A few years ago, I wrote about the limits of random quality inspections. My focus in that article was on the random elements, on human mistakes, and on the tricks that manufacturers can play.
Today I’d like to write about issues that simply can’t be detected during inspections, even if 100% of the goods are checked and inspectors do a perfect job.
I will write about a product line that I know well: apparel.
What issues can’t be caught in apparel QC inspections?
I always need to educate clients about what our QA team can, and cannot, detect in the factories. Here are some common issues with apparel that we simply can’t catch:
- Yellowing of white fabric — this often becomes obvious 2-4 months after production. A good chemical testing laboratory can help set up the right program for catching this issue.
- Fitting issues that can only be caught by a fitting model… We can’t catch this with Chinese or Indian people from the factory, who have different sizing. All we can do is flag issues in measurements found vs. the client’s size chart.
- Garment construction issues that only appear after a wearing period or several washing cycles — for example, on a bra, the wired piercing out of the bar tack seam.
- Damages that occur during transportation — for example, garments become wrinkled, or foam at the bottom get permanently deformed. The key here is to specify the right packaging.
- More and more factories, all across Asia, use special pens to guide stitching, in an effort to replace chalk (which might leave marks and lead to defective goods). After a few days, the ink of these ‘magic pens’ becomes invisible… until cold air in the importing country makes them re-appear!
The “mega issue” you may not be aware of
I addition, there is a “mega issue” that can hide many problems: the fact that factories often press garments — this operation consists of ironing and, to a variable extent, stretching the products. Then, the products are packed (and kept under pressure). And inspection might take place 2 hours after that.
Why is it a “mega issue”? It can hide these two problems:
- Wrinkles and puckering might be invisible (or reduced to the point where they are acceptable) during an inspection, but they re-appear after shipment.
- Measurements found are artificially larger than reality. If the factory cut the fabric in pieces that are too small and/or used excessive seam allowances, production might be under tolerance… and a good pressing job can get them back within tolerance for a few hours/days — just enough to fool inspectors.
What is enraging about this “mega issue” is, most Chinese suppliers refuse to acknowledge they did something wrong, once real problems become obvious again. If it looked good at one point, it should always be good, or so they pretend.
More examples of post-sale quality issues
On the same topic, last year, I wrote about post-sale quality issues on ChinaImportal.com. I gave three examples:
1. Electronic products
One product comes to mind immediately. A time-delayed fault caused worldwide news headlines, for the wrong reasons. I bet you remember the hoverboards whose lithium-ion battery packs overheated and caught fire?
At the time of manufacturing, one can assume that the products were tested for functionality and repeated charge / discharge cycling, as with most products that have rechargeable battery packs. One can also assume that the test results were positive. It was not until the products were in the market for some time that the failure mode appeared.
To get to the bottom of why these hoverboards kept exploding one would have to carry out a root cause analysis. For example, in this case, it could have been an incorrect component on the printed circuit board that limited the voltage when charging the batteries. (I have no insider knowledge on that precise incident.)
Photo credit: Image, Dodgertonskillhause, morguefile CC license
2. Products with parts glued together
Gluing two parts together is an extremely common process. And yet, many of the very serious quality issues coming out of China have their origin in the use of an improper glue. Let’s have a look at some of the potential failure modes that only show up after a period of time.
Exposure to the sun, heat, and/or to humidity can have a very strong impact on glue and reduce its ability to hold things together:
- UV rays break down double bonds and the polymer chain if there are no UV absorbers in it. (Years ago, one could see faded paint on many cars because their paint had no UV absorbers – now it is included in the paint of all cars.)
- If the glue is made of inferior polymers, its polymer chain can break down quickly due to heat and other factors.
- Humidity can cause certain chemical reactions, especially in water-based glues (which are very common).
Imagine a shipment that goes across the ocean in a container. There is much heat and humidity. If the products are held together by inferior glue, their quality will quickly degrade during that 2-4 week journey. Or it might take a few months and many customers will complain and return products.
3. Mechanical elements
Another product failure that we have come across in the past is gearbox failure on fractional horsepower drive trains (geared motors used in chairlifts, golf carts, wheelchairs etc.). Gear boxes were designed using all the best practices when it comes to gear design, even down to the amount of force each tooth can withstand on the gears. Prototypes were tested for harsh environments, rough terrain, over-speed, etc.
In other words, the prototype products were subjected to all sorts of testing, with a positive outcome. It led to the design being pushed through to mass production.
It was not until several thousand products had been shipped that the first of many failed products were reported. The failure mode was lost drive.
What happened? The products that failed were being used in a more extreme condition than what the product was designed for and tested to. All the failed products exhibited stripped teeth on the plastic gear…
Do you have any other examples of issues that apparel QC inspections couldn’t catch for you or post-sale quality issues? I think there must be an infinite amount out there. Please share yours in the comments below… thanks!
Featured image credit: Free photo 109888473 © creativecommonsstockphotos – Dreamstime.com
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