2um fiber laser for plastic welding

As a polymer material, plastic has been widely used in various industrial fields, and in now days consumption of plastic has even exceeded metal materials such as steel.

Plastic with resin as the main ingredient, it can be divided into thermoplastic and thermosetting plastics according to the molding method. Thermoplastics would become softened when being heated and solidified when being cooled, and the process can be repeated. Typical materials include general plastics, such as polyethylene (PE), polyvinyl chloride (PVC), polypropylene (PP), polystyrene (PS), acrylonitrile-butadiene-styrene (ABS), polymethyl methacrylate (PMMA);Engineering plastics, such as Nylon, polycarbonate (PC), polyurethane (PU), polytetrafluoroethylene (teflon, PTFE), polyethylene terephthalate (PET), etc. Special plastics, such as "medical polymer" class ones for "synthetic heart valve", "artificial joint" and so on. Thermosetting plastics would become softened after being preliminary heated, and then be solidified once reaching a certain temperature, the process is irreversible and cannot be repeated. Typical materials include phenolic resin (PF), epoxy resin (EP), amino resin, unsaturated polyester resin (UP), etc.

After plastic being molded, there will be a secondary processing, most importantly, is making plastic parts jointed according to different requirements. In general, plastic jointing methods include glue bonding, ultrasonic welding, friction welding, heat fusion welding, and laser welding etc. Among them, laser welding as a new method, which has been more and more commonly used. For global market, LPKF, Leister and Branson are the representatives. And for Chinese domestic market, Han’s Laser, HZ-Technology and SPK Laser are the representatives.

Most of the current laser plastic welding is for colored plastics, or adding light absorption solder for auxiliary purpose. These plastics are widely used in industries such as automotive electronics or mobile phones. For some specific fields, such as biomedical as well as the LED boxes, and other fields, there is great demand for transparent plastic or it is not allowed to use the light absorption solder, such as polymethyl methacrylate (PMMA), polycarbonate (PC) and acrylonitrile - butadiene - styrene (ABS), cyclic olefin copolymer (COC), and other materials. These transparent plastics are difficult to use traditional laser welding due to their extremely low absorption rate of visible or near-infrared light, but these materials have a strong absorption rate for 2 um wavelength IR laser (see figure below).

 

The 2 um fiber laser Powerwave2000 is developed by NPI Lasers for transparent plastic welding applications. The laser adopts all-fiber structure, the output power is up to 80W tunable, laser is air cooled, with 3m single-mode fiber, beam is collimated with 5mm spot size.

 

We used Powerwave2000 to weld commonly used PMMA materials and PP materials. After laser being focused by lens, we achieved welding seam as narrow as 100um for PMMA plastics with thickness of 1mm without using light absorbing additives.

 

NPI laser's own welding experiment platform

 

2 um laser welding 1 mm thick PMMA material 

 

Weld width：102um（measured under CCD）