RF welded seams

RF (RF) welding of synthetic textiles is a modern method for joining textile parts without using sewing techniques. It is performed using intense electromagnetic radiation, causing the synthetic fibers of the textiles to melt and bond. Compared to traditional sewing, welding has several advantages, the joint is stronger, there is no risk of the part coming loose if the thread in the seam breaks, and the welded joint is highly water-resistant and can also be used for unique design enhancements of the product. Unfortunately, RF welding can only join certain modern plastics and thermoplastics, so it cannot be used for all types of textiles.

How exactly does high-frequency welding work?

The method known as “RF welding” (“Dielectric Sealing” - dielectric welding) or also “high-frequency welding” is the process of joining materials using electromagnetic energy. Two electrodes create an oscillating electric field, causing the polar molecules in the material to move and rearrange themselves into a position forced by the electromagnetic field. As these molecules move, energy is released in the form of heat. When enough energy is applied, the molecules begin to melt and bond with each other. During this process, no external heat source is applied. However, the process also requires a certain degree of compression and pressure on the specific areas to ensure the weld forms correctly.

What materials can be welded using high-frequency welding?

Some modern thermoplastics present more challenges for a good high-frequency weld than others, and may even require a special process. Regardless of the product you choose, the manufacturer always strives to deliver quality products because poor quality products that don't hold up in extreme conditions in the wild have no chance.

High-frequency welding can be applied to the following materials:

• PET
• PETG
• PVC
• Thermoplastic polyurethanes (TPU)
• Open-cell/macro-molecule polyurethanes
• LDPE / EVA

What factors contribute to the quality of high-frequency welding?

There are numerous factors, each influencing the weld strength and insulation quality to some extent. Factors can include: the arrangement of welding tools, weld size, material thickness, proper operation of the high-frequency welding machine, … These are probably the most important factors in achieving a good weld. The beauty of high-frequency welding lies primarily in the completeness of its weld. When everything is applied and used correctly, the weld is immensely strong.

Every manufacturer also tests with specific tests – for permeability, tensile strength, optical verification, …

Why choose high-frequency welding over other methods?

When it comes to working with modern textile materials, several alternative methods are available specifically for high-frequency welding.

• High-frequency welding versus sewing – Unlike sewing, high-frequency welding provides a much more consistent weld (and thus higher air-tightness) than sewing. Sewing with regular threads is very stressful for them and they may break. High-frequency welding evenly distributes the stress across the entire material, ensuring a much stronger weld and joint durability. Additionally, it prevents any moisture, air, or dirt from getting in (either during the welding process or afterward).
• High-frequency welding versus gluing – In terms of achieving a quality and strong weld, gluing can provide similar results. However, gluing generally takes much longer than high-frequency welding. Moreover, during gluing, toxic solvents and similar substances are often used today. Glued seams are also more prone to failure when the adhesive wears out.
• High-frequency welding versus hot air – A hot air gun applies heat to the outer part of the processed material, partially melting it. This makes the material flow and sticky, so when joined with another or itself, a strong bond forms. Although an effective method, it's limited by thickness. If you use hot air welding on thick materials, it only melts around the edges and not in the center. Additionally, it causes unnecessary burning of the outer layers of the material. High-frequency welding, however, starts heating materials from the center outward, which is the ideal scenario.

What else should I know about high-frequency welding?

Although it might not seem so at first glance, high-frequency welding/dielectric welding/RF welding is a very mature method. It was first used around 1940.

Only plastic fabrics with dipoles can be used here, as only they can be heated with high-frequency welding. The process typically involves pressing on both sides. The frequency is usually 27 120 MHz. However, the weld temperature is not usually directly controlled during production.

High-frequency welding is a method that is fast and relatively easy. It ensures minimal degradation of the corresponding polymer and its advantages include no smoke or flames when welding thick polymers (note: urethanes release toxic cyanide upon heating). The energy requirement is not extreme, and high-frequency welding usually produces welds that are resistant to bacteria, air, and water.