Principles of Electron Beam Machining

1. Electron beam machining principle
Electron beam machining (EBM) is a process under vacuum conditions where electrons generated in an electron gun are accelerated and focused to impact a very fine beam with an energy density of 106-109w/cm2 at high speed onto a very small part of the workpiece surface. Within a fraction of a microsecond, most of the energy is converted into heat energy, causing the material at the impacted part of the workpiece to reach several thousand degrees Celsius, causing the material to melt or evaporate locally, thereby removing the material.

1-Emission cathode 2-Control grid 3-Accelerating anode 4-Focusing system 5-Electron beam spot 6-Workpiece 7-Workbench

2. Characteristics of electron beam processing
High power density It is a non-contact processing. The workpiece is not subjected to mechanical force, rarely produces macroscopic stress deformation, and there is no problem of tool loss.
The intensity, position, and focus of the electron beam can be precisely controlled. The electron beam can travel at any speed on the workpiece through the magnetic field and electric field, which is convenient for automatic control.
Less environmental pollution It is suitable for processing semiconductor materials with high purity requirements and easily oxidized metal materials.

3. Application of electron beam processing
1) Electron beam drilling
Small holes and deep holes on various materials such as stainless steel, heat-resistant steel, gemstones, ceramics, glass, etc. The minimum processing diameter can reach 0.003mm, and the maximum depth-to-diameter ratio can reach 10.
Like the holes in the wing adsorption screen and the cooling holes on the jet engine cover, there are huge numbers of such holes (up to millions), and the hole diameter is small, the density is continuously distributed, and the hole diameter also varies, which is very suitable for electron beam drilling
. Many microholes are punched in plastics and artificial leather to make them as breathable as real leather.
In order to increase the air permeability and elasticity of some synthetic fibers, their spinneret-shaped holes are often made into special-shaped hole cross-sections, which can be produced by scanning the pattern with a pulsed electron beam.
It is also possible to use the change of the deflection magnetic field to make the electron beam deflect in the workpiece to process curved holes,

2) Electron beam cutting
It can cut various materials with a cut width of only 3 to 6 μm.
The electron beam combined with the relative movement of the workpiece can process the required curved surface.
3) Photolithography
When a low-energy-density electron beam is used to irradiate a polymer material, the molecular chain of the material will be cut or recombined, causing a change in the molecular weight, which will produce a latent image. Then, the material is immersed in a solvent to develop the latent image.
This method can be combined with other processing techniques to achieve grooves on metal masks or material surfaces.