Laser engraving
This article has multiple issues. Please help improve it or discuss these issues on the talk page. (Learn how and when to remove these template messages)
|
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.[1] 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
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 mechanisms
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.[3] This technology is especially valuable for materials where thermal effects must be minimized, like metals, plastics, and sensitive electronics.
Laser engraving machines
A laser engraving machine consists of three main parts: a laser, a controller, and a surface.[2] The laser is a drawing tool: the beam emitted from it allows the controller to trace patterns onto the surface. The controller determines the direction, intensity, speed of movement, and spread of the laser beam aimed at the surface. The surface is chosen to match the type of material the laser can act on.
The point where the laser beam touches the surface should be on the focal plane of the laser's
If the surface material is vaporised during laser engraving, ventilation through the use of blowers or a vacuum pump are almost always required to remove the noxious fumes and smoke arising from this process, and for removal of debris on the surface to allow the laser to continue engraving.
A laser can remove material very efficiently because the laser beam can be designed to deliver energy to the surface in a manner which converts a high percentage of the light energy into heat. The beam is highly focused and
Different patterns can be engraved by programming the controller to traverse a particular path for the laser beam over time. The trace of the laser beam is carefully regulated to achieve a consistent removal depth of material. For example, criss-crossed paths are avoided to ensure that each etched surface is exposed to the laser only once, so the same amount of material is removed. The speed at which the beam moves across the material is also considered in creating engraving patterns. Changing the intensity and spread of the beam allows more flexibility in the design. For example, by changing the proportion of time (known as "duty-cycle") the laser is turned on during each pulse, the power delivered to the engraving surface can be controlled appropriately for the material.
Since the position of the laser is known exactly by the controller, it is not necessary to add barriers to the surface to prevent the laser from deviating from the prescribed engraving pattern. As a result, no resistive mask is needed in laser engraving. This is primarily why this technique is different from older engraving methods.
A good example of where laser engraving technology has been adopted into the industry norm is the production line. In this particular setup, the laser beam is directed towards a rotating or vibrating mirror. The mirror moves in a manner which may trace out numbers and letters onto the surface being marked. This is particularly useful for printing dates, expiry codes, and lot numbering of products travelling along a production line. Laser marking allows materials made of plastic and glass to be marked "on the move". The location where the marking takes place is called a "marking laser station", an entity often found in packaging and bottling plants. Older, slower technologies such as hot stamping and pad printing have largely been phased out and replaced with laser engraving.
For more precise and visually decorative engravings, a laser table (also known as an "X–Y" or "XY" table) is used. The laser is usually fixed permanently to the side of the table and emits light towards a pair of movable mirrors so that every point of the table surface can be swept by the laser. At the point of engraving, the laser beam is focused through a
A typical setup of a laser table involves the fixed laser emitting light
In other laser engraving devices such as flat table or drum engraving, the laser beam is controlled to direct most of its energy a fixed penetration depth into the material to be engraved. In this manner, only a particular depth of material is removed when the engraving takes place. A simple machined stick or
For surfaces that vary in height, more elaborate focusing mechanisms have been developed. Some are known as dynamic
"X–Y" laser engraving machines may operate in
Vector engraving follows the line and curve of the pattern to be engraved, much like a pen-based
Raster engraving traces the laser across the surface in a back-and-forth slowly advancing
Materials that can be engraved
Natural materials
The marking of organic materials like wood is based on material carbonisation which produces darkening of the surface and marks with high contrast. Directly "burning" images on
Paper masking tape is sometimes used as a pre-engraving overcoat on finished and resiny woods so that cleanup is a matter of picking the tape off and out of the unengraved areas, which is easier than removing the sticky and smoky surround "halos" (and requires no varnish-removing chemicals).
Plastics
Each plastic has specific material properties, especially the light absorption spectrum. The laser irradiation can generate direct chemical modifications, melting or evaporation of the material. Plastics are rarely seen in their pure state because several additives are used such as colorants, ultraviolet retardants, release agents, etc. These additives impact the result of laser marking.
Standard cast
For signage and face plates, etc., special laser-marked plastics were developed. These incorporate
Other plastics may be successfully engraved, but orderly experimentation on a sample piece is recommended. Bakelite is said to be easily laser-engraved; some hard engineering plastics work well. Expanded plastics, foams and vinyls, however, are generally candidates for routing rather than laser engraving. Plastics with a chlorine content (such as vinyl, PVC) produce corrosive chlorine gas when lasered, which combines with Hydrogen in the air to produce vaporised hydrochloric acid which can damage a laser engraving system. Urethane and silicone plastics usually do not work well, unless it is a formulation filled with cellulose, stone or some other stable insulator material.
Kevlar can be laser-engraved and laser-cut. However, Kevlar does give off extremely hazardous fumes (cyanide gas) when it is vaporised.
Metals
Metals are heat resistant and thermally conductive, making them more difficult to engrave than other materials. Due to their thermal conductivity, pulsed, rather than continuous wave lasers, are preferred in laser engraving applications. High peak power, low pulse duration lasers are able to ablate material off a metal engraving surface without delivering enough energy to melt the surface.
Metals can not be easily be engraved with common 10,600 nm
Coated 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 CO2 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.[5][dead link] 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
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.[6][7] 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[update], 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 CO2 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[8] at high-volume in full production environments.
Jewelry
The demand for personalized
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
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.[10]
Fine art
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.[11]
Trophies, plaques and awards
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.
Laser etched mirrors
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.
Industrial applications
Direct laser engraving of flexographic plates and cylinders
Direct laser engraving of
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[according to whom?] as the modern way to make printing forms for it is the first truly digital method.
As a competitive process, more recent[as of?] laser systems have been introduced to selectively engrave the thin opaque black layer of a specially produced photopolymer plate or sleeve.
Direct photopolymer laser imaging
Closely related[clarification needed] 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[who?] say there are around 650 digital platesetters installed in label, packaging and trade platemaking houses.
Laser engraving of anilox rolls
Prior to 1980,
Sub-surface laser engraving (SSLE)
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
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.
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.
See also
- Glass etching
- Laser beam machining
- Laser ablation
- Laser bonding
- Laser cutting
- List of laser articles
References
- ISBN 978-1420093544.
- ^ ISBN 978-9400773400.)
{{cite book}}
: CS1 maint: location missing publisher (link - ^ "Marking and Engraving". www.litilit.com. Retrieved 4 April 2024.
- ^ "Laser Engraving on Metal | Expert Guide". 16 January 2024. Retrieved 16 January 2024.
- ^ "TherMark Laser Marking - How It Works". Thermark.com. Retrieved 7 November 2012.
- ^ "Glass Laser Engraving & Etching – All You Need to Know". All3DP. 29 August 2019. Retrieved 31 May 2022.
- S2CID 137296053.
- ^ "Laser Marking on Glass: How to Achieve High Quality". FindLight Blog. 22 September 2015. Retrieved 31 May 2022.
- ^ "Guide to Jewelry Laser Engraving Machine". 30 December 2023. Retrieved 16 January 2024.
- ^ "Laser Welders Impacting the Jewelry Industry - Ganoksin Jewelry Making Community". Ganoksin. Retrieved 31 May 2022.
- ISBN 9789400773400.)
{{cite book}}
: CS1 maint: location missing publisher (link - ISBN 978-0470916209.
- ^ a b "Sub Surface Laser Engraving". Engraving Laser. Retrieved 7 November 2012.