People often consider laser marking and laser engraving are the same thing. In fact, they are slightly different.
Although both laser marking and laser engraving use laser to leave inerasable marks on the materials. But laser engraving makes the materials evaporate while laser marking makes the materials melt. The melting material surface will expand and form a trench section of 80µm depth, which will change the roughness of the material and form a black and white contrast. Below we will discuss the factors that affect the black and white contrast in laser marking.
3 Steps of laser marking(1) Step 1: Laser beam works on the material surface
What laser marking and laser engraving both share is that the laser beam is pulse. That is to say, the laser system will input a pulse after a certain interval. A 100W laser can input 100000 pulse every second. Therefore, we can calculate that the single pulse energy is 1mJ and the peak value can reach 10KW.
To control the laser energy that works on the material, it is necessary to adjust the parameters of the laser. And the most important parameters are scanning speed and scanning distance, for these two decide the interval of two adjacency pulses that work on the material. The nearer the adjacency pulse interval, the more energy will be absorbed.
Comparing with laser engraving, laser marking requires less energy, so its scanning speed is faster. When deciding to choose whether laser engraving or laser marking, scanning speed is a decisive parameter.
(2) Step 2: The material absorbs the laser energy
When laser works on the material surface, most of the laser energy will be reflected by the material surface. Only small portion of laser energy is absorbed by the materials and turns into heat. In order to make the material evaporate, laser engraving requires more energy, but laser marking only requires less energy to melt the materials.
Once the absorbed energy turns into heat, the temperature of the material will increase. When it reaches the melting point, the material surface will melt to form change.
For laser of 1064mm wavelength, it has about 5% absorption rate of aluminum and over 30% of steel. This makes people think that steel is easier to be laser marked. But that is not the case. We also need to think about other physical characters of the materials, such as the melting point.
(3) Step 3: The material surface will have local expansion and roughness change.
When the material melts and cools down in several milliseconds, the roughness of the material surface will change to form a permanent marking which includes serial number, shapes, logo, etc..
Marking different patterns on the material surface will also lead to color change. For high quality laser marking, black and white contrast is the best testing standard.
When the rough material surface has diffuse reflection of the incident light, the material surface will appear to be white;
When the rough material surface absorbs most of the incident light, the material surface will appear to be black.
While for laser engraving, the high energy density laser pulse works on the material surface. The laser energy turns into heat, turning the material from solid state to gas state in order to remove the material surface.
So choose laser marking or laser engraving?After knowing the difference between laser marking and laser engraving, the next thing to consider about is to decide which one to choose. And we need to consider 3 factors.
1.Abrasion resistance
Laser engraving has deeper penetration than laser marking. Therefore, if the work piece needs to be used in environment which involves abrasion or requires post processing like surface abrasive blasting or heat treatment, it is recommended to use laser engraving.
2.Processing speed
Comparing with laser engraving, laser marking has less deeper penetration, so the processing speed is higher. If the working environment where the work piece is used doesn’t involve abrasion, it is recommended to use laser marking.
3.Compatibility
Laser marking will melt the material to form slight uneven parts while laser engraving will make the material evaporate to form a groove. Since laser engraving requires enough laser energy to make the material reach the sublimation temperature and then evaporate in several milliseconds, laser engraving can not be realized in all materials.
From the above clarification, we believe you now have a better understanding of laser engraving and laser marking.
After deciding which one to choose, the next thing is to add an effective chiller. S&A industrial chillers are specifically made for different kinds of laser marking machine, laser engraving machine, laser cutting machine, etc.. The industrial chillers are all stand-alone units without external water supply and the cooling power range from 0.6KW to 30KW, powerful enough to cool the laser system from small power to medium power. Find out the complete S&A industrial chiller models at https://www.teyuchiller.com/products
