A. The ignition point is at least above 72°C. ----- The higher the height, the less prone to fire.
B. It must be non-toxic and odorless. -------------- Reduce harm to the human body.
C. Non-corrosive. --------------------------- Reduce harm to the human body.
D. No smoke. --------------------------- Reduce harm to the human body.
E. Low viscosity (<2.8 mm 2/s ). ----------- Exclude processing.
F. Good stability and low volatility. ---------- Can be used for a long time. 

Factory Brand
Viscosity at 20 ℃
Burning point

CST
E°
°C

Mobil oil VELOCITE 4
9
1.75
118

Castrol HONILO
409
6.4
1.52
135

Chevron EDM 71
5.7
1.46
116

BP insulating fluid 250
6
1.48
120

Esso LECTOR 40
6.8
1.55
132

Esso UNIVOLT 64
2 0
2.9
156

Socal Fina LYRAN D 50
1.
2.05
132

Fuchs RATAK FE
5.6
1.46
115

Gulf Mineral Seal Oil
5.8
1.48
132

Mobil oil VELOCITE 6
19.1
2.8
158

Esso MENTOR 20/SOMENTOR 43
7.4
1.6
124

Kerosene (for comparison only, use prohibited)
2
78 

The so-called slagging, that is, the correct circulation of the machining fluid between the electrode and the workpiece, is a very important factor for electrical discharge machining, and proper slagging can obtain the highest processing effect. 

This method of fuel injection and slag removal is to spray the machining fluid from the workpiece through an fuel injection station, or spray it through an electrode.
In the first case, the workpiece has been pre-drilled and installed on a fuel injection station, and then connected to the slag removal equipment.
In the second case, a hole is drilled in the middle of the electrode, and the machining fluid is directly input through the electrode holder.
The components processed by the jet slagging method are slightly tapered, even if the electrodes are processed with a constant surface shape.
This is the tapering effect caused by the discharged particles being pressed to both sides of the electrode, resulting in side discharge.
This slagging method is often used to process extrusion dies that require a slight taper gap. Of course, the extrusion dies must be processed in the opposite direction to obtain a proper taper.
When the graphite electrode is used for deep through hole processing, its slag removal effect is extremely good. Use the latest technology to introduce high-pressure machining fluid into the electrode.
The porosity of graphite allows enough processing fluid to pass through the electrode to discharge the slag into the gap. 

Using this slagging method, the processing fluid is passed through the workpiece through the bottom hole or sucked through the electrode.
Compared with jet slag discharge, because the suction discharges along the particles on both sides of the electrode, the cone effect can be avoided. In this way, a true cylindrical hole can be obtained.
The vacuum suction cannot be too strong. In some application examples, the suction can be taken from the jet, and the suction pressure can be exceeded by some.
The processing speed of the suction and slag discharge through the electrode is faster than that of the workpiece. 

This method must be used when one or more slag discharge holes cannot be drilled on the electrode or the workpiece: this is the case when processing a medallion mold or making a deep narrow groove plastic mold.
When performing side slagging, carefully adjust the required nozzles so that the entire electrode processing surface can be evenly slagging.
This technology is usually combined with the intermittent vibration of the electrode to facilitate the slag removal effect.
When processing a flat table, the slag discharge direction must be consistent with the forming entry angle. When the medallion mold is processed, its longitudinal shape is not flat, so a special nozzle suitable for the shape of the mold must be used.
When the slag discharge direction is not parallel to the side of the electrode, it will cause turbulence, and only a small amount of machining fluid enters the gap to cause poor slag discharge.
On the other hand, if the slag discharge direction is good, most of the machining fluid will enter the gap.
Side discharge slag must not be introduced from both sides of the pole at the same time, because the two flows will cancel each other out at the bottom of the hole and the residue cannot be eliminated.
When machining a rectangular groove, the flow direction of the machining fluid must be applied to the longer side of the electrode, so that it will flow into the bottom of the hole. 

Use the electrode intermittent pumping method to discharge slag. When the electrode rises, the gap becomes larger, allowing the clean machining fluid to flow in and mix with the contaminated machining fluid.
The residue is discharged when the electrode is lowered. 

使用金属电极加工时，可察知在喷流区域电极有不正常消耗之现象，这消耗随排渣压力之增大而增加。
为消除此事发生，发展出与电极上升运动同时喷出加工液之方法同步喷油。
这也就是说只有电极上升时加工液才受压在间隙中排渣，此时即非加工之际。

In order to prevent the machining fluid from flowing out of the opening side, the aluminum block can be fixed on the opening side and the workpiece can be discharged together.
In this way, the slag discharge pressure can be improved and the electric discharge machining can be performed under the best slag discharge condition.

Electrode materials can be divided into the following three categories:
(a) Metal materials
Electrolytic copper
Copper Tungsten
Aluminum alloy
brass
Tungsten (mostly linear)
steel
(b) Non-metallic materials
graphite
(c) Metal and non-metal complexes
Copper graphite