Laser engraving

Under laser inscription refers to the labeling or marking of objects using an intense laser beam. In contrast to the laser printer in which a weak laser beam, only the pigment application is controlled on the printed material, wherein the laser marking, the labeled material is even changed. Therefore, the method and the use of energy will depend on the material. Laser labels are water and smudge resistant and very durable. They can be fast, automated and generated individually, which is why the method is often used for numbering items. Also, placing a very small machine-readable markings such as the QR Code or Data Matrix code directly onto products has become possible.

Principle

Laser markings are used to identify or consecutive numbering of items. In addition to industrial applications - machine-readable bar codes, printing best before dates, speedometer discs or markings on tablets - there are different art forms. Three-dimensional images inside of glass is one of them. In contrast to laser print the labeled material itself is changed.

Organic materials

For organic materials such as paper, cardboard, wood or leather chemical conversion reactions are triggered by local heating, which are manifested in a color change. This is similar to setting a fire sign. Also with the organic polymers which can indeed be the case, but often special plastics are used. These usually contain silicates, and thus the resultant heat is dissipated more effectively. Are destroyed by the heating specific pigments, a color change takes place, causing the label to be assigned a different color than the base.

This expands the spectrum of realizable colors. An example of this method are computer keyboards.

The carbon dioxide laser can also be engraved in PMMA bring. Whose radiation is absorbed by almost all the light transparent organic material. Laser engravings in PMMA are not discolored, they form a contrast only due to their light scattering ( rough surface). They can be lit from within by illumination of the material edge (see floodlights), so that only light up the engravings in an otherwise transparent plate. For particularly high-contrast laser marking of PMMA merely material in cast quality, short PMMA "GS" or PMMA "Cast" is.

Color removal

Another variation of the laser marking is the selective color removal of coated articles, so that the underlying color of objects emerges.

The color removal among other things since the late 1980s used in the automotive industry to produce the symbols internally lit controls. In most cases, translucent plastics are used, which are painted in the desired color. The laser beam then the desired symbol is " burned out " from the paint surface. The advantages of laser marking are in the very short preparation time for changes in symbolism and in the robustness of the label. The laser represents the most rational and prozesssicherste possibility of labeling dar.

Many packages are laser marked. So be introduced batch numbers on metal-coated paper labels, for example. The lettering is done in the mask projection technique with one shot, so that the goods conveyed on a belt must not be stopped.

Another variation is the engraving dyed anodic coatings on aluminum. Here, the organic dyes must be pyrolyzed by heating only the anodic coating - the anodized layer remains partially intact. It uses a carbon dioxide laser, whose radiation is well absorbed irrespective of the anodized layer of dye in the mid-infrared.

Start label

In metallic surfaces, a start-up label is possible. Some metals are heated to a certain temperature to develop by oxidation processes on the surface of a layer with a color effect. For steel that is known as blueing on chrome exhaust pipes of motorcycles, the effect in the different temperature-dependent stages is good to watch. Just such a color change can also be achieved by the thermal effect of the laser. Even when heated with the laser to above the melting point ( remelting ) arise such tarnish. Prerequisite is always that with oxygen blowing gas (eg air) is engraved. The font color is usually brown.

Deep laser engraving

The laser deep engraving is the second most common application for the laser marking, which is done with a laser marking system. Especially in the area of the stamp or stamping production, this method is of great advantage, since a much deeper engraving can be generated by repeated removal of material layers.

Lasertiefengravieren is a mechanical metal-cutting process. Due to the laser-induced material removal is an engraving on all materials, even on and in glass, possible. This is done by pulsed lasers, which are deflected by the mirror scanner. There are both vectored and raster-oriented designs possible. To obtain clean edges and approximately at right angles, it is important to use a plurality of directions of the ablation. Due to their resistance to laser engravings of this kind can only be removed by grinding. They are, inter alia, for forgery-proof embossed metal parts ( bearings, etc.) therefore often used.

Glass engraving

In the " engraving " of transparent materials such as Plexiglas or glass, the laser is focused inside the material. Such high field strengths can be reached only in focus and in its immediate vicinity, that the material is no longer transparent and the laser energy is absorbed. This causes the material is briefly heated locally up to 20,000 ° C. After cooling, an opaque or light-scattering body is left in the material. Performs to the focus of the laser through the material can thus produce three-dimensional images.

Gallery

Laser engraving using CO2 laser source to batch-dyed PMMA ( GS Quality )

Scanning laser engraving a vector file using CO2 laser source on a commercial cardboard

Laser engraving on an egg

Laser engraving on food (pumpkin skin)

Glass engraving on a carafe in detail

Pros and Cons

  • Computerized laser control - automated engraving motifs
  • Durability - results insensitive to abrasion, solvents and other environmental influences
  • Material flexibility - acrylic, glass, wood, plastic, leather, metal, paper, cardboard
  • Non-contact method - no wear, lettering difficult surfaces possible

Meanwhile, multicolored motifs / engraving can be created by the different reactions in laser machining on metal for example.

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