As discussed in my previous blog post, Flank Milling, How Hard Can it Be?, turbomachinery blades are commonly designed as ruled surfaces, with the goal of making manufacturing easier and faster with flank-milling. While some non-ruled surfaces can be acceptably flank-milled, the programming and machining process for flank-milling is generally more dependable with ruled data. However, the ruled data should be well conditioned, and several pitfalls should be avoided during the design and construction process.