Modern turbocharging has imposed multiply stringent requirements on turbocharger compressor impellers. They must be highly efficient and quiet in operation, have longevity in service, be cheaply made and be quick to market. The traditionally cast compressor impellers are struggling to meet these demands. The turbocharger compressor impellers machined from solid have many advantages in geometric accuracy, material property and design-to-production time compared with their cast counterpart. However, the benefits of machined impeller had been hindered by high manufacturing cost. The high cost comes mainly from long machining time with traditional five-axis point milling. Compared with the point milling, five-axis flank milling has much higher material removal rate, and this significantly reduces machining cost and makes machining from solid competitive. Turbocharger industry uses to design their impellers for casting or five-axis point-milling, and the impeller blade surfaces are usually freeform surfaces. Current CAM (Computer Aided Manufacture) software has provided flank milling function for smooth straight-line-surfaces (SLS), but they cannot handle the freeform surfaces. The conversion from arbitrary surface to SLS becomes necessary. The conversion method has been developed, but few of them concern the important manufacturing constraints such as the smoothness of cutter movement and the developability of the SLS. Furthermore, the conversion may be used in the manufacturing process only, and the effect of the deviation between the original freeform surface and the SLS may be ignored. In this paper, we put forward a new approach. First a flank milling conversion method is described. It takes into account of important manufacturing constraints when converting an arbitrary surface into a SLS. The method is fast and produces good approximation. Next we describe how the method can be integrated into daily impeller design suite to make impeller design and subsequent manufacturing more effective. The approach is illustrated and verified by the design and machining experiment of a turbocharger impeller.

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