Beam Focusing

The focusing lens focuses the laser beam through the center of the nozzle at the end of the laser cutting head incident to the workpiece’s surface. By focusing the beam, the lens concentrates the beam’s energy into a smaller spot, which increases the beam’s intensity (je). The following equation illustrates the underlying principle behind this occurrence:

Where P. represents the power of the initial laser beam, and πr² represents the cross-sectional area of the beam. As the lens focuses the laser beam, the radius (r) of the beam decreases; this decrease in radius reduces the cross-sectional area of the beam, which in turn increases its intensity. Since its power is now distributed across a smaller area.

Localized Heating and Melting, and Material Ejection

As the beam strikes the material’s surface, the material absorbs the radiation, so that increasing the internal energy and generating heat. The high intensity of the laser beam allows it to heat, melt, and partially or completely vaporize a localized area of the workpiece’s surface. The weakening and removal of the affected area of the material forms the desired cuts. Siphoned into the laser cutting head and flowing coaxially to the focused beam, the assist gas—also referred to as the cutting gas—is used to protect and cool the focusing lens. And may be used to expel melted material out of the kerf. The width of the material removed and of the cut produced. And support the cutting process. Laser cutting employs several different types of material cutting and removal mechanisms. Including fusion cutting, chemical degradation cutting, evaporation cutting, scribing, and oxidation cutting.

• Fusion Cutting:

  Also referres to as inert gas melt shearing or inert gas cutting, CO₂ and Nd:YAG laser cutting machines emploies fusion cutting. The laser beam produced by the cutting machine melts the workpiece. And melted material is expelled through the bottom of the kerf by a jet of the assist gas employed. But the type of material determines the auxiliary gas and auxiliary gas pressure. But  we can select the inert gas depends on its lack of chemical reactivity to the material. This mechanism is suitable for laser cutting most metals and thermoplastics.

• Chemical Degradation: 

  CO₂ laser cutting machines employ chemical degradation. And is suitable for laser cutting thermoset polymers and organic material, such as wood. As thermoset and organic materials do not melt when heat is applied, the laser beam burns the material instead, reducing it to carbon and smoke.

• Scribing:

  CO₂ and Nd:YAG laser cutting machines employ scribing to produce partial or fully penetrating grooves or perforations. Usually on ceramics or silicon chips. These grooves and perforations allow for mechanical breaking along the weakened structural lines.

• Oxidation Cutting: 

  Also referred to as flame oxygen cutting, CO₂ and Nd:YAG laser cutting machines employ oxidation cutting. And is suitable for laser cutting of mild and carbon steel. Oxidation cutting is one example of the reactive gas melt shearing cutting mechanism, which specifically employs chemically reactive assist gases. As with inert gas, we choose which auxiliary gas  depends on the materialOxidation cutting, as the name implies, employs oxygen as the assist gas, which exothermically reacts with the material. The heat generated accelerates the cutting process and produces an oxidized melted edge. So we can easily remove it with a gas jet to allow for a cleaner, laser-cut edge.

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