Dear friends,

the time has come in the organisation i work for to use the AQL philosophy in its contracts with the suppliers. Top management gave me the chance to demonstrate to them what AQL stands for and how are we going to use it in order to minimise our expenses from non conformances caused by the suppliers.

Is it possible to show me a way of how to make such presentation in NON - technical words? I love statistics and i love technical language but in this case i am sure that i will not succeed if i use technical language.

Thank you for your time reading this question.

vasilist

Dear frinds,

the time has come in the organisation i work for to use the AQL philosophy in its contracts with the suppliers. Top management gave me the chance to demonstrate to them what AQL stands for and how are we going to use it in order to minimise our expenses from non conformances caused by the suppliers.

Is it possible to show me a way of how to make such presentation in NON - technical words? I love statistics and i love technical language but in this case i am sure that i will not succeed if i use it 100%.

Thank you for your time reading this question.

vasilist

How about zero defects instead of AQL's?

An advanced search on The Cove Forums on AQL revealed this (http://www.google.com/custom?domains=Elsmar.com&q=AQL&sa=Search&sitesearch=Elsmar.com&client=pub-1385417534940691&forid=1&channel=6124086287&ie=ISO-8859-1&oe=ISO-8859-1&cof=GALT%3A%23008000%3BGL%3A1%3BDIV%3A%23336699%3BVLC%3A663399%3BAH%3Acenter%3BBGC%3AFFFFFF%3BLBGC%3A000099%3BALC%3A000000%3BLC%3A000000%3BT%3A0000FF%3BGFNT%3A0000FF%3BGIMP%3A0000FF%3BLH%3A50%3BLW%3A350%3BL%3Ahttp%3A%2F%2Felsmar.com%2Fpng%2Fheader-G-search.png%3BS%3Ahttp%3A%2F%2FElsmar.com%2FForums%2F%3BFORID%3A1%3B&hl=en).

Some more searching through the threads and posts is necessary. ;)

Stijloor.

Thank you very much for your answer. Iwill be honest with you. We are no such mature to proceed with Crosby's philosophy!

Yes i would love to but my understaning of "how things work here" is that we are not in this level (at least now). Please do not take tis as a bad opinion of me for the organisation i work for. Just take it as a comment of knowing "where we are". Again thanks.

I used to think of Z1.4 type sampling plans as a way to determine quality and control processes, but I have been coming around to seeing them as providing a rough screening of quality. With a pass/fail test, the sample sizes needed to really determine the defect rate (and hence the quality of the lot) becomes huge.

Furthermore, AQL is more of a protection for the producer, not for the consumer.

AQL =1 mean that most of the time, a lot that is 1% defective will be accepted. Basically the producer is saying "You agreed to take lots that are up to 1% defective, so you have to come up with a sampling plan that almost always will accept the lots if they contain 1% defective parts." This means that you would often accept lots that are worse than 1% defective. :( How often you accept worse lots depends on the actual plan you choose.

Consider a typical plan: a lot of 1000 with AQL=1 and Type II normal inspection. You need to inspect 80 pieces. Lots with 1% defective will be accepted 95% of the time, but lots with 3.33% defective will be accepted 1/2 the time, and even 7.66% defective will be accepted 5% of hte time.

If you want to be better at catching slightly bad lots, you need a bigger sample = more cost.

So I see Z1.4 sampling plans a "insurance" against a truly horrible lot. Maybe a tool broke and 1/10 the parts are bad; maybe 2 different parts got mixed together and 1/4 off the shipment is the wrong parts; maybe something was miscalibrated and all the part are a little to big. But if you want to catch a slow drift in quality, or catch 2% defective instead of 0.5% defective, you won't have much luck if you use sampling.

Tim F

Dear friends,

the time has come in the organisation i work for to use the AQL philosophy in its contracts with the suppliers. Top management gave me the chance to demonstrate to them what AQL stands for and how are we going to use it in order to minimise our expenses from non conformances caused by the suppliers.

Is it possible to show me a way of how to make such presentation in NON - technical words? I love statistics and i love technical language but in this case i am sure that i will not succeed if i use technical language.

Thank you for your time reading this question.

vasilist

The basic answer is NO! If they don't know statistics, then they will be completely lost! Trying to explain how operating curves are derived etc. is futile.

Plus, by accepting this old philosophy of allowing for defects from a process, you will be on a slippery slope to poor quality.......believe me!

It has been my experience that behind every question there is a statement. Also, behind every statement, there is a question. I wonder why managemet is asking about AQL.

I suggest making a graph of AQL vs Cost. This would demonstrate the dimishing returns on increased sampling. I would anticipate some questions about sampling alternatives.

I have done much more SPC work than Acceptance Sampling, but I think sometimes sampling is a good strategy.

AQL (hopefully c=0) is simply a verification of product that should have been contractually verified as coming from a stable controlled process. It is sampling - and sampling always has error - in the parts you did not check, primarily. As Tim says, sampling plans are a cheap "insurance" against a truly horrible lot.

I guess one question may be what are you using in your system now, and: "How is that working for you?"

What is the risk of one bad part getting into your process? How about 5? 25? What is the cost in overhead, labor and materials when they do enter your system? At the board level (if I am interpreting that term correctly for your example) you need to talk money. How much money (overhead, labor and materials) are you losing now, and how much can you save if you implement the new overhead of sampling? Is there a payback? You need to estimate that, because there is a cost to sampling - inspectors, gages, labor, space, overhead, etc. They will get that more than nuts and bolts OC curves.

We use AQL alot but it is not very good at keeping customers satisfied even it passes the AQL it sometimes gets rejected on the fill line.

Here is the direction I would go.

AQL is for lot acceptance. It shifts the majority of the risk to the customer as it allows for a % of defects to be found in the sample and still be deemed an acceptable lot. The % of defects is not a direct representation thus you run the risk of accepting lots with higher % defects than what is found on the acceptance plan. It should not, in my opinion, be used for critical quality decisions but for things considered minor which are acceptable at some level (ie, minor print defects, pits in some types of glass, etc...). Other quality acceptance should be determined through SPC and better data than can be gleaned from AQL.


Mark

From my research and understanding, it seems to me that if you appraoch the selection of an AQL, you have to do a form of capability study on the process. After that, you have two practical routes to follow - defining an AQL with the risks that entails or implementing some form of SPC and avoiding the risks of any defectives getting out to the customer.........

I know which one I'd recommend.

I think the idea of knowing the reason behind the request for AQL (Acceptable/Acceptance Quality Level) is key to preparing a presentation for non-statistically trained board members.

As Deming tried so mightily to proclaim:
A System of Profound Knowledge (SoPK), to help an organization be successful, requires that knowledge of the "big picture" be available to ALL parties involved, not just the top managers. Personally, I extend the requirement to all the parties in the supply chain, not just the folks in one organization.

Let's explore some possible reasons this factor
how are we going to use it in order to minimise our expenses from non conformances caused by the suppliers. has become a big enough problem to attract the attention of the managers.


the flagging economy has had a ripple effect and incoming products from existing suppliers have fallen off in quality
(management errs in believing they can "inspect in" quality versus helping suppliers uncover the causes and subsequently "building in" quality.)
for some economic reason, the managers have new suppliers whose quality does not meet previous levels
(the selection process and contract review were not rigorous enough - it may be the capability and capacity of the new suppliers are not up to the task of providing the needed quality and adhering to an AQL level will merely result in making transportation companies wealthy in shipping poor quality product back and forth once rejected.)
upstream customers of your organization have mandated lower prices and your organization can no longer afford to eat the cost of nonconformances of your own products, which may have been always caused by nonconforming components in the past, just not a meaningful factor until the profit margin got squeezed - alternately, for economic reasons, the customers of your organization are tightening quality standards on your products because their profit margins are being squeezed.
(In either case, imposing an AQL without jointly working with other members of the supply chain on discovering and eliminating the root cause of poor quality is like putting a BandAid on a broken window - it will NEVER heal and poses an unknown danger if some outside force should impact the broken window.)

Thanks, Wes for highlighting something I'd over looked - the inclusion of the supplier aspects here.

Having run a Receiving Inspection function that was set up on the basis of an AQL, I can - confidently - tell you that it is of no use! We had a blanket AQL of 0.3% which in general terms required us to inspect 32 of everything! (our typical delivery quantity was 250 or so).

What a waste of effort! I could find no rationale for such an AQL and, once I'd looked into it, of course we were using it at the wrong end and had no control over suppliers processes (except for the poor specifications we supplied)

Clearly your management want to reduce the costs of supplied erors, but I can vouch for the fact that any AQL, even one close to 100% inspection will not be effective - and it will cost even more!

What we needed, and developed, was a far more effective supplier selection and development process! In the end, after about 4 years of work by myself and the Purchasing manager and Design Engineers, was the reduction of nearly 90 of traditional RI resources and more emphasis on supplier quality planning.

Of course, I had an enlightened Purchasing Manager to work with! One who knew that the total cost was far more than the price we paid for the parts we bought.

From:V.J.Brahmaiah

Counting defects in a supply by sampling is like counting the number of crows resting on a tree. By the time you finish the counting, some new crows might have arrived and some old occupants might have flown away. But if you assume that statistically the arrivals are equal to departures your sampling results are correct.

Let us believe in both god and statistics.

:topic:v.j.brahmaiah