RF Welding basics

The process of joining two materials which are placed on the table and under applied pressure and subjection of electro-magnetic waves is referred as RF Welding.

Let us understand characteristics of high frequency radio frequency signals which are helpful for welding two different materials.
• High frequency current flows only in the skin of the conductor unlike conventional line current of value 60 Hz which flows through the entire conductor area.
• The two conductors which are placed in close proximity and when the current is flowed through them then current only concentrates in the surface region of the conductors.

The surface depth depends on material, temperature of the material and frequency of the current. This is referred as skin depth. This concept is useful in RF welding process. High frequency welding process is applied to metals such as copper, steel, aluminum, brass, gold and titanium.

Skin depth = 3160 * ( ρ/(μ * freq))0.5
Where, ρ is resistivity of material

RF Welding process is also used for joining of thermo-plastic materials. In this method, RF energy produces molecular agitation in thermoplastic materials. This will melt the materials; which flows and forms the bond. The typical materials on which this RF welding process is applied are thermoplastic polyurethane,PVDC, PVC, PET, nylon, EVA and other types of resins.

During the welding process, materials are fixed and subjected to pressure using electrodes. H field is produced between them which passes through and fuse the materials. The electrodes are interfaced with higher voltage and higher power supply which is tuned to match with electrical impedance of the weld.

RF Welding ispopular for welding films as well as thin sheets. The thickness range vary from 0.03 to 1.27 mm.

Advantages of RF Welding

Following are the advantages of RF Welding process:

•  Material itself is used as heat source and heat is generated using RF in the region requires to be joined. The other surrounding material is not required to be heated.

•  RF heat can be produced when it is energized and needed/ RF energy can be concentrated to particular region of application and hence it prevents heat degredation.

• The RF Welding process is considered to be clean and do not required other by products such as adhesives and welding materials.

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