Home > News > Content

Plastic Laser Welding Process

Shenzhen MG Technology Co.,Ltd | Updated: Apr 25, 2016

1. Laser Wavelength

In metal materials by laser welding technology, generally use the YAG or CO2 laser as a light source, plastic welding is no exception. With the rapid development of semiconductor industry, semiconductor laser as a light source has been applied.

Among the three, because it is easy to obtain higher power, both in the traditional materials processing industry to use more common; and as to the magnitude of the power of a light source laser plastic welding, but of controllability and easy to operate high requirements, so semiconductor laser in plastic welding is also very handy.

Typical CO2, Nd:YAG and semiconductor laser light source wavelength, the maximum power and minimum diameter of focusing parameters are listed below:

CO2 laser: long wavelength of 10.6 microns, a far infrared band, plastic materials generally on the wavelength of absorption is good. The maximum output power of 50kW, the conversion efficiency of about 10%, the minimum focus diameter about 0.2 ~ 0.7mm. When the depth of plastic welding heat effect zone is deep, suitable for the welding of thick plastic material. CO2 laser can't use the optical fiber transmission, only $&* mirror lens is composed of optical system to construct rigid transmission path, thus affecting the operation of the laser head.

Nd:YAG laser: short wavelength of 1.06 microns, a wavelength of near infrared region, the absorption is not easy to be plastic. The maximum output power of 6kW, the conversion efficiency is 3%, the minimum focus diameter of 0.1 ~ 0.5mm. Nd: YAG laser is characterized in that the focus area is small, can be conveniently through optical fiber transmission to construct light path, the laser head to the robot arm, the welding process and CNC precision automatic; on the other hand can better through the upper layer to be welded material, arrived at the under layer to be the materials or intermediate layer welding and be absorbed, so as to realize the welding.

Semiconductor laser wavelength: 0.8 ~ 1 m, the maximum output power of 6kW, the conversion efficiency of 30%, the smallest diameter focusing 0.5mm. Because the output power is small, it is suitable for the precision welding of small plastic devices, which is suitable for the occasions where the laser power is low. Semiconductor laser energy conversion efficiency is high, easy to achieve miniaturization and portability of the laser.

2. Plastic Materials

The plastic that can be welded by the laser is a thermoplastic. In theory, all thermoplastic materials can be welded by laser.

Laser welding technology of plastics to be welded to the requirements of the plastic is: in the heat effect zone materials, the requirements of the laser light absorbent; does not belong to the heat effect zone of the material, the light permeability good, especially in the lap welding of two pieces of thin plastic parts. In general, the absorbent can be added to the heat action zone plastic. Currently able to use a single component of laser welding plastic including:

PMMA poly methyl methacrylate (PMMA), PC plastic, ABS plastic, LDPE (low density polyethylene plastic, HDPE (high density polyethylene plastics, PVC - poly vinyl chloride plastic, nylon 6 - Nylon 6, nylon 66 nylon 66 PS - PS resin, and so on.

All of the plastic parts made of plastic, such as molded plastic products, plastic sheets, films, artificial rubber, fibers and even textiles can be used as the object of welding. Because the laser welding has the advantages that the traditional welding does not have the advantages of small heat effect zone and precise control, the welding can be carried out between the various monomer materials.

3. Absorbent

The application of absorbent is very important in the process of laser welding of plastics. As mentioned earlier, the essence of laser welding of plastics is the heated region to be welded of the plastic melt, then realize the joint natural cooling of plastic parts. To melt the plastic plastic parts need to absorb laser energy enough. Plastic itself to a higher absorption rate of absorption of laser energy nature is best, but the general in the case without the addition of absorbent, plastic absorption of light is not very good, the absorption efficiency is very low, melting efficiency is not ideal.

Usually ideal absorber is carbon black, carbon black can infrared wavelength of the laser energy absorbed completely, so as to greatly improve the plastic heat absorption effect, heat effect zone melted material makes the faster, the better. Some other color dyes can also play the same effect on the absorption of light.

British Institute of welding (TWI The, Welding Institute) to develop a dye transparent to visible light a. This dye absorbent can be transparent plastic weld. Carbon black in the absorption of infrared laser light at the same time, but also absorb visible light wave, it is carbon black looks for causes of black, with carbon black as the absorbent the laser welding seam color become darker, and color of the parent metal. TWI electromagnetic wave transparent to visible light infrared absorption dyes only developed, do not absorb visible light, so the weld is still transparent.

In many cases, plastic welding requirements of finished products beautiful and delicate. Therefore, compared with the black carbon to visible light transparent dye absorber is very popular.

Adding absorbent. The method has 3 kinds: one is directly to be welded infiltration of absorbent material. It should be will percolate through absorbent plastic pieces are placed in the following, and no infiltrating absorbent plastic pieces are placed in the above, let the laser light through; the second is to plastic parts to be welded in the surface layer of absorbent. Only in this way has been infiltrated absorbent part of plastic will become the heat effect zone and melting; three is in two pieces to be welded plastic contact at the spray or printing absorption agent.

4. Other parameters

Different from metal welding, the laser power of plastic laser welding is not as big as possible. The greater the laser power, the greater the heat on the plastic parts, the deeper, will lead to overheating, deformation, or even damage to the material. Laser power should be selected according to the depth of the need to melt.

Plastic laser welding speed is relatively fast, generally get the welding speed of 1mm thick welding seam up to 20m/min; while the high power CO2 laser welding of plastic film, the maximum speed can reach 750m/min.

5. Software

Laser welding system, the role of computer software is general of the laser head trajectory and speed, laser power and other parameters of digital control, in order to improve the processing speed and accuracy, for improving the machining quality, these with traditional laser processing (laser OEM software control did not differ, but because of the special role of absorbents for the laser plastic welding, plastic laser welding control system and processing system and its own characteristics.

Based on the TWI plastic welding process, the ClearWeld Research Institute of the United Kingdom has designed and developed the software to calculate and predict the dosage and usage of absorbent. According to the different material thickness, color, absorption ratio, combined with laser power, light transmission rate and other parameters, before welding by software calculation amount of absorbent and adding method, according to forecast the amount of addition of absorbent.

Provide to the input data of the software include: plastic material characteristics: type, thickness and color; welding data: regional shape complex degree, width, welding speed of welding; laser power, infrared transmittance.

After calculation and selection, the output results of the software include: the type of absorbent, the amount and the requirement of the adding mode, the energy loss of laser light wave in the upper layer of the welding process.

The calculation results of the software are very close to the results of the actual welding. The comparison between the calculated value and the measured value of the heat affected zone (HAZ) after welding is made in Figure 6. The plastic material is PMMA.

It can be seen that the software calculation results are very close to the measured results. Because of the strong regularity of laser welding of plastics, it has good predictability. Therefore, it is very effective and feasible to predict the results by software method.

Home | About Us | Products | News | Exhibition | Contact Us | Feedback | Mobile | XML

TEL:   E-mail:

Copyright © Shenzhen MG Technology Co.,Ltd All rights reserved.