I will now have to inspect my wiper blades. Tim, at first your statement seemed to make sense. However it is highly unlikely that the blades are produced by cutting. The fact is that it is actually very unusual to want an "infitely" sharp edge. Such an edge will wear away almost immediately. Most sharp edges are actually very small radius curves and obviously such an edge would be most desireable on a squeegee. Such an edge would be molded as it is the most cost effective way to make suach a part.
Before more confusion ensues, maybe it should be specified if we're talking about cuts at both ends of the wiper (setting its length) or cuts to the actual blade (edge cuts). In reading the responses so far, I could make both assumptions.
If I were asked to produce wiper blades with a cut edge I would certainly think about extruding two profiles in one, joined at the blade. Cut down the middle and voila, two blades with cut edges and no waste.
Wiper blades are extruded, then cut to length. There is no reason to cut the contact edge and it would be difficult to get a perfectly straight and flat cut.
Also, I do not think that silicone rubber is used, unless it is used in a blend. If you want a quick and easy test for silicone rubber, burn it. Silicone rubber leaves a white char.
Wiper blades are extruded and in most cases they use EPDM-rubber because of its stability against ozone and other environmental influences.
It is a co-extrusion method where they extrude a hard compound and as oft compound together.
