This section answers basic questions related to laser markers. The information is grouped into sets of questions and answers related to basic knowledge starting with the question "What is a laser?"
Basic Knowledge vol.1
Q1What 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), and
(3) High coherence (the beam’s light waves are all in phase with one another).
Differences between ordinary light and laser beams
Lasers emit beams of light with high directivity, which means that the component light waves travel together in a straight line with almost no spreading apart. Ordinary light sources emit light waves that spread apart in all directions. The light waves in a laser beam are all the same color (a property known as monochromaticity). 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. As the light waves in a laser beam travel, they oscillate with their peaks and troughs in perfect synchronization, a characteristic known as coherence. 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.
Q2What is the difference between YVO4 laser and CO2 laser?
The following chart provides a brief description of various types of laser markers according to their typical use in applications.
Differences between CO2, YVO4 and YAG laser markers
CO2 and YVO4/YAG laser markers produce a different wavelengths of laser light, meaning that they're each suited for marking different types of materials. This makes it necessary to understand the strengths and weaknesses of each type of laser so that the best model can be chosen to suit your application
Q3Are laser markers hazardous?
The following chart lists the various classifications of lasers according to class and also the precautions that users should be aware of when operating each type.
|Laser class||Class Definition|
|Class 1||Lasers that are safe under reasonably foreseeable conditions of operation, including the use of optical instruments for intrabeam viewing.|
|Class 1M||Lasers emitting in the wavelength range from 302.5nm to 4,000nm which are safe under reasonably foreseeable conditions of operation, but may be hazardous if the user employs optics within the beam.|
|Class 2||Lasers that emit visible radiation in the wavelength range from 400nm to 700nm where eye protection is normally afforded by aversion responses, including the blink reflex. This reaction may be expected to provide adequate protection under reasonably foreseeable conditions of operation including the use of optical instruments for intrabeam viewing.|
|Class 2M||Lasers that emit visible radiation in the wavelength range from 400nm to 700nm where eye protection is normally afforded by aversion responses including the blink reflex. However, viewing of the output may be more hazardous if the user employs optics within the beam.|
|Class 3R||Lasers that emit in the wavelength range from 302.5nm to 106nm where direct intrabeam viewing is potentially hazardous but the risk is lower than for Class 3B lasers, and fewer manufacturing requirements and control measures for the user apply than for Class 3B lasers. The accessible emission limit is within five times the AEL of Class 2 in the wavelength range from 400nm to 700nm and within five times the AEL of Class 1 for other wavelengths.|
|Class 3B||Lasers that are normally hazardous when direct intrabeam exposure occurs.
(i.e. within the NOHD). Viewing diffuse reflections is normally safe.
|Class 4||Lasers that are also capable of producing hazardous diffuse reflections. They may cause skin injuries and could also constitute a fire hazard. Their use requires extreme caution.|
The CO2 laser marker (ML-G Series) and YAG laser marker (MD-H Series) are classified as Laser Class 4.
Q4What is the principle behind laser markers?
Laser light is amplified by reciprocating motion between reflection mirrors in the oscillator.
The amplified laser light is emitted from the output mirror, and focused on a target surface through the fθ lens.
The laser marker works by moving the focal point on the X-Axis, Y-axis and Z-axis with individual scanners.
Q5Can laser markers create color contrast on marked parts?
Depending on the type of material, color contrast can be achieved. YAG/YVO4 lasers are advantageous over CO2 lasers in color development, although it depends also on compatibility with the resin material.
Classification of laser marking
Q6Is laser light visible?
Laser light itself is invisible. Since lasers feature high directivity, we cannot see the beam path. Normally, we can see only the laser light diffused and reflected by any object. In an environment where mist or fine airborne particles exist, we can see the beam path because the light is diffused and reflected by the particles.
Q7Does laser marking disappear?
Since lasers physically process a target by engraving or color development, laser marking can be semi-permanent.
Examples of physical processing using laser markers
|Type of processing||Typical target materials|
|Peeling off surface||Plated metal, printed paper|
Reaction varies depending on type of resin.
Laser type (CO2 or YAG) is not defined.
Marking can be semi-permanently retained
Basic Knowledge vol.2
Q8Are any targets incompatible with larger marking?
In principle, marking is possible with any material. However, some materials cannot be marked depending on the type of the laser marker being used. As a result, the type of laser marker must be selected depending on the target material and purpose of use.Typical examples of materials that cannot be marked with certain laser markers are listed below.
Materials difficult to mark with CO2 laser markers (30 W class)
Materials difficult to mark with YVO4 / YAG laser markers
Q9How does laser marking create color contrast?
The principle of color marking is classified into four types:
- Marking by foaming
- Marking by condensation (with additives)
- Marking by carbonization (with additives)
- Marking by chemical effect
Q10What are the operating costs?
In principle, no operating cost is required except for daily electric costs. Marking with light makes “No consumables” and “long life” major features of the laser markers. The laser marker reduces a remarkable number of material management steps, in addition to zero cost for ink and label.
Comparison of running cost
Q11You 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.
If the eyes are directly exposed to laser light, it may result in loss of eyesight.
When using laser equipment, operators must wear dedicated protective goggles to protect their eyes.
Q12What does “marking space” mean?
The term “marking space” for 3-axis control laser markers is to the term “marking area” for conventional laser markers. Conventional laser markers allow only 2D marking, i.e. area. On the other hand, 3-axis control laser markers provide a concept of volume or “space”, because the focal point is variable. Therefore, for 3-axis control laser markers, the expression “space” is used, instead of “area”.
Conventional (2D control) laser marker
→ Marking area: 120 x 120 mm (example)
Focal adjustment is enabled only on a planar-basis, i.e. 2D.
3-axis control laser marker
→ Marking space: 120 x 120 x 42 mm (example)
Basic Knowledge vol.3
Q13How do laser markers create a printed image?
An amplified laser beam condenses light on the surface of a target. By scanning this condensing point with a mirror known as a scanner mirror, the laser can create the print image in a single pass. Previous models use two-axis control with an X-axis scanner and Y-axis scanner, only allowing for the possibility of marking on flat surfaces.
KEYENCE's latest models also have a Z-axis scanner enabling height control. They can mark clearly on a variety of 3 Dimensional shapes.
Q14What industries use laser markers?
Laser markers have traditionally been used for electrical products, electronic components, and metal parts.
Today, their use has expanded to include medical, automotive, food and drug, and a wide range of other consumer industries.
Q15Which are better at marking on preprinted boxes, laser markers or ink jet printers?
Laser markers offer better print quality, low running costs, and considerably less maintenance than ink jet printers.
When using a laser to mark preprinted boxes, a solid printed background is created, increasing print visibility. When printing on white backgrounds, laser markers can print burned-in print images.
Q16Is laser marker printing permanent?
One of the laser markers' strongest features is the ability to print images that last semipermanently.
Note that since laser markers physically process the target object, the printed image can’t be removed unlike images printed with ink. This feature has made laser marker security applications (preventing falsification) increasingly popular in recent years.
Q17What 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.
Q18What other processes are laser markers capable of?
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 lasers : Cutting and drilling are the main CO2 laser marker processing applications.
YVO4 lasers: Precision marking is the main YVO4 laser marker processing application.
Basic Knowledge vol.4
Q19What 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).
Q20Do KEYENCE laser markers operate on an infrared wavelength?
Yes, KEYENCE CO2 laser markers and YAG/YVO4 laser markers are infrared lasers. This means that the beam produces a wavelength longer than 780 nm. In general, laser markers have many different wavelengths — some have in the visible light spectrum (380 to 780 nm), and others in the ultraviolet range.
Q21What is the difference between ‘scanning’ and ‘masking’?
As discussed in the answer to Question 13, scanning laser markers scan a single laser beam across a target and print the image in a single pass. 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.
- - 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.
- - Print time increases as print data size increases.
- - The ability to print the same data continuously at high speed.
- - High resolution
- - 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, overcoming the method’s limitations, and making scanning the mainstream method for printing.
Q22How 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
- The 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 the total reflection mirror and output mirror, and passes through an f-theta lens and condenses on the target object’s surface.
- The condensed laser beam spot is scanned by X- and Y-axis scan motors to create the print image on the target object’s surface.
Q23What 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.
The structure is very similar to a diode’s. 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.
Q24What is a 3-axis control laser?
As the name suggests, 3-axis control lasers are able to print clear images on target objects with 3 Dimensional shapes. Conventional laser markers could only be controlled along the X- and Y-axes, only allowing them to print on flat (2 Dimensional) surfaces. Laser markers with 3-axis control can be manipualted along the Z-axis as well as the X- and Y-axes. This 3-axis control enables versatile printing on almost any shape, including cylindrical, conical, and slanted surfaces, as well as surfaces with height differences.
Conventional printing used an f-theta lens to align the focal point to the edges of the print area. 3-axis laser markers can use Z-axis control to align the focal point at every marking point on the print area, greatly increasing precision on both 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