See this page for a more thorough discussion on facets/bevels:
Have you seen these sharpeners before?
These sharpeners have multiple slots because each one grinds at a slightly different angle, resulting in a compound bevel.
Almost all western knives are sharpened this way, in one variation or another. The idea behind this approach is that the blade body itself, while originally made from a sheet of steel, is ground with a taper, but the actual cutting edge itself is at a slightly wider angle to resist going dull, but still cuts because in spite of the blunter angle, the metal is so thin (due to the tapering) that it cuts well anyway. Consider the fact that people can get paper cuts though the edge of paper isn’t sharpened. An unsharpened razor blade is thin enough to give you the same kind of cut if pulled along your skin. Thinness is enough to make something cut; the thinner the edge, the less acute the angle needs to be. But the angle still influences which directions the resistance forces push against the blade when cutting, so if you made your blade taper only from one side, and did a multi-bevel (micro-bevel, rather, if you want to keep the beveling small), you could get the look of the western style knife, but the thin slicing performance of the single-beveled Japanese knives.
The multi-bevel approach is also done to lessen the amount of metal that must be removed to obtain an edge. Sharpening another bevel at a steeper angle means less metal must be removed, whereas polishing the entire face of an already existing bevel at a finer grit is a lot more work. This kind of more labor-intensive polish is the way that Japanese swords are polished, mostly for aesthetic reasons. Some folks also want this kind of aesthetic for their kitchen knives:
(…but strictly speaking, using a one-angled bevel whose entire face is polished with each finer grit doesn’t do anything for the blade’s performance.)
The knives you’re designing might not look like they have a bevel, but here’s what’s actually going on in the geometry when they’re being sharpened:
Notice that in the graphic above showing the cross-section of the blade being sharpened, the blade body itself in this case is a wedge, and a small bevel is being applied to the edge via sharpening. (It is inevitable that if you grind metal away from the edge, a bevel will form.) If the blade body were a slab (like the Japanese single-beveled blades) rather than a wedge, that bevel wouldn’t be small; it would be large and visible, as was the case in the Japanese knife I showed you that had a large, visible single bevel.