LASER BEAM MACHINING

Done By:

Murad

Nontraditional Manufacturing Processes

Non-traditional manufacturing processes is defined as a group of processes that remove excess material by various techniques involving mechanical, thermal, electrical or chemical energy or combinations of these energies but do not use a sharp cutting tools as it needs to be used for traditional manufacturing processes.

Reason for Nontraditional

Very hard fragile materials difficult to clamp for traditional machining.

When the workpiece is too flexible or thin.

When the shape of the part is too complex.

Laser Beam Machining (LBM)

Laser-beam machining is a thermal material-removal process that utilizes a high-energy, coherent light beam to melt and vaporize particles on the surface of metallic and non-metallic work pieces. Lasers can be used to cut, drill, weld and mark. LBM is particularly suitable for making accurately placed holes.

Comparing to mechanical cutting

Advantages of laser cutting over mechanical cutting :

include easier work holding and reduced contamination of work piece.

Precision may be better since the laser beam doesn't wear during

the process. There is also a reduced chance of warping the material that is being

cut, as laser systems have a small heat-affected zone.

Some materials are also very difficult or impossible to cut by more traditional means.

A disadvantage of laser cutting is: the high energy required.

Laser beam cutting (drilling)

In drilling, energy transferred into the workpiece melts the material at the point of contact, which subsequently changes into a plasma and leaves the region.

A gas jet (typically, oxygen) can further facilitate this phase transformation and departure of material removed.

Laser drilling should be targeted for hard materials and hole geometries that are difficult to achieve with other methods.

Laser beam cutting (milling)

A laser spot reflected on to the surface of a workpiece travels along a prescribed trajectory and cuts into the material.

Continuous-wave mode (CO2) gas lasers are very suitable for laser cutting providing high-average power, yielding high material-removal rates, and smooth cutting surfaces.

Technology

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There is a direct correlation between cutting rate and laser energy.

There is a inverse relationship between cutting rate and material thickness .

The laser beam cutting may range 0.003175 mm to 0.00635 mm.

Tolerances and Surface Finish

Depends on laser type CO2 lasers. CO2 lasers are used for industrial cutting of many materials including mild steel, aluminum, stainless steel, titanium, paper, wax, plastics, wood, and fabrics.

Typical Work piece Materials

Effects on Work Material Properties

Effects of laser beam cuttingWork material properties

May affect hardnessNarrow heat-affected zone

Mechanical

 Grain size may change

Physical

Depends on shield gas/ cutting gas. May include oxidization or other effects

Chemical

Advantage of laser beam machining

No limit to cutting path as the laser point can move any path.

The process is stress less allowing very fragile materials to be laser cut without any support.

Very hard and abrasive material can be cut.

High accuracy parts can be machined.

No cutting lubricants required.

No tool wear.

Narrow heat effected zone.

Disadvantage of laser beam machining

Uneconomic on high volumes compared to stamping.

Limitations on thickness due to taper.

High capital cost.

High maintenance cost.

Assist or cover gas required.

Safety Factors

Contact with hot tools and work pieces

Eye contact with beam radiation

Inhalation of toxic fumes

Scattered Radiation

Deflection from surfaces

Smoke

Fumes and dust particles

Personal Environmental

Reverence

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