What is the Laser Cutting Process?

What is the Laser Cutting Process

1. Process Definition

Laser cutting is a non-contact machining process that uses a high-power, concentrated laser beam to melt, burn, or vaporize material away. The laser optics focus the beam into an intense spot sized 0.01-0.25mm. When this focused beam irradiates the workpiece, the laser energy gets absorbed by the material, heating it up instantly to melting or burning temperatures, causing precise localized material removal by thermal mechanisms.

This enables intricate cut shapes to be achieved with high speed, precision, automation, and low force across various materials. Laser cutting finds widespread use for high-production metal and non-metal cutting, transforming raw stock into finished parts. It is a staple machining process across manufacturing.

2. Process Principles

Laser cutting applies high-density coherent light energy to slice material. Inside the laser resonator optics, light amplification produces an intense laser beam. The beam light has high spectral purity, collimation, and energy density.

The cutting nozzle focuses this laser beam into a tiny, concentrated dot and directs it onto the workpiece. The laser beam melts or volatilizes a small amount of material where it contacts the part. As the laser head or part moves, the beam progresses along the cut path, removing material continuously by vaporization, melt expulsion, or chemical degradation.

An assist gas blows away debris while oxygen aids exothermic burning. The narrow kerf allows tight radii and details. Process monitoring automates optimal cutting parameters. The physics driving the intensity and beam properties enables versatile, high-quality laser cuts.

3. Equipment and Tools

• Laser resonator: The gain medium, excitation source, and optical cavity produce and amplify the coherent laser beam with intensities up to 100 kW. Common gain media are CO2 gas, crystal, fiber laser, and diode lasers.
• Beam delivery: The collimating and focusing lens steer the laser to the cutting nozzle with mirrors, fiber optics, or robotic arms. This directs the high-energy beam precisely.
• Cutting nozzle: The nozzle houses focusing optics and assists gas inputs to direct the focused spot with ideal gas coverage.
• Motion system: Multi-axis CNC platforms position the laser or part for accurate beam paths. This enables complex 2D and 3D cutting patterns.
• Exhausts capture cutting fumes. Filtered air handling improves cut quality and safety.
• Monitoring: Sensors and cameras inspect the process, measure the kerf, and adjust parameters in real time.
• Shielding prevents dangerous laser reflections. The equipment is fully enclosed with door interlocks.

3. Application Fields

Laser cutting sees diverse commercial and industrial uses where precision, speed, automation, and material versatility are valued, including:

• Sheet metal fabrication: The laser cuts complex part profiles from sheet metal while avoiding tooling marks typical of punching or machining.
• Automotive: It cuts body panels, dashboards, drivetrain, and electronics components for cars and trucks.
• Aerospace: Precision laser cutting shapes airfoils, bulkheads, and fittings from tough alloys.
• Medical devices: Cutting fine details in catheters, implants, and instruments.
• Electronics: Non-contact processing benefits delicate silicon wafers and circuits.
• Tool and die: Laser cutting excels at making blanking/piercing dies from steel.
• Signage: Acrylic plastic, wood, textiles, and patterns are readily laser cut for displays and letters.
• Architecture: Cutting decorative metal panels and stone veneer pieces.

1. Advantages and Limitations

• Advantages
• Extremely precise, narrow cuts with no tool contact. Tolerances to +/- 0.005in (0.13mm).
• High cutting speeds up to hundreds of inches per minute.
• Low machining forces and fine features. No tool chatter or work hardening.
• Minimal heat-affected zone or kerf. Small distortion.
• Cuts very hard, brittle, reflective materials like ceramics, and composites.
• Limitations
• High equipment cost. Limited workpiece size by machine volume.
• Consistent edge quality requires controlled parameters and gases.
• Limited to line-of-sight cutting paths only. Complex fixturing often needed.
• Not effective for high-volume bulk metal removal.
• Thermal damage risks without proper controls.
• Works for flat or 2D geometries mainly. Cutting formed sheets can be difficult.

1. Process Parameters

The cut quality depends greatly on selecting and controlling appropriate parameters:

• Laser power directly affects the cutting speed, width, angle, and edge finish based on material properties. More power increases cutting capability.
• Cutting speed must balance laser energy absorption with material removal rate. Too fast reduces cuts. Too slow cause excess heating.
• The beam focal point position relative to the surface impacts the kerf width and gas assist effectiveness.
• Optimal assist gas type and pressure cleans and cools cuts while aiding cutting reactions as needed.
• The number of cutting passes and sequences influences edge finish, precision, and throughput.
• Focal length, beam mode, and nozzle design affect cut geometry based on optical characteristics.
• Workpiece thermal properties, surface finish, and reflectivity determine laser compatibility.

Advanced computer modeling helps estimate ideal parameters before cutting. Adaptive process control further optimizes these settings during cutting.

7. Quality Control

Laser cuts involve detailed quality checks:

• Inspect cut profile accuracy against part design using optical comparators and CMMs. Measure critical tolerances.
• Verify cut edge straightness, surface roughness, and absence of dross or adhered debris. Check for delamination on composites.
• Confirm proper fusion to avoid uncut sections or adhered dross. Metallurgical samples were taken.
• Monitoring cut width shows beam focus consistency and checks that fusion penetrated the full material thickness with no drag lines.
• Check for heat damage like discoloration, melted surface, or cracks in the heat-affected zone.
• Mechanical testing assesses joint integrity. Tensile, peel, and fatigue tests were conducted.
• Ensure no laser beam damage to the back surface of the workpiece.
• Correlate process data to validate production settings stay in control.

ANSI and ISO cut quality standards apply to attributes like drag lines, striations, charring, taper, etc. Proper calibration, fixturing, and gas delivery help attain quality cut edges.

8. Development and Trends

The laser was invented in the 1960s but only adopted for manufacturing in the 1980s when higher powered CO2 lasers were developed. Precision CNC motion systems transformed laser cutting from a fixed process into a highly programmable technique. Cutting metals became viable by the 1990s with fiber lasers.

Recent trends include:

• Multi-kilowatt fiber and solid-state lasers enable faster cuts in thicker, more reflective materials. Diode-pumped fiber lasers offer wall plug efficiency of over 30%.
• Dynamic beam and process control adapts in real-time using sensor feedback, enhancing edge quality.
• Multi-axis cutting heads and robot integration improve access to 3D cutting.
• Ultrashort pulse lasers under 100 picoseconds minimize heat input, especially useful for electronics.
• Vision systems align sheets for cutting patterns or identify warped parts. AI-based flaw detection.
• Laser-arc hybrid processes combine laser cutting with arc welding or hardening.

1. Case Studies

• Aerospace turbine manufacturers use precision laser cuts to shape complex airfoils from tough nickel superalloys. The cuts avoid tool forces while handling tight radii in the airfoils.
• Laser cutting creates detailed stainless steel medical components like needles and stents where edges must have precise shapes, minimal burrs, and no heat damage.
• Automotive plants apply high-speed laser cutting of door panels, bumper beams, and aluminum/steel body components. Productivity exceeds punching or machining.
• Mobile phone glass screen covers with cutouts for ports and lenses are intricately cut from glass sheets by fiber lasers without cracking the brittle material.
• Laser hole drilling provides micro-perforations in filters where thousands of tiny holes enable critical filtration performance yet cannot be machined conventionally.

1. Conclusion

The focused coherent energy of laser beams provides exceptional versatility and precision for non-contact thermal cutting across industries. As an automated, competitive process, laser cutting will continue advancing in speed and capabilities through higher power lasers, improved dynamic control, and integration with other processes. With the laser’s unique attributes and continual technological improvements, its usage will keep expanding across manufacturing.