What is the phenomenon of electroerosion in metalworking practice?

1. To put it simply, the phenomenon of electric erosion refers to the electrification between the workpiece and the copper male, and the corrosion of the workpiece through discharge, so that the workpiece can achieve the required appearance shape and surface roughness.

Request. 2. Specific principle: During EDM, one pole of the pulse power supply is connected to the tool electrode, and the other pole is connected to the workpiece electrode, and both poles are immersed in a liquid medium with a certain degree of insulation.

The tool electrode is controlled by an automatic feed adjustment device to ensure that the tool and the workpiece maintain a small discharge gap () during normal machining. When the impulse voltage is added between the two poles, the liquid medium at the nearest point between the poles is broken down under the current conditions, forming a discharge channel. Due to the small cross-sectional area of the channel and the extremely short discharge time, the energy is highly concentrated (10 107 W mm), and the instantaneous high temperature generated in the discharge area is enough to melt or even evaporate the material, resulting in the formation of a small pit.

After the first pulse is discharged, after a short interval of time, the second pulse is recently clicked through between the other poles. In this cycle, the tool electrode is continuously fed to the workpiece, and its shape is eventually replicated on the workpiece to form the desired machined surface. At the same time, a small portion of the total energy is released to the tool electrodes, resulting in tool loss.

As early as the early 19th century, it was discovered that when the hoe of the electrical switch was opened and closed, there would be a discharge phenomenon that caused the contact parts to be ablated and damaged. This electrode ablation phenomenon caused by electrical discharge is the phenomenon of electrical corrosion.

The general name of Germany I is not the same, and it is called electroerosion processing in the early days of China, and it is also called EDM processing.

Russia is generally called electroerosion processing, and the early rise in China is actually learned from the Soviet Union.

In Japan, it is commonly called spark

EDM is a special processing method that uses the electro-erosion action generated when the pulse discharge between the two poles immersed in the working fluid to ablution of conductive materials, also known as EDM or electro-erosion machining.

In EDM, the tool electrode and the workpiece are connected to the two poles of the pulse power supply and immersed in the operating fluid.

or charge the working fluid into the discharge gap. When the gap between the two electrodes reaches a certain distance, the pulse voltage applied on the two electrodes breaks down the working fluid and is generated.

Spark discharge. A large amount of heat energy is instantaneously concentrated in the microscopic channel of discharge, and the temperature can be as high as more than 10,000 degrees Celsius, and the pressure also changes sharply, so that the local trace amount of metal material on the working surface immediately melts and gases.

It is splashed into the working fluid, rapidly condensed, and formed solid metal particles, which were carried away by the working fluid. At this time, a tiny pit is left on the surface of the workpiece, the discharge is interrupted for a short time, and the working fluid between the two electrodes is used.

Restore the insulation state.

Immediately after that, the next impulse voltage breaks down at another point where the two electrodes are relatively close together, resulting in a spark.

electricity, repeat the above process. In this way, although the amount of metal abroded by each pulse discharge is very small, because there are thousands of pulse discharges per second, a large amount of metal can be ablated, and there is a certain productivity. Keep the tool electric.

Under the condition of a constant discharge gap between the electrode and the workpiece, the metal of the workpiece is eroded, and the tool electrode is continuously fed to the workpiece, and finally the shape corresponding to the shape of the tool electrode is machined. So just change the tool.

The shape of the electrode and the relative movement between the tool electrode and the workpiece make it possible to produce a variety of complex profiles.

Tool electrodes are commonly used with electrocorrosion-resistant materials with good conductivity, high melting point and easy processing, such as copper, graphite, copper-tungsten alloy and molybdenum. During machining, the tool electrode also has losses, but it is less than the amount of metal removal from the workpiece, or even close to no loss.

As a discharge medium, the working fluid also plays a role in cooling and chip removal during processing. Commonly used working fluids are media with low viscosity, high flash point and stable properties, such as kerosene, deionized water and emulsion.

Answer: In electrolytic machining, the electrode gap ablution characteristic curve is a hyperbola, i.e., a = c (constant) as shown in Figure 4-3a; The erosion characteristic curve of EDM is an upward convex quadratic curve with an erosion velocity of zero at the beginning and end points, as shown in Figure 4-3b.

In electrolytic machining, as long as the electrode does not short-circuit, the smaller the electrode gap, the higher the erosion speed of the anode workpiece, and the higher the productivity. Conversely, when the electrode gap becomes larger, the erosion rate decreases.

In EDM, when the discharge gap is zero, the erosion rate is also zero. In fact, when the discharge gap is very small, chip removal is difficult, the short circuit rate increases, the erosion speed will be greatly reduced, and even normal processing will not be possible; When the discharge gap is too large, the gap cannot be broken down, and the erosion speed is also zero (equivalent to one in the electrolytic machining of the nonlinear electrolyte)."Cut the gap"）。