Among the materials used in industrial combinations, the demand for plastics is still increasing; and the superior mechanical and electrical properties of metals also ensure their position in hybrid applications. But the bond between metal and plastic is one of the most difficult physical bonds. Anyone who wears rimless glasses knows how fragile this bond is. The latest research results of the Fraunhofer Institute for Laser Technology (ILT) in Germany show a good way to combine metals and plastics better: using lasers.
At present, the main method of combining metal and plastic is injection molding technology, which uses a special fixture to fix the components during the injection molding process. However, in order to meet the requirements of positioning and high-precision components, this method requires tight tolerances; in addition, depending on the application, this method does not always achieve a high-strength combination. For larger areas, you can use simple gluing, or thread the plastic parts with threads. However, the reliability and robustness of these combination methods are poor.
To overcome these shortcomings, researchers have developed LIFTEC technology (laser induced bonding technology) to improve the bonding between metal and plastic. The laser method is similar to the traditional method. The traditional method heats metal parts by induction or ultrasound to melt the plastic around the metal parts. After cooling, a seam connection is formed between the plastic and the metal. LIFTEC technology is simple and effective, it uses laser to heat metal parts. In the simplest application, LIFTEC technology takes advantage of the fact that all uncolored thermoplastics are transparent or translucent. The laser focuses on the metal parts to be joined after passing through the plastic parts, causing local melting. Processing the metal parts into a shape with grooves or holes before bonding can further enhance the final bonding effect.
The advantage of LIFTEC technology may lie in its flexibility, it can even be applied to heat-resistant materials like Teflon (pictured). This kind of opaque plastic and metal combination method is slightly different from the laser passing through the plastic component and focusing on the metal component to be combined: the laser heats the metal on the side, and the metal is located on the surface of the plastic component, and then the metal component gradually enters the plastic . Most importantly, LIFTEC technology is not limited to metal parts, but can also be used to combine ceramics and plastics.
Compared with the existing technology, the accuracy requirement during the combination process of LIFTEC technology is greatly reduced, so this technology is expected to be widely used in industry. In addition, induction and ultrasonic heating have limitations on the thermal conductivity of the material, which is not required when using laser radiation. Researchers said that LIFTEC technology is expected to show its potential in some areas where existing technologies encounter difficulties.
The LIFTEC technology currently demonstrated uses a low-cost diode laser. Because this technology does not have high requirements on the beam quality of the laser irradiation, the fiber-coupled diode laser can certainly be used in industrial applications of this technology.
In order to further integrate the LIFTEC technology, ILT's renowned engineering-specific technology has also begun to emerge. Researcher Holtkamp said: 'We are working on a machine that meets the requirements of this particular process. Currently we use hydraulic equipment, but for the process, the hydraulic pressure is too high and inaccurate. The new machine will be powered by electricity and can be placed in On the table, this means that the optician can use the instrument in the store to instantly combine the lens and the frame. '
ILT has obtained a patent license for this technology, and some people in the industry have begun to consult the technology. Researchers are currently working on reducing heating time and studying the various binding forces that may be used in industrial applications.