technology sharing

Plastic is a renewable non-metallic material with excellent performance. As the second largest material system after metal, plastic has huge applications in the automotive, aerospace, transportation, medical treatment, electronic products and other industries, and the demand for lightweight is especially strong.
With the development of laser industry and the reduction of laser cost, laser plastic welding is gradually replacing the traditional welding method. Laser welding technology uses the heat generated by the laser beam to melt the plastic contact surface, and then bond the thermoplastic sheets, films or molded parts together. Compared with traditional plastic welding, laser plastic welding has the following unique advantages:
1. Laser plastic welding belongs to non-contact welding, which has no physical contact or chemical reaction with the welding workpiece, and can be operated in the industrial environment. The welding process is clean and pollution-free, suitable for health and safe medical and food industry.
2. Laser can be regulated by beam shaping beam size and change shape, easy to control the size of the thermal influence area and bonding area, with high degree of freedom and good flexibility, and no limit on the size and shape of welding parts, can realize 2 d and 3 d welding, provides a variety of customized services.
3. Laser plastic welding has a fast welding speed, high weld strength, no flying edge, no residue, and can ensure the good appearance of the welding area.
4. Laser plastic welding parts are precise and firm, airtight, not leaky, can greatly reduce thermal stress and vibration stress, suitable for welding precision electronic components and vulnerable devices.

Principle of plastic laser welding

The most commonly used form of laser welding is known as "laser transmission welding". In the laser welding process of thermoplastic, the two plastic parts to be welded are first closely fitted through mechanical fixtures. Then, after the laser penetrates the upper workpiece, the energy is absorbed by the surface of the lower workpiece and makes it melt, and then the heat melts the upper material through the way of heat conduction. During welding, the local heat causes the material to expand and create an internal welding pressure, which and the pressure applied by the external mechanical fixture ensures the formation of a firm and stable weld. Almost all thermoplastic and thermoplastic elastomers can be laser welded, including glass fiber reinforced plastic, and the weld strength is usually higher or stronger than the strength of the parent material body.
The closer the compatibility, fusion temperature and matching of plastic laser welding are, the better its effect is. The application mode of plastic laser welding is different from metal welding, including sequential circular welding, quasi-synchronous welding, synchronous welding and irradiation mask welding. The following is a brief introduction to these welding methods:
Profile welding
The laser moves and melts the outline of the plastic welding layer, gradually bonding the plastic layer together, or moving the interlayer along the fixed laser beam for the purpose of welding.
In practical application, contour welding has high quality requirements for injection workpiece, especially for the application of complex welding wire such as oil and gas separator. Contour welding can achieve a certain melting depth in the process of plastic laser welding, but the melting depth is very small and uncontrollable, which requires that the deformation of injection molding parts can not be too large.
Synchronous welding
A laser beam from multiple diode lasers, the laser beam is led to the contour along the welding layer while generating heat at the weld so that the entire contour melts and bonds together at the same time. Synchronous welding is mainly used in the automotive headlights and medical industry. Synchronous welding is a multi-beam, after optical shaping of the welding trajectory of the spot, which is characterized by reducing the internal stress. Because the requirements are relatively high, the whole price is also relatively high, so it is very widely used in the medical treatment.
Scanning welding
Scanning welding is also known as quasi-synchronous welding. Scanning welding technology combines the above two welding technologies of sequential weekly wire welding and synchronous welding. The mirror is used to generate a high-speed laser beam at a speed of 10 m / s, moving along the site to be welded, so that the whole weld will gradually heat up and fuse together. Quasi-synchronous welding is the most widely used, in the auto parts industry, it is through the XY high frequency lens inside, its core is the control of the collapse of plastic welding of two materials. Contour welding will produce a large internal stress, which will affect the sealing of the object. Quasi-synchronization is a high-speed scan, and with the current control, so it can effectively eliminate the internal stress.
Rolling pressure welding
Rolling welding is an innovative laser plastic welding process, which comes in many different forms. There are two main forms of rolling welding:
The first is Gobo ball welding, which has an air cushion glass ball at the end of the laser lens, which can both focus the laser and clamp the plastic parts. During the welding process, the Globo camera is driven by a moving platform to roll along the welding line, and the whole process is as simple as writing with a ballpoint pen. Globo welding process does not need complex upper clamps, only need to make a bottom mold support product. Globo ball welding process also has a variant Roller drum welding process, the difference is to change the glass ball at the end of the lens into a cylindrical glass barrel to get a wide laser line segment, Roller drum welding is suitable for a wide welding.
The second is the TwinWeld welding process, a plastic laser welding process fitted with a metal pressure wheel at the end of the lens, where the pressure wheel presses on the edge of the welding line. The advantage of this plastic laser welding process is that the metal pressure wheel will not produce wear, which is conducive to large-scale production. However, the pressure of the pressure wheel acts on the edge of the welding line, which is easy to produce the torque and form various welding defects. At the same time, because the lens structure is relatively complex, causing some difficulties for welding programming.

Radiation mask welding

 automotive industry 


 medical apparatus and instruments 


 CE(Consumer Electronics)