Imagine how many "forgot to" opportunities there are when someone is hand placing hundreds of pieces of carbon fiber into a mold, with no easy way of seeing if something is wrong once the next layer is applied.I think this gets overstated a bit when it comes to bike manufacturing. Aluminum alloy frames have a lot of areas to have manufacturing defects as well, there's probably more recalled aluminum frames than carbon out there. It turns out to be "easy" to forget to weld all the way around the headtube (the way the downtube, headtube and top tube come together and are welded turns out to be important), or drilled some extra vent holes, or "forgot" to heat treat the frames again after a thermal event that would weaken them. As price for aluminum frames went down, some of the fine art/attention to detail/process control gets lost in the higher volume facilities.
I have worked on large automated composite layup machines. They are significantly more repeatable than any human would ever be and have automated quality control systems, rework is regularly required. These have complex heating systems that closely controls temperatures ensuring there are no wrinkles or voids.
If you looked at the pictures from the GG auctions you can see they had people laying things down with an office projector and a hair dryer.
An advanced manual cell could have an overhead laser projector with an imaging system to check that every layer is in the correct position, but I suspect that isn't the case for bikes. Even then that can't ensure layers are compacted properly.
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