EDM oil, also known as “spark oil” by mechanics, is a type of dielectric fluid designed specifically for the electrical discharge machining (EDM) process. This oil doesn’t function as a lubricant like regular engine oil, but rather as an electrical insulator, a coolant, and a flushing agent for metal chips.
The main functions of EDM oil are:
• Electrical Insulator: It acts as a barrier between the electrode and the workpiece, preventing the flow of electrical current until a predetermined voltage level is reached, resulting in a precise and accurate spark.
• Cooling: It rapidly absorbs the enormous heat (up to 8,000 – 12,000 degrees Celsius) from the spark, preventing warping or damage to the electrode and workpiece.
• Flushing: It washes away soot and small metal chips that have been etched out of the workpiece groove, resulting in a smoother surface and continuous sparking.
Good Properties of EDM Oil:
• Very Low Viscosity: Typically around 2-3 cSt at 40°C, allowing for good flow and cleaning of deep grooves and narrow crevices.
• High Flash Point: Should be above 100°C for safety, preventing ignition and fire hazards during high-temperature sparks.
• Low Aromatic Content: Reduces pungent odors and provides a mild chemical composition, helping to prevent skin and respiratory irritation for operators.
• Clear Color: Allows operators to clearly see the workpiece and cutting area while the machine is running.
• Low Evaporation Rate: High boiling point, does not easily evaporate, helping to save oil and reduce pollution in the factory.
Types of EDM Oil:
1. Hydrocarbon-Based Oils (Mineral Oil Based): Produced from refined and improved petroleum oils. They are affordable and the most widely used.
2. Synthetic-Based Oils: Produced from pure synthetic materials. They have a much longer service life, are odorless, and have a very high flash point. And it is safest for health, but it is expensive.
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Precautions and Maintenance
• Efficient filtration system: Regularly check and replace the oil filter to separate metal shavings. If the oil is dirty, it will reduce its insulating properties and result in inaccurate dimensions.
• Temperature control: A chiller system should be used to control the oil temperature within standard ranges to maintain viscosity and prevent heat buildup to the flash point.
