Laser cutting and other industrial cutting methods
Laser cutting uses a focused laser to cut materials and is commonly used industrially with sheet metal parts and products.
It can also be used to cut diamond, glass, silicon, wood, and plastics.
Older laser cutting machines used mirrors, but modern machines increasingly use fiber optics.
There are two major types of laser cutting, ablative and fusion.
In ablative cutting material is removed layer by layer using a pulsating laser.
Like a chizel it removes material bit by bit, essentially evaporating the material, and can be used in etching or engraving materials; as it can be stopped at a precise distance at any depth in the cut.
Fusion cutting instead melts the material the laser is in contact with and uses a high-pressure gas stream to shear material away.
Both processes produce intricate and high-quality parts with clean edge finishes.
The cut also produces less waste, physical damage, and material contamination than other cutting processes like mechanical cutting, plasma cutting, or waterjet cutting.
Mechanical cutting uses dies and pressure to cut pieces from base material and often leaves tool marks and scratches on the surface of your part.
Plasma cutting uses a heated channel of ionized gas to cut through material, but as the workpiece needs to be part of the electronic circuit it must be a conductor of electricity.
Water cutting uses a high-pressure stream of water and an abrasive to cut through material, it also has the highest operating cost among industrial cutting processes.
Although these methods have some advantages over laser cutting in areas like large production runs, or in the thickness of the materials that they can process; overall laser cutting is extremely efficient.
This efficiency has led to it becoming the largest segment of the metal cutting machine market.
The process of a cut includes:
- Generating a laser beam
- Focusing that beam
- Heating and melting the cut area
- Ejecting the heated material
- Moving the beam to either start a new cut or follow the line of a current one
How it works
Typical laser cutting machines have a laser resonator assembly, mirrors, and a laser cutting head.
The laser cutting head is composed of a nozzle, a pressurized gas assembly, and a laser focusing lens.
All stages of this head are critical to the execution of a precise cut, along with configuring the machine software and part file.
CO2 and fiber lasers are the most common types of laser cutters.
CO2 lasers use an electromagnetically stimulated gas, which can be helium, xenon, hydrogen, nitrogen, or carbon dioxide.
Carbon dioxide is the most commonly used gas.
These were the first laser cutters, and have only recently been overtaken by fiber laser cutters.
Initially CO2 lasers were far better for cutting thicker materials, and this has changed as fiber cutting technology was refined leading to a smaller advantage for CO2 lasers.
This trend is strong enough to make many question whether the market of CO2 lasers will disappear.
Fiber lasers use rare-earth elements like erbium, ytterbium, neodymium, or dysprosium on an optical fiber as their focusing elements.
This allows them to have a more focused beam and more power applied to the cut.
Reflectance and thickness of materials have been the limiting factors for this technology with 1in mild steel material and below resulting in the best cuts.
Cut Efficiency
Cut efficiency also depends more on application of power and machine dynamics (acceleration and deceleration) than the overall power of the laser.
Using a laser that cuts material at the maximum thickness possible at its power is also a bad idea as tolerance for errors and aftercut cleanup increase, requiring a more skilled technician.
Overshooting the minimum power results in cleaner parts, and has less chance of flaws in the cuts allowing a less skilled technician to make high-quality parts.
Having the most powerful laser can lead to more expensive operation if it is stuck moving slowly on small, intricate cuts as it cannot reach its full cutting speed.
High speed cutting is becoming more common, with 2,000 inches per minute possible.
This speed is impressive, but the machine needs to stop moving to create a new cut.
Accelerating back to maximum speed is where time can be spent on multiple small parts, losing overall efficiency.
Other factors in making a clean cut include factoring in the width of the cutting beam, usually 30-300 microns, and supporting small parts with tabs so they are not blown away by the pressurized gas.
These tabs are kept small (0.2-0.4 mm wide) so that breaking them from the metal sheet is easy, aiding in post-processing.
Less reflective materials are more efficient to cut as more of the laser is concentrated, creating a hotter cut.
Some highly reflective materials like copper and aluminium can damage the laser machine as the beam can be bounced backwards into the lasers focusing components.
Maintenance also is a factor, with daily cleaning for nozzles and lens protection devices.
The skill of the operator in everything from editing the computer cut files, programming the machine, and keeping the machine clean; allow the machine to operate capable of the cleanest cuts.
Overview of benefits and limitations:
Benefits:
- Precision and accuracy increased
- CNC control
- Clean high quality edges
- Consistent production of complex or intricate parts
- Decreased finishing processes
- Kerf (Diameter of the cut) width far narrower
- Less material distortion
- Less wasted or contaminated material
- non-contact process creates less wear on both the material and laser
- Maintenance and repair costs are cheaper
- Decreased noise
- Increased Operator safety
Limitations:
- Selection of materials
- Material thickness
- Production rate inconsistent
- Metal hardening or cleaning can take more production time.
- High energy and power consumption
- Initial equipment cost
- Harmful gases produced when cutting materials like plastic
Summary:
Laser cutting is a high initial cost, but highly efficient and low maintenance method for producing parts from sheet metal.
It creates clean and accurate cuts that make creating precision parts easy.
Compared to other industrial cutting processes it has many advantages and is the most commonly chosen process for manufacture.
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