ELOX EDM High Voltage and Capacitance Settings
Using the right settings on your Elox power supply can make a big difference.
Elox EDM power supplies are designed to operate with a standard output voltage (gap voltage) of 70-80 volts depending on the incoming shop voltage. For most work this open gap voltage works well especially when using a graphite electrode on a common metal work piece like mild steel. If you are working with materials that are difficult to cut such as tungsten carbide, high nickel coatings, low conductive materials like PCD (polycrystalline diamond) and weld slag, you need to take advantage of high voltage and sometimes a combination of high voltage and capacitance. The high voltage setting increases the gap voltage (some Elox power supplies have both hi-pol and elo-pol settings, which are both high voltage settings). This does two things; one is that it increases the physical gap between the electrode and the work piece allowing for better flushing, the other is that it generates a hotter spark allowing the spark to push through low conductivity materials and more effectively melt hard materials with a higher melting point than mild steel.
Capacitance differs from the high voltage setting in that it produces a higher gap voltage spike at the inception of on-time only. The high voltage setting creates a constant high voltage throughout the on-time cycle. That initial high voltage spike created by the capacitors helps establish the cut and begin to melt the work material.
These two settings can be used in conjunction with each other for really stubborn jobs. They are also necessary a lot of times when a metal electrode is used like steel. Unlike graphite, metals conduct thermal energy very well which can rob heat from the cut, slowing metal removal rates. The high voltage and capacitance settings generate a hotter spark compensating for this issue. There is a cost though. Using high voltage and capacitance can significantly increase your electrode wear, especially if you are using a material like copper that has a lower melting point. Additionally, you should be careful to keep your on-time relatively short when using capacitance. Because of the time it takes to charge and discharge a capacitor, a long on time like 200ms for example, can create a situation where the capacitor is out of phase with the on-time/off-time cycle. This results in the capacitor discharging during the off-time portion of the cycle. At that point DC arcing occurs and your cut will become very unstable or stop all together.
EDM Zap offers EDM training either onsite or at their facility. Contact EDM Zap for more information.