The common lasers in the market are divided into several types, which are the ultraviolet laser, the green laser and the infrared laser, respectively, and the infrared light is near infrared (such as a YAG laser with a wavelength of 1064 nm and a fiber laser) and far infrared light (such as a wavelength of 10640 nm CO2 laser).
v Currently recognized plastic marking principle has the following two kinds:
"Cold working" refers to the use of photons with very high negative energy that can interrupt chemical bonds in materials (especially organic materials) or in the surrounding medium, causing non-thermal effects between the laser and the material to be destroyed, and on the surface and in the vicinity Region does not produce heat or heat deformation and so on. This "cold working" has a special meaning in laser marking
The above mentioned that "a sufficiently short wavelength can make the material molecules dissociate, resulting in color change is the most perfect effect," said "UV laser" (wavelength 355nm) can achieve the desired effect.
"Hot working" refers to the laser beam with a higher energy density (concentrated energy flow), is irradiated on the surface of the material to be processed, so that the surface of the material absorbs the laser energy, and then generates a thermal excitation process in the irradiation area so that Material surface (or coating) temperature rise, resulting in metamorphosis, melting, ablation, evaporation and so on.
Commonly used lasers for "thermal processing" are lasers with a wavelength of 1064 nm, such as YAG lasers and fiber lasers. With the development of science and technology, the current infrared laser has the flexibility to control a number of laser parameters, by adjusting these parameters, in some materials can play do not lose the effect of UV laser. The other because of fiber lasers compared to traditional lasers, has unparalleled advantages, such as small size, light weight, stability, maintenance-free, the use of air-cooled technology, good beam quality. The following will focus on the 1064nm wavelength fiber laser.
v 1064nm fiber laser parameters to adjust the plastic logo
① pulse width
Pulse width is called the laser pulse width, refers to a beam of light on the surface of the material time, it is a time measurement of parameters. For plastics, it is important that the laser be on the surface for an extended period of time: too short a time, there is not enough energy to react, with only a few light, blistering, light-colored markings, and severe carbonation , Ablation cracks and other phenomena. So choose a right pulse width, in order to make the appropriate changes in the plastic surface, get the effect we want. Whether laser pulse width can be adjusted becomes a very important reference condition for judging whether a laser can handle plastic products well.
Frequency, also known as laser repetition frequency, means how many lasers are emitted per second. Usually laser frequency level, corresponding to the speed of laser scanning speed. However, the higher the frequency, the shorter the distance between each beam of light, the plastic is a poor conductor of heat and the heat dissipation performance is generally not ideal. An excessively high frequency produces heat accumulation, which is not We want, it will make the material and the media around the emergence of "thermal damage", should not mark the place where there will be bubbles, melting and then cold solid, ablation and other phenomena sinking. Therefore, the processing should be based on the corresponding melting point of each plastic is not the same, select the appropriate frequency, to achieve both efficiency and efficiency. For lasers, having enough laser frequency adjustment range will give plastic marking greater potential.
③ beam quality
Beam quality M2 is an important parameter of a laser and is the ratio between the actual beam emitted by the laser and the theoretically calculated beam quality. The closer this ratio is to 1, the better this value. The larger the value, the worse the beam quality is and the most direct The effect is the energy distribution of the laser through the focus, the excellent beam quality will make the laser focus after the focus and uniform, poor beam quality after focusing large and divergent. The less effective M² is, the less available thermal energy is and the extra thermal energy causes the plastic marking to create a "heat-affected zone" that we do not want, making the effect tend to be worse.
④ peak power
Laser peak power refers to a bundle of light can reach the maximum instantaneous power, the higher the peak power, the effective available laser energy is more, the corresponding generated less heat, can make the material is not deformed, not melting Of the state of vaporization or carbonization. The mechanism is somewhat similar to the beam quality.
In summary, the material for the plastic, the processing of optional laser light source a variety of UV, green, infrared light can be competent, and when we decided to choose to use 1064nm infrared laser to do plastic When marking, if the laser can have a pulse width adjustment function, a larger frequency adjustment range, while the beam quality is good enough, the peak power is high enough, it is easier to tune out a satisfactory result.