Metal cutting by lasers

Lasers ( source: deposit photos)

The term LASER is an acronym for “light amplification by stimulated emission of radiation.”

When a laser is used, light is intensely focused onto an object at a particular point. This focused light (referred to as ‘spatially coherent’ light) causes an extreme elevation in the temperature of the illuminated area. The material under the illuminated area melts rapidly or is vaporized, and a cut or fissure forms in the material.

Precision metal cutting by lasers

Image source: factory.com

For industrial fabrication, the two laser types most commonly used in metal cutting and manufacturing are stimulated gas emission CO₂ lasers and fiber lasers.
One of the big general benefits of laser cutting is that lasers can be used to cut a wide variety of materials. It is necessary to select the right laser and cutting process for each material. However, lasers can be used on more materials than people sometimes expect.

Laser cutters can cut all types of metals, from mild steel to stainless and also non-ferrous metals. More reflective metals like aluminium are more difficult to cut, though. With the right kind of lasers and after following a few useful steps almost all metals can be cut with lasers.

The thickness of the metal can be anywhere up to 30 mm. The maximum thickness, however, depends on the laser cutting service.

Here are the materials most often cut with laser cutters:

Metals: Lasers are particularly useful for cutting metals. Not only can lasers cut most metals, but they also create accurate, clean cuts in metal. On top of this, lasers can cut metals quickly and at a relatively low cost. Lasers can also be used to cut both thin and thick metals, with high power CO₂ lasers being used for the thickest metals.

Metals that are commonly cut with lasers are: Mild steel, Cold rolled steel, Stainless steel, Steel alloys, Iron, Aluminum and aluminum alloys, Brass, Copper and copper alloys, Titanium and titanium alloys.

Here are some materials that can't (shouldn't be will be the right word here) be cut with a laser: ( although you asked about metals, I am giving other examples too to make people aware of these things)

Some Plastics: While some plastics can be laser cut, others can’t. Most of the materials that can’t be laser cut are plastics. Here are some common plastics that it isn’t possible to cut with a laser for various reasons:

Polyvinyl Chloride – High concentrations of acids and toxic fumes are produced when this material is laser cut. These can be dangerous and can also damage the laser cutter.

Polycarbonate – Very thin sections of this material can be laser cut. However, it tends to discolour badly or burn under a laser when thicker sections are cut.

High Density Polyethylene (HDPE) and Acrylonitrile Butadiene Styrene (ABS) – These plastics melt too readily when laser cut, resulting in poor quality cuts. ABS also produces toxic fumes, including cyanide, methyl styrene, phenol, phenyl cyclohexane and benzene derivatives.

Fiberglass consists of glass and epoxy resin, which are materials that both perform poorly when laser cut. Glass is highly reflective and difficult to laser cut, while epoxy resin creates a large number of toxic fumes. Those fumes include hydrogen cyanide, H2, CO, CH4, C2H6, C2H4, C3H6 and C3H8, ethane, ethylene, propylene and propane.

Another material that can’t be cut because of the presence of epoxy resin is coated carbon fiber. This is carbon fiber that’s been pre-impregnated with epoxy resin so it can be thermally bonded in a hot press.

Polystyrene and Polypropylene Foam: These materials are generally regarded as being too flammable to be laser cut. They are often burn or become misshaped at the cutting edge. Discolouration also occurs.However, it should be pointed out that nowadays these foams are actually cut with lasers more often by following certain methods.

Difficulties faced while cutting metals with lasers:

Material Limitations: Laser cutting can be used on a variety of metallic and non-metallic materials. However, laser cutter types and the assistive gases impose some limitations with certain materials.

Material Thickness: The thickness of materials that can be cut is limited with laser cutting. Thicker materials can also exhibit a higher incidence of edge micro-burrs and other issues.The upper limit on thickness when cutting metal with a fiber laser is around 25mm. The upper limit on thickness when cutting metal with a CO₂ laser is around 70mm. In comparison with plasma cutting, laser cutting for metals is generally more precise and uses less energy. However, most industrial lasers cannot equal a plasma cutter’s capabilities with metal parts of higher thickness.

Material Hardening: The hardening of laser cut edges due to processing may be problematic in some applications. Parts requiring further processing, such as powder coating or painting, may need intermediary processing following laser cutting before it can take place. The addition of this step increases both the turnaround time and total processing costs.

Reflectivity: Some shiny metals like aluminium can reflect lasers reducing its capacity to cut.

Thermal conductivity: Also metals that conduct heat well, like copper, can dissipate the laser's heat energy more effectively, making it harder to melt or vaporize them.

Melting point: Metals with very high melting points, like tungsten , require a much stronger laser to cut or melt through them compared to metals with lower melting points.

Factors that resist laser damage include the material composition of the optical component's outermost surface, the laser parameters affecting the accurate measurement of film damage threshold, the resist material platform used, and the coating design of the component. Specifically, using metal oxides or metal fluorides with metals that boil at lower temperatures than their oxides or fluorides can resist laser damage by allowing the vaporization and removal of the metal without melting the host compound. Laser parameters like energy error, focused spot size error, and beam quality influence the damage threshold of films, with M2 inversely related to the damage threshold. Additionally, the resist material platform's characteristics, such as fullerene-based, novolac-based, or metal-based materials, impact the patterning performance and resolution capabilities under laser ablation processes. Coating the optical components with specific anti-reflective coatings can also enhance their resistance to laser-induced damage.
So while using lasers to cut metals you have to consider these things to overcome the difficulties:

1. Choose the right type of laser for the metal.

2. Get right information on metals (This is why: Each metal has different requirements and reacts differently to the laser beam, so it’s crucial to understand the metal you intend on marking. Here is a list of specificities for common metal materials and alloys:

Aluminum: Aluminum absorbs fiber laser light efficiently and can be marked at high speed.

Steel: As a hard material, steel cannot be marked as fast as softer metals. White markings can be created faster than black markings. If white contrasts well with the bare metal color, it should be used to speed up the laser process.

Stainless steel: The chromium oxide layer on the metal surface must usually remain intact to prevent rusting. In these cases, annealing is the recommended laser process, especially in the medical and food & beverages industries.

Anodized aluminum: Permanent markings can either be created on the anodized layer or before the anodization process. To read identifiers through the anodized layer for example, deeper markings are required.

Copper: Copper does not absorb fiber laser light as efficiently as other metals, which means high-speed markings are not possible.

Lead: Lead is easy to mark at high speed, as it is one of the metals that absorbs fiber laser light the most efficiently. )

3. Optimize the Laser Power for Your Cycle Time

4. Choose the Right Laser Marking Process

5. Consider Post-Process Treatments

6. Optimize laser focus and beam quality to cut the right way

7. Minimize heat input to cut low melting point metals.

8. Optimize cutting parameters, such as power, laser focus position and speed, to minimize heat input and reduce discolouration of the metal

9. Use a laser cutting machine with high power and a high-frequency pulsing feature to minimize heat input and reduce the risk of warping ( distortion).

( Now I want to ask, “What do you mean by ‘other metals’?”)