MATERIALS
REVOLUTIONISING ROTORS
Building efficient rotors for e-mobility starts with the first drop of melt
T
he demand for induction motors is growing. Scarcity of rare earths, climate change, electrification of mobility and
other trends are driving this demand. However, the common industrial induction motor has weaknesses. With its laminar die casting
technology, German rotor manufacturer Wieland eTraction Systems boosts performance in asynchronous motors. While retaining the known advantages of asynchronous motors, these now aluminium and copper rotor types offer significant benefits in efficiency and safety.
PRODUCTION DIFFICULTIES IN CONVENTIONAL ROTOR MANUFACTURING Every rotor consists of multiple individually punched electrical steel laminations that are stacked in a surrounding cast cage. This cage is typically manufactured using high pressure die casting. With cycle times of one to two minutes, this process can be highly automated. But from the casting perspective, rotors are very complex structures. After placing the lamination stacks
in the tool, the casting chamber is filled with molten metal. A piston forces the liquid metal into the casting tool at high speed. Once in the mould, aluminium or copper melt solidifies rapidly. Industrial technology therefore requires short filling times of less than 0.1 seconds with flow rates of more than 50 m/s. To achieve this, the industry is using point gates. The disadvantage: these
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Zero porosity rotor in copper
gates do not fill all slots in the stack at once. The melt first flows through the slots directly at the gate, then into the opposite ring, and finally fills the remaining slots from the rear with a so called back-filling. As a result, air, process gases, and oil and oxide
contaminated melt fronts cannot escape.
HIGH POROSITY WASTES EFFICIENCY During the transition from liquid to solid state, there is a decrease
Zero porosity rotor in copper and aluminium
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