/3 Sigma. This does not mean the problem needs to be taken by Six Sigma Specialists to fix a routine QC issue. The control chart/limits has to be redrawn to reflect your current processes. I feel this shift of control limits in mfg. was used conveniently by Six Sigma people to their convenient theory of 1.5 Six Sigma shift and there is no mathematical basis for this one like that for Shewart’s charts. If you redefine only Z tables and call it sigma table to call 3Sigma as 93 instead of 99.72 to say that Six Sigma is better is in the hope we can somehow reduce common causes variation to temporarily reflect higher sigma rating. How about all other tables like t.F. X2, Control limit formulaes formulated by Shewart, Cp, Cpk etc………Maybe we need to change Binomail, Poisson tables etc…….also to suirt 1.5 sigma shift in any probability we want to predict.
    Only great discovery from the part of Six Sigma is Define phase which impresses me is combining with money to make Top management act. Quality costing etc…..are only for books and no companies really know their CTQ. Even if it is 10-30% it is lesser than the CEO’s paycheque and overheads of Marketing, Financae and HR. When they didn’t act with SPC, DOE, TQM, ISO…….etc Six Sigma can claim for all the downfall of economy and jobs to implement Lean. Now including countries like India talk of reducing obseity and implementing Lean when they need to be  creating more jobs to reduce poverty.
    To the extent Six Sigma people talk about belts, they won’t conveniently talk about the existence of QA Manager, MR, QA Engineers CQE, CQA  etc……in organizations who have higher knowledge in QA than these temporary belt weilding people. What to do with them???Dump them with pink slips and replace with these belts to screw up the established processes and businesses or what?????? 

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    #181691

    Say What?
    Member

    I am sure you had something good to say, I’m just not sure what.
    Motorola sales pitch? Wrong, they weren’t pitching anything except staying in business.
    The tying of problems to dollars belongs to Phil Crosby, not Six Sigma.
    Redraw control charts when process shifts? Wrong, who taught you that?
    The 1.5 shift is not important. Leave it at that.

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    #181693

    clb1
    Participant

    Binomail?  Well, thanks for the recommendation but where I live the postman just delivers the stuff unasked – I’ve never had to purchase mail from him.

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    #181694

    On Behalf of The Devil
    Participant

    So the reasoning comes down to there may be a shift (entropy, etc) but since we don’t know what the value is don’t bother using it.  Or as stated somewhere in these threads  “What do you gain?”
    I can accept that arguement over: “There is no shift – i.e. our representation is perfect and can be extended forward forever.”
    or: “Stan says it’s crap, so it must be true”  (not disparaging Stan, but that’s hardly an “arguement”)
    . . .and *That’s* why we have these discussions on these boards.
    (maybe the true “shift” is found in fractals or chaos theory?)
    mrmhead

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    #181695

    Mikel
    Member

    Hey, combine with a little attitude and it is truly an argument.

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    #181697

    Dan Dobyns
    Participant

    Ganesh,
    You are my new hero.
    People get so caught up in buzz words and wolf packs they forget what works. Lean manufacturing hurt our economy. Companies need inventory and “fat” to be healthy enough to withstand hard times.  A blackbelt does not teach someone how to think, it does seem to give many a big head.
     

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    #181705

    Mikel
    Member

    Ezweld,You are now an official member of the lunatic fringe. That had to be the dumbest post in February and that’s a pretty
    low bar considering Les has been here.

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    #181713

    Severino
    Participant

    Where can I get a copy?

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    #181716

    Mikel
    Member

    I sell them for 19.95 and if you order in the next 30 minutes, I’ll throw in a second one for free. I’ll also give you a PDF copy of the bailout bill (>450 pages).

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    #181717

    Severino
    Participant

    Or you could issue it to me on consignment and I can pay you as I read each page at which point you can issue me a refund check for the reduced carrying cost of inventory you have enjoyed which I can go and spend instead of putting one large lump sum into my bank account… right after I get done typing this run-on sentence that is.

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    #181718

    Taylor
    Participant

    Sign me up, after the reviting speach last night I can’t wait to get a copy of the bailout bill that $9 a week extra in paycheck is going to be awesome, I can now get that 2 for 1 pizza deal I saw on TV and enjoy while reading the facinating book of “If I was going to steal tax payer money, this is how I would do it”
     

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    #181721

    Tuguchi
    Member

    Funny
    Well-said

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    #181722

    Craig
    Participant

    Jsev607,
    When your goal is changed to 1.4 PPM, that is when you try to find ways to increase your opportunity count. (Sad but true)
    On a much larger scale, how could a company say it is setting a goal for six sigma quality if it is almost impossible to achieve. If it is truly 2 ppb, how many parts have to be produced to validate this?

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    #181723

    Craig
    Participant

    By the way….we should be optimizing processes and looking for ways to eliminate opportunities for error.
    I want to make it clear that my last post contained some sarcasm. (like changing the opportunity counting method to achieve a goal. Unfortunately, I have seen this game being played)
     

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    #181724

    Mikel
    Member

    500,000,000?

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    #181725

    Severino
    Participant

    The only time I would ever even consider looking at redefining an opportunity is to align it with how the customer would view it.  When I stepped into my job at my current employer I did just that and it hurt our numbers KPI wise, but also allowed me to make a strong case for why things need to be improved.  Prior to this my BU was actually claiming .0667 DPMO.  I spit my beverage on the conference room table when I heard them make the claim.

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    #181742

    Sankar
    Participant

    My simple concern of this 1.5sigma shift and sigma table is that it just ignore the Z-table evolved and used by QA professionals all over the world and it is evolved with permanent mathematical correlation irrespective of the sigma process for the last 60 years. 3Sigma limit with specifications tolerance is well established by Walter Shewart to be 99.73% and with this 1.5 sigma shift we want to call that as 93% why?  This only facilitates our redefining the limits of the existing process to 6 sigma which somehow at times  have an issue with it. The narrowing to 6Sigma doesn’t talk about the distribution how it should be for each sigma. If the whole population is close to the center in control charts we call it hugging the center. We don’t call that as a statistically controlled process. What should we call a heightened peack near the center in a six sigma process?

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    #181744

    Sankar
    Participant

    We are talking of process shift and I didn’t say we have to recalculate the control limits. Sometimes as long as process  is within spec. limits. we are asked to again calculate the short range capability if we want to calculate again the limits to accomodate the new process reality of shift in average. If we take the difference between the initial limits of the process and the new it is just process shift which again we can bring to the original level if we want to. This shift only I am saying is coupled with the 1.5 sigma shift to look that all processes we should expect that even if it doesn’t exist.

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    #181746

    Sankar
    Participant

    Spell mistake of Binomial to Binomail was found to six sigma accuracy by you. Thanks. We need to use the same accuracy to find out 1.5 Sigma shift how it can be located to accuracy in all processes?

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    #181747

    MrMHead
    Participant

    Ganesh,  What would be the DPMO of your posting process?
    Is your opportunity each day, each post, each subject/thread , each word, or each character?
    I think you should use Character, because you can make your numbers look better!  ;-)

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    #181751

    Obiwan
    Participant

    Oh…and just to jump on the bandwagon…Shewhart’s original 3 sigma limits have no basis in statistics either.  Shewhart developed them by basing it on what felt “about right”…as in…4 sigma limits would not give enough signals, 2 sigma limits gave too many.  Since his time, many of our peers have tried to rationalize his limits to 99.7% and other statistical issues…but Shewhart did not.
    Obiwan

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    #181752

    Obiwan
    Participant

    Darth
    This is a tiring subject…isn’t it?
    Obiwan

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    #181757

    Darth
    Participant

    That it is my friend. By the way, I talked to Anikan yesterday. He’s just waiting for the next shoe to drop. Also heard from Red Leader’s AA. She’s still having trouble finding a decent guy. Got a few Linked invites from some of the members of the Republic. Many disturbances in the Force.

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    #181763

    tcm
    Member

    Hi Hacl,
    Mind explaining what is meant by “ppb”? (Parts Per Billions?)
     
    Thx in advance :)
     
    Tcm
    27 Feb 2009

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    #181764

    Sankar
    Participant

    I can agree on what you say. But Shewart’s work was in 1930’s which opened the possibility of mass manufacturing with statistical control made possible. Big 3 automotives are the actual users of SPC for all of us to reach where we are to-day. Forget about 2 or 3 sigma limits or shifts.
    But now we have all sophisticated computers, simulations and CNC machines etc…….how many of us have analyzed the 1.5 Sigma shift on their individual processes  long range to arrive and claim precise sigma variation with time than having a theoretical assumption for all, which can’t be assumed on all working processes. We need to be specific and even in SPC control charts 1/3 variation have been mentioned by many for long range which is for you to bring back the process into control as you decided to monitori it every now and then. We don’t do that in the Z table to correct our sigma which we can always do it as per our actual long range variations. It could be anything from 0-33%.
    Expecting a shift, wanting to consider that as an opportunity on all processes,  we could be calling normal design practices as DFSS. Same normal process variation again as an opportunity for Six sigma instead of tackling with normal established QC practices. What is continual improvement in regular QA/ISO systems? That is the point I want to clear in this forum. With a Six sigma process what is the percentile distribution on a working process? Is it the same 68% for 1 Sigma, 95% for 2 sigma and 99.73 for 3 sigma or what is the distribution other than the fact that majority we get in the target like a hieghtened peak like a fine tuned fixed frequency amplifier. In regular SPC chart it could be called hugging the centreline. If that is the case, we have controlled the process to that precision statistically and we should not have 1.5 sigma shift at all as it shouldn’t drastically alter your rejections all of a sudden.
    In case that is what we should expect, we have forcibly fine tuned the process including the commoncause variations, without knowing the process characteristics over a period of time. What should be the monitoring methods? Shewart’s chart theoretically distinguishes the two variations in process very clear and for statistical equilibrium considers only assignable causes into consideration. That clarity is missing in Six Sigma education. Role of black belt, the requirement should be a clear project management capabilities before starting any project on Six Sigma and these skills are not included or strictly demanded  in the curriculum. Now anyone with a professional degree can learn the Six Sigma methodology and use it without bothering about the existing QA systems and long term effects on company’s processes due to  their individual short term achievements alone as goals. How can we prevent that? 
    Who will fix the after effects on this long range shift? Again we will have another Black belt project to bring it back to correct by1.5 sigma or what? Why not demand the QA Engineer should know Six sigma techniques in addition to the industrial  quality engg, QMS and project management skills to run the quality drive long range and stable in organizations?

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    #181768

    Tuguchi
    Member

    No the big 3 automotives are the actual users of Lean concepts ,not SPC!

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    #181773

    Sankar
    Participant

    Point I tried to make is SPC was invented in 1930’s but big way used by 3 big automotives for others to get enlightened to use in small industries also. Otherwise I don’t think ISO would have tried to model their standard in tune with QS-9000’s  20 elements in 1994 version. Then they left it to individual choise in 2000 version,  how one use or implement SPC without putting any conditions. That is not the case with QS-9000 which means big 3 have played a very  big role in promoting SPC inadvertently in the world.
    Lean management is left to individuals.organizations to do in the way they feel like as it is more of organizing your house in order with less fat.When you talk of Poke-Yoke or 5S or Andon it is left to our imaginations and cultural convenience to implement it to keep your house in order. But SPC is more of product /process related variabilitiy which requires sophisticated Statistical tools to keep things in order. There in statistics, we can’t play and invent without 100% sure it works and it will work for ever. Lean was promoted after seeing the success of SPC/ Six Sigma not the other way, I feel. You may be right that big 3 followed Lean also and may be before. But I would give the full credit to their system including  SPC madndatory at the operational level.

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    #181774

    Ganesh,There are many companies in the world who do not use a statistical approach to ‘control’ a process. They use one-by-one confirmation.If someone has a batch process and they need to use SPC then shifts can occur for three reasons.1. There was a lack of control
    2. The sample size was too small
    3. They used the wrong chart.For example, an I-Chart n = 30 can shift by up to 1.7 sigma, but an X-bar and R for n = 3, g= 10 only shifts by about 0.6 sigma. A Cusum chart for the sample sample size shifts by about 0.1 sigma. You can confirm this yourself using Minitab.If you want to go back to the original source of the 1.5 sigma shift it was a mistake – someone misinterpreted Shainin 1.5 sigma control limits with conventional 3 sigma limits. (I won’t tell you who :-)

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    #181775

    Sankar
    Participant

    Thanks a lot Mr. Andy U for your clear explanation with details for different cases. I will try it out in Minitab and this is what I was looking for. If we can arrive at the process shift for our process on our own, for the sample size, type of chart and control we use, this arbitrary 1.5sigma shift need not be taken into account and we can go by actuals in the conventional way.

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    #181801

    Obiwan
    Participant

    Disturbances are in abundance…but it all leads to balance in the force…which, hopefully, this thread has achieved so that we never have to deal with the 1.5 sigma shift again…
    Obiwan

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    #181805

    PB
    Participant

    There has been a LOT discussed on 1.5 shift. You should have done a search before posting question.PB

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    #181926

    GB
    Participant

    EZWeld:
    You are truly inspiring!   Please tell us more!

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    #181942

    Dan Dobyns
    Participant

    I am really sorry that I posted now. I was just showing support for someone that had a good point. All you guys do in this forum is blast each other now. I use to enjoy reading post here because I learned new things and got views that I would not get from any place else. Now all I find is people new to six sigma starting threads, a few textbook responses and then bashing. No matter what the subject the bashing is the same. I also doubt the sincerity of most of the helpful textbook responses; it looks to me like self promotion. I will ask this question, why would anyone post to every question and every thread? I too screw off at work but some of you guys must just live to post here. I am not saying that’s bad I am just saying I am sorry for adding to the problems of what could be a great forum.

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    #181945

    Mikel
    Member

    You were blasted because your post was dumb.

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    #181946

    Taylor
    Participant

    Stan is right your post was dumb, you have no idea what cash generation and preservation is and how Lean Tools can optimize the financials of a business………………..
     

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    #181948

    Dan Dobyns
    Participant

    Chad,
    Are you serious? You have no idea what I know or what I don’t know. My point was that Lean is misused. Many corporate decision makers try to save money at the cost of quality, up keep of machines and running low on stock levels. They hear the term and don’t care about the tools uses to optimize processes. Just like you see so many people misuse DOE, most think it’s just a trial plan or an organized experiment. Back to my point so many companies in the US run very low stock levels with a gut instinct forecasting, they run machine without doing needed PMs, and use a just keep it running attitude. So many companies care about quick quarter profits.
    So try this Stan and Chad, go talk to the nearest maintenance guy and ask him about the last machine he worked on. Get his view on if he just got the machine running or if he took the time to bring the machine back to the condition it was in when the machine was new. The tools of Lean and good manufacturing practice allow for a machine not to be run into the ground. The same tools allow a supply chain to be robust enough to withstand the demand.
     
    My post may have been dumb, but why are you insulting my knowledge of business? Nothing is untrue with what I posted.

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    #181949

    GB
    Participant

    Chad and Stan made a data-driven conclusion.   You were blasted based on what you wrote.   Dumb.
    If you truly believe what you wrote, you indeed, have no clue.
    Whine all you want…your own post is what brought this on, mate.

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    #181955

    Dan Dobyns
    Participant

    hbgb b^2,
     
    Wow! So Chad and Stan made a data-driven conclusion. Here is some data for you to review. I must have misunderstood the data because I don’t draw the same conclusion that you do.
     
    Stan’s Post It is just an idea, it is not valid.
    Ezweld,
    You are now an official member of the lunatic fringe.
    That had to be the dumbest post in February and that’s a pretty low bar considering Les has been here.
    You were blasted because your post was dumb.
    I sell them for 19.95 and if you order in the next 30 minutes, I’ll throw in a second one for free. I’ll also give you a PDF copy of the bailout bill (>450 pages).
    500,000,000?
    Hey, combine with a little attitude and it is truly an argument.
     
    Chad Vader’s Post
    Stan is right your post was dumb, you have no idea what cash generation and preservation is and how Lean Tools can optimize the financials of a business………………..
    Interesting Read, but hog wash non the less……………..
    MrMHead
    I think it comes down to you have real data in front of you. Why throw in an unknown constant for the sake of the model? At the end of the day real data for the Process is the true model.
    Now of course you can do all that other stuff you talked about, but why? What have you gained from this understanding? A realization of ………………? Nothing that I would react to, or put stock into making changes in my process.
    Just my Opinion
    Sign me up, after the reviting speach last night I can’t wait to get a copy of the bailout bill that $9 a week extra in paycheck is going to be awesome, I can now get that 2 for 1 pizza deal I saw on TV and enjoy while reading the facinating book of “If I was going to steal tax payer money, this is how I would do it”
     

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    #181956

    Mikel
    Member

    Ez,
    I agree with everything you said – this time.
    Why didn’t you start with that?
    We insulted your knowledge of business because your original post was stupid and had absolutely nothing to do with Lean or anything else you just talked about.
    And by the way, I suspect I’ve worked closely with more maintenance “guys” than you probably have ever known.

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    #181958

    Mikel
    Member

    Ez,
    If you are going to act like a crybaby – don’t come here.

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    #181959

    GB
    Participant

    I agree with your second post about running machines until they puke.  I was refrencing your first post.   As Stan said, why didn’t you get right to it.
    The data to which I was referring was your first post that smacked of “butt-hurtedness”.

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    #181966

    Taylor
    Participant

    EZweld, I’m the plant and facilities superintendent for 100 million gallon a year process plant, Its my job to talk to Maintenance guys everyday, I’m their freaking boss……………….So when I say you don’t know what your talking about, I can say it with conviction now.
     

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    #181969

    Dan Dobyns
    Participant

    Chad Vader,
    Look most people who come to this forum have very impressive credentials. I am sure I have one of the least impressive resumes. I do however know something about the automation controls you use in your facility. I am a Process Engineer and I cut my teeth as a Process Tech. I worked with automation and molding machines. So I got trained on programming PLCs, and operator interface controls. I worked on my fair share of machines and swung wrenches with Maintenance many times. One thing I learned working my way up is not to ever think someone does not know what they are talking about because everyone is a subject matter expert in their own experiences most time its finding a common language to understand. I would bet a great deal of your Job is translating between Management and Maintenance. I would also bet that both sides say “They don’t know what they are talking about.”. I’m not here to bash anybody, sometimes I come here to read post when I am stuck on a problem. I have often wanted to give back to others that are new to the SS tools but often find many others answer question before me so I feel bad that I use this forum and never get back. That maybe why I was a crybaby. Once again I am sorry.

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    #181970

    MrMHead
    Participant

    Amit, You had asked for an example:
    With proper operational defintions geared towards your own CTQ, you can examine this thread and its “sigma value” with regards to relevance.
    Early in the thread there were a significant number of relevant answers – maybe they didn’t agree with one another, but they were none the less relevant to the topic.  If you took that as a sample and calculated a sigma, it was probably fairly good.  It was a calculation based on short-term results.
    As this thread dragged on and out and all over the place, the number of “Relevant” posts,  according to your CTQs and OpDefs, probably decreased.  So your apparent Answer Sigma shifted down.  Whether it was by 1.5 or not is TBD.
    But this isn’t the case for Every Thread!  So whatever “shift” number you may come up with for your thread, is not necessarily true for all others.
    To bring back the relevance:  It was pointed out that the value of “1.5” had no statistical basis.  And from that,  I liked the arguement that If you don’t know the true value (1.5?), why muck things up with an unknown.  At least you know what you Do have in ST.
    Any Students out there want to do a quick study?  ;-)
     

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    #181972

    Gary Cone
    Participant

    Ezweldnc,I am glad you came back to explain your point of view. There are several of us on here that have been learning and
    fighting for the right to do right things often to the detriment of our
    careers. I hope you can see how your first post alienated some of us. Welcome to the forum. Come back to help others learn.

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    #181973

    Taylor
    Participant

    Ok Ezweldnc, I’m going to back off and approach this way.  As a manager I’m responsible for 1.8 million dollar maintenance budget, I have to reduce this budget by 10% a year over the next 3 years. I am also responsible for 1.3 million in spare parts inventory. I have to reduce this number down to 850,000 over the next 3 years. How am I going to do that? Well the first thing I’m going to do is apply some basic lean tools and evaluate my  spare parts movements, determine cycles and change ROP & ROQ accordingly, at the same time I’m applying OME (Overall Maintenance Effectiveness) and cutting out unnecessary work orders. I manage strictly by the numbers and my KPI’s tell me exactly when I’m doing things wrong and when I’m doing them right. A plant that runs 24-7 and scheduled 352 days this year there is no room for error, turn arounds must be perfect.
    So I’m doing two things, I’m reducing my maintenance repair and operational expense from .018 per gallon to .013 per gallon, and also reducing spare parts, which is direct hit to the P&L by ~.5 million This  combined is a million dollars to the bottom line in 3 years. Just one department. Is it doable? Yes, and with no consequence to operations.
    The statement that you made “Lean manufacturing hurt our economy” couldn’t be any further from the truth. The lack of using Lean Correctly has hurt our economy.  I have been doing this for a long time, and this is my third company to walk in to and turn the maintenance and engineering dept around and force Lean manufacturing and other tools into the system. It takes time and patience beyond compare to change a culture of people who’s previous “Run it till it breaks” attitude is all they have every known. But having “fat” is not the way to do it. You have to have discipline and a thorough Root Cause Analysis of every failure. You have to treat each and everyone of those as if it were a personal incident. You apply the Six Sigma tools and Lean tools together and the outcome will be the best it can be. In a addition If my PM to Work Order Ration is below 75% I know I have a problem. I am the biggest proponent of PdM and PM and I know the value of keeping equipment serviced and repaired before a failure ocurrs. It is the life blood of any company to be able to predict failure, analyze the MBTF, and adjust waste out accordingly. It is an ever changing chess match. If your working around a company that does not put emphasis on PdM and PM programs then look for another company to work for, because they wont be around long or the business will be overseas or just gone.
     

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    #181980

    Dan Dobyns
    Participant

    Chad Vader,
    I should have said people misusing Lean. And what I meant by fat was things like spare parts inventory. Say for example you have a GE 9030 series plc and you have an output card go bad. If you have spare parts you can pop one and be running in a few mins then send the old one out to be repaired. If you don’t have one you could be looking at a day or six weeks of downtime plus the cost of a new or used card with rush shipment. To most managers justifying having a card in stock is a waste of money. They think that you should be able to tell when it is going bad and there is only a short lead time to get a new card in. They use the same style of thinking in all aspects of busness and for the most part it works. But I think by using the SS and Lean tools like you said you can justify having and maintaining inventory. My complaint is that most people who misuse Lean want no inventory and try to run JIT as much as possible.

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    #181982

    Taylor
    Participant

    OK, now we are on the same page. Another part of managing Inventory is Risk analysis of specific systems. Your example of not having a card in stock is classic. And your correct, some managers see it as a waste of money because they have not made or cannot make the case to their boss about the potential risk of not having this card in stock. I will tell you though, its even more of a crime to not understand why the card failed and just replace it then it is not having it in stock to begin with.
     

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    #181985

    Dan Dobyns
    Participant

    Chad,
    If you have worked with the 9030 you know there rep for failing, most just get too hot and have resistor failure or get zapped by brown outs. I loved the 9030s but they last so long then they start to fail unexpectedly. That’s why I used it as an example.
     

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    #181989

    Taylor
    Participant

    Understood, but every and I mean EVERY failure has a root cause. Determine that and maybe you never have a failure. Just trying to point you outside the box a little bit.
    For Example
    1) Why did the board get too hot?
    2) Whyd did you have a brown out?
    3) If the usable and expected life is 5 years or whatever, then plan for it in a PdM program. Even if the unit didn’t fail at least have a spare for the anticapted change out or failure. Risk Analysis/Failure Analysis, whatever you want to term it.
    All of these are preventable from happening.
    Here is a classic example that I like to talk about: we all drive cars, every car has a battery, most cases its a 72 month or 84 month (7-9) years now a days. Some people trade cars every 2-3 years so they dont have to think about it. But some guys like me still like to drive old used beat up trucks. So if I dont pay attention the battery life then someday I’m going to be stranded. Either some Very cold winter morning or some very hot summer day its going to happen, Now I’ll admit that a battery will usually if treated right will often last longer than the nameplate, but do I really want to take the risk of not changing out when its due? Thats the same question you have to ask yourself when keeping spare parts inventory. What is the risk? What is the leadtime? How often do you make a point to your boss that “hey we don’t have this part and that other one has been through some rough days, not sure how long it will last?” It is frustrating, but someone has to keep up the good fight.

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    #181997

    Herbie
    Participant

    Ganesh,
    You feel lean followed the success of SPC/Six Sigma? That wouldn’t pass any sort of logic test. Some of the original concepts around what is today called lean were developed ain the Ford River Rouge Plant which began construction in 1917 and completed in 1928. Automotive manufacturing in 1928.
    Shewhart didn’t develop control charts until the 30’s.
    Six Sigma wasn’t even close to the same decade. Try the 80’s.
     

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    #182000

    Sankar
    Participant

    Hernie
    I didn’t mean to take any credit away from Lean invention. In fact if you look at my initial discussion I wanted to say thanks to the automotive big three industries interest on SPC was sustained to develop into Six-Sigma later and even QMS like ISO-9001 was based on QS-9000 initially. In the same vein, I am willing to accept the credit for Lean also to the automotive industries.
     I would also like to say that Shewart’s control charts are fundamental discovery which is the foundation for control of mass manufacturing. and reducing variability.  1930 SPC stands even to-day and forever like laws of Physics. While Lean can be done by various organizations to their facility, taste and culture when we talk of 52 or Poke-Yoke,Kanban etc……SPC can’t be left to individual methodologies or ways to do in any fashion as it requires a complete statistical understanding and process control. To the extent SPC or Six Sigma was promoted to be used by lots of industries , Lean is gaining momentum again after the success of Six-Sigma. We can’t deny that. Process variability is fundamental to the process when we talk of machines and technology and we can control that too is a breakthrough discovery.

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    #182001

    Hal
    Participant

    It was invented by Mikel Harry.  Read his original derivation and you will find that it was based on stacks of disks !!!  Incredible but true.
    The 1.5 drift (and later “correction” then “dynamic mean offset”) is pure rubbish ! 

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    #182003

    Hal
    Participant

    This paper explains the 1.5 nonsense :
    http://www.qualitydigest.com/inside/six-sigma-article/six-sigma-lessons-deming-part-1
     … and this one for more detail on the origins of the 1.5:
    http://www.qualitydigest.com/node/5900

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    #182005

    Herbie
    Participant

    Ganesh,
    That is Herbie not Hernie. I assume a ketstroke error since the n and b are side by side. Maybe a control chart will help with that problem.
    SPC was very well misunderstood by the former Big 3 long before ISO or QS. The only thing those documents have driven is a completely lame third party NVA industry. If you want to know what drove ISO look at the original version and compare it to Mil-Q-9858D the military standard that drove that industry to benchmark quality levels.
    SPC had its heyday in the in the early to mid 1900’s because we did not have much in the way of controllers. It is of more value for analysis than for actual control in current times.
    You seem to have a love affair with SPC and Quality professionals. Both are misguided particularly the quality professionals. It has been discussed on this forum peviously that if the certified quality professionals had done their jobs we would never have needed Black Belts.

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    #182007

    anon
    Participant

    You make a lot of noise about it being rubbish but you don’t seem to be able to articulate the reason. At least when people like Perez Wilson make the comment they can defend their belief.
    Perhaps we are better off without your contribution. At this point any further reasoning on this issue would in all probability be redundant and actually someone elses original thinking.

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    #182010

    Sankar
    Participant

    Herbie
    Thanks for pointing out my typo error. Control charts distinguish clearly what is the difference between assignable cause and common causes. It is an opportunity for me to perfect in my  typing also. I have no problems with that as Quality professional.
    We need to blame the top management and other relevant people for not allowing the Quality professionals to do their job.  There is no single medicine for cure for all pains yet in the world. So I don’t want to get into that debate. Blamegame also won’t help anything.
    For me all Quality discoveries starting from Dr. Shewart to Dr.Juran to Dr. Deming and many other Quality stalwarts, including Six Sigma, Lean  all can be used correct if you understand it and use it  prudent.
    Six Sigma is yet to have any accreditation body in all countries monitoring the certifications of all the belts for your kind information. Anyone in the World can get Green Belt certified easily without any Quality background and experience or knowledge to startwith. They are tested only when they do the live project for Black Belts as they have to prove their credibility with the client organization.
    When it comes to Quality,  the World war precipitated the need for Mil Std. and then many discoveries, tools,  methodologies evolved  and adopted by many in the world to achieve their quality objectives. Six Sigma is also one like that for me as a Quality Professional.
    You cannot  complete a  house without foundations built first and all the tools including SPC, ISO etc., helped you to do that as otherwise you and me wouldn’t be talking about doing on-line global businesses or discussing this in Six-Sigma forum.
    After the advent of SPC,TQM, ISO etc…..only top management understood the need for quality, systems, processes, data driven approach etc…. If Internal auditors can do a sincere job, you don’t need to bother about third party audits and you can’t balme only Quality professionals for that. In a buyer’s world when ISO had demanded Quality and thrown open the quality manual to the customers it is more transparent , it all depends upon how an organization is interested in quality. What you are trying to prove is even if they don’t bother, Six Sigma people alone can help the management and shareholders. This can be only for short-sighted approach. 
    Still Quality  is a long way to go. Life is a long journey to the humanity and if we think of only the end of the world, none of us can claim to be an optimist and it is against Quality/Six-Sigma philosophy. Just because you need a commando force to clear some problems, you can’t demean the quality professionals and use commando force alone to safeguard all your processes at all times. You can’t establish process/business  continuity with temporary people.
    All technical inventions starting from Transistors etc…all happened after 1930. I am a Scientist and a passionate Quality Professional for the last 20 years who embraced all techniques and tools ,   preach and practicle all facets of quality including Six Sigma, Lean practices in my career and now pass on that passionate experience  to students also without any prejudices. The point I am trying to make is one new invention can’t take away the credit of earlier inventions. All Scientists know that as ethical requirement so as Quality professionals. I expect the same ethics from Six Sigma Professsionals also. I also don’t claim Six Sigma invention is meaningless and I always say in my classes  that the Define phase of Six Sigma definitely helped all the organizations who took the bold step to Six Sigma  and top management can be made to wake up atleast for their selfish/organisational  interest which is good for Quality improvement. I don’t think that can be done for ever by discarding Quality professionals as most humans don’t want to accept their mistakes first. Quality professionals are by nature call spade as spade first to all. To improve on quality further  the otherside has to bite that truth. Equilibrium of the lorganization for long-range also need tobe considered.
    If we have very good Design engineers who can follow Dr.Taguchi or Dr.Phil Crosby’s thinking about quality in the product/process design and a dedicated workforce, you don’t need anything including ISO or special teams. Unfortunately in reality that is still too far away.

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    #182011

    Mikel
    Member

    I can feel your passion, but many of your “facts” aren’t and your history is out of order.
    The easiest one to point out is Phil Crosby had no PhD.

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    #182013

    Sankar
    Participant

    Stan
    Thanks for pointing out my error. Phil Crosby deserves more than a Ph.D. I didn’t insist on Ph.D as a requirement for any field and I don’t normally attach importance to Qualifications alone. Quality is all about attitude, relevance, consistency and not having any bias. It requires dedication and perseverance and commitment..  Mr. Phil Crosby , Dr.Taguchi, type of people’s idealistic thinking and various  tools evolved  only helped  us to reach where we are to-day in Quality.
     I just named a few to remind that Six Sigma is a branch of Quality .Most of the breakthorugh achievements also are made with the ideas of operators who work with the processes more closely than others. I fully credit them for their ideas and work with commitment with floor people and educate them also about development in Quality.
    The point I wanted to make was not to highlight historical perspective alone and want to credit any one particular individual line of thinking alone. I wanted to ensure that Quality profession includes  Six Sigma also and I am in that mission also now, but  not Six Sigma alone at the cost of all other established thinking and practices and that would be a short-sighted approach with total disregard to all in Quality field.
    Why not like a sof-ware engineer is expected to know several new softwares for a company, Quality professionals can also be demanded to have various strengths including Six-Sigma and that will strengthen more long-range quality and minimize short-range losses also. After all QMS won’t be possible without a separate Quality function and an MR. Same would definitely be applicable to Six-Sigma as otherwise any processes altered by an individual Six Sigma team, if there is no continuity with the existing quality function, you can’t expect it to have any long-range continuity. You can’t trace back the Six Sigma team which had left already to come and fix it again. How to ensure normal QC problem is not hijacked into a Six Sigma project? This can be ensured by existing Quality functions only.

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    #182014

    cobb
    Participant

    Ganeshyou should have also replaced the last ‘e’ with an ‘i’

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