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Laser Engraving Explained

 

 

 

1. Like many inventions of recent times, lasers were first conceived in a laboratory. It was in the early 1960’s when scientists first discovered, that they could create a light source, focus the energy and have a tool powerful enough to affect certain materials.

2. They named these first light sources LASER, an acronym for Light Amplification by Stimulated Emission of Radiation.

3. Think of a laser as a light source similar to a light bulb. A light bulb will emit energy out all around it. A laser puts energy out of a tube, usually 1/2" diameter. The energy is collected from a larger area and focused onto a fine spot size, where the energy is denser. This is like adjusting the beam of a flashlight down to a small dot of light. It is also is similar to using a magnifying glass in the sun. Move the magnifying glass up and down and you lose concentration of the energy. Just like the sun through a magnifying glass can be powerful enough to burn through paper, a leaf, or other material, so can a laser.

4. Similarly to light bulbs, lasers are rated by wattage. Simply put, the higher the wattage, the more powerful the tool. Engraving lasers generally range in power from 10 - 100 watts.

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5. Laser engraving, cutting and marking is a viable and versatile technology that is being by many engravers to improve productivity, add more services to their customers and increase profits. Engraving with a laser is actually a fairly simple process. A laser is merely a tool. Like most tools it help to understand how the tool works. The laser emits the beam of light. The beam goes though a corner block and is turned by a mirror and out to a focusing assembly which focuses the beam down to the material, where it actually vaporizes the material. Moving the beam on the X and Y axis is how the letters and graphics are created.

6. There are a variety of advantages to using a laser over other methods of engraving. First of all, because the tool is a beam of light, there is no product contact, which translates into less chance of product damage or deformation. Tooling does not wear out, or need to be replaced as in other methods of engraving. Additionally, a laser will provide more versatility in material and product choices. Laser can engrave most materials. The most popular in the engraving fields are coated metals, wood, acrylic, glass, leather, marble, plastic, and host of synthetic materials made specifically for lasers. Additionally, the same machine that engraves can also cut through thin materials, providing even more versatility for an engraver. Lasers are also faster engraving up to 80”/second. (depending on machine, material choice, artwork and desired effect) There are no consumables so operating costs are minimal, and the laser system, if properly exhausted, runs clean, so that costly cleanup or by product disposal is unnecessary.

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7. It didn't take long for the engraving industry to notice lasers and soon lasers were being used for a wide variety of industrial applications including welding, heat-treating, etching and engraving. There were early experiments with several types of methods to generate the light source, thus creating several types of lasers.

For the engraving industry, CO2 lasers, named for the gasses used to create the light source, are the tools of choice. The CO2 laser uses a mix of CO2 and Helium gases to excite the beam of light. The CO2 Laser is very inexpensive and efficient at marking on materials that are not good conductors of heat and electricity. It also uses a plotter beam technology and can cover a large engraving area. The CO2 lasers operate at a wavelength of 10.6 microns.

8. The more costly laser is the Nd YAG that operates at 1.06 microns. This laser uses a solid crystal made of Yttrium Aluminium Garnet with a small amount of Neodynium. YAG lasers operate more

repeatable than gas lasers because they are not affected by day-to-day variations in gas mixture. Mechanical vibration is all but eliminated because the YAG crystal requires no circulation blower (like those needed for CO2 lasers). These lasers are used more for marking on bare metal. They are not suited for vector cutting because they normally use the steered beam or beam deviation technology. A restricted engraving area is also a considerable drawback.

Ultra violet Visible Infra Red

Excimere lasers Chemical lasers YAG CO2

400 700 1064 10600

Wave length

in nanometers

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9. There are five (5) basic components that make up the laser system, the control panel, the motherboard, the DC power supply, the laser tube assembly, and the motion system.

A. DC Power Supply

The DC power supply converts the incoming AC electricity to DC voltage. This is used to power both the laser tube assembly and the motherboard.

B. Motherboard

The motherboard is the “brains” of the system and controls everything. Located on the motherboard are standard computer memory SIMMS. This is where incoming files, from the computer, are stored while the power is on. The motherboard gets input from the computer and the control panel. It outputs precisely timed signals to fire the laser beam and to move the motion system simultaneously.

C. Control Panel

This is where the operator controls the laser system. It is composed of push buttons, indicator lights and a LCD display. From this panel, the operator can position the motion system, move around through the menu system in the LCD display, and run the laser system.

D. Laser Tube Assembly

The laser tube assembly is a very sophisticated device. It is composed of a plasma tube filled with a special mixture of CO2 and other gases, and RF (radio frequency) electronics. The function of the entire assembly is to turn electrical energy into concentrated light energy.

It receives power from the DC power supply and its “trigger signal” from the motherboard. When the laser system is powered ON and the trigger signal comes from the motherboard, the RF electronics produce a high frequency AC signal across the electrodes located inside the plasma tube. This causes spontaneous photon emissions from the gas mixture that produces an invisible, infrared light beam at a frequency of 10.6 microns. The laser beam exits the laser tube through its output optics, bounces off the #1 mirror, passes through the beam window, bounces off the #2 and #3 mirror, and finally passes through the focus lens. The width of the laser beam as it exits the tube, called the “Beam Diameter”, is about 4 mm. The focus lens focuses the beam into a very small spot who’s “Spot Size” is dependent on the “Focal Length” of the lens. The “Focal Length” is the distance from 4

about the center of the lens to the point where it converges the beam into the smallest spot possible. Using a standard 2 inch focal length lens, the spot size produced is approximately .005 inches. The “ Focal Range” of the lens, where the beam is considered to be “in focus”, is equivalent to +/- 5% above and below the focus point. Shorter lenses produce a smaller spot size but also have a very narrow focal range. This means that it would only be useful for engraving very flat objects. The longer lenses have a much wider range of focus but also produce a larger spot size that would prohibit the engraving of fine detail. This can be related to trying to write small text with a wide, felt tip marker. There are pros and cons to the different lenses that are available for different applications. “Wattage” signifies the amount of heat energy that the laser light is producing over a period of time. Laser energy is measured with a laser power meter. Do not confuse the electrical wattage rating of a light bulb or a hair dryer with the wattage rating of the laser system. They are two different types of measurements.

E. Motion System

The motion system consists of the mechanically moving parts of the laser system. It is made up of rails, motors, bearings, belts, mirrors, a lens, and other parts. There are two directions of motion, left and right is called the “X” direction and front to back is called the “Y” direction.

The motherboard controls the movement of the motors, which moves the mirrors and focus lens across the engraving area and over the material. At the same time, it is synchronizing the laser pulses with the position of the focus lens. It is this precise positioning and timing of the laser pulses that produces the highest quality and fastest speed of engraving. In summary, the five (5) components work together to take the graphic image that is downloaded to the laser system from your computer and burn it into the material located on the engraving table inside of the laser system.