> Sir,
>
> i would like to know if we can use 5 pieces per lot during inspection instead
> of using AQL? what would be the possible advantages and the disadvantages of
> using the "5 piece-inspection"?
>
> is it really necessary that we follow the AQL in the inspection process? or
> can we define the sampling size depending on our company's decision?
>
> thank you.
> libie

The first question I have is: Whose AQL are we talking about?

The supplier's? You don't have to use a supplier's AQL, but it helps to know how they inspect their products.

A customer's? Is the customer requiring a certain level of inspection? If so, this is a question for them.

Your own? Why have an inspection process if you don't want to follow it? Change it to what you want to do, but I'd have ample justification in case a customer or regulator asks why it was changed.

thank you for the reply...

it is the AQL stated in the JIS (Japanese International Standard).

sir, if we would be having our own sample size for inspection, what would be the possible justifications? i have here some ideas wherein i can get some justifications: 1. history of nonconformanaces, 2. documented procedures (we can change it to 5 pcs/lot), 3. process capability, 4. costs, 5. we have existing supplier audits. sir, what would be the other items to be be considered so that we would have objective evidence during the surveillance audit.

thank you for the reply...

it is the AQL stated in the JIS (Japanese International Standard).

sir, if we would be having our own sample size for inspection, what would be the possible justifications? i have here some ideas wherein i can get some justifications: 1. history of nonconformanaces, 2. documented procedures (we can change it to 5 pcs/lot), 3. process capability, 4. costs. sir, what would be the other items to be be considered so that we would have objective evidence during the surveillance audit.

The points you stated should be ample justification for the change. If the history of the incoming product is good enough, your wasting your time inspecting more.
Just make sure you address what happens if there is a drop in the quality of the incoming product. i.e. sampling goes up, and suspect product rechecked etc.

James

sounds like you have enough controls in place to not take out rec. inspection completely.

If you are going to do sampling inspection, you need to understand what sampling plans are all about. A blanket 5 piece per lot inspection is probably not going to achieve anything of real value. Here's a link to a fairly good article about sampling that may answer a few questions:
http://www.variation.com/techlib/as-7.html

If you are only concerned with a sampling plan that is 'acceptable' to an ISO9000 auditor - you can use anything you want. as long as you can rationalize it and (in the case of incoming inspection) that you satisfy the requirements for supplier controls. (I've worked at companies where there was virtually no incoming inspection and it can work if you are controlling your suppliers.)

On the other hand - if your customer has specific requirements - you need to satisfy them.

from a technical perspective, a blanket sampel size of n=5 is not effective. When dealign with categorical data (pass fail) 5 is no where near enough - you might as well do none. If dealign with continous data and you have performed the appropriate capability studies, 5 may well be enough to detect a shift or trend in the data - as long as you continue to use continous data.

First of all, 5 pic. per lot ........

1) Its totally depand upon lot size. U canot only inspect 5 pic from 20,0000 pic its 00025% of inward

2) As from u will find 5 pic inspection just as an case find out allpha & beta error. Its too risky for buyer as well as supplier.

When u use AQL or AOQ their is Logic behind that that u must understand.