AQL Inspection Interpretation - AQL Percentage Inspection Methods

R

rajtechnic

Hi everyone,

Can somebody help me to understand this ?

One of my customer needs like this, QC requirement: cpk=1.33 min on critical characteristics, vendor need to perform 0.05% AQL Inspection. (DPPM=500)

Non critical characteristics shall be measured in accordance to this drg to an AQL of 0.65% (DPPM=6500)

My question is, When using SPC, At what frequency i have to take my SPC study( i mean the quantity) or How would i interpret & prove to the customer about my inspection methods?

Hope to get an answer soon.

Thanks & Regards

Arockia.:(
 
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Stijloor

Leader
Super Moderator
Re: AQL Inspection Interpretation

SPC and Sampling Experts at The Cove...
Can you help?

Thanks!!

Stijloor.
 

Statistical Steven

Statistician
Leader
Super Moderator
Re: AQL Inspection Interpretation

I am confused by the question. An AQL level does not imply or ensure a certain PPM level. More importantly, a Cpk value usually calculated from continuous data (though can be done with attribute) data does not have a AQL. If the problem statement is clearer I might be able to assist.
 

bobdoering

Stop X-bar/R Madness!!
Trusted Information Resource
Re: AQL Inspection Interpretation

My question is, When using SPC, At what frequency i have to take my SPC study( i mean the quantity) or How would i interpret & prove to the customer about my inspection methods?

SPC frequency is solely a function of your process, its performance and the correct application of SPC techniques.

AQL is simply a sampling plan based on risk, not capability. In fact, the more capable you are the less likely a sampling plan will discover problems - even if they exist. They are divergent.
 

Bev D

Heretical Statistician
Leader
Super Moderator
Re: AQL Inspection Interpretation

SPC frequency is solely a function of your process, its performance and the correct application of SPC techniques.

AQL is simply a sampling plan based on risk, not capability. In fact, the more capable you are the less likely a sampling plan will discover problems - even if they exist. They are divergent.

yes but some customers don't get that...
 

Bev D

Heretical Statistician
Leader
Super Moderator
Re: AQL Inspection Interpretation

Some clarification from the OP would be nice. I'm assuming (ALWAYS a bad thing) that he is confused about the sampling required to determine the Cpk and the sampling required to meet the AQL level specified by the Customer. Both needs can be met with the same sample plan OR they can be two different plans.
 

QMMike

Involved In Discussions
Re: AQL Inspection Interpretation

Hi everyone,

Can somebody help me to understand this ?

One of my customer needs like this, QC requirement: cpk=1.33 min on critical characteristics, vendor need to perform 0.05% AQL Inspection. (DPPM=500)

Non critical characteristics shall be measured in accordance to this drg to an AQL of 0.65% (DPPM=6500)

My question is, When using SPC, At what frequency i have to take my SPC study( i mean the quantity) or How would i interpret & prove to the customer about my inspection methods?

Hope to get an answer soon.

Thanks & Regards

Arockia.:(

Did you get more information from your customer?
To me it sounds like two entirely different things. As previously stated, your process determines your sampling size/frequency as it relates to SPC. Also if your customer wants you to use a certain AQL level for inspection you also need to find out what sampling plan he is referring to. At my work we use "Zero Acceptance Number Sampling Plans, Fourth Edition – Nicholas L. Squeglia". If you refer to Juran's Handbook there are many others. Each with their own sample sizes based off AQL levels. Sorry if this causes more confusion but better clarification is necessary.
 
R

rajtechnic

Re: AQL Inspection Interpretation

Hi all,

Thanks for the soon replies!!!!

I appreciate that. But still i don't get the exact answer.This is my customer needs in AQL percentage inspection methods.

Can you just tell me, How i have to perform my AQL sampling ?

If anybody has a sample form in word or excel format that would be much better for me!!

Thanks in advance.

Arockia
 

Bev D

Heretical Statistician
Leader
Super Moderator
Re: AQL Inspection Interpretation

I'm assuming now that you don't have any sampling tables? or access to ANSI Z1.4 standard?

a quick free resource is to go to the folowing AQL sample plan calculator:
http://www.sqconline.com/mil-std-105.html

It will give you the sample size and accept/reject numbers
 
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