Spot welding with ultrasonics
Ultrasonic spotwelding is used predominantly when, for instance, flat mouldings without weld preparation (ED) have to be welded (e.g. semi-finished products, thermoformed, blow moulded, extruded and large-surface mouldings).

The tip of the sonotrode penetrates through the upper part into the lower part. Heat is produced on the contract surfaces of the mouldings, as a result of which the material is plasticised and welded. The expelled plastic flows upwards and forms a ring shaped elevation. The back of the lower part remains largely free of marks. The mouldings can be fixed appropriately by hold-downs or clamping devices. The thickness of the moulding adjacent to the sonotrode should not exceed 8 mm. Spot welding can also be carried out with a moveable ultrasonic hand welding apparatus (welding gun).

The principle of ultrasonic spot welding technology refers to two flat plastic parts without tongue or rivet, and the welding head is designed in the shape of a pistol, which welds one end through and fuses to the other plane. The advantage of spot welding technology is that the welding surface does not require any special design. It is mainly used for large flat workpieces, and the welding head has high vibration amplitude. The design of the welding head surface needs to be designed according to actual needs.

Ultrasonic spot welding features

Ultrasonic spot welding can produce strong structural welds with high weld bond strength and short cycle times—typically less than 1 second—no molded joint designs are required, and no consumables such as screws, staples, rivets or adhesives are required. No special fixture is required, one side has a beautiful surface and the other side has a neat protruding ring, can be spot welded with a hand-held welding machine, can seal multi-layer materials, and is suitable for automation.

Ultrasonic spot welding applications

Ultrasonic spot welding is suitable for large parts, thermoplastic extruded or cast panels, thermoplastic corrugated panels and workpieces with complex geometries and difficult to access joint surfaces. It is mainly used for flat molded parts without energy director ribs, such as semi-finished products, thermoforming, blow molding, extrusion molding, and large flat molded parts.

Ultrasonic spot welding is often used to vacuum form parts such as blister packs to provide a tamper-evident seal. Ultrasonic spot welding is typically used in the fixing of wall panels, ventilation pipes, spot welding of heat insulation layers and plastic parts. It can also be used for large plastic parts such as snowplow parts, trailers, furniture, parts that require precision or are difficult to weld with ordinary welders.