Validation of Processes for Injection Moulding - Special Process? Clause 7.5.2

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rui12524

We had a pre-audit for TS16949:2002 where, among other things the auditors wrote that "injction moulding is a process for wich some faults will be detected only in the customer - ex impact resistance"; yabadabadu, although this requisite doesn´t speak about "special processes", the idea is more or less the same. Of couse we didn´t agree (totally), but now we have to do something. My question is the following? as somenone came across with this problem? feedback would be much apreciated.
Note: we are now thinking about process qualification, but the resources and time it consumes to fulfill 7.5.2 is a BIG problem.

best to u all
RMC:ko:
 
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Sporty

We am currently registered to TS16949:1999 and we do injection molding here....I have been reading the 2002 standard and trying to figure out what information you are looking for.
I took a Lead Auditor course for TS16949:2002 and it shows 7.5.2 as the same as 4.9 in the 1999 version....it also explains when auditing 7.5.2 look for evidence that validation of the processes is taking place, including equipment, personnel, etc....or "does the validation process give confidence that the process will produce a good product?"
As for impact resistance, we have an in house lab here compliant to ISO17025 and test our product, but not for that.....what are you molding? That might help.

I don't think I've been much help but I'm still searching and hopefully will have a better answer eventually....
 
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Sam

RMC,
Just a couple of thoughts;
- is impact resistance a customer requirement?
- is impact resistance a concern to you?
If you answer yes to either question then you should develop a method to test and monitor impact resistance.
 
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rui12524

Hi,

The part i mentioned is an auto part, and yes, we do perform destructive tests on impact weekly. The auditors mentioned very clearly that they weren´t talking about special process's... the arguement is the following "how do you assure that 100% of the parts are ok, regardin inpact?" This is a BS question to me, since we are talking about EVERY part we mould... how do I assure any other characteristic, if I don´t perform 100% testing? The idea behind the auditor's thoughst I agree in theory, but as I told them, what is the added value of doing a thing that will not enhance anything in my process?
 
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M Greenaway

The auditors question is utterly stupid. If you can only test for impact resistance by performing a destructive test clearly testing all your components will mean you have nothing to sell.

Perhaps he is looking for some statistical sampling, or a capability study ?

You could defend your corner by saying that you have had no complaints of failure under impact (maybe).
 
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Sam

1- "... the arguement is the following "how do you assure that 100% of the parts are ok, regardin inpact?"
2- ... how do I assure any other characteristic, if I don´t perform 100% testing?"

R.M.C.,
1- Do you have a control plan?
- Are the customer requirements identified?
- Do you have a procedure for impact testing?
- Are your results plotted on a control chart?
- Are you maintaining your customer designated process
capability requirements?
Evidence of this should satisfy your auditor.

2- Has the customer identified additional special
characteristics?
- Have you identified additional special characteristics?
- Evidence of statistically based inspection methods will satisfy
your auditor.

I'm not sure about the other two, but Ford has a variety of ES specifications for injection molded product that describes the methods of test and inspection required. You may want to contact the engineer for your product for additional information.
 
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rui12524

hi

question 1; Yes for all
Question 2:
"Have you identified additional special characteristics?" yes, process parameters. But I don´t have estblished a correlation betwen impact results and process parameters...

"Evidence of statistically based inspection methods will satisfy
your auditor"; what do you mean with statistically based inspection methods for the case of impact testing?

This particular part in not a concern, but the other 1500 codes are ... I don´t have a method yet to "treat" this parts...

Thanks for the input:ko:
 
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Sam

By ststistically based inspection., I mean utilization of documented sampling plan for control charting; who takes the samples, when are the samples taken, how are the samples taken, what is the accept/reject criteria.

Based on your responses you appear to have a handle on the process. I would suggest getting back with the auditor and asking him to provide more informatiomn on what he is looking for.
 
S

Steve Andrews

OK- so it looks like your next step is to establish a correlation between impact results and process parameters.
How about a Taguchi study with impact strength as the measurable?
I know you are short of resource and you might be reluctant to carry out the study, but look at it as a one of hit.
You might find that your material supplier has done some research on impact resistance that you could use to support your case.
It wouldn't hurt to ask - some times the answers are right under our noses.
 
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Dave.C

By ststistically based inspection., I mean utilization of documented sampling plan for control charting; who takes the samples, when are the samples taken, how are the samples taken, what is the accept/reject criteria.

I agree with Sam - the auditor was asking you to qualify what you have based your sampling on, - (i.e. BS6001 is a standard statistical sampling method that's been around for years), also supplier data and certification of the materials used, and the significant process characteristics likely to affect impact resitance as it has been identified as a significant characteristic by your customer.

You are probably already doing enough to satisfy your auditor: he was probably just doing a good Yoda impression and appearing mysterious simply by not clearly explaining what he was looking for, relying on you to understand and explain to him that what you do, and how it satisfies your customers requirement. :frust:

Dave.C
 
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