Several Reasons Why Electrodes Are Prone To Carbon Deposition

1. Improper use of processing specifications, exceeding the current density bearing capacity of the discharge section, and the pulse space is too small.

Generally speaking, the peak current is determined by the number of power amplifier components put into the discharge circuit and the voltage applied by the circuit, and has nothing to do with the pulse width and pulse interval; while the processing current is not only related to the peak current, but also can be adjusted by adjusting the pulse width and pulse. time to change.

2. Poor chip removal

A. The influence of processing depth.

The smaller the discharge cross-sectional area and the deeper the processing depth, the more difficult it is to remove chips. For this type of processing, improving the quality of chip removal is the key.

When it comes to EDM chip removal, there are currently two conventional methods, one is the flushing method, the other is the immersion method, and the flushing method is used to assist in the immersion process at the same time to improve the fluidity of the liquid To enhance the chip removal effect. In terms of processing accuracy and chip removal effect, the immersion method is much better than the simple flushing method.

The chip removal mechanism of the immersion processing method is to use the high-speed movement of the spindle to cause the cavity to be in a state of high pressure or vacuum, causing strong disturbance of the liquid to achieve the purpose of chip removal.

Flushing processing method, due to the uneven flow direction and pressure, the chip removal may not be complete, and it is easy to form two discharges in the place where the chips gather, which affects the accuracy of the cavity; secondly, it is also easy to cause carbon deposits, so in If conditions permit, the immersion processing method should be used for processing as much as possible.

B. The influence of the processing part.

The EDM part is related to whether it is easy to form carbon deposits. It does not necessarily mean that the discharge stability of open EDM is higher than that of blind holes. Processing only one surface is sometimes more likely to cause processing stability than processing all surrounding surfaces at the same time. worse.

EDM chip removal mainly depends on the disturbance of machining fluid, or scouring, or extrusion, etc. The stronger the fluidity of the liquid, the more thorough the chip removal. In the case of machining only one surface, the up-and-down movement of the electrode cannot cause strong disturbance of the machining fluid. Moreover, if the up-and-down jumping distance of the spindle is relatively small, the electrolytic corrosion products cannot escape the discharge gap, which may easily cause poor machining stability. Even carbon deposits.

In this case, if the machine tool has good performance and can realize three-axis linkage processing, it is best to adopt lateral servo processing, so that the electrode is slightly away from the processing surface when it is retracted, so that the electrolytic corrosion products can be washed away smoothly . If there are no conditions, try to increase the movement range of the spindle as much as possible, so that the processing surface is exposed to the processing fluid as much as possible, so as to eliminate electric corrosion.

C. Effects of liquid handling.

In electrical discharge machining, liquid flow treatment is very important, and the direction of liquid flow should follow the direction of the generation of electro-corrosion products.

D. The influence of electrode material quality.

Of course, the quality of the electrode material is also the main reason for abnormal processing. The manufacturing process of graphite is complicated, and it is a non-metallic material. Many characteristics are different from metal materials. But not all of them must be caused by graphite quality problems. Poor processing conditions and improper processing conditions will also cause these problems. Only after these possibilities are ruled out can the material problem be considered.