TWI Frequently asked questions
by Felicity Chipperfield
As hot plate welding is a relatively slow process, it is not suited to high volume mass production of small components (for which ultrasonic or friction welding would be preferred). However, its simplicity and ability to weld the majority of thermoplastics make it attractive where time is not such a restriction, and it is widely used in applications where high integrity joints are required, for instance for fluid containment. Examples are automotive header tanks, hydraulic reservoirs, and welding fittings and filler pipes for polyethylene petrol tanks.
The dimensional accuracy and good cosmetic appearance that can be achieved with hot plate welding have made it important in the building industry where it is used in the manufacture of uPVC door and window frames, which are made from extruded sections and welded at each corner.
Hot plate welding is also used for:
- automotive lamp assemblies & battery casings
- domestic appliance components - e.g. washing machine agitators & soap dispensers
- pump bodies
- transport pallets & crates
- HDPE barrels
Another important application of the process is the joining on-site of polyethylene pipes for gas distribution, water mains, sewers and sea outfalls. The high integrity of the joints and the ability to weld pipes of diameters up to 1600mm have made hot plate welding the only suitable process, although for smaller pipes (<500mm diameter) alternatives exist.
