So confused with AQL - How does AQL (Acceptable Quality Level) fit with my company

K

ktout

#1
So, we're a small (less than 20 employee) manufacturing company. I do almost all of our purchasing, we're working toward ISO:9001. One of my customer's is requiring that we "develop and implement inspection receiving plans using AQL chart to determine sample size & frequency."

1. I'm confused as to what the AQL chart is. Is it a chart that you can go to to determine a lot sampling size for inspection?
2. We don't receive in any parts, per say, more or less we receive in base/raw materials, printing inks, drill bits, chemicals ect. So, I'm not sure how exactly I am supposed to be doing an incoming inspection more in depth than a visual and making sure the products/qty's match my issued PO's. We do not do any chemical testing in house, so I would have no idea for example, how to test an incoming drum of chemicals to make sure it is correct. I have to rely on the fact that my vendor has labeled everything correctly,
3. Based on the info above, how would I implement and use an AQL chart? Most of the items I order are in small quantities (less than 10 pcs). Occasionally I will order higher quantity of say, drill bits, which I can see how an AQL would be helpful. But, for all of my small orders, I'm just lost.

Thanks in advance for the help, I need it.
 
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Stijloor

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#2
Re: So confused with AQL - How does AQL (Acceptable Quality Level) fit with my compan

A Quick Bump!

Can someone help with this?

Thank you very much!

Stijloor.
 
#3
Re: So confused with AQL - How does AQL (Acceptable Quality Level) fit with my compan

One of my customer's is requiring that we "develop and implement inspection receiving plans using AQL chart to determine sample size & frequency."
Can you please ask your customer what AQL he uses to inspect and accept your parts in his receiving inspection plans?
For me you are pretty much OK in your approach.
 

Statistical Steven

Statistician
Leader
Super Moderator
#5
Re: So confused with AQL - How does AQL (Acceptable Quality Level) fit with my compan

So, we're a small (less than 20 employee) manufacturing company. I do almost all of our purchasing, we're working toward ISO:9001. One of my customer's is requiring that we "develop and implement inspection receiving plans using AQL chart to determine sample size & frequency."

1. I'm confused as to what the AQL chart is. Is it a chart that you can go to to determine a lot sampling size for inspection?
2. We don't receive in any parts, per say, more or less we receive in base/raw materials, printing inks, drill bits, chemicals ect. So, I'm not sure how exactly I am supposed to be doing an incoming inspection more in depth than a visual and making sure the products/qty's match my issued PO's. We do not do any chemical testing in house, so I would have no idea for example, how to test an incoming drum of chemicals to make sure it is correct. I have to rely on the fact that my vendor has labeled everything correctly,
3. Based on the info above, how would I implement and use an AQL chart? Most of the items I order are in small quantities (less than 10 pcs). Occasionally I will order higher quantity of say, drill bits, which I can see how an AQL would be helpful. But, for all of my small orders, I'm just lost.

Thanks in advance for the help, I need it.
Let's start with the basic that AQL is the process average percent defective that is acceptable 95% of the time (a general intepretation). It is not lot/batch specific but a process average.

Any visual test you do is considered a go/no-go testing. It either passes or fails. The question you need to answer is how many do I need to visually inspect, and how many "failures" are acceptable. For every combination of sample size and accept number, an AQL can be calculated, as well as an OC curve that gives the probability of accepting a lot with any percent defective. If I had to guess, I would assume your customer wants you to generate these OC curves for different sampling plans.

I am not a big fan of AQL without understand the other end of the OC curve, the LTPD (sometimes called rejection limit or limiting quality) which is the percent defective that I would have a 10% probability of accepting.

There is NO right answer to the AQL or LQ values. It MUST be based on the risk of making a "wrong" decision. For example, an AQL of 1% means that 5% of the time your sampling plan will reject lots that at no worse than 1% defective on average. Where a LQ of 5% would mean that your sampling plan will accept 10% of the time lots with a greater than 5% percent defective on average. Are these numbers acceptable of the risk of the raw material you are purchasing?
 
B

Bunny

#6
Re: So confused with AQL - How does AQL (Acceptable Quality Level) fit with my compan

Your customer is referring to this.
ANSI/ASQ Z1.4-2008: Sampling Procedures and Tables for Inspection by Attributes

ANSI/ASQ Z1.4-2008 Sampling Procedures and Tables for Inspection by Attributes is an acceptance sampling system to be used with switching rules on a continuing stream of lots for Acceptance Quality Limit (AQL) specified. It provides tightened, normal, and reduced plans to be applied for attributes inspection for percent nonconforming or nonconformities per 100 units.

You can implement this practice for all of some of your items. If it is not practical to use a sampling plan for some items, like the simple ones. You should implement a visual inspection instead.

I my case, we can receive anything from a simple bag of screws to custom made printed circuit boards to finished medical product that requires testing. I have set of 3 levels of inspection dependent on the type. Screws and other simple hardware just receive a basic visual inspection and documentation check. Boards and other more complicated items follow the ASQ sampling guidelines and the most important items receive 100% testing.
 
K

ktout

#7
Re: So confused with AQL - How does AQL (Acceptable Quality Level) fit with my compan

I guess my dilemma with the AQL is that the majority if not all of our products that are incoming are simply a raw material. So, I can pretty much only do a visual pass/fail inspection and counting the qty. If a product comes in and is incorrect or is bad, we reject it and request a replacement. We really don't have a % of parts that we would allow to be rejected. With all that said, I don't really see how an we can implement the use of an AQL chart? I don't usually get anything of qty over 10 pcs. To me the AQL seems more fitting to someone that receives in thousands of parts.
 
B

Bunny

#8
Re: So confused with AQL - How does AQL (Acceptable Quality Level) fit with my compan

I agree and I would think that your supplier would agree too.
 
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