The basic components of an ultrasonic plastics welding system are an electric generator which transforms mains electricity of 50 cycles into a controlled high frequency electrical energy of 20,000 to 40,000 cycles with 200 to 3000 Watts of electrical power available. A transducer converts electrical frequency into mechanical vibration and a booster is used to increase or decrease or simply couple the mechanical vibration to the sonotrode. The sonotrode transmits the vibration to the area being joined. It is usually made from an aluminium alloy or an acoustic titanium material and is tuned to the relevant frequency. The mechanical vibration is then transmitted to the part to be welded with a controlled weld pressure and accurate weld time. The function of the press is to deliver this vibration under consistently rigid and controlled conditions. The jig must support and locate the part or parts to be welded with complete stability.
Methods and techniques for joining plastics, and the quality of the joints have advanced and developed dramatically in recent years. Plastics component manufacturers and parts assembly specialists require highly sophisticated plants to furnish an ever increasing market demand. Because of the inherent complexity of plastics welding, whether it is plastic to plastic or plastic to metal, industry requires expert guidance in order to determine their actual plant.
Driving Force for Development
One of the major instigators for the advancements that have been made, within Europe, in ultrasonics plastics welding is the automotive industry. As plastics have continued to supersede metal, leather and wooden finishes in cars, the assembly and jointing capability demanded has increased enormously. Not only has the automotive industry dictated investment in the continued development of ultrasonics plastics welding techniques but also that the control of these new techniques provides the highest finished quality. Industry has benefited from these developments.
Recent ultrasonic plastics welding machines have a high level of sophistication which allows them not only to be completely automatic but also able to control, adjust and protect themselves. This enables the user to aim at total weld quality control.
Reactive Welding System
The Forward Technology Industry Group's reactive welding system (RWS) ensures that the plastic parts are precisely assembled regardless of their dimensional tolerances. RWS is an operating mode which enables the machine to identify the ultrasonic disconnection time corresponding to a precisely welded part. Once the joint has been correctly welded, the ultrasonics are instantly switched off. Dependent on the joint tolerances, the sonotrode will determine the ultrasonics required to perfect the weld.
The reactive welding system ensures that quality welded joints can be achieved even though the tolerances of the components may vary considerably throughout an entire production programme. This allows all production units real control over their individual welding process and provides much more flexibility with regard to component tolerances, resulting in a more efficient and effective assembly production.