Introduction

CNC laser cutting is a fabrication process that uses a high-power laser to precisely cut material. CNC stands for Computer Numerical Control, meaning the laser cutting machine is controlled by a computer.

The laser beam is directed at the material, melting, burning, or vaporizing it to cut intricate patterns and designs. CNC laser cutting is highly accurate and can cut complex two-dimensional profiles from sheet material. It’s used across many industries including manufacturing, construction, aerospace, and sign making.

How CNC Laser Cutting Works

CNC laser cutting works by directing a focused, high-energy laser beam at the material to melt, burn, or vaporize it along the desired cut path. Here is an overview of the main components and how they work together:

Laser Cutter

The laser cutter contains the laser source, beam delivery system, cutting head, and motion control mechanisms.

• Laser source – This generates the powerful laser beam, typically a CO2 laser or fiber laser. The beam is focused through optics to a small spot size for precision cutting.
• Beam delivery – The beam is routed via mirrors or fiber optic cable to the cutting head. This provides a stable path for the laser beam.
• Cutting head – This houses the focusing lens that concentrates the laser beam on a tiny spot on the workpiece. It also includes assist gas nozzles.
• Motion control – Precision linear stages move the cutting head (or workpiece) in the X, Y and Z axes to trace out the programmed cut path.

CNC Controller

The CNC controller is the computer that controls the laser cutter. It takes the design file and converts it into instructions for the motion control system.

• Reads the CAD file and orientates the design on the workpiece.
• Generates the toolpath for the cut pattern.
• Controls the linear stages and laser power level during cutting.
• Monitors position sensors and system performance.

Design File

The laser cutter needs a digital design file to follow the cut pattern. Common file formats are DXF, DWG, AI, EPS. It defines vectors for the cut paths and outlines for any holes or cutouts.

Materials

CNC lasers can cut a range of materials including:

• Metals – stainless steel, aluminum, titanium, brass, copper alloys
• Acrylics and plastics – acrylic, delrin, polycarbonate
• Wood – plywood, MDF, wood veneers
• Paper and cardstock
• Fabrics – cotton, wool, synthetic fabrics
• Rubber – silicone rubber, urethane rubber

Not all lasers can cut all materials. The laser must match both the material type and thickness.

Assist Gas

Assist gases like oxygen, nitrogen, or air are blown at the cutting point through the nozzles on the cutting head. The gases help blow away molten material from the cut and reduce charring.

Exhaust System

A fume exhaust system removes smoke, fumes, and debris from laser cutting. It filters the air to capture fine particles before exhausting clean air. Proper exhausts are vital for operator safety and cleanliness.

Enclosure

The laser cutter is housed in a protective enclosure for safety. It shields the intense laser beam and contains any stray reflections. The enclosure has interlocks that automatically shut down the laser if opened during operation.

The Laser Cutting Process Step-By-Step

Now let’s look at how all these components work together in the laser cutting process from start to finish:

1. Design Creation

First a 2D vector design is created in CAD software. Common formats like DXF or DWG files precisely define the geometry to cut with lines and curves.

2. File Import

The design file is imported into the laser cutter’s control software. The operator checks the file and orientations, assigns appropriate laser settings, and defines the cut sequence.

3. Material Loading

The raw material is prepared and loaded into the laser system. A fixture or clamping holds the material firmly in place on the cut bed.

4. Focus & Calibration

The laser head positions itself over the workpiece and the focus lens heights are calibrated. This brings the material into perfect focus for the sharpest, most precise cuts.

5. Cut Path Generation

The laser cutter software calculates the toolpath to trace out the pattern. Optimal path strategies help maximize cutting speed and efficiency.

6. Gas Initiation

The assist gas is turned on and aimed at the workpiece. Oxygen is commonly used for clean, fast cuts.

7. Laser Cutting

The high power laser beam traces the toolpath according to the digital file at rapid speeds. The material melts, burns or vaporizes along the precise cut lines. Fumes are exhausted away.

8. Completion

Once the cut pattern is fully traced the laser shuts off. The finished parts are removed from the machine for any secondary operations.

9. Production Run

For production runs, these steps repeat to precisely cut multiple copies of the design from sheet materials.

Main Types of CNC Laser Cutting Machines

There are a few main types of CNC laser cutting machines, differentiated by the laser source and how the beam is delivered:

CO2 Laser Cutters

• Uses a CO2 gas laser, typically rated 1500-6000 watts
• Infrared wavelength (~10 μm)
• Beam delivery via mirrors
• High power allows fast cutting of thick materials like steel
• Excellent for production environments
• Medium upfront cost

Fiber Lasers

• Uses a fiber laser, power from 500-6000 watts
• Near infrared beam (~1 μm wavelength)
• Beam delivery through fiber optic cable
• More precise and sharper cuts than CO2
• Higher upfront cost of ownership

Diode Lasers

• Uses laser diodes, typically 30-120 watts
• Visible or near infrared wavelengths
• Beam delivery through optics or fiber
• Lower power limits cutting capability
• Very low cost option good for thin materials

Galvo Laser Cutters

• Laser beam steered by galvo mirror motors
• Very fast cutting speeds
• Ideal for cutting soft materials like textiles and paper
• Limited cutting area

The choice depends on the materials, precision, and budget. A 2000 watt CO2 laser cutter offers the best balance for most applications.

Laser Cutting Advantages and Limitations

Like any fabrication method, laser cutting has some specific benefits as well as limitations:

Advantages

• Extremely precise, accurate, and repeatable cuts
• Minimal heat affect zone for clean edges
• No tooling contact or wear
• High cutting speeds minimize production time
• Low force and no vibration on workpiece
• Minimal kerf width and scrap material
• Cuts complex 2D profiles even in small spaces
• Automated process improves efficiency

Limitations

• Initial setup is required in CAD software
• Limited by line of sight (2.5D cutting only)
• Better suited for flat sheet materials
• Not ideal for thick metal materials
• Higher equipment cost than mechanical cutting
• Potential heat damage if settings not optimized
• assistance gas and exhaust systems required

Laser Cutting Safety

Working safely with industrial laser cutters requires care and the right precautions:

• Machine operation – Only trained technicians should operate the laser cutter
• Enclosure – Ensure the safety interlocks work prior to use
• Eye protection – Wear appropriate goggles when operating or observing
• Fume extraction – Properly exhaust all gases and fumes from the bed
• Material hazards – Review material MSDS for any risks like off-gassing
• Fire prevention – Keep extinguishers nearby and area clean of flammables
• Utility connections – Shut off gas and power when not in use
• Maintenance – Follow routine service schedules and parts replacement

Always refer to the manual and understand the risks before cutting.

Typical Laser Cutting Tolerances

The accuracy of CNC laser cutting depends on factors like the machine, materials, and part complexity. Typical tolerances are +/- 0.005 in (0.13 mm) but can range from +/- 0.001 in (0.025 mm) for precision systems, up to +/- 0.020 in (0.5 mm) on complex shapes.

Maintaining precision requires properly calibrating the machine, checking focal distance, using fixtures, and accounting for potential material shrinkage. Precision cuts and fine details usually require slower feed rates and multiple passes.

Laser Cutting vs Other Cutting Methods

How does CNC laser cutting compare to other common cutting processes? Here is a quick overview:

Laser Cutting

• Non-contact thermal cutting
• Extremely precise with no tooling
• Excellent edge quality in most materials
• Very small kerf and HAZ
• No vibration or mechanical forces
• High cutting speeds

Plasma Cutting

• Thermal cutting with compressed plasma arc
• Good cut quality in thicker metals
• Higher heat input leads to larger HAZ
• Limited use in delicate materials
• Relatively low costs

Waterjet Cutting

• Cold cutting using high pressure abrasive water
• No heat affect, good for all materials
• Limited by line of sight
• Slower than laser cutting
• Abrasive causes some edge rounding

CNC Router

• Mechanical cutting with rotary end mill
• Contact cutting leads to tool wear
• Clamping can mark soft materials
• Limited fine details based on end mill
• Lower equipment cost

For precision, speed and cut quality, CNC laser cutting is often the best option but each process has advantages for different scenarios.

Typical Materials and Their Laser Cutting Settings

The optimum laser settings like power, speed, and assist gas depend on the specific material to be cut. Here are typical ranges:

Wood

• Material: Plywood, MDF, actual wood
• Thickness: Up to 1/4 in
• Laser: CO2
• Power: 25-50 watts
• Speed: 10-30 mm/s
• Gas: Air

Acrylics

• Material: Cast acrylic, extruded acrylic
• Thickness: Up to 1/4 in
• Laser: CO2
• Power: 30-100 watts
• Speed: 10-30 mm/s
• Gas: Air

Metals

• Material: Carbon steel, stainless, aluminum
• Thickness: 20 gauge up to 1/2 in
• Laser: CO2 or Fiber
• Power: 1500-4000 watts
• Speed: 5-20 mm/s
• Gas: Oxygen or Nitrogen

Fabrics

• Material: Natural and synthetic fabrics
• Thickness: All reasonable thicknesses
• Laser: CO2 or Galvo
• Power: 5-25 watts
• Speed: 100-500 mm/s
• Gas: Air

These provide a starting point but extensive testing and calibration is needed to optimize laser parameters for a given material type and thickness. Machine manufacturers provide suggested settings.

How to Design Parts for Laser Cutting

Designing parts and files for laser cutting requires some best practices:

• Use vector line/curves not raster images
• Set line widths in CAD program rather than in cutter
• Optimize part orientation to avoid distortions
• Add tabs to hold separate pieces in place
• Avoid sharp corners (use rounded corners or dogbones instead)
• Provide precision holes to aid alignment
• Allow room for cutting kerf and heat affect zone
• Identify the cut order and direction for best results
• Specify etching and vector marking paths as additional layers
• Clearly indicate material type so proper settings are used

Well designed files lead to efficient, accurate laser cutting with no unintended consequences.

Secondary Operations After Laser Cutting

Laser cutting can produce finished parts but often additional fabrication steps are required:

Part Removal

Parts are removed from the machine’s bed once the cut cycle is complete. This may require manually breaking tabs or dislodging pieces.

Deburring

Most thermal cutting leaves rough edges from slag or hardened dross. This can be removed by deburring processes like grinding, sanding, or chemical washing.

Hole Finishing

Cut holes may also have burrs requiring further machining such as reaming or drilling for smooth, accurate holes.

Bending and Forming

Laser cut sheets are commonly formed into 3D shapes using press brakes or other metal forming equipment.

Welding

Complex assemblies can be welded together from individually laser cut pieces. Spot welding, MIG welding, and laser welding are common techniques.

Painting and Finishing

For products and signs, laser cut metal and other materials are often powder coated, wet painted, or otherwise finished for aesthetics and protection.

Proper part handling is key to avoiding any damage after the precision laser cutting step.

Advantages of Laser Cutting for Manufacturing

Here are some of the benefits that make CNC laser cutting valuable for modern manufacturing:

• Flexibility – Easy changeovers between jobs with no hard tooling. Make different parts without costly downtime.
• Speed – Cut intricate details faster than manual fabrication. Higher throughput results in shorter lead times.
• Accuracy – Precise cutting tolerance within +/- 0.005 inch (+/- 0.13 mm) range for precision components.
• Quality – Excellent edge finish and small heat affect zone. Parts often need minimal post-processing.
• Complexity – Intricate 2D profiles with small curves and features are no problem.
• Automation – CNC control allows automated, unattended production. 24/7 operation possible.
• Prototype friendly – Ideal for fast and affordable short-run prototype cuts before final production.
• Material savings – Small kerf means less waste material than band sawing and other methods.

Laser cutting improves productivity, quality, and capabilities for all scales of manufacturing.

Conclusion

In summary, CNC laser cutting uses a precise, high power laser beam to instantly vaporize material along programmed cut paths. It is extremely accurate with minimal heat impact, and can cut detailed profiles from sheet materials faster than manual processes allow.

With the right laser cutter, design approach, and settings dialed in for your specific material, laser cutting can take your manufacturing capabilities to the next level. Understanding the core principles of how it works helps ensure optimal results.

Frequently Asked Questions

Here are answers to some common questions about CNC laser cutting:

What materials can be laser cut?

Lasers are used to precision cut metal, plastic, wood, acrylic, textiles, paper, cardboard, glass, and more. Lasers best cut flat sheet materials up to about 1/4 inch thick. Results vary based on the laser type and power.

What are the different gases used in laser cutting?

Oxygen is most commonly used to enhance cutting of metals like steel and stainless steel. Nitrogen provides cleaner cuts in delicate materials like titanium. Compressed air is suitable for cutting wood, plastic, and fabric.

How precise is laser cutting?

Precision laser cutters can reliably hold tolerances of +/- 0.005” (+/- 0.13mm) or better for straight cuts. Precision decreases for tight curves and small features due to beam spot size limitations.

What file formats can the laser cutter accept?

DXF and DWG files are the most common design files used for laser cutting. Other supported formats are AI, EPS, PNG, JPG, and PDF depending on the laser cutter model.

What thickness of materials can be laser cut?

Lasers are usually limited to cutting about 1/4 inch thickness for metals, and less for other materials. Extremely high power lasers can cut metal over 1 inch thick. Cutting capacity also depends on the material being processed.

How do you design parts for laser cutting?

Best practices include using closed vector shapes, avoiding intersections and overlaps, including tabs to hold parts together, allowing corner radii, and applying a cut sequence. These help avoid issues when laser cutting.

What safety precautions are required?

Requirements include proper machine operation training, wearing eye protection, activating fume extraction, isolating high voltages, checking for flammable materials, fire prevention tools, and more. Follow all guidelines provided by the laser manufacturer.

Can a laser cutter make engravings?

Yes, laser engraving is often performed on the same machine by using lower power settings that mark the surface rather than cut completely through the material. It provides permanent marks, labels, textures, and images.

How does laser cutting compare to plasma or waterjet cutting?

Laser cutting provides the smallest kerf and highest precision on thinner materials. Plasma cutting is faster for much thicker steel. Waterjet has the least heat impact but lower accuracy. Each method has advantages.