I thought about "The Innovator's Dilemma" not too long ago, when a machine-tool-industry engineer spoke about NURBS interpolation. He had studied the capability, expecting his customers to need this knowledge. They didn't. Despite its advantages, NURBS interpolation has not been important to most machining center users, simply because traditional interpolation continues to perform well enough.
The power of "well enough" is a theme of "The Innovator's Dilemma." The book (by Clayton Christensen) describes how new technologies overtake established ones. Both technologies advance, the book says. A new technology is clumsy at first. It gets better, but still it remains behind, because the established technology may be advancing just as quickly. The problem is the users. They don't advance so fast. Thus the established technology's available features can advance far ahead of users' needs. Meanwhile, the new technology advances to the point where it's no longer clumsy, but now does the job well enough.
That pattern describes how PCs overtook mainframes and their successors—not by performing better, but by climbing up from below to meet users' needs. The same scenario can explain minimills challenging integrated steel mills, and even hydraulic earthmovers replacing mechanical ones.
Do machining centers fit this pattern? Thinking back on machining center developments that have been offered to the market in recent years, I think I can see examples of these machines developing beyond what users are asking for.
Then again, if machining centers do fit this pattern, it's hard to see what the up-and-coming technology might be. Machining centers are essentially the only choice for many types of parts—large oblong parts among them.
For certain parts that are more compact in their shape, however, there is an alternative that may indeed be coming up from below. That alternative is the lathe—or more specifically, the turning machine with milling capability.
These machines used to be clumsy at milling and drilling, perhaps as clumsy as a PC doing a mainframe's job. But now the machines are routinely used for square-part applications, and some shops that might have bought two machines for milling and turning are deciding that one machine can do instead.
Where pure milling is concerned, these machines may not represent the leading edge. But they do represent a development that is no less significant, which is the changing threshold of what simply can get the job done.