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Determining Melt Flow Range of Product

Discussion in 'Gage R&R and MSA - Measurement Systems Analysis' started by Nikki, May 25, 2016.

  1. Nikki

    Nikki Well-Known Member

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    Hello All -

    I have been tasked with determining the average Melt Flow / Molecular Weight measurement for certain compound products.

    I am collecting data by Polymer Grade type, and then formulation. For example:

    Polymer Grade #1
    Polymer Grade #1 with colorants only
    Polymer Grade #1 with colorants and 20% Barium Sulfate
    Polymer Grade #1 with 50% Bismuth Subcarbonate

    Now for each category listed above - there may be 25 formulations that fall into that category. Because there is a slight variance on the actual ingredients going into the compound, the Melt Flow Range is somewhat different for each individual formulation.

    While one formula gives me a range of 16 - 21 g/10, another may give me 26 - 50.

    What is the best way to determine the average range? Do I just talley them all up and then choose the smallest and largest result and call that the range? Or is there a more accurate method I am just not seeing?

    Thank you,
    Nikki
     
  2. Eric Twiname

    Eric Twiname Well-Known Member

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    How precise is needed?

    From one point of view, "average" is meaningless...it is a different formula, therefore it is a different product, there for averaging it with another product has no purpose.

    From another point of view, having an average for a family of products gives a chance to screen through your products more easily.

    Which is the target? What you use the final result to accomplish may steer which calculation is most appropriate
    MW is a fairly rough number to begin with...
     
  3. Nikki

    Nikki Well-Known Member

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    No target - this is merely for a reference for Sales as customer's call them up and say they want a Polymer with a melt index of XXX g/10.

    The information I am putting together will be the average range for each family of products as you put it.

    What I am seeing - is that here and there are outliers.

    So I took an excel spreadsheet and high-lighted the range of each formula that I found.

    I think the way I want to do it, is to use a range that at least 3 of the formulations fall into, high-lighted below.

    Does this make sense?

    If I were to use this method, the range for this one would be 29 - 42 g/10 - and it would exclude those that seem to be out of the ordinary. upload_2016-5-25_15-6-48.png

    upload_2016-5-25_15-6-48.png
     
    Last edited: May 25, 2016
  4. Eric Twiname

    Eric Twiname Well-Known Member

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    Whatever method you use...make sure that the folks using the info (salespeople) agree with it.

    If it is a family of similar formulation, you might choose to take the median of each range, then break into families of similar median.

    Sales literature is not a spec...but you might have trouble getting a customer to agree with that statement.
    Make sure the range you set covers the normal variation of the product.

    In your row#6, if you tell me that the range is 29-42, then ship me 27...we would have a problem...
     
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  5. Nikki

    Nikki Well-Known Member

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    Thanks Eric. This is going to be more of a reference for Sales - so that they know if the customer asks for a product with MFI range of X g/10 - they can explain to the customer almost immediately the "general" MFI range.

    Melt Flow specifications are set once we have produced 3 to 5 lots - to come up with a specific range for that exact formulation.
     
  6. Eric Twiname

    Eric Twiname Well-Known Member

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    Lol...sounds good. But you've gotta know it won't be used that way...

    Scenario:
    Customer: I want a flow range of about 30
    Salesman: Any of these products meet that, here is the spec from our QC department (holds out the sheet of "general" MFI range you gave them)
    Customer: I need the spec tighter than that
    Salesman: No problem, we can do that...when will you order?
    ...and downhill it goes...

    If it is going outside the four walls...make it tight, make it right.
     
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  7. Chris Brockway

    Chris Brockway Member

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    And our regional Quality Manager has instituted a sign-off system for spec changes to address this very problem. For a spec change to occur, there must be agreement from Technical, Operations and Commercial. Unfortunately this doesn't address the millstones hanging around our necks from silly decisions in the past.
     

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