Sep 16, 2020
With the development of lasers and laser processing technology, lasers are increasingly used in synthetic resin materials, including IT, automotive, aerospace, electronics, and medicine.
1.Principle of resin marking and color development
The phenomenon of "reflection", "absorption" and "transmission" occurs when materials are irradiated by laser. The core element of laser marking and laser processing is the absorption of light energy by the material. After the material absorbs the light energy, the chemical bonds on the surface of the material are Destroyed, the processed place shows different physical properties from other places.
a)The surface layer of the multilayer material is peeled off
Material characteristics: resin base, paint surface
Processing features: low average power, small single pulse energy, high frequency, multi-angle filling, high-speed scanning
Recommended laser type: high frequency low power ultraviolet pulse laser
The paint surface of this type of material is generally thin, and the base material is more sensitive to ultraviolet light, so the processing energy should not be too large, otherwise it will damage the base material; multi-angle filling is mainly to ensure uniform and thorough peeling.
b)The surface layer of the homogeneous material is peeled off
Material characteristics: the same physical properties perpendicular to the surface of the material
Processing features: high-frequency fast scanning, direct vaporization of the surface
The difficulty of this type of material processing is to control the peeling depth, the peeling depth must be uniform, and the color of the peeled surface must be uniform. These can be controlled by adjusting the scanning speed and frequency.
Example: peeling of resin surface
c)The surface color of the material
The laser irradiates the resin to color the workpiece itself.
Different resin materials, the principle of the laser to make the color is different, mainly the following methods
(1) Blistering type: Use lower laser energy to cause color change and surface reconstruction through the destruction of molecular structure, and the color of the marking part is slightly raised on the surface of the substrate.
(2) Engraving type: by raising the local temperature above the melting point of the material, melting it, and then solidifying it again, the surface will appear in the form of etching. As shown in Figure 1
(3) Color engraving type: the laser intensity is relatively high, ridged grooves are generated by local evaporation of the surface material, and the carbonization of the material causes the color to change. as shown in picture 2
(4) Color: Use a sufficiently short-wavelength laser to break the molecular chain of the material to change the color. You can also increase the contrast of the mark by adding quantitative additives. As shown in Figure 3
2. The influence of laser on resin
The absorptivity of the material varies with the wavelength. Infrared (1064nm), green light (532nm), and ultraviolet (355nm) are shown in the experimental data of the transmittance of different resin materials. The transmittance of polystyrene is low (that is, the absorptivity is high), and it can perform good marking.
As a new technology that replaces printing and traditional cutting, laser processing technology will be used in more and more fields with its unique advantages and wide practicability in the processing of synthetic resin. In addition, advances in synthetic resin manufacturing processes will accelerate the development of laser processing.