An automated approach to calculating the maximum diameters of multiple cutters and their paths for sectional milling of centrifugal impellers on a 4_(1/2)-axis CNC machine

Power generators and chemical engineering compressors include heavy and large centrifugal impellers. To produce these impellers in high-speed machining, a 4?-axis milling machine(or a 4-axis machine plus an indexing table) is often used in the industry, which is more rigid than a5-axis milling machine. Since impeller blades are designed with complex B-spline surfaces and impeller channels spaces vary significantly, it is more efficient to use multiple cutters as large as possible to cut a channel in sections and a blade surface in patches, instead of only using a small cutter to machine a whole blade and a channel. Unfortunately, no approach has been established to automatically calculate the largest diameters of cutters and their paths, which include the indexing table angles. To address this problem, an automated and optimization approach is proposed. Based on the structure of a 4?-axis machine, a geometric model for a cutter gouging/interfering the impeller is formulated, and an optimization model of the cutter diameter in terms of the indexing table angle is established at a cutter contact(CC) point on a blade surface. Then, the diameters of the tools,their orientations, and the indexing table angles are optimized, and each tool's paths are generated for machining its corresponding impeller section. As a test, an impeller is efficiently machined with these tools section by section; thus, this approach is valid. It can be directly used in the industry to improve efficiency of machining centrifugal impellers.

Optimal design of wind machine impeller for frost protection based on CFD and its field test on airflow disturbance

Wind machines have been increasingly applied to prevent frost damage through airflow disturbance in tea fields and orchards.An impeller is the most important component of the machine.However,there are few studies on customized impeller design or airflow disturbance performance.The objective of this study was to design a new impeller for frost protection wind machines based on reverse engineering and CFD simulation.The characteristic parameters of an impeller include blade cross-section shape,installation angle,sweep angle,hub ratio and blade number.The optimal combination of the above parameters was obtained through the simulation of the impeller’s aerodynamic performance.Field tests were conducted in a tea field to evaluate airflow disturbance performance of the designed impeller.The result shows that at a certain rotation speed and rotation diameter,the optimal combination of impeller parameters was:single arc cross-section ofϕ2400 mm,installation angle of 15°,sweep angle of 87°,hub ratio of 0.3 and blade number of 4,of which the impeller could achieve the highest usage of 0.56,the least consumed power of 1.363 kW and more uniform distribution of surface pressure on the windward side.Compared with other commercial frost protection wind machines,the maximum airflow velocity of the developed impeller was higher at 12 m in front of it.The probability of airflow velocity above 3.0 m/s within 30 min was the highest(71.7%),indicating its improvement of airflow stability.Without swing the new impeller could cover an effective area of 300 m2,which was similar to that of the commercial ones.