iSixSigma

ANOVA Maybe?

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  • #248956

    jfelten
    Participant

    Hey all!

    My name is Josh and I am a quality and process improvement engineer at a flexible film manufacturing facility. We have embossing machines that produce 8000ft rolls that are 33in wide of embossed material. There are several different things these machines do, they emboss the material to a specified thickness, and they stretch the material to the proper width for the next process downstream. These machines also produce several defects in the film like not deep enough emboss thickness, not enough stretching, or telescoping or collapsing rolls. We know that a majority of these defects are caused by incorrect tension during the winding portion of the embossing process. We had a DOE planned to define new run parameters for the machine as well as a new way to monitor web tension during the embossing process. However, with production demand being so high right now, the quality team does not have support or permission do perform this DOE. I am looking into other possibilities for determining what may be causing most of these issues, particularly the film stretching. One thought I had is to measure tension, unwind and rewind motor outputs, and some other machine outputs (temperatures and pressures) to then do a regression analysis or some sort of ANOVA to determine which machine output hs the greatest effect on the stretching of the film. Does anyone have any experience with this situation or advice for a young black belt? Feel free to email me if you do not want to discuss this on here [email protected]

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    #248965

    Robert Butler
    Participant

    In summary:

    1.    [The defects are] not deep enough emboss thickness, not enough stretching, or telescoping or collapsing rolls (and what is telescoping and collapsing – are these other ways of expressing not enough stretching or are they something else?

    2.    We know that a majority of these defects are caused by incorrect tension during the winding portion of the embossing process.

    3.    One thought I had is to measure tension, unwind and rewind motor outputs, and some other machine outputs (temperatures and pressures)… to determine which machine output hs the greatest effect on the stretching of the film

    Questions:

    1.    How do you know what constitutes a majority of the defects?  Have you done a bean count of defect types and summarized your findings with a pareto chart or some other method to make sure you know which defect occurs the most often?

    a. are all defects created equal – that is regardless of the defect the cost in terms of lost time/product/etc. is the same or is there an order to defect severity?

    2.    How do you know this majority is connected to incorrect tension?

    a.    Do you have required settings for tension?

    b.    If so how were these settings determined?

    c.     How well are they controlled?

    3.  Do you have prior production data where you have simultaneous measures of tension and defect type and counts?

    4.  For the third summary point – are the listed variables the ones you wanted to look at in your design or are they something else?

    5.  You say you have a new way to check the tension. Can you run the new and old side by side without stopping production?

    6.  If you are going to gather the data on the variables for the third summary point how do you plan to record the defects – type and frequency so you have some assurance of a connection between the process parameters and the defects?

    If you can provide the answers to the above then perhaps I or someone else might be able to offer some suggestions.

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    #249017

    Dennis
    Participant

    Robert sure did a great job covering the ground on questions and things to do. Robert did lay out a very good plan of questions.  Though you give the impression that may of these good questions may not be covenient for you to answer.

    This process gives me the impression very little PM is done on the equipment.  This is the first place to start with.  If management can not shut down the equipment for PM then I am sorry to say you will have little chance of solving the problem.

    Too many times there is the rush to capture data without truly watching the process.  A technique that many fail at, is to watch STUDY the entire process looking for variations.  Talk and listen to the operators especially senior operators. Question what are they doing today that they did not do several years ago.  What have they done to keep the machine running.  Look for the Duct Tape

    A obivous failure that many do not see with this process is that the rollers are not parallel to each other.  If this is the case then the pressure is not even across the width of the product.  The operators then try to compensate for the weak embrossed area by closing the rollers tighter.  Then the domino effect starts with stretch, tearing, variation between the ends and the middle.

    Keep the basics in your bag the W’s and a 6th one is to ; Watch,Watch, and Watch again.  Then implement Robert’s total plan

    Good Luck.

     

     

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    #249061

    Chris Seider
    Participant

    Have you considered following the classic DMAIC process?  You should already have gathered data on some of the X’s and looked for POTENTIAL/PROBABLE X’s in the measure/analyze phases.

    If you are trying to create a DOE and can’t get support–are you 1. making sure the process participants are part of the team and 2. giving updates to the team and project champion and 3. are you being aggressive on “levels” for your DOE’s?  It’s not uncommon for DOE’s to have to provide statistical significance with want to move X’s as much as possible but good/productive during the DOE’s is also a consideration.  I’ve dealt with this balance but if working with a team that includes process participants and have engaged them along with the project champion you should be able to find some support.

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