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An In-Depth Guide to Laser Cutting: Everything you need to know

Laser cutting in manufacturing is nothing new. The first lasers were developed in the 1960s and adapted for use in manufacturing in the 1970s. The aerospace giant, Boeing, was the first company to use lasers for cutting specialist alloys like titanium and Hastelloy. From there, lasers have become an everyday part of metal fabrication.
 

What is laser cutting?

Imagine a lightbulb which throws light waves out in every direction. A laser beam is a concentrated stream of invisible light. As you’d imagine, laser cutting is using that laser beam to melt through the material. 
Nowadays, there are essentially three types of laser cutter:
  • CO2
  • Crystal
  • Fibre
CO2 is the most widespread type of laser used in metal fabrication. However, fibre lasers are becoming more affordable, and their popularity is growing.
 

How does a CO2 laser work?

At the risk of this article turning into a physics lesson, picture a glass tube filled with CO2. A voltage is passed through the tube and reacts with the gas particles. The particles then release energy in the form of light. This light is then reflected between mirrors to increase its intensity. A focusing lens is used to bring the beam from around 7mm in diameter down to 0.1mm. At that level of focus, the heat is intense enough to vaporise the material you need to cut.
The final part of the sequence is to use an assist gas to blow away molten material. Usually, these assist gases will either be oxygen or nitrogen. Both have their pros and cons:
  • Oxygen is cheaper and reacts with the cutting zone to speed up the cutting process. But it also reacts with the air and leaves a hard, oxide layer on the cut face which will need a second operation to clean off.
  • Nitrogen is inert, so doesn’t react and provides a clean edge that needs no further cleaning. However, it’s a more expensive gas to use. Typically, we will use nitrogen to give the best finish when we laser cut stainless steel for medical use. 

How does a fibre laser work?

Fibre lasers create their light from a bank of diodes rather than from a gas tube. The light is then channelled into a fibre optic cable which focuses it further—about 100 times further than in a CO2 laser, so the end result is far more powerful. A fibre laser will still need an assist gas as detailed above. 
The main benefits of a fibre laser over CO2 are the running costs. 
  • Although the capital cost of the machine is higher, energy consumption is significantly less. 
  • Fibre lasers can run much faster than CO2 when cutting thin-gauge material. 
  • As there are no moving parts and expensive mirrors and lenses, the maintenance costs are slashed.
However, when cutting thicker materials (5mm and over), CO2 is usually the better option as it can cut quicker in a straight line.
 

What are the benefits of laser cutting?

One of the main benefits over other methods of metal cutting (e.g. punching) is versatility. 
  • Lasers can cut any shape required. Arcs and circular cut-outs are a breeze, and the cut edge is perfectly smooth. Nibbling rounded shapes with a CNC punch always leaves a serrated edge which needs a secondary operation to remove.
  • Tooling costs are zero as the laser doesn’t need any. However, replacement lenses are expensive, so maintenance costs can be high.
  • Still on the topic of versatility, lasers can cut through a variety of materials. Steels and metal alloys, wood, certain plastics, paper are all possible on the same machine with little need for alternate setups.
  • Compared to CNC punching, lasers can cut much thicker material. How thick depends on the machine and material. At Pegasus, we can cut up to 6mm thick aluminium, 8mm thick stainless steel, and 12mm thick mild steel.
  • Besides flat sheets of material, tube-cutting lasers can create all kinds of holes, slots and cut-outs in circular, square, and rectangular hollow sections, saving hours of manual cutting time.
  • As laser cutting is a non-contact process, there’s no mechanical damage to the part. The laser melts the material, so heat distortion is a factor to consider. However, the laser beam is thin and travels through the material quickly, so heat-affected zones are minimal.
  • When cutting multiple parts out of a sheet, they can be nested close together as the laser beam is thin. As such, material utilisation increases and cost per part decreases.
  • As well as cutting, lasers can be used for marking and engraving. Part numbers and company logos can be etched into the material or guidelines for subsequent operations can be added, e.g. centre marks for weld studs or bending lines. Therefore, the laser can reduce time and cost on downstream processes.
At Pegasus Precision, our laser cutting specialists are always on hand to offer help and advice on our laser cutting process. Their knowledge and experience can help you save significant costs on your bought-out metalwork.
 
Give them a call anytime on 01233 801649.