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Injection Molding Capability Studies for PPAP Submission
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Injection Molding Capability Studies for PPAP Submission
Injection Molding Capability Studies for PPAP Submission
Injection Molding Capability Studies for PPAP Submission
Injection Molding Capability Studies for PPAP Submission
Injection Molding Capability Studies for PPAP Submission
Injection Molding Capability Studies for PPAP Submission
Injection Molding Capability Studies for PPAP Submission
Injection Molding Capability Studies for PPAP Submission
Injection Molding Capability Studies for PPAP Submission
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Some Related Topic Tags
injection molding, ppap (production part approval process), process capability
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  Post Number #17  
Old 30th March 2010, 01:10 PM
bobdoering's Avatar
bobdoering

 
 
Total Posts: 4,089
Re: Injection Molding Capability Studies for PPAP Submission

Quote:
In Reply to Parent Post by bfore View Post

The tooling was mfg prior to the program being sourced to us...However, they used the industry standard shrinkage for the material being molded..We know better because of our past history, hence the over sized parts.
They will require giving us a variation or have significant tooling changes to make..
So where do i stand now?? They are aware of the out of tolerance issue, and have been submitted dimensionals to the customer...
Where do i go next?? Complete at cap study? submit the ppap with or without? I'm unsure...
You may need to contact your customer SQE if you are unfamiliar with their PPAP requirements when there is a problem. Some ask for an interim PPAP, with the capability data you have, and a plan (corrective action) to correct it or a plan to have the print changed to accept it. They may reject the PPAP anyway, if they do not want out of spec parts. It has a lot to do with how important the dimension is and how willing the customer is to work with you through the situation. Generally, it is better to be up front with them than try to bury it...as it will come back to bite you.

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  Post Number #18  
Old 18th July 2013, 07:53 AM
Antyp

 
 
Total Posts: 21
Re: Injection Molding Capability Studies for PPAP Submission

I will refresh this thread, as i suppose is most proper for my doubts.

Issue is Cm/Cmk, Pp/Ppk and finally Cp/Cpk at multi cavity injection process.

My current understanding is:
Cm/Cmk - for each cavity separately to be counted - to see machine capability.
Pp/Ppk - for all cavities together (mixed) - to see potential process capability.
Cp/Cpk - for all cavities together - to see what i am sending to the customer.

Important is, that the custmoer do not receive parts from each cavity specially marked, but all mixed together.

Could someone tell me if this approach is proper or not? If not please explain.

Thanks in advance for Your time and patinence!

Last edited by Antyp; 18th July 2013 at 07:55 AM. Reason: spelling
  Post Number #19  
Old 18th July 2013, 08:24 AM
bobdoering's Avatar
bobdoering

 
 
Total Posts: 4,089
Re: Injection Molding Capability Studies for PPAP Submission

Remember this: mixing all cavities is typically a multimodal distribution. If the measurement system does not mask that fact with a large normal distribution from measurement or gage error, then the output has a high probability of being non-normal. If that is the case, you may need to analyze the data with transformation or other technique.
  Post Number #20  
Old 18th July 2013, 11:29 AM
Antyp

 
 
Total Posts: 21
Re: Injection Molding Capability Studies for PPAP Submission

You have right, acquiring a proper Cpk values is difficult in mixed approach.

In this understanding You have presented, Cm/Cmk will be equal to Pp/Ppk is that correct?

I am asking, because we in fact are counting all indicators for each cavity separately, and no one could clearly explain to me why, so i thought that it could be a perfect opportunity to reduce a number of measurements and paperwork.

Last edited by Antyp; 18th July 2013 at 11:32 AM. Reason: explanantion added
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