The hottest laser welding polypropylene and polyca

Laser welding polypropylene and polycarbonate

Plastic laser technology is more and more used in the production of automotive front and tail lamps. Radiation technology is specially used in laser plastic welding. The main features of this technology include: combining a material that can clearly distinguish from the host and can pass through the wavelength of the laser beam with an absorbent material. The laser beam is focused on the absorbent fitting below through the penetrable material, which melts the surface of the workpiece below. Due to heat conduction, the upper parts also absorb heat, so the connection between materials is formed. The weld is welded by the relative motion between the laser beam and the workpiece. In this way, the pressure used in the welding process ensures better hot contact between fittings, which is very important for achieving high weld strength

lq hybrid welding system in the processing process

laser and radiation heater become one

this technology uses both laser radiation (for primary radiation) and radiation heating gas heat source (for secondary radiation) as the energy source of the welding process (Figure). In contrast to the laser beam, the infrared wavelength spectrum released by the radiation heater used here is quite wide. As a result, when two kinds of radiation sources are focused on the same weld, the focus diameter of radiant heat is much larger than that of laser beam. In this way, each weld point is heated by a radiant heater before and after laser irradiation. However, the key reason for the additional use of radiant heaters in laser welding is the absorption characteristics of the heaters. Unlike laser, when the parts to be welded are exposed to radiant heat, the transparent parts on them are also heated because they partially absorb infrared radiation. At the same time, the radiant heat is absorbed by the opaque parts

for the welding process, there are two decisive advantages of directly heating transparent fittings by radiant heat. First, the above components have been preheated when the two accessories receive laser radiation. Therefore, the heat flow needed to melt the material to form the weld for the transfer from the lower part to the upper part is reduced. Secondly, as the temperature rises, the hardness of the material decreases, which increases the possibility of bridging the small irregularities produced by the injection molding process. In this process, the main reason is that the transparent parts lose their hardness, which makes it easier to match the geometric contour of the parts below

application of composite welding technology

an inevitable application field of composite laser welding technology is the waterproof sealing welding of new automobile headlights. The traditional connection methods in this field are adhesive or vibration welding, which often show many shortcomings. For example, joints are always laminated to cover unsightly joints. Figure 1 shows the automobile tail lamp connected by the composite laser welding technology

Figure 1 Application examples of automobile tail lamps (lamp holder: ABS, shell: PMMA)

lamp holder is composed of acrylonitrile butadiene styrene (ABS) resin with black, gray or red pigments added. Polymethylmethacrylate, which is not filled and added with red pigment, is used to make a transparent shell. The total weld length is about 1000 mm. These taillights show very good weld quality and highly uniform mechanical properties. In addition, during the automatic shutdown and melting of (3) preset test times for the entire weld length, no bubbles were formed (Fig. 2)

Figure 2 Flawless welding

the processing speed of composite laser welding is five times that of traditional laser welding, and can provide higher weld strength. Regardless of the coloring of absorbent accessories, the above lamps can be welded in only 30 seconds

meanwhile, laser welding has become a recognized connection technology for the production of automotive tail lamps. However, for the front lamp, this new processing method has not played its maximum potential, because there is also a problem of material combination. Most front lamps are made of polypropylene lamp holder and polycarbonate shell. Due to the high chemical incompatibility between the two, such a material combination cannot be connected by any welding process. For this reason, a very special adhesive has been used to connect the polycarbonate shell of the front lamp with the lamp holder so far in order to provide various equipment information at the same time. However, this method also has disadvantages, such as long cycle time, poor connection reliability, and environmental compatibility of adhesives. In fact, the adhesive connection has long become a weak link in the front lamp system. If a leak occurs, the entire front lamp unit needs to be replaced

welding of incompatible materials

the lamp holder made of polyfort LH 400 material can now be connected to the PC shell by laser welding process

the expected good connection performance was confirmed by a large number of laser welding and weld tests of various material samples (Fig. 3). These results confirm the unique high strength and permanent connection characteristics of laser welding process. Moreover, from the perspective of process value, especially from the perspective of cycle time, no limitations have been established in the testing process. With the combination of polyfort LH 400 material and composite laser welding technology, the adhesive connection method can no longer be used. This welding technology can bring a lasting seal to the front lamp. Because the weld shows excellent optical characteristics, it can be used as a design element of a new generation of front lamps

Figure 3 Welding example of polypropylene (grade: polyfort lh400) and polycarbonate

since polyfort lh400 can also be connected with PMMA, this material is not only suitable for front lamps, but also for tail lamps, or a material for lamp holders in the electrical market. (end)