Reducing distortion in simulated injection-molded wind turbine blades

The small wind turbine commercial market is very competitive and has small profit margins. Injection molding (IM) of plastic turbine blades is one means by which a higher cost component can be produced efficiently in large production volumes. However, establishing IM process parameters for the turbine blades is not an easy task; the long, thin shape of the blades tends to result in warped parts. Research conducted by Northern Arizona University Sustainable Energy Solutions group demonstrates how to reduce the amount of warp in the part through a combination of simulation and Design of Experiments (DOE) methodology. Two measures of warp were used: Tip deflection and an average warp parameter developed by the researchers. Based upon typical molding research, the governing parameters that affect the amount of warp are the mold temperature, melt temperature, injection pressure, and packing pressure. The results for a generic, small wind turbine blade show that overall warp in a blade can be minimized by seeking optimal IM parameters. Simulations were organized for a Central Composite Design; the resulting response surface was optimized for minimum warp, yielding the optimal process settings. For this particular blade shape and material, injection pressure was discovered not to be a major factor in warp. The maximum settings for packing pressure, melt temperature, and mold temperature were found to minimize warp.