What is a laser?
LASER stands for Light Amplification by Stimulated Emission of Radiation. It is basically a single colour beam of light in the infrared, visible or ultraviolet. The light is used in materials processing for supplying heat energy.
A laser for industrial materials processing is a ‘black box’ out of which a powerful beam of light emerges (usually invisible infrared or ultraviolet light is used for materials processing). This light, when focused, provides an intense source of power for cutting welding, marking, drilling etc. and is a key technology for the manufacture of world-class products.
What is a laser processing machine?
A laser processing machine is one that utilises a powerful laser beam (appropriate sources of such beams are termed ‘industrial lasers’) to process a material eg to cut, weld, heat treat, mark. To achieve this, the laser beam generally has to be focused.
The laser processing machine generally comprises the laser source, workpiece handling equipment, laser generated fume removal , guarding for the laser, mechanical and other hazards and a control system to integrate the operation of the different components.
What materials are suitable for cutting by laser?
Most types of steel, mild and stainless, titanium, aluminium, molybdenum, thin copper and brass. It is more challenging to cut highly reflective materials like copper. Most plastics can be cut, but results greatly depend on plastic type. Care should be taken to ensure good fume extraction, especially when cutting plastics. PVC produces very dangerous fume, so should not be cut with laser. If in doubt, consult the laser system manufacturer who should be able to let you have more details. Or contact safety organisations (like those listed in the Products & Services Directory, for more advice.
What can laser cutting of flat sheet metal achieve in terms of materials, speeds and quality?
In recent times, cutting of flat sheet metal has been carried out predominantly by high power fibre lasers (commercially available in outputs from 10s of watts to 10s of kilowatts. A wavelength of around 1 micron is commonly used, though for some materials like paper, wood and some plastics, it is still more appropriate to cut with a carbon dioxide (CO2) laser, which has a wavelength of around 10 microns.
Cutting stainless steel can be achieved at very high speeds (for example 60 m/min) in 1 mm thick material and cutting with 12 kW fibre laser. As thickness increases, for the same laser power the cutting speed will decrease according to a set of parabolic curves. Most laser cutting of metal is in material less than 25 mm thick – though thicker sheets can be cut if the speed is reduced significantly.
What are the laser safety issues relating to the use of high power industrial lasers?
As well as the laser beam (a hazard to both eyes and skin), there are a range of other safety issues that should be taken into account, including high voltage, machine entrapment and fumes resulting from the process. Where the wavelength of light is less than 1.5 microns (as in most fibre laser systems), the laser beam can penetrate the retina and even with a diffuse reflection at a distance from the machine can cause permanent eye damage. Longer wavelengths (like 10 microns for a CO2 laser) can still damage the outer surface of the eye as well as burning skin if the beam is sufficiently concentrated to exceed the damage thresholds. By the use of guarding and containment it is possible to produce a safe system that is harmless to the operator – defeating interlocks and accessing the raw beam should only be attempted by trained engineers who are aware of the risks and wearing suitable eye protection to allow safe diagnosis or measurement of the beam.
A training package containing all aspects of safety should be undertaken with all laser machine purchases. This training should be available on an ongoing basis.
What are the benefits and limitations of laser drilling?
Depending on the thickness and material type, holes can be laser drilled with a high aspect ratio (thickness is much greater than diameter – perhaps over 50:1). In thin materials it is possible to drill very fine holes (from a few microns in diameter) at high speed in most materials. Wavelength, material, thickness, pulse duration and energy all have a bearing on the results. Contact AILU for guidance or consult our members who are expert in this field.