Copper Rotors Cast Vertically Die-Casting Machine Manufacturer Offers an Alternative Process Most of the practical elements of the program were undertaken at Formcast Development Inc., Denver, and subsequently at V-Forge, Inc., Englewood, both in Colorado. Casting was performed on a 750-ton (660-tonne) Bühler horizontal, real-time, computer shot-controlled die-casting machine. The development work, therefore, deliberately simulated what would become normal industrial production. But “horizontal” die-casting machines, those in which the shot sleeve, plunger and principal axis of the casting are aligned horizontally, are not the only style of machines used in the production of motor rotors. In fact, in the USA, the majority of motor rotors — certainly in larger-than-fractional-horsepower sizes — are cast in “vertical” machines similar to the one shown in Figure 1 — and for good reasons, which we’ll address in a moment. THT Presses, Dayton, Ohio, is the leading manufacturer of vertical die-casting machines in the world. A 30-year-old company, THT has been manufacturing vertical machines since 1977. Since the early 1990s, the company has pursued the development of copper motor rotor die-casting technology independent of the CDA-led consortium. The company was associated with the consortium shortly after it was organized in the 1990s, but, for a number of technical and commercial reasons, the company soon opted to undertake its own development program. In THT’s version of the vertical method, the shot sleeve and piston are located directly beneath the die, Figure 1. In preparation for casting, the lower die assembly is withdrawn sideways, allowing the molten charge to be poured into the exposed shot-sleeve cavity. The lower die is then shuttled back into position under the upper die, and the entire assembly is sealed by means of a multi-ton clamping force applied from above. The piston is then raised, directing molten metal upward through multiple orifices (gates) in the gate plate and into the die cavity. Piston travel is computer-controlled to minimize turbulence, as molten metal flows into the die. In some respects, the vertical die-casting process closely resembles low-pressure die- or permanent-mold casting, except that casting pressures are considerably higher. MORE >>

Update: Copper Motor Rotor is published monthly by the Copper Development Association Inc. to provide current information of interest to those in the electric motor and related industries. CDA assumes no responsibility or liability in connection with this publication and makes no warranties of any kind with respect to the information contained herein.