No abstract

Abstract. Recent research by the Copper Development Association (CDA) has demonstrated the feasibility of diecasting electric motor rotors using copper [1]. Electric motors using copper rotors are significantly more energy efficient relative to motors using aluminum rotors. However, one of the challenges in copper rotor die-casting is low tool life. Experiments have shown that the higher molten metal temperature of copper (1085 °C), as compared to aluminum (660 °C) accelerates the onset of thermal fatigue or heat checking in traditional H-13 tool steel. This happens primarily because the mechanical properties of H-13 tool steel decrease significantly above 650 °C. Potential approaches to mitigate the heat checking problem include: 1) identification of potential tool materials having better high temperature mechanical properties than H-13, and 2) reduction of the magnitude of cyclic thermal excursions experienced by the tooling by increasing the bulk die temperature. A preliminary assessment of alternative tool materials has led to the selection of nickel-based alloys Haynes 230 and Inconel 617 as potential candidates. These alloys were selected based on their elevated temperature physical and mechanical properties. Therefore, the overall objective of this research work was to predict the number of copper rotor die-casting cycles to the onset of heat checking (tool life) as a function of bulk die temperature (up to 650 °C) for Haynes 230 and Inconel 617 alloys. To achieve these goals, a 2D thermo-mechanical FEA was performed to evaluate strain ranges on selected die surfaces. The method of Universal Slopes (Strain Life Method) was then employed for thermal fatigue life predictions.

The main goal of this research was to develop a method of prototyping injection moulded parts which produces a representation of the production part, including not only the part shape and functionality but the process as well. A prototyping method that meets all of these requirements could greatly aid in reducing the time required to bring a new product to the market by using the information gained from this prototype to manufacture a production tool that will be right the first time. Tooling constructed of laminations is appealing for prototyping or production because of the flexibility it affords in terms of rapidly altering mould geometry, gating or cooling passage design. This report summarizes a ‘proof of concept’ project which took a selected part geometry through the entire laminate tool manufacturing process. This report is divided into five sections: (1) introduction to the prototyping process, (2) background of current prototyping processes and description of the laminate tooling method, (3) description of the geometry selected for this work and the manufacturing details, (4) evaluation of the performance of the laminate injection mould and (5) conclusions.

The plaster moulding process is commonly used for casting prototypes of aluminium components designed for subsequent production by die casting. Plaster moulded prototype castings possess dimensional tolerances and surface quality comparable to die castings, but without the high tooling costs and lead times. Unfortunately, the mechanical properties of plaster castings are significantly inferior to their die cast counterparts. This is due primarily to the low thermal conductivity of plaster which extends casting solidification time significantly compared to die or even sand casting processes. Long solidification times result in large grained castings demonstrating low strength and hardness. This work is an experimental investigation into the effects of various levels of silica sand and carbon fibre additions on the properties of foaming plaster moulds and associated aluminium castings. Data and statistical analyses are presented and conclusions drawn regarding the wet and dry strength of plaster moulds as a function of sand and carbon fibre content. Likewise, conclusions regarding the associated casting characteristics such as surface finish, solidification time, hardness and tensile strength are presented. The effectiveness of silica sand and carbon fibre additions with respect to improving the properties of plaster moulded prototype castings is also discussed.

No abstract