How Materials React to a Laser

There are generally three ways that a material can react to a laser: Engrave, mark or cut.

Laser engraving is defined when material ablation (removal) occurs. In this case the laser engraving machine will vaporise some of the material to create some depth.

Some materials can only be laser engraved, such as wood for example. In other words, the material cannot be exposed to the laser without some ablation occurring, however, in this example ablation is desirable because the perceived quality and value of laser engraved wood is further enhanced when there is a significant degree of ablation.

Some materials work well with minimal ablation but react adversely when over-exposed to the laser. Cast acrylic is a good example in this case where some ablation by a 10.6µm laser creates a beautifully lustrous effect but when over-exposed the engraving can become very powdery and tainted by an adverse reaction to an excessive degree of thermal stress.

Laser marking constitutes the majority of laser applications and is where the material reacts without ablation to show a contrast between the area exposed to the laser and the area that has not been exposed to the laser. Laser marking is usually some form of colour change but can also include a reaction called ‘foaming’. Foaming is a material specific phenomenon that occurs when the laser marking machine heats the material to release gasses that raise and then solidify above the surface of the material.

Polycarbonate is a good example of a plastic that if exposed to a 1µm laser will colour change and foam with a highly contrasting and desirable effect.

Laser marking without ablation can provide for an incredibly detailed result, at super-high speeds and with zero to minimal adverse reactions from the base material.

Some materials can be laser marked or laser engraved according to the system configuration used and the laser parameters set. For example, a CO2 laser at the 10.6µm wavelength can only mark the surface of anodised aluminium. Increasing the intensity of the exposure can cause removal of the anodised surface but this is not very noticeable. Using a solid state laser, like a fiber laser at the 1µm wavelength, the same material can be surface marked or ablated to a considerable depth.

Laser cutting occurs when the laser vaporises the entire thickness of the material to create a void from upper to lower surface.

Solid, flat sheet materials are used for the vast majority of laser cutting where highly accurate and detailed cuts can be made by the laser that are impossible to produce by other forms of cutting technology.

For example, laser cut acrylic provides for an instantly polished edge and some textiles, such as silk for example, are heat-sealed by laser cutter where they may otherwise fray.

For some applications a finely controlled cut takes place by the laser. For example, ‘kiss-cutting’ of adhesive labels where the adhesive surface is laser cut but the backing material is not and also, the laser scoring of some materials to form a line that can form a break point, for example for snapping-off labels out of a sheet format.

At Lotus Laser Systems we manufacture a wide range laser marking and engraving solutions ideally configured for laser cutting, laser marking and laser engraving all types of materials. Our experts would be happy to recommend which configuration best suits your application.