Laser machining, which is also called laser beam machining or LBM, is a procedure which involves drilling, cutting, welding, soldering, and heat treating different kinds of materials. Some of these materials include ceramics, silicon, plastics, and metals. Continuous light beams or pulses are used by the laser cutter in order to cut metal sheets that are typically as thick as 0.5 inches (sometimes more). The laser cutting system also cuts non-metals that are of a much larger thickness and can sometimes approach speeds up to 100 feet per minute.
In laser cutting, laser optics and computer numerical control or CNC are used to guide the material or the generated laser beam. Although it is still a costly route, CNC machines make the process more economical, more adaptable, and more precise.
Why Lasers are Used for Cutting and Other Processes
Lasers serve many purposes, including welding and cutting. A laser cutter is typically made for cutting metal plates. Compared to other means of cutting metals, this laser process is highly accurate and can be used in various types of metal plates, such as mild steel, aluminum plate, and stainless steel. The cut quality is excellent with just a tiny kerf width and heat affect zone. Lasers make it possible to create very small holes and cut intricate shapes.
Laser beam machining involves two mechanisms:
- Pyrolytic: Where laser energy is taken in by the material surface layer, therefore, resulting in a rise in temperature, evaporation, and melting
- Photolytic: Where laser light presents chemical reaction, leading to the disintegration of the material. The pyrolytic mechanism is generally the leading means for processing metals, plastics, and ceramics.
Laser Machining - Great Lakes Engineering, Inc.
Laser Welding, Cutting, and More
Laser welding makes use of a beam of light that is highly focused in order to join materials through deformation and heat. In this process, two different kinds of lasers are used. One of the lasers has a solid part of neodymium-doped yttrium aluminum garnet, which is used as the laser medium. This is known as the solid state laser. The other laser variety needs carbon dioxide gas to operate and this is known as the gas laser.
Meanwhile, laser cutting is the opposite of laser welding since it separates materials. This is performed by melting a small portion of the workpiece or sometimes through vaporizing the item. The two lasers mentioned above are effectively used in cutting as well, not just in welding. They can be used with continuous beams, too. The yttrium lasers may also be directed through fiber optic cables to a device that is right for the process. This allows more versatility in the capability and the design of the equipment.
Both laser welding and cutting can achieve remarkable accuracy, normally within 0.001 inches. Plus, these two can perform at an extremely rapid pace. More often than not, both processes use the shape and the material of the workpiece as the determinants of the necessary wavelengths of the laser.
Lasers can also be used for marking, engraving, and etching. These three processes may sound alike, but they do have some differences. Thanks to industrial guidelines as well as government regulations about having clear part and product identifications, the procedures of laser etching, marking, and engraving has become more popular than ever during the recent years.
The above-mentioned laser services are permanent marking solutions that add features while fulfilling government regulations to products and parts. The three terms are often used interchangeably, but there are differences, particularly when it comes to their applications and attributes.
Laser engraving is considered the most common option for those who want personalized items. The laser beam eliminates the material’s surface in order to uncover a cavity to reveal an image to the naked eye. In engraving, the laser causes the material to evaporate due to the high heat it creates during the entire process. Every laser pulse vaporizes the work piece, which makes laser engraving a very fast process. A cavity is created in the surface, which is noticeable by the naked eye and even through touch. In order to create deeper marks, the engraver will repeat the process with numerous passes. Often, engraving is considered a subsection of marking.
Laser etching is when high heat from the beam results to a melted surface of the material. Once the material melts, it will expand and a raised mark will be visible. Although laser etching is considered a subset of engraving, etching has a depth that does not exceed 0.001 inches, unlike with engraving that can reach 0.020 inches for engraving metals but can reach up to 0.125 inches in other materials.
Laser marking is not as common as etching and engraving using lasers. A laser beam touches the with the material’s surface, changing a little bit of its appearance or properties. A low-powered beam is gradually shifted across the material with the use of a method known as discoloration. This method creates high contrast marks but does not disrupt the material. The laser then heats up the material, resulting in oxidation under the exterior of the material, causing it to blacken. Low temperatures are applied to metal to strengthen the surface. These things are all performed while making sure the surface remains intact.
Laser machining is utilized in different industrial jobs, including printing, aerospace, automotive, tooling, electronics, military and defense, oil and gas, and even in the medical field. There are many systems that are available and ready for purchase, thus making the process more accessible and economical to the manufacturer.
However, care should be taken when these laser systems are used. This is because laser light can scatter or reflect on work pieces and may cause them to shatter. Aside from yttrium aluminum garnet and carbon dioxide lasers, there are also other kinds of lasers, such as ruby, argon, and neodymium glass. These lasers are all pulse lasers though neodymium glass and ruby lasers are not as cost efficient for almost all applications. Additionally, argon lasers are only useful for low power applications.
Laser Beam Machining Principles
There are different kinds of lasers used in LBM. These lasers may include solid state, semiconductor, and gas lasers. There are times when there is a need to use high powered lasers to perform etching, machining, cutting, and welding jobs. In such a case, only solid state lasers are used since they are the ones that can meet the required power levels.
Examples of solid state lasers are ruby, sapphire, and crystalline aluminum oxide. Generally, these mentioned lasers are constructed in into the rods with lengths of about 150 mm. The ends are quite well furnished so that they can seal optical tolerances.
Small amounts of chromium oxide are inserted as the dopant for the ruby crystal. To pump the laser, a flash of light with high intensity is required. Oftentimes, this light is filled with xenon and to fire it up, a huge capacitor should be discharged through it. Additionally, electric power with a capacity of 250 up to 1000 watts will be required as well.
The intense radiation will excite the chromium atoms, which will reach a high level of energy. After passing through different series of energy levels, an intense beam will be emitted and is then reflected back from the rod ends, stimulating more atoms which cause them to go back to ground level.
The stimulated light avalanche will be obtained and transmitted through the rod end. The light is highly coherent in space and time, has a very constricted frequency band, and is quite parallel and in phase. The light is focused along with the ordinary lenses on the spot of the work piece, which causes the metal to melt and vaporize.
Laser Beam Machining Applications
Laser machining is used in many manufacturing processes as well as in various industries. It can be used for different applications, including:
- Welding of refractory and non-conductive materials
- Making of tiny holes
- Producing fine and very minute holes
- Cutting complex outlines for thin and hard materials alike
- Mass micro machining
Laser beam machining can also be applied for some special heat treatment of a variety of materials. It can also be used for balancing of rotating parts. Its most dominant application though is drilling micro-sized holes in materials that are hard to machine. For this process, the laser beam is concentrated on the spot size. If it is a thin sheet, pulse laser is often used. Meanwhile, if it is a thick sheet, continuous laser is utilized to achieve the requirement.
The Advantages of Laser Beam Machining
Whether a manufacturer works in the automotive or aerospace industry, laser beam machining can be useful. In fact, it has many advantages over non-laser processes, which is why it has become a popular process. Here are some of the reasons why laser beam machining is a better choice for welding, cutting, and other procedures:
- There is no tool wear simply because there is no direct contact between the workpiece and the tool itself.
- Both metals and non-metals, such as rubber and plastic can be machined no matter how hard or brittle the materials are.
- Laser beams can move through long distances. This is why laser beam machining can be used in many different ways, such as cutting, drilling, welding, etching, and graining areas that are quite difficult to reach.
- Any environment can be suitable for a laser beam machining process with the use of transparent medium. It is possible with magnetic fields.
- When it comes to welding, laser beam machining can provide opportunities to cut or weld magnetic materials as well as those that are heat treated and these materials will not lose their properties. Of course, there are some changes that can be observed in the zones that are affected by heat.
- In LBM, very little distortion is detected. Plus, tow materials can easily be linked together.
- Drilling of materials that are refractory or difficult to machine is not a problem with laser beam machining.
- It does not matter what kind of material it is as LBM can create micro-sized holes in them.
- The energy created is of high density and as a result, it is easy to obtain high heat.
- The configuration of the laser beams, as well as the size of the exposed spot or area, can easily be controlled.
- The location of the exposed area is precisely ensured.
- Drilling of deep holes of such a short diameter is not a problem as well. This is possible through the application of unidirectional multiple pulses.
The Disdvantages of Laser Beam Machining
Without a doubt, laser beam machining has many uses and advantages. However, it is not perfect and therefore there are disadvantages as well. Those in the manufacturing and other industries should know about these disadvantages, which can include the following:
- Initially, the cost involved is very high.
- The life expectancy of the flash lamp can be very short.
- It is important that the machine, whether it is a laser cutter or any process, should have its safety procedures followed very strictly.
- The removal rate of the material can sometimes not meet the standards.
- If very deep holes are required, this job may sometimes be impossible to do.
- Some plastics may have noticeable burn or char while they are being machined.
- The machined holes may not be straight or round shaped as they should be.
- The overall efficiency can be quite low from 0.3 ~0.5 %.
While there are indeed some disadvantages as stated above, the great advantage of laser beam machining is that it has the capability to machine no matter what kind of material it is. Machining is not necessarily conductive based on the interaction and laser intensity. Compared to other processes, laser beams operate with the use of photons with high energy. Therefore, it is not a usual tool for use since laser beams can directly target the machines and the workpiece to break the chemical bonds of the workpiece.
Additionally, there is a laser ablation mechanism that makes it possible to provide the desired shape of the workpiece even if there are no preparations beforehand.
With laser beam machining’s applications and numerous advantages, it is no wonder that LBM is a widely utilized thermal energy based advanced machining process that does not involve contact with the material and workpiece.