Laser engraving

Laser engraving is the practice of using lasers to engrave an object. The engraving process renders a design by physically cutting into the object to remove material. The technique does not involve the use of inks or tool bits that contact the engraving surface and wear out, giving it an advantage over alternative marking technologies, where inks or bit heads have to be replaced regularly.

That process is distinct from laser marking, which involves using a laser to mark an object via any of a variety of methods, including color change due to chemical alteration, charring, foaming, melting, ablation, and more. Laser marking is a common method for applying variable dates, lot and batch codes, 2D codes, alphanumeric text, and graphics to products and packaging during production. However, 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 sometimes the same, so the two terms are sometimes confused by those without relevant expertise.

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.

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. 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 optical system and is usually synonymous with its focal point. This point is typically small, perhaps less than a fraction of^[vague] a millimetre (depending on the optical wavelength). Only the area inside this focal point is significantly affected when the laser beam passes over the surface. The energy delivered by the laser changes the surface of the material at the focal point. It may heat up the surface and subsequently vaporise the material, or perhaps the material may fracture (known as "glassing" or "glassing up") and flake off the surface. Cutting through the paint of a metal part is generally how material is laser engraved.

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.