Doing an inspection in China is really nothing more than looking in cartons to figure out if what the vendor made is to spec. Depending on the size of your production order you can inspect 100 % of the order or a part of it. Usually however, the size of the order mandates that you inspect only a part of it. For example, it is simply not possible to inspect every piece of a 20,000 pc apparel order unless you have a few people helping you. And even then it would take at least a week. The trick then is looking at enough of production so that you really come to an idea as to overall quality of the production. If you look at too little of production then you may miss bad production lots, bad cartons and come away from your inspections thinking your product is better than it actually is. If you try to inspect too much fatigue will set in and you may start to miss bad product or just start passing everything. I have experienced the fatigue factor before on inspections and it really can slow you down.
Probably the best method for doing an inspection in China is AQL, which stands for Acceptance Quality Level. AQL is based on statistical sampling methods first implemented during WW2 to monitor procurement of wartime supplies. At that time 100% sampling of military supplies was found to be ineffective, costly and time-consuming. So AQL was devised as a means of verifying if a production lot was acceptable or not based on looking at a fixed number of pcs.
This is a very simplified version of how AQL works.
There are 3 levels of an inspection, 1, 2 and 3, 1 being the most lax and 3 the most rigorous. You determine the level of inspection you want based on your customer. If you are doing plastic promo items for a chain restaurant, for example, you probably don’t need a strict inspection and a level 1 inspection might suffice. If you are doing high-end décor for a well known retailer with severe chargeback penalties, on the other hand, you need the strictest, Level 3 inspection to ensure that your product is in compliance. At the same time if you are working with a vendor whose quality leaves something to be desired, and who was sure to fail a Level 3 inspection, then a Level 2 inspection might be the best. So as you can see there are a lot of subjective variables involved in determining the framework for your inspection. For this reason you need to be flexible with the results.
Your PO QTY then determines your sampling lot. For example if I had an order of 20,000 pcs for level 2 customer, I would pull 315 pcs from the order and inspect those. If among those 315 pcs I found 14 or more broken pcs and more than 21 pcs showing other “minor” problems then the inspection would fail. The vendor would then have to open up all the cartons and inspect and repair the whole order. Needless to say, this is why vendors do not like inspections.
The key to doing an AQL is, as I said above, flexibility. You cannot always just take a pass/fail for what it is. For example, if you pulled 315 pcs from production and 14 were broken but the rest of the sampling lot looked very good, then you might just want to accept the order especially if you only needed only 80 % to fulfill an important order on your end. It also depends on your vendor. If a good vendor fails an AQL inspection there may still be plenty of good product in the order and you may just have made a mistake in picking your sampling lot. If a bad vendor fails an AQL inspection then you will probably find more bad product.
Once again, this is a simplified version of AQL. There is a lot more involved, for example how to pick your sampling lot and establishing your own acceptable quality levels. But if you are going to do an inspection in China it is a good idea to familiarize yourself with the AQL. It will save you a lot of time, sweat and aggravation.