Lasers are used to heat, solidify, melt, or vaporise materials, allowing objects to be manufactured, cut, marked, soldered, brazed, welded, annealed, or engraved.
The techniques used to achieve material modification through the use of lasers include “additive manufacturing” and “laser machining”.
Additive manufacturing (“3D printing”) is a technique used to create complex objects by depositing materials such as polymers, ceramics, metals, and composites layer upon layer.
Stereolithography (SLA), Selective Laser Sintering (SLS), Selective Laser Melting (SLM), and Laminated Object Manufacturing (LOM) are some laser-based methods used in additive manufacturing.
- Stereolithography (SLA) uses a laser to scan a pattern onto the surface of a vat of liquid polymer resin. The scanned resin cures and then solidifies. The next layer is then scanned on top of the preceding layer. Layers are built up repeatedly until the whole object has formed.
- Selective Laser Melting (SLM) scans a laser onto the surface of a vat of powdered metal. The powder liquifies, fuses, then solidifies layer by layer.
- Selective Laser Sintering (SLS) fuses powdered polyamide (nylon), ceramics, or glass without liquefaction. A laser scans across the surface of the powder to solidify the material layer by layer.
- Laminated Object Manufacturing (LOM) is a technique that cuts shapes from plastic or metal laminates using a laser, stacks the shapes, and fuses them together one after another until the object has formed.
These methods enable the production of prototypes or products for end-use in a range of industries.
Laser machining includes the engraving, cutting, marking, soldering, brazing, welding, and annealing of a variety of materials, from metals to plastics, using the heat generated by a focussed laser beam.
Using physical force to cut, drill, or engrave materials often results in large inaccuracies that are undesired when micrometre scale modifications are needed. Laser machining uses the heat generated by a focussed spot and high peak power to precisely modify solid material. This enables the production of micron-sized shapes, patterns, and edges without using physical contact.
Laser marking produces a visible mark such as a bar code, serial number, product code, copyright/trademark symbol, or company logo by altering the physical composition of material surfaces. This generates a layer that contrasts with the surrounding material, enabling permanent identification codes on components with long service lifetimes.
Laser soldering, brazing, and welding are used to fuse similar or dissimilar materials, potentially without the use of flux or filler material. The laser is focussed on the surface of the material. The energy from the laser converts into thermal energy, producing heat-affected zones (HAZ) and then melt pools. As a result, melted material diffuses across the surface. The beam energy is optimised and maintained to avoid vaporising the material, allowing other materials to fuse with the melted surface upon cooling.
Laser hardening, annealing, and heat treating are techniques that use the heat generated by a laser to increase the hardness of a metal surface. The metal is heated to just under the melting temperature, and the arrangement of atoms within the metal lattice changes. When the laser beam is removed from the heated region, the surface of the material cools before the metal lattice can return to its original structure. This transformation of the metal lattice produces greater hardness.