Laser Cutting 101:

Laser cutting is a fast, non-contact method for cutting or slitting a wide range of metal and non-metal materials. Unlike most other processes laser cutting does not suffer from tool wear which eliminates a myriad of part tolerance and maintenance issues.

Advantages of laser cutting include:

  • Fast setup time
  • No tooling or blades
  • Narrow cut kerf
  • Reduced heat input
  • Low operational costs
  • No electrode wear
  • Non-contact process
  • Because laser cutting does not require any hard tooling as does a punch press or shear, it is a very "lean" manufacturing method eliminating the need for tool changeover, tool storage and tool sharpening maintenance. Unlike plasma cutting, laser cutting does not suffer from electrode wear from each hole drilled in the workpiece.

    When compared to other thermal cutting processes such as plasma or flame cutting, laser cutting utilizes a much more focused spot, or smaller cutting tool, so it puts much less heat into the workpiece and removes a narrower path of material. This allows the laser to cut more precise parts to a higher tolerance and with less taper on the cut edge.

  • LASER Defined
  • Cutting Principles
  • Cutting Machine Basics
  • Assist Gases Basics


Definition:
The word LASER is an acronym:

  • Light
  • Amplification by
  • Stimulated
  • Emission of
  • Radiation

A laser is a light generator and amplifier that generates a single wavelength or color of light. Laser cutting uses a beam of infrared light or heat, focused to a small and intense spot to vaporize or melt a whole through a workpiece. Because laser light is a single wavelength it does not diverge, or spread out, as quickly and can be focused to a much smaller spot than ordinary white light.


A 100 Watt Incandescent Bulb
Focused to 1cm spot (0.4")
Power Density = 127 Watts /cm2
A 100 Watt Laser
Focused to 150 micron spot (0.006")
Power Density = 550,000 Watts /cm2


Cutting Principles:

Typical cutting process:

  • Start with a drawing file (usually a dxf file).
  • Use a post processor program to create machine movement commands.
  • Assign laser parameters for piercing and cutting.
  • Drill or pierce through the material.
  • Move the workpiece or cutting head to create a shape.

General Principles:

  • Higher power lasers cut thin materials faster.
  • Higher power lasers allow you to cut thicker materials.
  • Shorter focal length lenses cut thin material faster.
  • Longer focal length lenses allow you to cut thicker materials.
  • The laser beam does expand as it travels away from the laser, some applications require compensation for this.
Key Cutting Parameters Include:
  • Laser Power
  • Laser Frequency
  • Laser Duty Cycle
  • Beam Diameter
  • Cut Speed
  • Acceleration
  • Assist Gas Type
  • Assist Gas Pressure
  • Nozzle Diameter
  • Nozzle Standoff
  • Lens Focal Length
  • Focal Standoff


Cutting Machine Basics:

A laser cutting system has three major sections:

1) The Laser:
  • Generates a round beam 1/2" - 1.2" (12 - 30mm) in diameter.
  • First pulses to drill or pierce a whole through the workpiece.
  • Then will output variable power based upon the material being cut and desired process speed.

2) The Beam Delivery:
  • Transmits or delivers the beam to the focusing head via a series of mirrors called "beam benders".
  • The focusing or cutting head uses a lens to focus the beam down to a spot 0.004" - 0.010" (100-250 microns).
  • Cutting Head

    • Typical lens focal lengths for laser cutting are 3.75", 5", 7.5" and 10". The choice of lens will depend on the material type and thickness to be cut.
    • Beneath the lens, a pressurized assist gas is injected to help remove material from the cut zone.
    • There will usually be an interchangable nozzle attached to the bottom of the cutting head that allows the user to change the dynamics of the assist gas jet for different materials.
    • Critical parameters to consider on the cutting head are:
      • Lens Focal Length
      • Lens, or focal spot standoff from the material
      • Nozzle diameter
      • Nozzle standoff from material
  • The focused laser beam will vaporize and or melt a small area of the workpiece.
  • A pressurized gas, or "assist gas", will be added beneath the lens coaxially with the laser beam to push the molten material out of the cut zone.


3) The Motion system will be used to move...
  • the workpiece (fixed optic)
  • the beam delivery (flying optic)
  • or both (hybrid)
                                                 ...by CNC control in order to contour a shape.


Fixed Optic
Flying Optic
Hybrid


Assist Gas Basics:

    Air is used for:
  • Thin metals
  • Paper
  • Wood
  • Plastic
    Oxygen is used for:
  • Steel
    Nitrogen is used for:
  • Steel up to 1/2" thick
  • Stainless Steel
  • Aluminum

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