Лазерлік гравировка және таңбалау технологиясы

Engraving objects using lasers

Laser engraving is the practice of using lasers to engrave an object. Laser marking, on the other hand, is a broader category of methods to leave marks on an object, which in some cases, also includes color change due to chemical/molecular alteration, charring, foaming, melting, ablation, and more. The technique does not involve the use of inks, nor does it involve tool bits which contact the engraving surface and wear out, giving it an advantage over alternative engraving or marking technologies where inks or bit heads have to be replaced regularly. The impact of laser marking has been more pronounced for specially designed "laserable" materials and also for some paints. These include laser sensitive polymers and novel metal alloys. The term laser marking is also used as a generic term covering a broad spectrum of surfacing techniques including printing, hot branding and laser bonding. The machines for laser engraving and laser marking are the same, so that the two terms are sometimes confused by those without knowledge or experience in the practice.

Laser engraving is the process of selectively removing microscopic layers of material, thus creating visible marks on the treated surface. Depending on the materials, the laser material interactions can be different. On harder surfaces, the mechanism of action is primarily the ablation where the focused beam of laser dislodges microscopic particles from the substrate. Engraving can achieve depth of 100μm and beyond, whereas laser marking is typically shallower. The choice of lasers is important for the quality of the mark. To create a clean mark, short bursts of high quality laser pulses are preferable, since they are able to transfer large amounts of energy without causing significant heating and melting of the sample. For example, engraving using femtosecond lasers enhances precision, as these lasers emit extremely short pulses that create high resolution marks without significant heating, avoiding material distortion or alteration. This technology is especially valuable for materials where thermal effects must be minimized, like metals, plastics, and sensitive electronics.

A laser engraving machine consists of three main parts: a laser, a controller, and a surface. wavelength CO2 lasers, on account of many metals having high reflectivity around this wavelength. Yb:Fiber Lasers, Nd:YVO, both emitting light of approximately 1000nm wavelength, Nd:YAG lasers at 1,064nm wavelength, or its harmonics at 532 and 355nm, emit light that is more readily absorbed by most metals. They are thus more suitable for the laser engraving of metals.

The same conduction that works against the spot vaporisation of metal is an asset if the objective is to vaporise some other coating away from the metal. Laser engraving metal plates are manufactured with a finely polished metal, coated with an enamel paint made to be "burned off". At levels of 10 to 30 watts, excellent engravings are made as the enamel is removed quite cleanly. Much laser engraving is sold as exposed brass or silver coated steel lettering on a black or dark enamelled background. A wide variety of finishes are now available, including screen printed marble effects on the enamel. Anodized aluminum is commonly engraved or etched with laser machines. With power less than 40W this metal can easily be engraved with clean, impressive detail. The laser bleaches the color exposing the white or silver aluminum substrate. Although it comes in various colors, laser engraving black anodized aluminum provides the best contrast of all colors. Unlike most materials engraving anodize aluminum does not leave any smoke or residue. Spray coatings can be obtained for the specific use of laser engraving metals, these sprays apply a coating that is visible to the laser light which fuses the coating to the substrate where the laser passed over. Typically, these sprays can also be used to engrave other optically invisible or reflective substances such as glass and are available in a variety of colours. Besides spray coatings, some laser markable metals come pre coated for imaging. Products such as this transform the surface of the metal to a different color (often black, brown or grey).

Stone and glass do not vaporise or melt easily. As a result, this makes them generally a better candidate for other means of engraving, most notably sandblasting or cutting using diamonds and water. However, when a laser hits glass or stone, it fractures. Pores in the surface expose natural grains and crystalline "stubs" which, when heated very quickly, can separate a microscopic sized "chip" from the surface because the hot piece is expanding relative to its surroundings. One should avoid large "fill" areas in glass engraving because the results across an expanse tend to be uneven; the glass ablation simply cannot be depended on for visual consistency, which may be a disadvantage or an advantage depending on the circumstances and the desired effect. as of 2021, recent advances in UV laser technology now supply 10W (or greater) of UV lasing energy and produce significantly better engraving results on glass than prior, lower powered iterations of UV laser marking systems (i. e. 3W) or classic laser marking systems. The newer UV systems engrave cleanly and clearly without a high degree of micro fracturing on the mark surface. Since modern 10W UV laser systems heat the surrounding substrate less than other laser marking systems, glass substrates are significantly less prone to fracturing from the laser marking process. High quality fill engravings on thin glass and crystal substrates are now regularly reproducible at high volume in full production environments.

The demand for personalized jewelry has made jewellers more aware of the benefits of the laser engraving process. Jewellers found that by using a laser, they could tackle an engraving task with greater precision. In fact, jewellers discovered that laser engraving allowed for more precision than other types of engraving. At the same time, jewellers discovered that laser applied engravings had a number of other desirable features. These features include the customization, personalization, and sheer beauty of these engravings. At one time jewellers who attempted to do laser engraving did need to use large pieces of equipment. Now the devices that perform laser engraving come in units. Some entrepreneurs have placed such units in mall kiosks. That has made laser engraving jewelers much more accessible. The makers of machines for laser engraving jewellers have developed some very specialized equipment. They have designed machines that can engrave the inside of a ring. They have also created machines that have the ability to engrave the back of a watch. A laser can cut into both flat and curved surfaces such as the surfaces on jewelry. That points out the reason why jewellers have welcomed all the adaptations for the creation of laser engraved jewelry.

Laser engraving can also be used to create works of fine art. Generally, this involves engraving into planar surfaces, to reveal lower levels of the surface or to create grooves and striations which can be filled with inks, glazes, or other materials. Some laser engravers have rotary attachments which can engrave around an object. Artists may digitize drawings, scan or create images on a computer, and engrave the image onto any of the materials cited in this article.

The relatively low cost of laser engraving, driven by automation and inexpensive materials, makes it an ideal solution for personalization of trophies and awards. Whereas hand engraving may be a viable solution for more expensive champion’s trophies, laser customization lends itself to team and participation trophies which are often ordered in quantity and carry relatively low margins. Many also prefer the legibility afforded by a laser, which often delivers a crisper appearance than other methods at a much lower cost. Laserable materials, whether plastic or FlexiBrass, are available in a variety of colors, adding to the popularity of laser personalization for trophies and plaques. The two most popular combinations are gold lettering on a black background and black lettering on a gold background. While the same color combinations are common for plaques as well, the variety of colors used in plaque engraving is more varied.

As with regular etched mirrors, the initial focus of laser engraving machines was to etch an image onto the glass surface of the mirror. When power, focus and speed are optimized, similar results to sandblasting or chemical etching can be achieved. In a new form of mirror engraving the laser pulsates through the reflective silver layer at the rear of the mirror. As a result, the glass side of a laser engraved mirror remains intact, maintaining the full reflective qualities of the original mirror. After the engraving process in finished, the rear of the mirror needs to be "filled" with a new coating to bring out the lasered detail. When a photograph or text is laser engraved, a rear coating of solid black will lend monochromatic images the greatest definition. Coloured coatings can supply chromaticity.

Direct laser engraving of flexographic printing cylinders and plates has been an established process since the 1970s. This first began with the use of a carbon dioxide laser used to selectively ablate or evaporate a variety of rubber plate and sleeve materials to produce a print ready surface without the use of photography or chemicals. With this process there is no integral ablation mask as with direct photopolymer laser imaging. Instead a high power carbon dioxide laser head burns away, or ablates, unwanted material. The aim is to form sharp relief images with steep first relief and contoured shoulder supported edges to give a high standard of process color reproduction. A short water wash and dry cycle follows, which is less complex than in the post processing stages for direct laser imaging or conventional flexo platemaking using photopolymer plates. After engraving, the photopolymer is exposed through the imaged black layer and washed out in the traditional photopolymer process requiring photography and chemicals. Before the year 2000, lasers only produced lower quality results in rubber like materials due to their rough structure. In the 2000s, fiber lasers were introduced, giving a much increased engraving quality directly into black polymeric materials. At the Drupa 2004 printing exhibition, the direct engraving of polymer plates was introduced. This had also an effect on the rubber developers who, in order to stay competitive, developed new high quality rubber like materials. The development of suitable polymeric compounds has also allowed the engraving quality achievable with the fiber lasers to be realized in print. Since then, direct laser engraving of flexo printing forms is seen by many as the modern way to make printing forms for it is the first truly digital method. As a competitive process, more recent laser systems have been introduced to selectively engrave the thin opaque black layer of a specially produced photopolymer plate or sleeve.

Closely related is the direct imaging of a digital flexo plates or sleeves "in the round" on a fast rotating drum or cylinder. This is carried out on a platesetter integrated within a digital prepress workflow that also supports digital proofing. Again, this is a filmless process, which removes one of the variables in obtaining the fine and sharp dots for screened effects, including process color printing. With this process, the electronically generated image is scanned at speed to a photopolymer plate material that carries a thin black mask layer on the surface. The infrared laser imaging head, which runs parallel to the drum axis, ablates the integral mask to reveal the uncured polymer underneath. A main ultraviolet exposure follows to form the image through the mask. The remaining black layer absorbs the ultraviolet radiation, which polymerizes the underlying photopolymer where the black layer has been removed. The exposed digital plate still needs to be processed like a conventional flexo plate. That is, using solvent based washout with the necessary waste recovery techniques, although some water washable digital plates are in development. This technology has been used since 1995 and is only now becoming more widely used around the world as more affordable equipment becomes available. Trade sources say there are around 650 digital platesetters installed in label, packaging and trade platemaking houses.

Prior to 1980, anilox rolls were produced by a variety of mechanical processes. These metal anilox rolls were sometimes sprayed with ceramic to prolong their life in the flexographic printing press. During the 1980s laser engraving systems were produced which used a carbon dioxide laser to engrave the required cell pattern directly into the polished ceramic surface. Since then Q switched YAG lasers were used for a period as they provided a more focusable laser beam as well as increased pulsing frequencies capable of engraving the finer cell configuration demanded by the ever evolving flexographic printing process. Since approximately the year 2000 the direct anilox laser engraving process has been dominated by the use of fibre lasers which provide the high powers of the carbon dioxide lasers together with the finely focusable beam of the YAG lasers. Optical systems providing the rapid switching of multiple beams have allowed the fibre laser system to be dominant in this market. This technology has become known as Multi Beam Anilox or MBA.

Sub surface laser engraving is the process of engraving an image in a transparent solid material by focusing a laser below the surface to create small fractures. Such engraved materials are of high grade optical quality (suitable for lenses, with low dispersion) to minimize distortion of the beam. BK7 glass is a common material for this application. Plastics are also used, but with far less desirable results when compared to the engraving done in optical crystal. Since its commercial application in the late 1990s, SSLE has become more cost effective with a number of different sized machines ranging from small (~US$35,000–60,000) to large production scale tables (>US$250,000). Although these machines are becoming more available, it is estimated that only a few hundred are in operation worldwide. Many machines require very expensive cooling, maintenance and calibration for proper use. The more popular SSLE engraving machines use the Diode Pumped Solid State or DPSS laser process. The laser diode, the primary component which excites a pulsed solid state laser, can easily cost one third of the machine itself and functions for a limited number of hours, although a good quality diode can last thousands of hours. Since 2009, use of SSLE has become more cost effective to produce 3D images in souvenir 'crystal' or promotional items with only a few designers concentrating on designs incorporating large or monolithic sized crystal. A number of companies offer custom made souvenirs, called bubblegrams or laser crystals, by taking 3D pictures or photos and engraving them into the crystal.