History[ edit ] The erosive effect of electrical discharges was first noted in by English physicist Joseph Priestley. Lazarenko, were tasked in to investigate ways of preventing the erosion of tungsten electrical contacts due to sparking. They failed in this task but found that the erosion was more precisely controlled if the electrodes were immersed in a dielectric fluid.
History[ edit ] The erosive effect of electrical discharges was first noted in by English physicist Joseph Priestley. Lazarenko, were tasked in to investigate ways of preventing the erosion of tungsten electrical contacts due to sparking.
They failed in this task but found that the erosion was more precisely controlled if the electrodes were immersed in a dielectric fluid. This led them to invent an EDM machine used for working difficult-to-machine materials such as tungsten. Initially constructing their machines from feeble electric-etching tools, they were not very successful.
But more powerful sparking units, combined with automatic spark repetition and fluid replacement with an electromagnetic interrupter arrangement produced practical machines. Later machines based on their design used vacuum tube circuits that were able to produce thousands of sparks Micro wire edm thesis second, significantly increasing the speed of cutting.
The tool electrode in wire EDM is simply a wire.
To avoid the erosion of material from the wire causing it to break, the wire is wound between two spools so that the active part of the wire is constantly changing. The earliest numerical controlled NC machines were conversions of punched-tape vertical milling machines.
Machines that could optically follow lines on a master drawing were developed by David H. Master drawings were later produced by computer numerical controlled CNC plotters for greater accuracy. Electrical discharge machining is a machining method primarily used for hard metals or those that would be very difficult to machine with traditional techniques.
EDM typically works with materials that are electrically conductive, although methods for machining insulating ceramics   with EDM have also been proposed.
EDM can cut intricate contours or cavities in pre-hardened steel without the need for heat treatment to soften and re-harden them. This method can be used with any other metal or metal alloy such as titaniumhastelloykovarand inconel.
Also, applications of this process to shape polycrystalline diamond tools have been reported. However, caution should be exerted in considering such a statement because it is an idealized model of the process, introduced to describe the fundamental ideas underlying the process.
Yet, any practical application involves many aspects that may also need to be considered. For instance, the removal of the debris from the inter-electrode volume is likely to be always partial. Thus the electrical properties of the dielectric in the inter-electrodes volume can be different from their nominal values and can even vary with time.
The inter-electrode distance, often also referred to as spark-gap, is the end result of the control algorithms of the specific machine used.
The control of such a distance appears logically to be central to this process. Also, not all of the current between the dielectric is of the ideal type described above: The control system of the electrode may fail to react quickly enough to prevent the two electrodes tool and workpiece from coming into contact, with a consequent short circuit.
This is unwanted because a short circuit contributes to material removal differently from the ideal case.
The flushing action can be inadequate to restore the insulating properties of the dielectric so that the current always happens in the point of the inter-electrode volume this is referred to as arcingwith a consequent unwanted change of shape damage of the tool-electrode and workpiece.
Ultimately, a description of this process in a suitable way for the specific purpose at hand is what makes the EDM area such a rich field for further investigation and research. In this way, a large number of current discharges colloquially also called sparks happen, each contributing to the removal of material from both tool and workpiece, where small craters are formed.
The size of the craters is a function of the technological parameters set for the specific job at hand. They can be with typical dimensions ranging from the nanoscale in micro-EDM operations to some hundreds of micrometers in roughing conditions.
The presence of these small craters on the tool results in the gradual erosion of the electrode.National Jet Company offers small hole manufacturing via micro EDM (Electrical Discharge Machining). We produce both round and shaped holes in our EDM department.
We have designed and built most of our own EDM machines and electrodes for producing small holes in conductive metals. FIGURE 1.
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Request PDF on ResearchGate | Monitoring and control of the micro wire-EDM process | A new pulse discriminating and control system has been developed for process monitoring and control in micro.