As a renewable non-metallic material with excellent performance, plastic is increasingly widely used in the design and manufacture of parts in various industries. Traditional metal parts are increasingly being replaced by plastic parts with the same working performance. In the automotive, aerospace, and transportation industries, the demand for lightweight is particularly strong, which has also given birth to various plastic products to replace metal. At the same time, higher requirements are placed on the connection technology and quality of plastic parts.
Plastic welding has always been the most effective way to permanently connect plastic parts. The traditional plastic welding processes are mostly ultrasonic welding, vibration friction welding, hot plate welding, etc. The pain point is that the welding method has certain limitations, such as poor welding quality , Low production efficiency, difficulty in welding complex shapes, serious environmental pollution, short life span, and follow-up treatment. These problems have always plagued people in the plastics industry.
Nowadays, with the continuous innovation of laser technology and the continuous development of composite materials, the emergence of plastic laser welding has just made up for this defect, and will gradually replace the traditional plastic connection method with its obvious advantages.
Compared with traditional hot plate welding, friction welding, ultrasonic welding and other technologies, the advantages of laser welding technology are as follows:
1 Local heating, non-contact welding. No abrasion of processing equipment, no damage to the substrate, and cost reduction;
2 High processing precision and good quality;
3 The welding process is clean, pollution-free, and environmentally friendly, especially suitable for the medical industry with high hygiene requirements;
4 Solve the problem of product depression after welding, and the appearance of the product after welding is excellent;
5 Fast welding speed, high degree of automation and high production efficiency;
6 The laser transmission is controllable, easy to calculate and control, and can be flexibly applied to small parts to reach areas that cannot be welded by other welding methods;
7 There are no restrictions on shape and size, greatly improving the design freedom of product form and appearance;
8 The laser heat source has high energy density, which can optimize the temperature of the plastic joint surface and ensure the high speed and high precision of the welding process;
9 The scope of influence is small, the vibration stress and thermal stress generated are small, the product stability is high, the internal structure aging speed is slower, and the service life is long.
It is precisely based on the above advantages that plastic laser welding technology has obvious advantages and is widely used in some occasions with high welding efficiency and strict appearance requirements, such as the automotive industry, medical industry, home appliance industry, electronic appliances, and lighting industries. Wait.
Principle of plastic laser welding
Two or more (same or different) plastic parts, through the laser beam penetrates the upper layer of light-transmitting material, and transmits to the lower layer of light-absorbing material, the two parts are heated and expanded, and the laser energy is absorbed by the lower layer of light-absorbing parts and converted into heat energy, melting it The surface, through heat conduction, transfers heat energy to the upper layer of light-transmitting parts, and under the synergistic action of the internal expansion force and the external clamp pressure, it is fully fused to complete the firm welding of the upper and lower parts. The relative movement of the laser beam and the welded part forms a weld. The welding principle is shown in the figure below:
Two typical plastic laser welding structures
According to different welding process requirements, welded structure design can be divided into two categories: Collapse and No Collapse.
For large-deformed injection molded parts, it is generally suitable for melt-down structures, which can compensate for the influence of product deformation on the welding effect. There are strict requirements on the appearance and size of the product welding, and the products with high requirements for injection accuracy are generally suitable for non-melting structures.
Process method of plastic laser welding
The application method of plastic laser welding is different from that of metal welding. According to different welding tasks and requirements, laser welding methods generally include contour welding, quasi-synchronous welding, synchronous welding, mask welding, reflection welding and diffraction welding. United Win Laser can provide corresponding welding schemes according to product characteristics. The schematic diagram is as follows:
Material factors affecting plastic laser welding
Plastic laser welding requires a combination of light-transmitting and light-absorbing materials. Transparent + black is the most common and excellent combination of plastic laser welding colors.
Ordinary black plastics are generally black by adding carbon black. Because carbon black has very good light absorption, it cannot form transmission welding, so traditional ordinary black + black cannot be welded. If the device needs to be designed to be completely black for confidentiality reasons, the upper cover can be made of infrared transparent black plastic (such as BASF’s Ultramid A3WG6 LT (PA66) black nylon plastic), and the lower shell can be made of carbon black plastic to achieve a black appearance under the eyes. Using laser welding technology. The white plastic will reflect most of the laser, so white + white welding is more difficult.
Generally, it is necessary to ensure that the transmittance of the upper layer material in the laser wave band is greater than 20%. Too low light transmission effect will cause the upper layer material to overheat and decompose during the welding process.United Win Laser has been deeply involved in the field of plastic laser welding for many years, and has now developed professional measuring equipment that can complete the light transmittance test of the material.
Finally, the galvo scanner system is the key part to the laser welding system. Sino-Galvo Tech. is the leading galvanometer scanner manufacturer. The laser welding machine equiped with our scanner system can reach the heighest precision leavel. Welcome to contact us for further information.
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