Laser engraving

[2] Laser engraving is the process of selectively removing microscopic layers of material, thus creating visible marks on the treated surface.

On harder surfaces, the mechanism of action is primarily the ablation where the focused beam of laser dislodges microscopic particles from the substrate.

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.

The controller determines the direction, intensity, speed of movement, and spread of the laser beam aimed at the surface.

The beam is highly focused and collimated—in most non-reflective materials like wood, plastics and enamel surfaces, the conversion of light energy to heat is more than {x%}[vague] efficient.

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.

Older, slower technologies such as hot stamping and pad printing have largely been phased out and replaced with laser engraving.

A simple machined stick or angle-iron can be used as a tool to help trained technologists adjust the engraver to achieve the required focusing.

Much early engraving of signs and plaques (laser or otherwise) used pre-stored font outlines so that letters, numbers or even logos could be scaled to size and reproduced with exactly defined strokes.

Unfortunately, "fill" areas were problematic, as cross-hatching patterns and dot-fills sometimes exhibited moiré effects or uber-patterns caused by the imprecise calculation of dot spacings.

The introduction of the PostScript page-description language now allows much greater flexibility—now virtually anything that can be described in vectors by PostScript-enabled software like CorelDRAW or Adobe Illustrator can be outlined, filled with suitable patterns, and laser-engraved.

Raster engraving traces the laser across the surface in a back-and-forth slowly advancing linear pattern that will remind one of the printhead on an inkjet or similar printer.

While traditional sign and plaque engraving tended to favour the solid strokes of vectors out of necessity, modern shops tend to run their laser engravers mostly in raster mode, reserving vector for a traditional outline "look" or for speedily marking outlines or "hatches" where a plate is to be cut.

Marking softwood requires the lowest power levels and enables the fastest cut speeds, while active cooling (e.g. a fan with sufficient airflow) inhibits ignition.

Much laser engraving is sold as exposed brass or silver-coated steel lettering on a black or dark-enamelled background.

High quality fill engravings on thin glass and crystal substrates are now regularly reproducible[9] at high-volume in full production environments.

[12] The relatively low cost of laser engraving, driven by automation and inexpensive materials, makes it an ideal solution for personalization of trophies and awards.

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.

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.

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.

In the 2000s, fiber lasers were introduced, giving a much-increased engraving quality directly into black polymeric materials.

The development of suitable polymeric compounds has also allowed the engraving quality achievable with the fiber lasers to be realized in print.

laser systems have been introduced to selectively engrave the thin opaque black layer of a specially produced photopolymer plate or sleeve.

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.

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.

Such engraved materials are of high-grade optical quality (suitable for lenses, with low dispersion) to minimize distortion of the beam.

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).

The more popular SSLE engraving machines use the Diode Pumped Solid State or DPSS laser process.