Heated Tool Welding of plastics

Heated tool welding is one of the simplest and most direct plastics welding process. To make a weld a heated tool is brought into contact with the parts to create a zone of melted polymer. A weld is created by fusing the melted zones together under pressure. The process is simple enough to be used for applications in the field such as joining gas distribution pipe and adaptable enough to be used for complex part geometries like front seat consoles in the automotive industry. It can be used successfully with both rigid engineering thermoplastics like polycarbonate and nylon and soft polyolefins like LLDPE.

Unlike some other welding techniques, hot tool welding can make good welds with filled polymers providing the type of filler material and filler levels that allow the polymer to interdiffuse on forging. Weld times vary with the volume of polymer to be fused and the thermal conductivity of the substrate, but they normally fall in the range from 5 to 60 seconds. The weld times for film substrates are usually much shorter -- often fractions of a second. The heated tool process is also capable of welding dissimilar but compatible thermoplastics with the use of two platens to compensate for different polymer melting or softening points. Tool temperature and heating time must be carefully controlled to get high strength welds.

Heated tool welding is also used for welding thin polymer sheets and films. In this situation, it is often referred to as heat sealing. The process, which can be as simple as contacting a heated wheel or bar with a pair of films to create a seal, is commonly used in food packaging where complex multilayer barrier films can be sealed with a heated tool and a properly selected low melting point seal layer. Very high line speeds can be achieved. This process can also be used to seal other types of consumer packaging and liquid containment bladders.

The staff at EWI has more than 20 years experience in polymer welding including joint design, tool design and process parameter determination.

Contact EWI now to learn how we can help develop, optimize, and troubleshoot heated tool welding processes for you.

• Ultrasonic welding of platics
• Laser (IR) welding of polymers
• Other plastics welding capabilities