HF Welding and sealing uses this property of plastics

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There are some plastics with polar molecules like polyamides, acetates and PVC, which can be heated using high frequency electromagnetic waves. HF Welding and sealing uses this property of plastics to soften them for fusing. Let's see how High Frequency Welding and sealing work.

The process of heating can be localized and made continuous. This process is also called high frequency or dielectric sealing. In this article, we'll look at the principles of HF welding, the common methods of implementation, and the benefits of using HF welding in real life scenarios.

High frequency welding, often referred to as HF welding in short, is a very organized technology that has been widely used for over 60 years. Commonly used materials for HF welding are polyurethane and PVC. However, other polymers like EVA, PET, Nylon, and a few ABS plastics can also be welded using this process.

HF energy used in the process has the ability to excite the polar molecules present in a few kinds of plastics, and as we all know, heat is created when molecules move faster. When these molecules are excited, they start moving faster thus giving rise to heat, this heat energy in turn melts the plastics and joins them together.

The two parts of the material that are to be welded are kept on a table press that applies pressure to the surface area of the materials. The welding process is directed by dies, when the table press comes together, radio frequency waves are sent through the small area between the table and die where the sealing happens. The radio frequency (normally 27.12 MHz) excites the molecules to move around and get hot. The application of heat and pressure thus welds the pieces in the shape of the die.

The reason for the presence of a buffer is to facilitate usage of more HF energy for welding. When the welding process is in progress, the plastic is melted for decreasing the thickness. The HF energy continues to excite the molecules and like any other electrical field, it looks for the easiest way to complete the circuit easily.

In the absence of a buffer, once the plastic becomes thin enough, the HF energy is likely to create a hole in the plastic. When a buffer is used, it provides electrical resistance to the HF Welding Machine , thus diffusing it all through the surface of the die.

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