Quote:
Originally Posted by lucid
I mainly referring to the manipulation of soft variables such as the ones you mentioned--hence my use of the word "tweak". However, no design is free of errors. One can test the subsystems to perfection individually (for example the engine), but many new issues come up, especially at the interfaces, when the subsystems are put together. Therefore, there is only so much "freezing of specs" that can be done before the whole car is put together and thoroughly tested. Since rigorous testing of the full product takes time (how about the A380?), it is not that uncommon to find out a few months prior to launch that the dimensions on a machined part absolutely needs to be changed as the alternative would be a recall. So, even seemingly frozen specs might need to be changed shortly before production. That doesn't make the manufacturing people, the suppliers, or the customers happy, but that's the way it is unless one wants to build in huge catch-all redesign phases into the timeline and stretch the product development process on paper in advance, but that would be hard to justify to the CEO.
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It seems that we are in agreement that design and engineering specs are frozen well in advance of production. Changes are sometimes (always?) necessary after the specs are frozen, but that is something the development phase is at least intended to avoid.