high speed and pressed against the stationary component. The rotational friction between the two components generates heat. Once the joining surfaces reach a semi-molten state, the spinning component is stopped abruptly. Force on the two components is maintained until the weld joint cools and re-solidifies. This is a common way of producing low- and medium-duty plastic wheels, e.g., for toys, shopping carts, recycling bins, etc. This process is also used to weld various port openings into automotive under hood components. Laser welding This technique requires one part to be transmissive to a laser beam and either the other part absorptive or a coating at the interface to be absorptive to the beam. The two parts are put under pressure while the laser beam moves along the joining line. The beam passes through the first part and is absorbed by the other one or the coating to generate enough heat to soften the interface creating a permanent weld. Semiconductor diode lasers are typically used in plastic welding. Wavelengths in the range of 808 nm to 980 nm can be used to join various plastic material combinations. Power levels from less than 1W to 100W are needed depending on the materials, thickness and desired process speed. Diode laser systems have the following advantages in joining of plastic materials: Cleaner than adhesive bonding No micro-nozzles to get clogged No liquid or fumes to affect surface finish No consumables Higher throughput Can access work-piece in challenging geometry High level of process control Requirements for high strength joints include adequate transmission through upper layer, absorption by lower layer, materials compatibility (wetting), good joint design (clamping pressure, joint area), and lower power density. Some materials that can be joined include polypropylene, polycarbonate, acrylic, nylon, and ABS. Specific applications include sealing, welding, or joining of: catheter bags, medical containers, automobile remote control keys, heart pacemaker casings, syringe tamper evident joints, headlight or tail-light assemblies, pump housings, and cellular phone parts. Transparent laser plastic welding New fiber laser technology allows for the output of longer laser wavelengths, with the best results typically around 2,000 nm, significantly longer than the average 808 nm to 1064 nm diode laser used for traditional laser plastic welding. Because these longer wavelengths are more readily absorbed by thermoplastics than the infrared radiation of traditional plastic welding, it is possible to weld two clear polymers without any colorants or absorbing additives. Common applications will