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1. INTRODUCTION
Electronic magnetic Forming (EMF) is a process of using electromagnetic forces to form metal, without a tool or punch coming into contact with the part. It is also an ideal process for mechanically joining or assembling dissimilar metal components. An appropriate electromagnetic coil driven by an electric current in the form of a sharp pulse generates the required force for metal forming. A product formed by this process is free from toll marks and heat effects as there is neither tool coming in contact with the job nor any abnormal heat being produced during the process.
This process is ideally suited for forming techniques on aluminum leave wrinkles on the job and has other problems such as spring back and poor reproducibility. Aluminum is one of the potential lightweight materials for certain automobile and other components and parts. Hence EMF process has potential application in automobile and other industries especially for forming sheet metal components.
2. PROCESS DESCRIPTION
Electromagnetic forming relies on the force generated by a magnetic field to produce the desired shapes in electrically conductive metal work pieces. Essential components of an EMF system include a conductive coil, called the work coil, a charging and control system and energy storage capacitors. A typical setup is shown schematically fig 1.
The capacitors are charged from the line voltage supply, then the entire circuit is isolated from the power source. When the forming circuit switch is closed, charge stored in the capacitors flows as current through the work coil. The current creates a strong magnetic field (lenze’s law) between the coil and the work piece. This field in turn induces a current in the conductive work piece and sets up an opposing magnetic field. The integration between the two magnetic fields creates a magnetic pressure pulse strong enough to force the work piece into a new shape. The shape created depends on the type and location of the work coil. A tubular coil around the outside of a work piece will deform it inward. This is the most common application for EMF since it can be used to attach and assemble a wide variety of components. A tubular coil inside a work piece will bulge or flange it outward. A flat coil is used most frequently for electromagnetic riveting for removing dents in sheet products.