What are the material requirements for plastic laser welding?

Plastics that can be welded by laser are thermoplastics. In theory, all thermoplastics can be broken by laser: Plastic laser welding technologyRequires that the material in the heat effect zone during welding has good absorption of micro-light waves: Materials that are not thermoplastics can be melted by laser, especially when two thin materials are welded by laser, especially when two thin materials are overlapped and welded. Adding absorbent to the plastic can achieve the purpose of thermal efficiency.

Single-component plastic PMMA-polymethyl methacrylate (plexiglass), PC plastic, ABS plastic, LDPE low-density polyethylene plastic, PVC-PVC plastic, nylon 6, nylon 66, PS resin, etc. Such plastic products, such as molded plastics, plastic sheets, films, artificial rubber, fibers, and even textiles can be used as welding objects. Since laser welding has the characteristics of small heat effect zone and high control accuracy that traditional welding does not have, the above-mentioned monomer data can also be welded.

The application of absorbent is an important part of laser plastic welding process. The essence of plastic laser welding is to melt the welding plastic in the heat effect zone and then cool it naturally to complete the connection of plastic parts.

To melt plastic, it is necessary to make the plastic absorb the laser energy to a certain extent. When no absorbent is added to the plastic, the plastic's ability to absorb light waves is not very good, the absorption efficiency is very low, and the melting efficiency is not ideal. Carbon black is an ideal absorbent, which can completely absorb the laser energy in the infrared band, thereby greatly improving the heat absorption effect of the plastic, making the material in the heat effect area melt faster and with better effect.

Carbon black absorbs the laser light waves in the infrared band, and also absorbs the visible light waves, which is why carbon black is black. The color of the laser welding weld becomes darker, and carbon black is used as an absorbent to change the color of the weld. Some dyes of other colors can also play a role in absorbing light waves. TWD is a visible light dye developed by the British Welding Association. Using this dye as an absorbent, ordinary plastic welds can be obtained. This dye only absorbs electromagnetic waves in the infrared band and does not absorb visible light, so the weld looks very bright. In many cases, plastic welding requires products to be beautiful and exquisite, so compared with carbon black, it is very advantageous to use dye absorbers that are transparent to visible light.

Plastic laser weldingUnlike metal welding, the requirement for laser power is not that the larger the better. The greater the laser power after welding, the larger and deeper the heat effect zone of the plastic parts will be, which will cause overheating, deformation and even damage to the data.

The choice of laser power should be selected according to the required depth. The speed of plastic welding equipment is relatively fast. Generally, the welding speed of a 1mm thick weld can reach 20m/min; and when a high-power CO2 laser is used to weld plastic film, the maximum speed can reach 750m/min. In the laser welding system, the role of computer software is also very important.

In addition to digitally controlling the general process parameters such as the motion trajectory, speed, and laser power of the laser head, the software can also achieve the purpose of improving processing speed and accuracy and improving processing quality. At the same time, the welding simulation software can obtain the required absorbent dosage and increase method before welding according to the thickness, color, absorption rate, etc. of different materials, combined with the power of the laser, light wave transmittance and other parameters, and the energy loss of the laser light wave in the upper material layer during welding. The software calculation results are very close to the actual results.

Because plastic laser welding has strong regularity and good predictability, it is very effective and feasible to select software calculation selection method and predict the result.