Ndc less than 5 (purchased part) - Auditor suggest I get waiver from customer

S

sunita

Hi!
I did gauge R & R on a dimension with specification 42 +0 /-0.012. I used a micrometer for that dimension. My Gage R & R value was 27% and my ndc was 4.85 ~ 4. I know that i cannot use a micrometer to measure the above dimension as it does not measure to at least 1/10th of the tolerance. The above part is a purchased part and the cost of investing in a high precision equipment to measure a purchased part is not justified in my company. My auditor says that he can accept the gauge R & R value of 27% as it is still below 30% and has a justification remark. But he has asked me to obtain a waiver from my customer for the ndc value, which is less than 5. Should i get waiver from my customer ( This purchased part (Bearing) is press fitted into my Product ( Insulator), and sold to my customer). I can always verify with my supplier for a more accurate measurement. If i don't do gauge R & R on the purchased part is that OK? :rolleyes:
 
J

justncredible

Re: ndc less than 5

If you are using the gage to sort I do not think you have to meet the NDC, and since you are 20 to 30 all the gage is good for it sorting. You are not making any process changes with that gage, it is a adjustible go-no-go gage. But I am not certain, as my MSA book is out of the office this week.
 
bobdoering

bobdoering

Stop X-bar/R Madness!!
Trusted Information Resource
Re: ndc less than 5

MSA Chapter II- Section D:
"For measurement systems whose purpose is to analyze a process, a general rule of thumb for measurement acceptability is as follows:"

"Further, the number of distinct categories (ndc) the process can be divided into by the measurement system ought to be greater than or equal to 5."

Incoming receiving inspection is lot verification, not process analysis. So, as far as AIAG reference manual, ndc>= 5 does not apply. But, you may have some customer specific documentation that erroneously requires that all gages may have to meet that. It would be good to check.

You - and your auditor - are correct that you are working with a dicey gage at best. If you reject parts based on that gage, you may get into measurement arguments with your supplier that you may not win if the rejection is borderline.

Why your auditor feels he has the "authority to accept or reject gages", I have a hard time digesting. Is this a TS-16949 auditor? If so, ask him to point to the requirement not the reference or general rule of thumb that the ndc>=5. I like the ndc concept, but the AIAG book does not deal with it well, as in this case. For SPC, the ndc should be greater >= 10, calculated to the control limits, not PV. You won't see that in there, either. But when I see a supplier providing SPC data or capability values, that is the first thing I look for. Otherwise, the data is usually nonsense. :cool:
 
S

sunita

Re: ndc less than 5

sunita said:
bobdoering, You have aptly pinpointed to my question. :thanx:
Click to expand...


As you rightly mentioned my customer's "Supplier Quaity Manual" has asked us to comply to latest version of AIAG MSA manual. However in the manual on a section on MSA, the acceptance criteria did not mention anything about the ndc. My Supplier quality manual is dated Dec 2006. As you might know the AIAG MSA 3rd edition was out in March 2002. So i asked my auditor, since my CSR on MSA did not mention anything about ndc ( although there is a clause in front page to comply to all latest manual of AIAG), whether i can skip the waiver application from my customer. However he said " doesn't matter when the "SQM" was released i still have to stick to MSA 3rd edition as customer requirement.
 
bobdoering

bobdoering

Stop X-bar/R Madness!!
Trusted Information Resource
Re: ndc less than 5

sunita said:
However he said " doesn't matter when the "SQM" was released I still have to stick to MSA 3rd edition as customer requirement.
Click to expand...

Even if he does not recognize the difference between requirement and reference, I would still ask him to point to the specific ndc requirement - not general rule of thumb - that the ndc>=5. He simply can not do it. We can all be thankful of that.

Again, I think knowing the difference between the physical resolution of a gage and the statistically valid resolution of a gage is important. Most people on the shop floor still believe that the physical resolution is all you need to know, but they are very badly mistaken. But, as I have said in the past, Gage R&R is a tool box, not a tool. It can do many different things - and it tries to do too many at one time. But, beyond its imperfections, using it with the understanding of what it is trying to say is valuable. It is simply not "plug and chug."

Remember, the fundamental question the auditor is always asking is: "How do you know?" In your case, does you supplier provide data on their certificate of compliance? What device do they use to measure the dimension on their control plan? What is its ndc and gage R&R look like? Do they use SPC? What is their Cpk (if applicable - and it may not be if the dimension is ground or machined because it would be non-normal, a whole other story). Is this check on your control plan? So, right now with all of the current controls in place - how do you know that dimension is in spec? If you can answer this question confidently, you should be OK.

Something to consider...:cool:
 
Miner

Miner

Forum Moderator
Leader
Admin
Re: ndc less than 5

sunita said:
As you rightly mentioned my customer's "Supplier Quaity Manual" has asked us to comply to latest version of AIAG MSA manual. However in the manual on a section on MSA, the acceptance criteria did not mention anything about the ndc. My Supplier quality manual is dated Dec 2006. As you might know the AIAG MSA 3rd edition was out in March 2002. So i asked my auditor, since my CSR on MSA did not mention anything about ndc ( although there is a clause in front page to comply to all latest manual of AIAG), whether i can skip the waiver application from my customer. However he said " doesn't matter when the "SQM" was released i still have to stick to MSA 3rd edition as customer requirement.
Click to expand...
The key argument against ndc in this scenario, is that in the AIAG manual, ndc is a metric used to assess the suitability of a gage for process control.

Your situation, as I understand it, is a gage that is used for inspection not process control. ndc does not apply to an inspection gage. The MSA manual is clear on this point.
 
S

sunita

Re: ndc less than 5

Hi! bobdoering,

Thanks, I appreciate your effort.
 
You must log in or register to reply here.
Thread starter Similar threads Forum Replies Date
J Is a ndc less than five is also acceptable? Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 6
T Gage R&R Sheet Formula error?! NDC less than 4 Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 3
bobdoering Informational Ndc Calculation Error Caution Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 0
B Gage R&R with NDC=1 Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 19
J Question on very low NDC number with tolerable GRR ratio's Capability, Accuracy and Stability - Processes, Machines, etc. 7
C Acceptable NDC for %GR&R part inspection to Tolerance (%Tolerance) Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 3
bobdoering "nds" or Number of Discriminate Samples - the Necessary Tool to Work With "ndc"! Imported Legacy Blogs 0
leftoverture Number of Distinct Categories" or NDC Calculation in MSA Studies Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 44
R Count NDC from Graphik Sample Range vs R chart Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 9
B Process Control - Selecting Parts - NDC & Study Variation Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 1
B Capability Study => Check %Study Variance and NDC? Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 7
B NDC - Gauge R&R Studies with results where NDC = 1 or 0 Manufacturing and Related Processes 1
Y Poor Gage R&R Results - High R&R result and poor ndc value Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 6
B Help with NDC (Number of Distinct Categories) Please Six Sigma 2
R ndc=0 and GRR=14% ??? Interpretation - basic question Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 9
S Using Range/Tolerance to Guesstimate NDC or % SV? Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 1
C Conclusions from weird GR&R (Gage R&R) Results - 9 of 12 points have NDC of 1 Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 3
M MSA Manual asks for NDC higher than 5 - NDC (number of distinct categories) Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 1
J Impossible to achieve NDC (Number of Distinct Categories) greater than 2 Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 28
V Can Anyone Give a Simple Explanation on ndc (number of distinct categories)? Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 1
J %Study %Tolerance NDC - R&R Criteria Acceptability when the Tolerance is used Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 2
D Gage R&R %Tolerance NDC Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 12
C Minor NC - NDC of 0.4 yet the system had been accepted with no investigation Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 9
B NDC relates which type of MSA Study Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 16
M Minitab number of distinct category (ndc) problems Using Minitab Software 4
S The assessment of ndc figures in MSA studies. Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 3
S What is NDC (Number of Distinct Categories)? MSA 3rd Edition Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 6
M Interpreting my R+R chart - NDC's and Out of Control Limits Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 5
C Can someone clarify "Resolution", "Discrimination" and "ndc"? General Measurement Device and Calibration Topics 4
N Average range of measurement system NDC number Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 6
C Tolerance vs. Part to Part - Is it ndc? When using % of tolerance everything is fine Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 5
Y Is NDC needed for gage used for ATE? Automated Test Equipment IC Testing Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 6
K During Gage R&R, is calculation of ndc value required? Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 24
G Gage R&R derivation with respect to ndc - Lessons Learned Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 2
G Please clarify the Rule of 10 to 1 - AND - What is the ndc number? Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 66
M Calculation of ndc is 1.41PV/GRR - Origin of this coefficient? Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 13
A Number of distinct categories (NDC) - Non ferrous metal industry Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 4
D Resolution, Discrimination, NDC and the Tower of Babel in Metrology General Measurement Device and Calibration Topics 5
S Number of Distinct Data Categories - NDC - AIAG's MSA Manual 3rd edition Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 4
C Discrimination - Use ndc to analyse the discrimination power? Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 1
Y NDC (Number of Distinct Categories) - Long Gage R&R Study in MSA 3rd Edition Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 76
D Number of Distinct Data Categories:nDC: Where does the constant 1.41 come from? Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 1
M Customers Request AS9100 certification - Small Company (less than 20 employees) AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 8
Nicole Desouza ISO / AS Certification - Small business with less than 100 employees ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 7
shimonv Products certified by one of the less familiar NRTL labs Other US Medical Device Regulations 1
O P-Value less than 0.05. but everything else in control Statistical Analysis Tools, Techniques and SPC 19
O CPK with a P value less than 0.005 Manufacturing and Related Processes 15
R Female auditors earn 18% less than male auditors - IRCA Salary Survey 2014 Career and Occupation Discussions 0
T Promotion with Less Pay and more hours Career and Occupation Discussions 37
L Inexpensive Gage Management Software recommendations for less than 75 Gages Calibration and Metrology Software and Hardware 8

Similar threads

Top Bottom