Home Categories Send inquiry

Laser cutting bright surface skills

Using fiber laser cutting machine to cut bright surface materials (such as mirror stainless steel, high-gloss aluminum, copper, brass, etc.) has fundamental differences and great advantages with the use of traditional CO₂ laser, but it also requires special skills to obtain the best results and ensure safety.

Core principle: The wavelength of fiber laser is 1.06 microns, and the absorption rate of metal materials is much higher than that of CO₂ laser with 10.6 microns. This means that the fiber laser is less likely to be reflected, the energy utilization efficiency is higher, and the risk of equipment reflection damage is greatly reduced. But that doesn’t mean there are no challenges.

The following are the bright surface cutting techniques specially designed for fiber laser cutting machine:

Core Advantages and Premises

First of all, it is clear that for the most common bright surface 304 stainless steel, modern fiber laser cutting machines can usually cut directly without complicated pretreatment like CO₂ laser, and the risk of reflection is extremely low. The difficulty lies mainly in how to obtain a “flawless” cutting surface to prevent surface scratches and oxidation.

Key Skills and Parameter Optimization

1. Gas selection and pressure control (the most critical)

  • Nitrogen/high purity nitrogen cutting
  • Purpose: To obtain a bright surface cutting edge without oxidation, silvery white or natural color.
  • Pressure requirements: Very high air pressure is required (usually> 1.2MPa or even higher). High pressure nitrogen can quickly blow away the molten metal, to prevent its oxidation on the cutting surface discoloration, while cooling the cutting seam.
  • Purity Requirements: Use nitrogen of 99.99% or higher purity to avoid oxygen impurities causing the cut surface to oxidize and turn yellow and black.
  • Oxygen cutting:
  • Only applicable to the pursuit of cutting speed, and do not mind the cutting surface of the black oxide layer. For workpieces that need to maintain a “bright surface” appearance, they are generally not used.

2. Nozzle selection and height control

  • Use double-layer/compound nozzle: double-layer nozzle (such as HighSpeed, LowSpeed nozzle) can form a more stable, aggregated air flow, the slag removal ability is stronger, especially suitable for high-pressure nitrogen bright surface cutting.
  • Nozzle aperture: according to the thick plate selection, usually use a slightly larger aperture (such as φ2.0, φ3.0) to ensure sufficient air flow.
  • Focus position: Try adjusting the focus slightly down (deeper into the sheet) to help get a more vertical, smooth cut.
  • Cutting height: maintain a constant and precise tracking height to ensure stable airflow.

3. Laser parameter optimization

  • Power: Using higher power with high speed can reduce the heat affected zone and avoid excessive melting or yellowing of the cutting edge.
  • Frequency: Increasing the pulse frequency (such as 500-1000Hz or higher) can make the cutting line more delicate and smooth.
  • Duty cycle: adjust the appropriate duty cycle, under the premise of ensuring the stability of cutting, to find the best parameters of finish.
  • Cutting speed: in the case of ensuring the cut through, try to use a faster cutting speed to reduce heat accumulation.

4. Focus Management

  • A focus test was performed to find the best focus position for the bright surface material and thickness. Usually a slightly negative focus (the laser focus is inside the plate) helps to obtain a better vertical section.

Special considerations for different glossy materials

mirror stainless steel:

  • The first protective surface: the use of high-quality laser cutting special protective film! This is the most effective way to prevent the spatter generated during cutting and the machine table surface from scratching the mirror surface.
  • After cutting, the protective film can be easily torn off to get a smooth surface.

Aluminium and aluminium alloys (especially high gloss):

  • Reflectance risk: The reflectivity of pure aluminum and high silicon aluminum is still high. Although the risk is lower than CO₂, ultra-high power fiber lasers (e. g., 10,000 watts or more) still need to be alert to the possible impact of back reflections on the internal components of the fiber head when cutting.
  • Parameters: Aluminum conducts heat fast, requires higher peak power and faster speed. Use high purity nitrogen and may need to add a small amount of argon to obtain a brighter section.
  • Slag hanging: Aluminum cutting is easy to produce bottom slag hanging, which needs to be overcome by optimizing air pressure and focus.

copper and brass:

  • High reflectivity: Pure copper (copper) is one of the most reflective metals and is also a risk to fiber lasers. Always start the test with low power.
  • Absorption problem: A green fiber laser (wavelength 515nm) can be used. Copper has a very high absorption rate of green light. It is an ideal choice for cutting copper, but the equipment is expensive.
  • Brass: zinc, zinc vapor will be generated when cutting, the section is easy to black. High pressure nitrogen is required and the parameters are optimized.

Safety and operational recommendations

1. First test: For highly reflective materials (pure copper, pure aluminum), when cutting for the first time, scrap can be used first, and tested at a lower power to observe the cutting state and machine feedback.

2. Equipment inspection: Make sure that the laser head of your fiber laser cutting machine is equipped with anti-reflection protection device (such as back reflection isolator). Most modern mid-to-high power fiber optic machines come standard.

3. Cleaning and maintenance:

  • Clean the surface of the material with oil before cutting.
  • Regularly check and clean the nozzle and protect the lens. The high-pressure gas during bright surface cutting may more easily raise dust and attach it to the lens.

4.Trial cutting and parameter library: Establish a “bright surface cutting parameter library” for different materials, different thicknesses and different surface requirements, and conduct small-scale trial cutting verification every time the material is replaced.

Summary points

Conclusion: For fiber lasers, the core of cutting bright surface materials has changed from “how to prevent reflection damage” to “how to optimize the process to obtain a perfect cut surface and protect the appearance of the material”. Through the combination of “fine parameter adjustment of high-purity nitrogen high-pressure cutting surface film protection”, high-quality bright-faced workpieces can be processed stably and efficiently.