Welding is a widely used form of material joining thermoplastic-coated materials coated used in the technical textile industry. Virtually all thermoplastics exhibit excellent weldability.
The process of thermoplastic welding consists of the same basic elements: heat, pressure, and cooling. These three elements are controlled based on the materials being welded, the welding method, and the speed of the manufacturing process. What defines most welding techniques is how the heat is generated and applied. We’ll take a look at three of the most common types of thermoplastic welding: High Frequency (HF), Hot Air, and Hot Wedge (HW).
High Frequency (HF) Welding
HF welding, also radio frequency (RF) or dielectric welding, fuses materials together by applying a rapidly alternating electric field to the joint area. The electromagnetic field is normally applied between two metal bars often at 27.12MHz.
RH typically has weld cycle times from 2 to 5 seconds and can handle material from approximately 1/1,000” to 50/1,000” (0.0254mm to 1.27mm) thick. A welding bench holds the material in place. Heat is generated only when the field is turned on, reducing heat-degradation of the material abutting the weld.
Be aware that HF can heat up humans as well, and the machine operator needs to be protected from the HF field. To operate high-powered HF welders safely, operators must receive thorough training from experienced in-house personnel or manufacturers’ representatives, who will often conduct free training at your site.
HF welding plates can be engraved, profiled, or embossed for lettering, logos, or decorative effects on the welded items. The process can simultaneously weld and cut a material too.
Hot Air Welding
Hot air welders generate the heat required for welding by blowing compressed air across electrical heat elements. The temperature can range from 1000°F to 1,350°F (400°C to 750°C). The resulting hot air is injected at the welding point thus melting the surface of the thermoplastic and allowing a weld to develop.
Hot air welding can also be done by hand-held welders. Because of this, hot air welders can construct welds with many different shapes, including curves. It is ideal to use when the weld width needs to change often or when repeated starting and stopping is required throughout the welding process. Hot air plastic welding is generally used on thermoplastic materials that have a thickness of 1/16 (mm) of an inch or more. Hot air welding is excellent for the manufacturing of tubes and boat collars.
Hot Wedge (HW) Welding
Hot wedge welding uses a heated metal wedge precisely positioned at the weld point to provide the required heat. Two sheets of fabric or film are pulled across the heated wedge, then subject to pressure to form the weld. The highly controlled temperature of the wedge can range from 700F to 920F (370C to 490C). The advantage of HW welding is that is can be used to weld very thick material. It is also noiseless and smokeless (unlike hot air) and is also available in handheld models. HW welders can run welds at speeds ranging from 0.5 – 42 m/min.
Nearly all thermoplastic coated fabrics can be welded using any of the above methods. Which one is right for your needs depends on your applications, the materials you are using, and your current manufacturing line’s layout. Your employees’ current skill levels and work environment may be influential as well. For more information on welding, keep an eye out for our upcoming new Guide to Welding Thermoplastic Textiles, out soon. In the meantime, feel free to reach out to Erez for help deciding how best to solve your technical textile welding challenges.