This article will take an in-depth look at laser marking and engraving machinery.
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Laser marking is the technique of applying discernible text or codes onto the surface of a component with minimal or no surface penetration. On the other hand, laser engraving uses a laser to create information with significant penetration beneath the surface of the material.
A focused beam of light is used to create permanent marks on a surface. Numerous types of lasers, including fiber, CO2, pulsed, and continuous wave lasers, can perform this function. Laser marking employs a concentrated light beam to generate permanent labels on target surfaces. Typically, this involves a laser system with components like an oscillator, scanning mirror, and focusing lens.
Laser marking technology works by applying focused, high-energy light beams to imprint permanent marks on component surfaces. The energy is condensed into a coherent light beam, which is directed onto the material's surface via mirrors. This interaction transfers heat energy, changing the material’s properties and appearance. Based on energy levels, the laser precisely engraves, etches, anneals, or discolors surfaces. The focused beam allows for high-contrast, high-quality marks by targeting specific material areas, ensuring marks are both readable and scannable, making it perfect for accuracy and durability-requiring applications.
This method can vaporize coatings on metals, making it effective for such materials. Consequently, the coating is effectively removed.
Wood is a versatile material that can be used for a variety of laser cutting and engraving techniques, which is why it is commonly chosen for these processes. Although wood is prone to ignition due to its flammability under high temperatures, careful adjustment of the laser marker's power allows for safe engraving without causing fires. Popular types of wood for laser engraving include plywood, MDF, and cardboard.
Granite and marble are ideal for engraving detailed images due to their ability to produce strong contrast. Black granite or marble, in particular, offers excellent contrast without needing additional coloring, resulting in clear, high-contrast engravings that appear white or dark gray. When choosing between marble and granite, consider where the engraved piece will be displayed. For indoor settings, either marble or granite will work, but granite is preferred for outdoor use due to its superior durability. Marble has a Mohs hardness rating of 3, while granite scores a 7, with diamond being the hardest at 10. This makes granite significantly more resilient than marble.
Laser engraving can be applied to a variety of glass items, producing stunning effects. Examples include wine bottles, glasses, vases, and mugs. Many esteemed wineries and distilleries use laser engraving to imprint their logos on bottles. One advantage of laser engraving on glass is that it creates a frosted effect without significantly cutting into the material. However, caution is needed during the engraving process, as the laser can sometimes cause chipping, which may lead to a roughened surface.
Laser engraving is highly effective on various fabrics, whether they are natural or synthetic. Cotton and microfiber are particularly popular choices for laser etching. Microfiber, which typically consists of materials such as polyamides and polyester blends, is known for its durability and suitability for laser engraving. Cotton, especially when woven tightly, also yields impressive results. For best outcomes on cotton, choose fabric with a dense weave, as loose threads may result in poor quality engravings. Other suitable materials include denim, felt, twill, and fleece, all of which can withstand the heat from the laser. To achieve optimal results, use low power and high speed settings on the laser. This approach allows the top layer of the fabric to be effectively removed. It is advisable to test on a few samples first to determine the best settings and avoid burning the fabric. Generally, avoid engraving fabrics with loose weaves, such as terry cloth, as they may not hold up well under the laser process.
Acrylic sheets, sometimes referred to as polymethyl methacrylate (PMMA), are strong and lightweight and make excellent substitutes for glass. PMMA can be produced using either a cast or an extruded process. The responses of these two varieties of acrylic to laser engraving vary. Cast PMMA's icy white appearance contrasts sharply with its clear substance. On the other hand, extruded acrylic does not provide much contrast when engraved and stays clear. Therefore, extruded acrylic is best for laser cutting tasks, while cast acrylic is best for all other laser engraving applications.
For cast acrylic, mirror reverse engraving is a popular technique. This involves reversing the image so that the engraving appears on the back side of the acrylic sheet, creating a striking "look-through effect." Some users also apply paint to the surface of the acrylic before engraving to reveal the underlying material through the paint. Although chemical etching is another method for working with acrylic, laser engraving is preferred for its safety, durability, and ability to handle intricate designs with precision, as it avoids the rapid deterioration of equipment that can occur with other methods.
Similar to granite, both bricks and stones are highly suitable for engraving items that will be exposed to outdoor conditions. These materials are also ideal for marking objects intended for external use, including patios, memorials, and various outdoor installations. Engraved bricks, often produced with laser technology, are commonly utilized in parks, pathways, and educational institutions as a means of recognizing donations. Typically, a predetermined design is used for these engraved bricks.
Historically, businesses used sandblasting to create the etched look on bricks. Sandblasting, however, is a labor-intensive and intricate procedure. As if that needed to be more, it could be more precise, and despite improvements in computer control, sandblasting frequently puts too much stress on the bricks, causing them to easily break when installed.
In this process, laser beams target specific areas on the surface of materials, removing them through melting and evaporation caused by the heat. This results in impressions or depressions on the surface. The exposed material often changes color upon contact with air, enhancing the visibility of the engraving. Laser engraving does not require any consumables, making it a cost-effective option compared to other methods that need specialized inks or tools. Lasers are versatile and effective on a range of materials, including metals, plastics, and ceramics, which makes them widely used in various engineering applications.
This incredibly flexible method melts the surfaces of the workpieces to leave imprints on them. The laser beam leaves a raised mark by concentrating much energy in a condensed region. As a result, the surface will melt and expand, turning it from white to gray or black. Permanent markings like serial numbers, data matrix codes, logos, and barcodes are frequently created through etching. Additionally, it is a flexible method that works well for various metals, including stainless steel, lead, aluminum, steel, and magnesium.
Laser ablation is commonly employed to strip paint from the surface of a material rather than affecting the material underneath. This technique allows users to quickly add barcodes or other identifiers without the need for metal etching capabilities.
This method involves using a single or multi-fluted cutting tool to remove material from metal components, creating a groove where the core material is exposed. This process can either completely sever a letter or object or create a deeper incision. The depth of the cut is generally controlled by adjusting the spindle micrometer setting, making this technique suitable for many commercial and industrial applications.
Rotary engraving, known for its durability, can produce both two-dimensional and three-dimensional effects and accommodate letters of nearly any size. However, it does come with some drawbacks, such as the need for a diverse range of cutting tools, a rotary spindle, and a motor, as well as the requirement for additional cleaning after the process.
A non-rotating tool with a diamond tip in the shape of a cone is used in this technique. The metal component receives an impression after being passed through by the engraving tool. Diamond-drag engraving is as exact and high-quality as hand engraving. The stroke's depth does not change while its width remains constant. Diamond drag is suggested for engraving jewelry and awards on soft metals.
This method is advantageous for being one of the fastest and most cost-effective options, and it can produce small engraved letters thanks to the narrow stroke width. However, a limitation is that the stroke width is restricted, which may affect the detail and flexibility of the engraving.
This technique involves using a laser to remove the layers of a workpiece, exposing the layer underneath. The top layer vaporizes upon absorbing the laser's heat, creating a visible contrast. For optimal results, it is crucial that the color of the top layer contrasts significantly with the underlying material. Coated materials, such as anodized aluminum, produce clear and prominent markings with this method. Laminated, film, and foil materials also respond well to this process, making it effective for labeling items, fixtures, and packaging materials.
In laser annealing, the material's surface is locally heated by the laser to create markings. The laser beam penetrates only 20 to 30 micrometers into the surface, resulting in minimal alteration. This localized heating causes a change in color, which can appear red, yellow, green, or black, depending on the heated layer. Laser annealing produces permanent, abrasion-resistant marks and is particularly effective on titanium and ferrous metals. Due to its durability, this method is utilized across various industries, including healthcare, automotive, food and beverage, and aerospace.
In this process, the heat energy from the laser breaks down plastic bonds, releasing oxygen and hydrogen. This reaction causes the target area to darken, resulting in gray or blue-gray markings. Carbonizing or migration is the most effective technique for marking synthetic polymers and organic materials. It works well on materials such as paper, wood, leather, and packaging. However, carbon migration may not be ideal for dark-colored items, as the gray mark produced might offer less contrast and be harder to read against the rest of the workpiece.
For creating light-colored marks, carbon migration might be less effective, and foaming can be a more suitable alternative in certain cases. In this method, the laser heats the material's surface, causing it to melt and release gas bubbles. These bubbles oxidize and create a foamy effect that reflects light. This technique is particularly effective for dark-colored components because the raised, foamed mark provides a sharp contrast against the surrounding surface. It is also highly effective for marking plastics.
Fiber laser machines are versatile tools capable of both marking and engraving various materials. These lasers offer adjustable engraving depths by varying the wattage according to the application. However, they may operate slowly on thick materials with high reflectivity and may not achieve deep engraving on many metals.
For surface marking, fiber laser markers are typically set to a lower wattage of around 20 to 30 watts. As the wattage increases, the machines are capable of engraving materials more deeply.
These solid-state lasers, with power outputs ranging from 20 to 50 watts, use ytterbium, a rare-earth metal, to generate photons at a wavelength of approximately 1,090 nm, which is ideal for marking metals. For depth engraving or etching, fiber laser marking machines are recommended. They offer superior performance on tougher metals and are ideal for applications requiring high resolution with small spot sizes. Additionally, their small spot sizes, excellent beam quality, and larger lenses make them well-suited for marking small components in batch production.
The fiber laser system is highly adaptable, allowing for faster and more efficient labeling of objects. It is also more cost-effective compared to CO2 lasers due to its lower power consumption, reduced energy requirements, and minimal maintenance needs. Additionally, the high degree of monochromatic beam filtration ensures consistent beam power. As a result, fiber lasers are versatile and can be utilized across a wide range of surfaces.
These laser markers are frequently galvo steered sealed-tube marking systems intended to mark nonmetal surfaces. For markings like logos, date stamps, and many more, CO2 laser markers are a popular alternative. On electrical devices, integrated circuits, food and medical packaging, and electronic components, these machines assist with the creation of serial numbers, logos, and barcodes. When marking organic materials like papers, wood, and some plastic polymers, sealed-off CO2 lasers produce the best results. They work well for glass and leather markings as well.
Increasing the output wattage on CO2 laser machines enhances their ability to engrave non-metal materials. Higher wattage results in more intense engraving.
UV lasers, with a wavelength of 355 nm, are highly effective for part marking due to their excellent absorption characteristics. This makes them perfect for "cold marking," as they minimize thermal stress on the material. UV lasers can mark a variety of surfaces, including plastics, glass, and ceramics. They are also well-suited for precise micro-marking of electronic components and medical devices due to their high-quality, exacting beam.
Green lasers, operating in the visible light spectrum between 510 and 570 nm, typically have a power range of 5 to 10 watts. They are designed to mark surfaces that have high light reflectivity, offering high precision and excellent performance on delicate substrates like silicon wafers. These lasers enhance material absorption and minimize heat generation, making them well-suited for applications involving soft plastics, computer chips, and printed circuit boards. Green lasers are used in a variety of fields, including laser pointers, projection screens (as part of RGB systems), printing, interferometers, bioinstrumentation, medical imaging, and solid-state laser pumping (e.g., titanium-sapphire lasers). Due to their higher absorption coefficients in materials like copper, gold, or silicon, green lasers can be more effective in laser material processing compared to near-infrared lasers. This means they can achieve superior processing results with lower power levels, which often justifies their higher cost per watt. Below are the various types of green lasers:
These laser markers feature a compact and lightweight design, making them highly popular for marking thin metal sheets without causing warping or distortion. Their precision is valued by manufacturers for creating fine markings on a range of substrates, including aluminum, steel, and other plated metals.
The term "Master Oscillator Power Amplifier" (MOPA) describes a system that integrates an optical amplifier with a "master" laser to boost output power. In contrast, traditional fiber lasers utilize Q-Switch technology to produce laser pulses lasting only a few billionths of a second. This brief pulse duration condenses the laser's energy into extremely powerful bursts. Consequently, MOPA lasers can deliver more pulses per second and offer a broader pulse frequency range compared to Q-Switch lasers.
Annealing, as a laser technique, does not involve material removal but rather uses heat to create colors on stainless steel. While the ability to produce colors with lasers has been established for some time, the MOPA laser source represents a recent advancement in achieving precise engraving and color replication.
When engraving metals, the heat applied can cause the material to react with its environment, potentially leading to rust formation. This reaction is due to the heat melting or burning the metal's surface. MOPA lasers, which produce less heat, mitigate metal damage and improve the corrosion resistance of the finished product.
Laser coding involves applying codes to objects through various laser marking methods, such as ablation, engraving, and etching. This technology ensures precise and permanent markings, offering several advantages. For instance, laser ablation removes material from a package's surface by vaporizing it. In this process, ink is first turned into vapor and then removed. Laser engraving, on the other hand, involves removing part of the material's surface to create space for inscribing codes. All these high-quality laser marking techniques used in laser coding produce codes that are both readable and of superior quality.
The two most common laser marking techniques in the laser coding system are vector and dot matrix.
Vector marking produces high-quality codes but tends to be less time and energy efficient. This method involves using a focusing lens, two rotating mirrors, and other components to create graphics. The image is built up gradually as the lens is activated and deactivated during the marking process.
This approach results in images with lower resolution but allows for a faster marking process. It works by directing a laser through a rotating polygon, which then reflects the beam to a water-cooled dump to produce the codes.
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