Improvements on Single Point Incremental Forming Through Electrically Assisted Forming, Contact Area Prediction and Tool Development
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Single Point Incremental Forming (SPIF) is a die-less sheet metal forming method. Because SPIF does not use custom tooling, this process allows for parts to be made at low cost and short lead times. In this thesis electric current is applied through the tool to alter the formability of samples formed with SPIF. The research goal of this work is to determine if formability is effected by resistive heating alone or if there is some formability change due to the current interacting with the material. An apparatus that allows electrical current to be applied through the tool during forming is designed and implemented. A method is also developed to allow the contact area between the tool and sheet to be estimated, with particular focus on developing a method that allows for experimental measurement. The effect of applied current on formability is estimated by evaluating the maximum wall angle that can be formed in a single pass, using a variety of tool sizes and current settings. Using the contact area model to estimate current density, a signicant increase in formability is found at a current density range that agrees with previously published literature on electrically assisted forming of the same material. The results show that across multiple tool sizes, a significant increase in formability is observed when applying a current density (A/mm2) larger than the current threshold density published in the literature. A study is also performed to test the performance of a set of novel tool shapes. By using parabolic tools, it was found that formability can be improved while maintaining low surface roughness. Finally, a series of case studies are presented documenting the production several parts for a variety of design groups and researchers at Queen's University. These case studies provide examples for the uses of SPIF, as well as document the methods used to produce these parts in greater detail than is present in the literature.