Radio frequency welding of plastics

After a brief reference to the welding of thermoplastic materials by the heated tool and hot gas methods, the advantages of the radio frequency process are explained. It is shown that thermal conduction of the welding electrodes profoundly modifies the power requirements from the associated radio frequency generator when material thickness is small. The influence of frequency, voltage and variations in physical constants with changing temperature are studied whereby the specification for a suitable radio frequency generator for the work in view may be determined. The latter part of the paper deals with the problem of designing radio frequency generator circuits to meet pre-selected load requirements. Typical oscillator circuits are discussed and analysed in some detail. The paper concludes with a review of the present and future trends of radio frequency welding technique.