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Initial capability studies

Discussion in 'IATF 16949:2016 - Automotive Quality Systems' started by bkirch, Oct 1, 2018.

  1. bkirch

    bkirch Member

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    In the AIAG Production Part Approval Process Fourth Edition blue book, for initial process studies it states that for initial process studies, you should use 25 subgroups of at least 100 from a significant production run. It defines a significant production run as a minimum of 300 consecutive parts. If I have multiple cavities or multiple fixtures, would a significant production run be interpreted as 300 from each cavity or fixture, or would it be a minimum 300 total as long as each cavity or fixture was part of the production run?
     
  2. Golfman25

    Golfman25 Well-Known Member

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    My guess is your customer may want capability on every cavity (it may even be in the AIAG book somewhere). So in that case, 300 cycles.
     
  3. tony s

    tony s Well-Known Member

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    As per the Section 2 of PPAP Process Requirements:

    upload_2018-10-9_9-59-0.png
     
  4. ncwalker

    ncwalker Well-Known Member

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    Here we go :)

    So the problem is, if you have a multiple cavity tool or multiple parallel processes, this becomes A LOT of parts. And it's not just good quality practices, there's significant COST involved. If the studies were dirt cheap to do, we'd just do them, right? Add to this, with the accelerated launch timelines we are all seeing, there's now significant risk that if you do this PPAP run as 300 cycles of a multi-cavity tool, you run the risk of having to eat a LOT of orphaned parts. You do this once and your financial folks are going to be pretty upset. With that said, here's some food for thought:

    1) If your customer SQ wants capability on 300 pieces of a 12 cavity tool, that's 3,600 pieces. How many PPAP parts did they order? You can push back and tell them you will run as many as they order. Because if they get orphaned by a revision change or plain just don't work in validation, then that's THEIR problem.

    2) Once you give them a bit of pause with this request, you can propose an alternate study.
    a) Let's say you have a 4 copies of a machine making parts. You can do the study on only one of them, prove out the cell design is capable. It's on you to make sure the copies are tracking the original once the first one comes into play. If they want evidence, you can certainly show this with an SPC chart. It doesn't HAVE to be a capability study. Remember - it's a prediction, and a sketchy one at that. It's not a control metric.
    b) Let's say you have a mutliple cavity tool, and you have to make 16 per cycle. You can do a study and get a feel for things with 5 or 6 cycles. You're looking for how alike the different cavities behave, easily done by looking at delta mean vs tolerance. And you're looking for consistency. Harder to do when you're cycling a few times. Do you have a similar process in production? You can use THAT data to show that the PROCESS is stable. Also, right after PPAP you should be going into Early Containment or GP-12. You can use that period to demonstrate stability as well.

    If you're lucky, you will have an SQ who can think. If you have a "check the box" SQ, push hard on the "they have to order the PPAP parts" angle.

    The goal is to gain confidence in the repeatability and stability of the process so that everyone is comfortable with opening the flood gates. There's options to do this OTHER than capability studies.
     
    Atul Khandekar likes this.

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