Electron Beam Machining (EBM)

19.1

Process Principles

19.2

Equipment

19.2.1 Electron Beam Gun
19.2.2 Power Supply
19.2.3 The Electron Beam Machining Systems
19.3

Process Parameters

19.4

Process Capabilities

19.5

Application Examples

19.6

Process Summary

19.7

References

19.1 PROCESS PRINCIPLES
Electron beam machining (EBM) is a thermal material removal process that utilizes a focused beam of high-velocity electrons to perform high-speed drilling and cutting. Just as in electron beam welding (Chap. 18),

material-heating action is achieved when high-velocity electrons strike the work piece. Upon impact, the kinetic energy of the electrons is converted into the heat necessary for the
19.2.2 Power Supply

The high-voltage power supply used for EBM systems generates voltages of up to 150 kv to accelerate the electrons. The most powerful electron beam machining systems are capable of delivering enough power to operate guns at average power levels of up to 12 kw. Individual pulse energy can reach 120 joules/pulse. To avoid the possibility of arcing and short circuits, the high-voltage sections of the power supply are submerged in an insulating dielectric oil.
AB power supply variables, such as the accelerating current, focus current, pulse duration, and others, are controlled by a CNC unit or by a microcomputer. To ensure process repeatability, the process variables are monitored and compared with set-points by the power supply computer. If a discrepancy arises, the operator is alerted.

Figure 19.2 Computer-controlled multi axis EBM system (Source: courtesy, Messer Griesheim GmbH, Puchheim, W. Ger.).

19.2.3 The Electron Beam Machining Systems
An EBM system, as shown in Fig. 19.2, has an appearance very similar to an electron beam welding system. A vacuum chamber is required for EBM and should have a volume of at least 1 m3 to minimize the chance of spatter sticking to the chamber walls.

The time necessary to pump the chamber to an operating level of 10-2 mbar is approximately 3 min for each cubic meter of volume.
Inside the chamber a positioning system is