Dielectric welding

RF (radio frequency) welding Utilizes specific bands of radio frequency waves which are directed through specially constructed tooling to form localized melting/joining of certain dielectric thermoplastic materials. Can be used to form hermetic seals. Also known as high frequency or dielectric welding. 

In high-frequency dielectric welding thermoplastic materials are joined by applying simultaneously pressure and alternating high-frequency fields, using electrodes of suitable design and shape. ... 

ISO 472 defines high-frequency welding , dielectric welding and RF welding ... 

Mains-borne Interference. When welding equipment is being used there is a possibility that both fundamental and harmonic currents might flow back into the mains electricity supply however, this can be a more serious problem at the frequencies used for induction heating as distinct from those for dielectric welding. 

Dielectric welding (RF) alternating waves from an electromagnetic generator excite the bipolar molecules of a dielectric material to such an extent that the molecular vibration causes friction between the molecules, which results in the fabric interface melting. In seaming, the fabrics are placed between two electrodes—one live electrode and the other a ground electrode. 

Radio-frequency welding (dielectric welding, high-frequency welding) n. 

Variables in the bonding operation are the frequency generated, dielectric loss of the plastic, the power applied, pressure, and time. The materials most suitable for dielectric welding are those that have strong dipoles. These can often be identified by their high electrical dissipation factors. Materials most conunonly welded by this process include polyvinyl chloride, polyurethane, polyamide, and thermoplastic polyester. Because the field intensity decreases with distance from the source, this process is normally used with thin polymer films. 

Dielectric welding is also commonly used for sealing thin films such as polyvinyl chloride for lawn waste bags, inflatable articles, liners, and clothing. It is used to produce high-volume stationery items such as loose-leaf notebooks and checkbook covers. Because of the cost of the equipment and the nature of the process, industries of major importance for dieleciric welding are the commodity industries. 

Plastic Adhesives Dielectric Welding Induction Bonding Mechanical Fastening Solvent Welding Spin Welding Thermal Welding Ultrasonic Welding... 

Because of the cost of the equipment and the nature of the process, applications for dielectric welding are generally high-volume, commodity-type articles of... 

A typical dielectric welding tool consists of two platens that are electrically connected to a generator that imposes an alternating electric field. The platens are used both as electrodes and apply pressure to the joint area. Various parameters will affect the quality of the dielectric weld. These include the type of fibre in the fabric, its propensity to heat in a dielectric field (called the material s dielectric loss), the thickness of the fabric, and the melt temperature of the fabric. Time, pressure, and field frequency (directly related to temperamre) will also affect the quality of the joint. The frequency of the field being generated can be from the radiofrequency range (13—100 MHz) up to microwave frequency (2—20 GHz). 

For induction welding, the energy source is an electromagnetic field for dielectric welding, the energy source is an electric field of high frequency. 

Radio-frequency or dielectric welding and microwave welding rely on internal heat generation by dielectric hysteresis losses in thermoplastics with dipoles [2,6,8]. As illustrated in Fig. 26.32, dipoles... 

---