Laser cutting is an advanced, precise process whereby a focused laser creates a high-energy-density point of an incredible intensity that can melt, burn, or vaporise almost any material it contacts. Cuts can be made with exceptional accuracy and precision, and the energy concentration/density of the laser beam can be controlled to adjust for different material compositions.

Laser cutting is a game-changing process in the field of metal fabrication that provides several significant features and benefits, including:

  • Unrivalled precision
  • The ability to manufacture to remarkably tight tolerances
  • Minimised HAZ (Heat-Affected Zone)
  • Increased design complexity and complex geometries
  • Improved productivity due to fast-cutting speed
  • Reduced post-cut processing, as most cuts are clean and burr-free
  • The ability to handle a wide range of materials and thicknesses

Heat-Affected Zone (HAZ) 

The HAZ is the area between any melted metal and the unaffected surrounding metal that undergoes unwanted microstructural property changes due to its proximity to intense temperatures during processes like cutting or welding. 

Most metal absorbs and transfers heat, which radiates away from the cutting edge. Although unlikely to melt, changes in the HAZ can weaken the metal and make it more prone to failure. It is seldom the weld itself that will break, but rather the surrounding metal in the HAZ that has been structurally compromised. Depending on the material being cut and the laser in question, temperatures can range anywhere between 150°C and 5,550°C (302°F to 10,022°F). 

The HAZ is easily identified as a series of differently-coloured (from light yellow to dark blue) bands that appear between the cut/weld and the surrounding base metal. This inherent weakness is sub-optimal in almost every scenario, and laser cutting minimises this issue in the following ways:

  • Advanced lasers

State-of-the-art CO2 and fibre lasers are exceptionally efficient at focusing their energy only where required. This minimises the HAZ and prevents dramatic heat spread and strength loss. 

  • Pinpoint accuracy and maximum control

The precise, computer-guided nature of laser cutting allows for incredibly accurate material targeting, helping to reduce heat spread to surrounding areas.

  • High cutting speed 

Because lasers operate and cut so quickly, the associated heat has less time to spread to the surrounding material before the laser moves on. 

  • Assist gases 

Gases like oxygen, nitrogen or air help cool the cutting area. The cut generates molten material that is quickly blown away to minimise heat transfer.

  • Optimised parameters 

Several adjustable parameters play a crucial role in minimising the HAZ, depending on the density and thickness of the target material, including:

  • Laser power
  • Cutting speed
  • Focus position

By keeping these values within safe but effective parameters, unnecessary heat transfer can be avoided. 

The Four Types of Laser Cutting

There are four distinct types of laser cutting methods, each used to address diverse requirements, different materials/applications, and varying production factors:

Fusion cutting

A focused laser beam works alongside an inert cutting gas (nitrogen or argon) of high purity. This provides a protective atmosphere that prevents oxidation and expels molten material from the cutting area. Because it is non-reactive, the gas does not react with the material or the thermal reaction in the cutting zone. 

Because the energy requirement for melting material is lower than that of vaporisation, fusion cutting achieves extremely high cutting speeds, especially with higher-powered lasers. Thicker materials reduce cutting speed, as do those with higher melting points and increased thermal conductivity which dissipates the heat and prolongs melting time.

Common uses:

  • Non-oxidized cuts in reactive metals like titanium and steel and titanium

Vaporisation cutting

The surface temperature of the target material is rapidly raised to its boiling point, skipping the melting phase of standard heat conduction. The material is partially vaporised and a high-velocity gas flow expels any excess. Due to the substantial power demands of instant vaporisation, this technique requires an exceptionally high-powered laser.

When cutting thin plates, the maximum cutting speed is limited by the assisting gas jet’s velocity rather than the laser’s capacity. This demonstrates the multifaceted nature of vaporisation laser cutting, as the laser and auxiliary systems significantly affect the overall cutting performance.

Common uses:

  • Vaporisation laser cutting is invaluable in industries where molten material may cause issues, especially when making precise, small-scale cuts in ferrous alloys. Materials like wood and ceramics that do not undergo a distinct molten phase are less suitable.

Fracture-controlled cutting

Brittle materials that experience heat damage can be cut by strategically inducing thermal stress across a minuscule area (typically a few micrometres in diameter). An intense, concentrated laser beam creates a drastic thermal difference between the target zone and the surrounding material. Thermal expansion creates substantial mechanical stress that fractures the material in a controlled manner. Fracture-control cutting offers a level of control that facilitates cutting in any direction, ideal for creating complex patterns and curves that conventional cutting methods cannot achieve. 

Common uses:

  • Processing heat-sensitive materials like semiconductors, glass, advanced ceramics, and other brittle components used in aerospace industries, optics, and electronics.

Laser flame/oxidation melting cutting 

Instead of the inert gas used in other types of laser cutting, a reactive gas, (usually oxygen) is introduced. The material ignites under the laser beam, and an exothermic chemical reaction with the oxygen occurs. This reaction adds further heat to the process, enhancing cutting efficiency.

Although oxidation melting cutting achieves higher cutting speeds, the quality of the cut is negatively affected, generating a larger HAZ and a rougher surface. This trade-off means oxidation melting is preferred for components and surfaces where fast, accurate cuts are advantageous, but a pristine finish is not required.

Common uses:

  • Laser flame cutting is unsuitable for precision components, sharp corners, or high tolerances. It is ideal for heavy industrial use, cutting thick steel plates and other durable materials quickly and efficiently. It is also employed in the automotive, construction, shipbuilding, and aerospace industries.  

Contact Bend-tech

Please contact our experienced, knowledgeable representatives today to learn more about Bend-tech and our meticulously designed and tested laser-cutting equipment. We have an unwavering commitment to providing top-of-the-range products and full client support for your complete satisfaction.