**5.2 Mechanism of material removal in LBM**

Laser based machining processes is identified as a material removal technique in industrial application. Materials removal is accomplished by the interaction between the laser beam and work material. It is severely a localized thermal process. Higher amount of light energy is received by base material and then higher heat is created between the locality of interaction while hitting the laser source on the base material. Due to highly elevated temperature at the beam spot, the material becomes soft, melt, burn and vaporized. Additionally, the interaction of laser beams and work material is associated with the material removal by photochemical process which is often called photo ablation. **Figure 9** schematically represents the effects of laser beam-work material interaction [5].

#### **Figure 9.**

*Laser beam-work material interactions: (a) heating, (b) melting of surface, (c) vaporization of surface, (d) formation of plasma, and (e) ablation.*

The parameters of LBM such as intensity of laser light, distribution of beam, spot size, scanning speed, and relative motion between laser beam and work piece can be changed according to the requirements for different work materials. As presented in the introduction section, lasers are replacing conventional machining processes due to many advantages. Many developments have been made in the laser technology to shorten the pulse time for different machining processes. Longer pulse duration increases the heat affected zone (HAZ) and leaves high thermal

**95**

**Figure 11.**

*(milling) machining operations.*

*Laser Machining*

**Figure 10.**

*DOI: http://dx.doi.org/10.5772/intechopen.93779*

long and short pulse durations [6].

**5.3 Types of LBM techniques**

stresses resulting in crack and void formation, and surface debris. Short pulse duration leads to lesser thermal conduction thus resulting in precise machining operation and good surface finish. **Figure 10** shows the difference between the effects of

*Difference between the effects of (a) long-pulsed and (b) short-pulsed lasers.*

Machining using laser is generally categorized into three types namely onedimensional, two-dimensional and three-dimensional machining processes. In one dimensional machining process, the laser beam will have no relative motion with the work piece material. In this relatively stationary arrangement, the erosion front is located at the work piece and focused laser beam removes the material in the path it propagates through which is a straight line. Hence one-dimensional LBM process is generally used for drilling applications. In contrast, the work piece also will move along with laser source in two-dimensional LBM process. The erosion front placed on the beam edge and the material removal happens in a two-dimensional plane

*Schematic of (a) one-dimensional (drilling), (b) two-dimensional (cutting), and (c) three-dimensional* 
