Interesting topic, I all up in the middle of it myself. I have made many impeller patterns over the years as a traditional wood patternmaker. We are moving into the real world now with a 5 axis router. Just completed a 5 axis training course and the instructor had some difficulty programing an impeller vane. He ended up creating a drive surface behind the actual vane surface amd comped to the model surface and it worked fairly well, just combersome. He did suggest blade expert but had no experience with it and is looking for a demonstration. But sounds that the cost is very high.