About Lasers

1. What is a laser?
2. How does laser cutting work?
3. What is the difference between CO₂ and YAG lasers?
4. Is the laser sealed beam or gas flow-through?
5. Is beam alignment a problem I have to worry about?
6. Does your laser burn materials?
7. What laser power is right for my application?

 

1. What is a laser?

Everything in the universe is made up of atoms. Atoms are constantly in motion, but can be in different states of excitation. If a lot of energy is applied to an atom, it can leave what is called the ground-state energy level and go to an excited level. The level of excitation depends on the amount of energy that is applied to the atom via heat, light, or electricity. Once an electron moves to a higher-energy level, it will eventually return to the ground state. When it does, it releases its energy as a photon—a particle of light. A laser is a device that controls the way energized atoms release photons. "Laser" is actually an acronym for light amplification by stimulated emission of radiation.

2. How does laser cutting work?

Industrial laser cutting concentrates high amounts of energy into a small, well-defined spot. The resulting heat energy created by the laser vaporizes materials in this small-defined area and a gas, or mixture of gases, such as oxygen, CO₂, nitrogen, and/or helium is used to blow the vaporized material out of the kerf (the width of a groove made by the laser beam). The beam's energy is applied directly where it is needed, minimizing the Heat Affected Zone (HAZ) surrounding the area being cut.

3. What is the difference between CO₂ and YAG lasers?

While there are many different types of lasers, at this time there are really only 2 families of lasers that have the efficiency and output power to perform large-scale material processing: CO₂ and YAG. CO₂ lasers are gas lasers that use carbon dioxide as the lasing medium. YAG's are solid-state lasers that use the element Neodymium (Nd) diffused in a crystal of Yttrium-Aluminum-Garnet (YAG) as the lasing medium.

Beam Dynamics uses a range of powerful sealed CO₂ lasers that emit far-infrared light at a wavelength of 10.6 microns. This wavelength is highly effective in processing a wide range of materials including wood, paper, plastics, glass, textiles, rubber and metals.

Gas lasers are very rugged—the material that creates the beam is a gas and therefore cannot be damaged. Solid-state lasers use a crystal to generate the beam. The crystal rods are very expensive—several thousand dollars for an industrial size laser. If the laser is improperly tuned or operated the crystal can be almost instantly destroyed.

Gas lasers have a direct energy transfer, resulting in an extremely high efficiency. YAG lasers utilize a pumping source, such as a flashlamp, to supply energy to the crystal rods. The process is not direct, and is far less efficient. Because the flashlamps have a definite lifetime, at a typical pulse rate the operating life is 1,389 hours. Compare that to the CO₂ laser's operating life of 25,000 hours.

CO₂ lasers can be focused to a smaller spot, which improves cut quality. At the power levels required for material processing, YAG lasers have terrible beam quality so they can't be focused as well. Also, CO₂ lasers produce a beam that is far more symmetrical and even than any industrial-class YAG laser.

Finally, CO₂ beams are much safer optically than a YAG laser. With a CO₂ laser, processing can usually be directly observed with minimal precautions. Laser-safety eye-wear is sufficient to meet government guidelines. On the other hand, a beam scattered from a process by a YAG beam will be focused to a point in the eye, probably destroying the spot where it focused. As such, all YAG workstations must be sealed off and light-tight during processing.

4. Is the laser sealed beam or gas flow-through?

The laser used in our laser cutting machines is a sealed CO₂ laser. Sealed lasers feature slab-discharge technology, which permanently confines the lasing gas mixture between two rectangular plate electrodes. These lasers require no replacement gas and no scheduled maintenance to the laser head for up to 25,000 hours of continuous operation. Consequently, sealed lasers eliminate maintenance downtime, thereby increasing productivity and reducing costs. Sealed lasers keep the beam path away from contaminants, ensuring a steady beam alignment and eliminating the need for cleaning.

Sealed lasers also have lower electrical and cooling-water requirements than flow-through lasers that flow consumable gases through the laser head. The combination of these features results in an hourly operating cost of well under one dollar. By comparison, the hourly operating cost of flow-through lasers can be five to ten times higher.

5. Is beam alignment a problem I have to worry about?

Because we use a sealed laser, the beam path is concealed from contaminants and does not have to be taken apart to be cleaned, unlike lower end lasers where the beam path is exposed. This helps keep a steady beam alignment. Our machines are also very stable. After the initial installation, the machine should not ever require a beam alignment. Other companies do not provide machines that are as robust as Beam Dynamics, and these may lose their positioning over time.

6. Does your laser burn materials?

No. The laser vaporizes materials to cut it. This process should go as quickly as possible, to minimize heat being imparted to the material near the cut. Lasers that don't vaporize quickly will take longer to cut through an area, resulting in more heat which causes burning. The lasers used in our machines have an extremely high peak power so parts are vaporized much faster, with higher edge quality. Lower watt lasers can't accomplish this quality because they cut too slowly, and burning is more likely to take place.

7. What laser power is right for my application?

There are a variety of considerations when selecting the right laser power for your application.

It is important to note that Beam Dynamics uses pulsed lasers that pulse ON/OFF thousands of times each second. The laser powers indicated are an Average with pulse ON power being three or more times the average. It is the Peak Pulse ON power that does the cutting. On many materials a higher Peak Pulse ON will result in quicker vaporization of material and a cleaner cut with less heat being imparted to the material near the cut. In laser cutting terms, high Peak Pulse power results in less Heat Affected Zone (HAZ) damage.

 

* Note: Laser Machining Centers are optimized for top cutting speeds of 600" to 1200" per minute.