Editing Laser engraving (section)

==Industrial applications==

===Direct laser engraving of flexographic plates and cylinders===
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|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.<ref>{{cite book |last1=Hitz |first1=C. Breck |title=Introduction to laser technology |date=2012 |publisher=John Wiley & Sons |location=Hoboken |isbn=978-0470916209 |pages=229–237 |edition=Third}}</ref>

Before the year 2000, lasers only produced lower-quality results in rubber-like materials due to their rough structure. In the 2000s, [[fiber laser]]s were introduced, giving a much-increased engraving quality directly into black polymeric materials. At the [[Drupa|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|date=November 2019}} as the modern way to make printing forms for it is the first truly digital method.

As a competitive process, more recent{{as of?|date=March 2024}} 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{{clarify|reason=…to "direct laser engraving of flexographic cylinders"?|date=November 2019}} 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 [[polymer]]izes 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|date=March 2024}} say there are around 650 digital platesetters installed in label, packaging and trade platemaking houses.

===Laser engraving of anilox rolls===
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 (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 [[Dispersion (optics)|dispersion]]) to minimize distortion of the beam. [[BK7|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.<ref name="Sub surface" >{{cite web|url=http://www.engravinglaser.net/Sub_Surface_Laser_Engraving.html |title=Sub Surface Laser Engraving |publisher=Engraving Laser |access-date=2012-11-07}}</ref> 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,<ref name="Sub surface" /> although a good quality diode can last thousands of hours.

[[File:GLASWURF BEDNARIK.JPG|thumb|right|A 3D image engraved in a glass cube, seen from various angles]]

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 [[bubblegram]]s or laser crystals, by taking 3D pictures or photos and engraving them into the crystal.