Welding methods, advantages and applications of laser welding heads
A laser welding head is a welding head that uses the heat generated by a laser beam to melt plastic contact surfaces and then bond thermoplastic sheets, films or molded parts together. It first appeared in the 1970s, but due to its high cost, it cannot compete with earlier plastic bonding techniques such as vibration welding head welding technology and hot plate welding head welding technology. However, since the mid-1990s, due to the reduction in the cost of equipment required for laser welding head welding technology, the technology has gradually gained widespread popularity.
1. Commonly used welding methods for plastic laser welding head welding
In practical applications, there are several different welding processes for plastic laser welding head welding.
01) Sequential Circumferential Welding
The laser head moves along the contour of the plastic welding layer and melts it, gradually bonding the plastic layers together; or the interlayer moves along a fixed laser beam for welding purposes.
02) Simultaneous welding
The laser beams from the multiple diode lasers are shaped by optical elements and the laser beams are directed to the contour lines along the weld layer, while generating heat at the weld seam such that the entire contour lines are melted and bonded together at the same time.
03) Scan welding
Scan welding is also known as quasi-simultaneous welding. Scanning welding technology combines two welding techniques, sequential girth welding and simultaneous welding. The reflector is used to generate a high-speed laser beam at a speed of 10 meters per second and move along the part to be welded so that the entire welded part gradually heats up and fuses together.
04) Radiation mask welding
The laser beam is positioned through a stencil to melt and bond the plastic, the stencil only exposes small and precise welds on the underlying plastic layer, and the laser beam heats only the parts of the product that are not covered by the mask. Using this technique, high-precision soldering down to 10 microns can be achieved.
2. Advantages of plastic laser welding heads
The advantages of laser welding head applied to the welding of plastic parts include: precise and firm welding, airtight and watertight seal, less resin degradation, less debris generated during welding, and the surface of the product can be tightly connected around the weld. Laser welding has no residue. Advantages, more suitable for medical products and electronic sensors controlled by the State Food and Drug Administration.
Easy to control, can weld workpieces of small size or complex external structure. Because the laser is easy to be controlled by computer software, the output of the fiber laser can flexibly reach every minute part of the part, and laser welding can be used to weld areas that are difficult to reach by other welding methods, and can weld products with complex shapes and even three-dimensional geometric shapes.
Compared with other welding methods, laser welding head welding greatly reduces the vibration stress and thermal stress of the product. This means that components inside a product or device age at a slower rate and can be applied to products that are prone to damage. Many different materials can be welded. For example, polycarbonate and glass fiber reinforced black polybutylene terephthalate via a near-infrared laser can be joined together, whereas other welding methods simply cannot join two polymers whose structure, softening point and reinforcement are so different thing.
3. Plastic laser welding head welding application
Laser head welding is a vibration-free welding technique, so it is especially suitable for machining precision electronic components such as mice, mobile phones and connectors, as well as complex components that need to be welded in a cleaner way, such as plastic product boards containing circuits, medical equipment, etc.
01) In the automotive industry
In the automotive industry, laser welding head welding plastic technology can be used to manufacture many automotive parts such as automatic door locks, keyless entry and exit devices, fuel nozzles, gear shifters, engine sensors, cab frames, hydraulic tanks, filter frames, front Lamps and other automotive applications, including the manufacture of intake manifolds and auxiliary water pumps.
02) Medical field
In the medical field, laser welding head welding technology can be used to manufacture liquid storage tanks, liquid filtration equipment, hose connectors, ostomy bags, hearing aids, implants, microfluidic devices for analysis, etc. The laser head can also weld plastic films together. It moves along the edges of the film and forms a sealed structure for packaging by gluing. The operation process can be completed very quickly.
03) Application of new material activated laser welding head welding
Studies have shown that the transmittance of polymers to near-infrared lasers is at least 20-50%, and only laser welding technology can achieve excellent welding results. Most natural colored plastics and many colored translucent plastics can meet light transmittance requirements. In other words, laser welding can be applied to most plastics.
On the other hand, the absorption rate of the plastic to the near-infrared laser is also an important factor affecting the welding effect of the laser welding head. Most thermoplastics can greatly improve their laser absorptivity by adding an appropriate amount of carbon black, but for some materials, the application of laser welding head welding still has certain limitations. For example, if both materials are transparent or white, they can transmit near-infrared laser light, resulting in extremely low absorption of near-infrared laser light by the material. In this case, laser welding cannot be used.
Another typical example is PPS and LCP plastics. The transmittance of both materials to near-infrared laser light is very low. If both materials are filled with carbon black at the same time, laser welding cannot be performed because the laser cannot penetrate. Additionally, many mineral filler compounds are not suitable for laser head welding. In order to overcome these limitations of laser welding head welding, some plastic manufacturers are actively developing new materials, which help to improve the laser transmittance and absorption rate, and have made gratifying progress, bringing broader application prospects for laser welding heads .
