Basic Knowledge
Basic Knowledge vol.1
What is a laser?
The term laser is an acronym for ‘light amplification by stimulated emission of radiation.
Lasers have the following properties:
(1) Outstanding monochromaticity (the beam consists of light waves of a single unadulterated wavelength),
(2) Outstanding directivity (the beam consists of parallel light waves that don’t spread apart as they travel),
(3) High coherence (the beam’s light waves are all in phase with one another).
Let's take a closer look at these features.
Differences between ordinary light and laser beams
Monochromaticity simply means the light waves in a laser beam are all the same color. Ordinary light, such as the light from a fluorescent bulb, is generally a mixture of several colors that combine and appear white as a result.
Directivity simply means that the component light waves travel together in a straight line without really spreading apart.
Coherence simply means that as the light waves in a laser beam travel, they oscillate with their peaks and troughs in perfect synchronization. When two laser beams are superimposed on each other, the peaks and troughs of the light waves in each beam neatly reinforce each other to generate an interference pattern.
| Directivity (light waves travel in straight line) |
Monochromaticity | Coherence | |
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| Ordinary light |
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| Laser beam |
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What is the difference between YVO4 lasers and CO2 lasers?
A laser's principle medium often determines what applications that laser can perform. Here's a brief description of various laser markers and their typical applications.
| Gas |
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| Solid |
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| Liquid |
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Principal medium used for a laser marker
Differences between CO2, YVO4 and YAG laser markers
CO2 and YVO4 laser markers produce different wavelengths of laser light, meaning they're each suited for marking different types of materials. Both lasers have their own strengths and weaknesses, and understanding how materials react to different wavelengths is vital to choosing the right laser for a job.
Primary laser marking applications
- CO2 Laser Marker (Wavelength: 10600 nm)
- Often used to mark paper, plastic, glass and ceramic
Can be used for film marking applications since the wavelength is absorbed by transparent materials
High-powered models can perform gate cutting and PET sheet cutting - YVO4 Laser Marker/Fiber Laser Marker (Wavelength: 1064 nm)
- These are some of the most versatile laser markers. 1064 nm light is considered the "standard" wavelength and can be used to mark a wide range of materials, from resins to metals. However, marking on transparent materials is not possible with standard wavelength laser markers.
Are laser markers hazardous?
The following chart lists the various classifications of lasers and the precautions that users should take when operating each type.
IEC standard
| Laser class | Class Definition |
|---|---|
| Class 1 | Laser products that are safe to use. This includes long-term intrabeam viewing, even when exposure occurs while using optical viewing instruments such as eye loupes or binoculars. |
| Class 1M | Laser products that are safe for long-term, direct intrabeam viewing by the naked eye (unaided eye). Eye injury may occur when viewing the beam while using optical viewing instruments. The wavelength region for Class 1M lasers is restricted from 302.5 nm to 4,000 nm. |
| Class 2 | Laser products that emit visible radiation from 400 nm to 700 nm. These products are safe for momentary exposures but can be hazardous if you deliberately stare into the beam. Using optical instruments does not increase the risk of ocular injury from a Class 2 laser. |
| Class 2M | Laser products that emit visible beams of light and are only safe for short exposures to the naked eye (unaided eye). Eye injury may occur when using optical viewing instruments to view a Class 2M laser. |
| Class 3R | Potentially hazardous laser products with a relatively low risk of injury. The chances of injury increase with the exposure direction, and direct ocular exposure is hazardous. |
| Class 3B | Laser products that are hazardous when intrabeam ocular exposure occurs (including accidental short exposures). Viewing diffuse reflections is normally safe. |
| Class 4 | Intrabeam viewing of Class 4 lasers is hazardous, as is skin exposure. Viewing diffuse reflections may also be hazardous, and these systems often represent a fire hazard. |
KEYENCE laser markers are Class 4 laser systems.
What is the principle behind laser markers?
Laser markers use mirrors to scan a focused beam of high-energy light across the surface of a part. Almost any marking pattern is possible, from characters to 2D codes to logos.
Laser markers require minimal maintenance and don't use consumables such as ink and solvent. Their marks are also permanent, making them the ideal system for many marking applications.
Can laser markers create color contrast on marked parts?
Yes, depending on the laser's wavelength and the type of material being marked.
Is laser light visible?
Since lasers feature high directivity, the beam path typically cannot be seen. Normally, only diffused and reflected laser light can be seen. In an environment where mist or fine airborne particles exist, the beam path can be seen because the light is diffused and reflected by the particles.
Does laser marking disappear?
Since lasers physically process a target by engraving it, etching it or changing its color, laser marking can be semi-permanent.
Laser processing examples
| Type of processing | Typical target materials |
|---|---|
| Melting | Resin |
| Burning | Paper, resin |
| Surface removal | Plated metal, printed paper |
| Oxidizing surface | Metal |
| Engraving | Glass, metal |
| Discoloration | Resin |
Marking is retained
Basic Knowledge vol.2
Are any targets incompatible with larger marking?
In principle, any material can be laser marked. However, some materials cannot be marked by certain wavelengths. Therefore, it’s vital to understand how different materials react with laser light in order to choose the right system for your application.
Materials difficult to mark with CO2 laser markers (30 W class)
General metals, zirconium ceramics
These materials absorb almost zero CO2 laser light, which makes them very difficult to mark with a CO2 laser. YVO4, fiber, and hybrid laser markers are better at marking these materials.
CO2 laser-processing machines (e.g. 100 W class or over) allow for laser machining (e.g. metal cutting).
Materials difficult to mark with YVO4 / YAG laser markers
Transparent objects
The wavelength of YVO4 /Fiber Laser Markers passes through transparent objects, making marking impossible.
For marking on a transparent surface, use a CO2 or UV laser marker.
How does laser marking create color contrast?
Laser marking to produce color is commonly accomplished by:
- Foaming
- Condensation (using additives)
- Carbonization (using additives)
- Chemical changes
1. Foaming
When laser light generates bubbles on a material through heat. Gas from the bubbles is trapped under the surface layer of the material, which then swells with a white color. Specifically, dark base colors becomes lighter, resulting in high visibility (e.g. red turns pink).
2. Condensation
When dye ingredients contained in a base material absorb laser energy, the molecular density of the dye increases. This causes the dye to condense and become a darker color.
3. Carbonization
When polymer material around a dye is carbonized and turns black (as a result of continuous laser emission).
4. Chemical change
Metal ions are contained in the dye ingredients of a base material. Laser light can chemically change the crystalline structure of metal ions and the hydration level in the crystal composition of the ingredients. AS a result, the dye concentration increases and coloration occurs.
What are the operating costs?
In principle, no operating costs are required except for daily electricity costs. Laser markers require zero consumables and have a much longer working life compared to conventional marking systems.
Comparison of running cost
You should not look directly at laser light, right?
Do not stare directly into the laser light, mirror-reflected laser light or diffuse-reflected laser light.
You may lose your eyesight if you directly expose your eyes to laser light.
Operators must wear dedicated protective goggles to protect their eyes while using laser equipment.
What does “marking space” mean?
Conventional laser markers can only mark in 2D, so their total marking window is called a "marking area." 3-axis laser markers open up marking in 3D, so their total marking window is referred to as a "marking space."
Conventional (2D control) laser marker
→ Marking area: 120 x 120 mm (example)
The laser's focal distance cannot be adjusted.
3-axis control laser marker
→ Marking space: 120 x 120 x 42 mm (example)
The laser's focal distance can be freely adjusted within the marking space.
Basic Knowledge vol.3
How do laser markers create a printed image?
Laser markers use mirrors to scan a focused beam of high-energy light across the surface of a part. Almost any marking pattern is possible, from characters to 2D codes to logos.
Typical laser marking systems can only scan laser light in two dimensions, but KEYENCE's 3-axis systems can mark in three dimensions (X, Y and Z).
What industries use laser markers?
Laser markers were traditionally used for electrical products, electronic components and metal parts. Today, laser markers have expanded to most industries including medical, automotive, and food/pack.
What systems are better at marking on preprinted boxes: laser markers or inkjet printers?
Laser markers offer better print quality, lower running costs and considerably less maintenance than inkjet printers. Laser markers create solid print backgrounds and burned-in images depending on the material.
Is laser marker printing permanent?
One of a laser marker's strongest features is the ability to print images that are basically permanent.
Since laser markers physically process a target object, the printed image can't be removed or washed away. This has made laser marker security applications (preventing falsification) popular in recent years.
What is ‘single mode’ and what advantage does it provide?
A single-mode laser beam is condensed into a single-point cross-section and exhibits point symmetry. Single-mode beams enable finer, higher-quality marking than multi-mode beams (which have non-uniform power distributions).
MD-X series (super single-mode laser)
The laser's power peak is condensed at the beam’s center. Since the beam prints with many short pulses, it doesn’t apply excessive stress. This allows for an unprecedentedly high level of print clarity.
Ultra-clear printing, ultrafine processing
- Low particle generation
- Uniform print quality
- Improved coloring ability
Conventional YAG (multi-mode) laser
Power peaks are generated at random throughout the beam. Uniform print quality is difficult to achieve with a large number of low-power pulses.
What kind of processes can laser markers perform?
TYPES OF LASER PROCESSING
Laser processing applications fall into three categories: removal, bonding, and surface reforming.
- Removal processes
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Heating a material above its boiling point to evaporate parts off.
- Cutting
Cutting thin metallic or non-metallic objects - Drilling
Drilling holes through a material - Scribing
A method of scoring materials to make them easier to separate into smaller pieces - Trimming
Removing portions of thin film - Marking
Producing print quality characters or barcodes
- Cutting
- Bonding processes
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Heating a material above its boiling point to cause fusion.
- Welding
High-speed metal welding
- Welding
- Reforming processes
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Heating a material below its boiling point to improve its properties.
- Tempering
Improves material wear-resistance and strength - Vapor deposition
Improves material wear-resistance and corrosion-resistance
- Tempering
While most of KEYENCE’s laser markers are used for marking, a large number are being used for processing applications, such as the ones shown below.
LASER MARKER PROCESSING EXAMPLES
CO2 laser markers are commonly used for cutting and drilling applications.
YVO4 laser markers are primarily used for precision marking applications.
(anodized aluminum)
Basic Knowledge vol.4
What is ‘peak power’ ?
Peak power is the value of a laser’s single-pulse energy divided by its pulse width. It is expressed in watts (W).
Do KEYENCE laser markers operate on an infrared wavelength?
KEYENCE's CO2, YVO4, fiber, and Hybrid laser markers are infrared lasers. However, KEYENCE also offers green laser markers (532 nm wavelength) and UV laser markers (355 nm wavelength).
What is the difference between laser 'scanning' and laser 'masking'?
"Scanning" laser markers use mirrors to move a single laser beam across a target. "Masking" laser markers emit the laser beam as a planar surface through an LC mask or metal mask. Only the portion that passes through the mask prints the target object.
Scanning
- Benefits
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- Print data can be varied for each print job, enabling ‘lot’ and ‘serial’ printing applications.
- Eliminates the need for setup changes.
The target object can be changed frequently, since only the registered data needs to be changed. - Printing on moving objects is possible.
- Drawbacks
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- Print time increases as print data size increases.
Masking
- Benefits
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- The ability to print the same data continuously at high speed.
- High resolution
- Drawbacks
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- Many applications require assist gas, creating high running cost.
- Not able to print on moving objects.
- Requires masks (stencils).
- Equipment is relatively large.
Scanning lasers can achieve high speeds and overcome masking limitations, making them the preferred laser marking type.
How does a YVO4 laser marker work?
YVO4 stands for yttrium (Y) vanadate (VO4; vanadium tetroxide). YVO4 lasers use Nd (neodymium) and a crystal as the laser medium. Using a lamp or laser diode (LD) as the light source, they shine a fixed wavelength of light on the YVO4 crystal to generate a 1,064 nm beam—the YVO4 laser itself. In the past, YAG (yttrium aluminum garnet) was often used as the medium for oscillating 1,064 nm lasers instead of YVO4 crystals. This category of lasers is known as YAG lasers.
Operating principle of YVO4 laser markers
- Excitation light is sent from the LD module to the laser unit through the fiber optic cable.
- Light leaves the terminal and irradiates the YVO4 crystal (end pumping), creating a laser beam (single-mode beam) with a high condensation ratio and uniform energy distribution.
- The laser beam is amplified between a total reflection mirror and an output mirror.
- The laser light passes through an f-theta lens and converges on the target object’s surface, where it is scanned by X- and Y-axis motors to create a print image.
What is a semiconductor laser?
In short, a laser made using semiconductor material. The activation layer between the p-n junctions generates light when p-side holes combine with n-side electrons.
A semiconductor laser's structure is very similar to that of a diode laser. The only difference is the use of GaAs as the host, in which the energy takes the form of light instead of heat, and changes the diode into an LED (light-emitting diode).
The semiconductor's crystal (activation layer) amplifies the light and is structured to prevent it from leaking out. Semiconductor lasers are generally used for communications, optical disks, and laser excitation sources.
What is a 3-axis control laser?
Conventional laser markers can only scan light along the X- and Y-axes, meaning they can only print on flat (2D) surfaces. 3-Axis laser markers unlock the ability to scan light in the Z-axis. As a result, 3-Axis lasers can print on almost any shape, including cylinders, cones, inclined plans and multi-level surfaces.
Conventional lasers use an f-theta lens to align their focal point to the edges of the print area. 3-Axis laser markers use Z-axis control to align their focal point everywhere in the print area, greatly increasing precision on curved and flat surfaces.
3-Axis control features
3D control laser marker setting example
3D control laser marker printing examples
Large reduction in man-hours needed for setup changes
