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Y = f(X): How to define Y without the customer?

Six Sigma – iSixSigma Forums Old Forums General Y = f(X): How to define Y without the customer?

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  • #48596

    boettler
    Member

    During the Define stage of a Six Sigma project it is important to get a clear understanding of the project Y. Here you would define Y as a measurable process metric that tells how well the process is performing today (the baseline) and how performance should be after process improvement (the goal). Y (sometimes called CTQs) is a result of the drivers (Xs) within processes. To reach a clear definition of the Y, the voice of the customer (VOC) is normally used.My question is what if the customer never sees the failure mode in question and the problem is purely experienced and captured internally? The problem is the customer will not know what the CTQ factors are which we have to improve and control to prevent or eliminate the failure? The failure mode in question here is a pass/fail at final inspection.Any ideas on how to identify these CTQ factors and verify these?

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    #164421

    Brandon
    Participant

    Rob – you are inspecting in quality. What are the drivers for the Fail test? Someone has established what the fail mode is and the definition must come from what the customer’s expectation is. This is your hidden factory.
    Appears someone knows the CTQ’s for the customer already – that’s not your problem. Your project should be around defining the failure modes you are rejecting and identfying the causal factors for those failure modes. There’s your savings – fewer rejects or reworks.
    Unless I’m misunderstanding what you’ve tendered that’s the drill you need to go through.

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    #164427

    boettler
    Member

    Brandon – you are entirely correct about inspecting in quality. The drivers for the fail test is if the product leaks then it won’t be shipped. The customers expectation is that they won’t get a product which leaks and they don’t. All products which leak are captured internally. This is the problem; no one really understand why they leak.I guess what I’m asking here is what tools and techniques can be used to define the CTQ’s, as you say, “identfying the causal factors for those failure modes”.How do I identify these causal factors? Brainstorming, Cause and Effect, etc.

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    #164436

    Brandon
    Participant

    As I said in another post – now you’re getting techincal and that’s not my strong suit. But, yes, you now have to find the source of the defect. Back up through the manf., assembly & handling processes to find where leaks are introduced. Then find the causal factors. Others on the site can be of more help as to how to do that.

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    #164442

    New ATI
    Participant

    5Whys,pareto,multi-voting,NGT,etc.

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    #164821

    porch45
    Participant

    In situations like this, I have always used my internal customer  (final inspection) as my customer.  Essentially if you think about it, in a way they work for the benefit of the real customer.  Sounds like what you are trying to do is increase your first time yield or ppm to your internal customer.  You probably need to identify what the yield is, determine how much that is costing you, and then go from there to fix the problem and improve the situation.

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    #164836

    Dr. Scott
    Participant

    Rob,
    You already know the Y (leaking products). You also stated that your customer never gets a leaking product due to your “inspecting in quality” process.
    A concern that I would have is how well are you inspecting in quality. To have zero defectives reach the customer might mean you’re rejecting too many products. For an extreme example, if you reject all products at the inspection point, then you customer would receive zero defectives. So briefly, your first step is to do, what others have suggested, consider the inspectors your customer. Then verify that their measurement system is precise and accurate (with respect to the Y or leaks). Then start moving from there up the value stream or manufacturing to “fix” what causes leaks.
    But start at the measurement system first. Make sure you are not “over rejecting” (i.e., calling good product bad) which can be extremely costly.
    I might be off topic here. But trust me it is something to look at first.
    Regards,
    Dr. Scott

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    #164845

    AlexanderSO
    Participant

    Hi Rob.
    I understand from your post that your final customer isn´t getting defective parts, however following the product road just before the final customer is the quality audit, and this guys are receiving defective products, so you can use them as your project customer.
    With them you can build a QFD matrix (Quality Function Deployment or usually known as the quality house) to try to obtain a relation between the reject causes they use and the variables of the up stream processes.

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