Isamu Takahashi

Defect prediction in copper motor rotor die casting using numerical simulation

Copper die-casting is still a relatively new casting process and the numerical formulation of this process is still in its developmental stages. A casting simulation software - ADSTEFAN was used to numerically determine the porosity in edge-gated copper rotor die-casting. The results obtained from simulation were then compared to the real die-cast copper rotors that were produced. Shot profiles are shown to be very instrumental in controlling porosity. Profiles designed to pre-fill a portion of the gate end ring at the slow shot speed prior to accelerating to the fast velocity to fill the conductor bars and ejector end ring are shown to be very effective in minimizing and controlling porosity. Since the electrical conductivity of copper is nearly 60% higher than that of aluminum, substituting copper for aluminum in the rotor would markedly increase the electrical efficiency of the motor.

Simulation tools for practical die casting processes

A casting CAE system named ADSTEFAN has been developed through an industry-university cooperative project in Japan. It is specifically designed for casting engineers to realize ease of use. A couple of days are enough to learn how to use it even if the casting engineer may have little knowledge and experience with numerical simulation. Only a few operations are necessary to prepare input data for solidification and mold filling simulation. Quick calculation with less memory is one of the main features of ADSTEFAN. A huge scale simulation, such as over 100,000,000 meshes, can be solved on an engineering workstation or PC. The various modules to estimate cyclic steady state, size and shape of shrinkage defects and flow pattern in shot sleeve are incorporated into the system in addition to fundamental solidification and filling simulation. Some typical results of application to die casting process are also described.