What is Laser Beam Machining?- Types and Working

What Is Laser Beam Machining?

Laser Beam Machining (LBM) is a manufacturing process that removes material from both metallic and nonmetallic surfaces through the application of heat generated by a focused laser beam.

This method relies on the intense thermal energy provided by monochromatic, high-frequency light, which, upon striking the surface, causes localized heating. As a result, the material at the target site undergoes melting and vaporization due to the energy transferred by the incident photons.

LBM tends to perform especially well with brittle materials that have low thermal conductivity, though its versatility extends to a wide range of other materials. Notably, when applied to glass, laser machining can be accomplished without melting the surface itself.

In the case of photosensitive glass, exposure to the laser modifies the glass’s chemical structure, which then allows for selective etching. This specialized glass, often called photo-machinable glass, presents distinct advantages.

A key benefit of photo-machinable glass lies in its capacity to produce sharply defined, vertical walls during fabrication. Additionally, the native properties of this glass make it particularly suitable for various biological applications, such as serving as substrates in genetic analysis.

Definition of Laser Beam Machining

Laser beam machining represents a non-traditional approach to material processing, relying on the use of concentrated laser light to carry out machining tasks.

In this method, the laser delivers intense thermal energy directly to the surface of the workpiece, creating extremely high temperatures at the point of contact.

As a result, the targeted area of the material melts. The entire process utilizes this localized heat to effectively remove material from metallic surfaces.

Types of lasers

Lasers come in several varieties, with gas lasers, solid-state lasers, and excimer lasers among the most prominent types. Within the category of gas lasers, some of the most frequently used gases include helium-neon (He-Ne), argon (Ar), and carbon dioxide (CO₂).

Solid-state lasers, on the other hand, are constructed by incorporating a rare element into a host material. Unlike their gas counterparts, solid-state lasers typically rely on optical pumping, which is often achieved with flash lamps or arc lamps. Ruby has been a classic example of a host material for this type of laser.

To illustrate, the ruby laser employs a synthetic ruby crystal as its active medium. This synthetic rod is energized—often with a xenon flash tube—before it serves as the source of laser emission.

YAG, short for yttrium aluminum garnet, refers to crystals frequently used in solid-state lasers. When these crystals are doped with neodymium, they are known as Nd: YAG (neodymium-doped yttrium aluminum garnet), and this configuration is widely recognized as a standard laser medium.

YAG lasers are notable for emitting light at high-energy wavelengths. Another related material, Nd: glass, involves neodymium-doped glass, either silicate or phosphate-based, which is commonly used as the gain medium in fiber lasers.

Parts of Laser Beam Machining

1. Power Supply

Lasers require a high-voltage power supply to function properly. This power input is essential for exciting electrons within the system. Once energized, these electrons reach an excited state, making them ready to participate in the laser process.

2. Flash Lamps

Flash lamps play a crucial role by emitting intense, coherent white light—but only for brief moments. This short, powerful burst of light is an important part of the laser’s operation.

3. Capacitor

Most people are familiar with capacitors as components that store and release electrical charge. In the context of laser systems, the capacitor is specifically involved in powering the flash lamp during its operation.

4. Reflecting Mirror

Reflecting mirrors are used to direct the laser light precisely where it’s needed, typically onto the workpiece. Depending on their placement, these mirrors can be categorized as either internal or external to the laser system.

5. Lenses.

Lenses are included to improve visibility. By magnifying the image of the work area, lenses make it easier to see fine details and perform accurate operations on the workpiece.

6. Workpiece

The workpiece is simply the object undergoing laser processing. To put it in perspective, if a medical procedure uses a laser on the human body, the person becomes the workpiece. Similarly, in manufacturing, objects requiring drilling or cutting serve as the workpieces for the laser machine.

Working Principle of Laser Beam Machining

In this method, a laser beam essentially a concentrated form of monochromatic light is focused onto the material that needs to be machined. This focusing is accomplished with the help of a lens, which brings the beam down to a fine point, resulting in an exceptionally high energy density. At this intensity, the beam is capable of melting and even vaporizing the targeted material.

The core component here is the laser crystal, typically a ruby shaped into a cylindrical form with flat, reflective ends (as shown in the referenced figure). This crystal is positioned inside a flash lamp coil, usually around 1000W.

When the flash lamp is activated, it emits an intense burst of white light, often from a Xenon source. This sudden illumination excites the ruby crystal, prompting it to emit a laser beam.

Once generated, the laser beam is incredibly narrow and can be focused down to a minuscule area small enough to reach a power density of about 1000 kW per square centimeter.

At such a concentrated point, the heat produced is more than sufficient to melt and vaporize a portion of metal, making the process both precise and highly effective for machining.

Applications of Laser beam machining

Lasers have found a wide range of applications in manufacturing, serving functions such as welding, cladding, marking, surface modification, drilling, and cutting, among others. Their versatility has made them indispensable in industries like automotive, shipbuilding, aerospace, steel production, electronics, and even medicine, particularly when precision machining of complex components is required.

One of the notable benefits of laser welding lies in its speed, with welding rates reaching up to 100 mm per second. Another practical advantage is the ability to join dissimilar metals—a task that often presents difficulties with more conventional techniques. When it comes to laser cladding, the process allows manufacturers to reinforce inexpensive or less durable parts by adding a harder surface layer, significantly enhancing their wear resistance and extending their service life.

Drilling and cutting operations also benefit from the unique properties of lasers, as these methods minimize tool wear due to the non-contact nature of the process—there’s simply no physical edge to dull or damage. Laser milling, which is inherently a three-dimensional operation and typically requires two lasers, stands out for its potential to reduce machining costs quite substantially.

Beyond these processes, lasers also offer the capability to alter the surface properties of a workpiece, adding another layer of flexibility to their industrial use.

The specific role of laser beam machining can vary significantly from one industry to another. In light manufacturing, for instance, lasers are employed for engraving and drilling various metals. The electronics sector often relies on lasers for precise tasks such as wire stripping and the preparation of circuit substrates. Meanwhile, in the medical field, laser technology has enabled advancements in procedures ranging from cosmetic surgery to hair removal, highlighting its adaptability and ongoing relevance across disciplines.

Advantages of Laser beam machining

• Because laser beams are both monochromatic and perfectly parallel essentially having zero etendue they can be focused to an extremely fine point. This means it’s possible to concentrate up to 100 megawatts of power into just a single square millimeter of area.
• One notable advantage of laser beam machining is its versatility; it can engrave or cut almost any material, including those that often present challenges for conventional cutting methods.
• Lasers come in a variety of types, with each designed for specific applications depending on their properties.
• Maintenance costs for lasers tend to be fairly modest. This is largely due to the fact that there’s no direct physical contact between the tool and the workpiece, resulting in minimal wear and tear over time.
• Laser machining is recognized for its high degree of precision. In most cases, the work produced does not require any additional finishing processes.
• Often, gases are used alongside laser beams during machining. These assist in making the cutting process more efficient, can help prevent the oxidation of surfaces, and also serve to clear away melted or vaporized material from the workpiece.

Disadvantages of Laser beam machining

• The initial investment required to acquire a laser beam system tends to be fairly substantial. This is largely because numerous essential accessories must be included alongside the primary laser unit. Since these supporting components play a critical role in the machining process, the overall startup costs are driven even higher.
• Effective operation and upkeep of laser machining equipment demand a skilled workforce. Because the technical aspects of handling a laser beam are quite advanced, it is often necessary to rely on specialists with specific expertise in this area.
• It is important to note that laser beam systems are not intended for large-scale metal production. Their design and capabilities are best suited to more specialized applications.
• Another consideration is the significant energy consumption associated with laser beam machining. Running these systems can require considerable power, which can impact operational costs and efficiency.
• Achieving deep cuts poses challenges, especially when working with materials that have high melting points. Such attempts typically result in the formation of a taper, making precise, deep machining more difficult.

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