Welding is one of the most common ways to join thermoplastic-coated materials used in the technical textile industry. Fabric welding is straightforward, relatively inexpensive, and offers unparalleled flexibility and strength when it comes to joining technical fabrics together. While not all types of fabrics can be easily welded, virtually all thermoplastics exhibit excellent weldability.
The process of thermoplastic welding consists of the same basic elements: heat, pressure, and cooling. How these three elements are combined is controlled by the materials being welded, the welding method, and the speed of the manufacturing process. In addition, textile industrial welding techniques differ in how heat is generated and applied.
In this article, 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 known as 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, most often at 27.12MHz.
HF welding cycles are fast, typically lasting between 2 to 5 seconds, and this thermoplastic welding technique is suitable for joining material from approximately 1/1,000” to 50/1,000” (0.0254mm to 1.27mm) thick. A welding bench holds the fabrics in place while they are being joined. Heat is generated only when the electric field is turned on, reducing any potential heat-induced degradation of the material abutting the weld.
There are a few key advantages to HF welding. Most notably, the fast cycle times reduce load on your equipment and reduce the cost of tooling for this process. Another reason to turn to HF welding is that there is no subsequent drying and hardening of the joined fabrics.
It’s important to be aware that HF welding can heat up humans as well, so the machine operator needs to be protected from the HF field. To operate a high-powered HF welder safely, operators must receive thorough training from experienced in-house personnel. In many cases, manufacturers’ representatives will conduct free training at your work site upon request.
HF welding plates can be engraved, profiled, or embossed for lettering, logos, or decorative effects on the welded items. This process can simultaneously weld and cut a material, too.
- Rapid welding cycles
- Inexpensive tooling
- Clean process
- No subsequent drying/hardening
HOT AIR WELDING
Hot air welders generate the heat required for fabric welding by blowing compressed air across electrical heat elements. The temperature of the resulting hot air can range from 1,000°F to 1,350°F (400°C to 750°C). The hot air is then injected at the welding point, thus melting the surface of the thermoplastic fabric and allowing it to be joined to another thermoplastic sheet. A set of rollers is typically used to apply pressure to the materials to join them at the weld.
Hot air welding is considered to be one of the fastest, most affordable, and simplest techniques for textile industrial welding. It can be performed using hand-held welders, which is important since it means that hot air welders can construct welds with many different shapes including curves. Hot air welding is suitable when the width of the fabric weld needs to change frequently, as well as when repeated starting and stopping is required throughout the fabric welding process. This technique is also good for joining long, continuous thermoplastic fabrics or for welding different materials with the same thicknesss.
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, since the resulting seal is watertight and airtight.
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 subjected to pressure from rollers 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 it can be used to weld very thick thermoplastic-coated materials. It is quiet and doesn’t produce any smoke, in contrast to hot air welding, and hot air welders are available in handheld models. This process is ideal for welding long, continuous thermoplastic fabrics and can be used to fuse previously welded materials to a third fabric layer. HW welders can run welds at speeds ranging from 0.5 – 42 m/min.
What Types of Thermoplastics Can You Weld?
One of the best things about these thermoplastic welding techniques is that they are flexible enough to work with most common industrial textiles. HF, hot air, and HW welding can join thermoplastics such as polypropylene, polyurethane, polyethylene, and polyvinyl chloride (PVC) and PVC-coated fabrics.
Industrial fabric welding can make these materials more resistant to abrasions and give them a longer seam life than other methods of joining. Plus, hot air and HW welds result in watertight and airtight joins with smooth finishes, ensuring that these textile welding techniques are suitable for a wide variety of applications.
Which of these thermoplastic welding methods is right for your needs depends on your intended applications, the materials you are using, and your current manufacturing line’s layout. You will also need to consider your employees’ current skill levels with different welding techniques and the environment in which you will be working.
For more information on welding, keep an eye out for our upcoming Guide to Welding Thermoplastic Textiles, out soon. In the meantime, you can contact us here at Erez to get help with solving your technical textile welding challenges. We have years of experience working with and welding thermoplastics and other industrial textiles and can provide support for all your industrial welding needs.
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