Laser Beam Machining: A coherent beam of monochromatic light is focused on the workpiece causing material removal by vaporisation. Machines are generally CAD/CAM compatible, with 3-axis and 5-axis machines being generally available. Profile creation of sheet metal parts is the most common applications, but it is also possible to drill holes and create blind features in many different types of material. Gas-assisted laser beam machining is common. The gas type can be oxygen, inert gas, or air, depending on material type and quality requirements.
- Profiling of sheet parts.
- Holes (0.005mm diameter to 1.3mm), profiling, scribing, engraving and trimming.
- Prototype parts.
- Non-standard shaped holes, slots and profiling.
- Features in silicon wafers (electronics industry).
- Small diameter lubrication holes.
- Suitable for thin or delicate parts as there is no mechanical contact.
Design guidelines for Laser Beam Machining
- Lasers work best on materials such as carbon steel or stainless steels. Metals such as aluminium and copper alloys are more difficult to cut due to their ability to reflect the light as well as absorb and conduct heat. This requires lasers that are more powerful.
- LBM is not a bulk material removal process. It is most suited to contour cutting, slitting and drilling small diameter deep holes (length to diameter ratios of up to 50:1 are possible).
- There are special methods to create blind or stepped features, but they are less accurate.
- Sharp corners are possible, but radii should be provided for in the design.
- Some distortion may be caused in very thin parts.
- Maximum workpiece thickness: mild steel = 25mm, stainless steel = 13mm, aluminium 10mm.
- Localised thermal stresses and heat affected zones result.
- LBT (Laser Beam Torch). Uses a simultaneous gas stream
- Laser Texturing and Laser Etching are performed at lower energy levels.
- Surface hardening. Laser Beam Welding (LBW).
- Laser marking or laser printing can be used to create graphics, text or barcodes on most materials.
- LBM can also be integrated well with sheet metal cutting processes. For example, the Trumpf Laserpress (created in 1979).
- Laser Cutting
- YAG laser cutting
- LaserTex (Laser Texturing)
- The heat may potentially cause the generation of toxic fumes.
- Production rates are moderate to high.
- Higher material removal rate than with conventional machining.
- High power consumption.
- Short lead times.
- Tooling and equipment costs very high. Some skilled labour required.
- Very fast with high degree of automation possible.
- Burrs are very small, reducing the need for secondary finishing operations.
- Considerable economies can be obtained by stacking sheets for simultaneous cutting.
- There are many different lasers that are used for different reasons. Carbon Dioxide lasers are used for higher power applications. Pulsed Nd:YAG lasers develop a high pulse energy that allows percussion drilling and the cutting of metals at angles and thickness not possible with CO2 lasers.
- The principal lasers used in metal processing are the neodymium-glass (Nd:glass), the carbon dioxide (CO2), and the neodymium-doped yttrium aluminium garnet (Nd:YAG) lasers.
- Material thickness, surface reflectivity, thermal conductivity, absorption coefficient, specific heat and heat of vaporisation affect machine settings, cutting speeds and choice of laser type.