Ultrasonic Plastic Welding

Create clean, strong, and permanent bonds in seconds. Our ultrasonic welding service provides a fast, reliable, and cost-effective method for assembling thermoplastic components without adhesives or fasteners.

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A medical device housing, an application where ultrasonic welding is used to create a permanent seal

The Process: High-Frequency Vibration

Ultrasonic welding is a process that uses high-frequency (typically 20-40 kHz) acoustic vibrations to create a solid-state weld between two plastic parts. The parts are held together under pressure in a custom fixture (nest).

A vibrating tool called a "horn" or "sonotrode" is brought into contact with one of the parts. The intense vibrations are transmitted through the part to the joint interface. This high-frequency energy creates intermolecular friction, which rapidly generates heat and melts the plastic at the joint. Once the plastic has melted, the vibrations stop, the pressure is maintained for a brief period as the material cools and solidifies, and a permanent, often hermetic, weld is formed.

Why Choose Ultrasonic Welding?

Speed and Efficiency

The entire weld cycle is typically completed in less than a second, making it an extremely fast and highly repeatable process ideal for high-volume production.

Clean and Consumable-Free

The process requires no adhesives, solvents, screws, or other consumables. This creates a clean assembly process with no curing time and no foreign materials.

Strong, Hermetic Seals

When designed correctly, an ultrasonic weld creates a very strong molecular bond. It can also be used to create a complete hermetic seal, which is critical for medical devices and waterproof electronics.

Designing for Ultrasonic Welding: The Energy Director

Focusing the Energy

A successful weld requires designing a specific feature at the joint interface called an **Energy Director**. This is typically a small, sharp, triangular ridge molded onto one of the parts. The purpose of the energy director is to concentrate all of the ultrasonic energy into a very small initial contact area. This allows the material to melt very quickly and precisely where it's needed, without heating up the entire part. As the director melts, the molten material flows across the joint surface to create the final weld.

Material Compatibility: The two parts being welded must be made of the same or highly compatible amorphous plastics (like ABS, PC, Acrylic).
Joint Design: A simple butt joint with an energy director is common. Tongue-and-groove joints can be used for added strength and self-alignment.

Ultrasonic Welding FAQ

Which plastics can be ultrasonically welded?

The best materials are amorphous thermoplastics with high stiffness, such as ABS, PC, ASA, and Acrylic. Semi-crystalline plastics like Nylon and PP are much more difficult to weld because their crystalline structure absorbs vibrations rather than transmitting them to the joint.

Can you weld dissimilar plastics together?

Generally, no. For a strong, reliable weld, the two parts must be made of the same material. Welding dissimilar materials is very difficult because they have different melt temperatures and molecular structures, which prevents them from forming a strong bond.

What is ultrasonic staking?

Ultrasonic staking is a related process used to capture or lock another component in place. For example, a plastic boss can be passed through a hole in a PCB. The horn is then used to melt and reform the top of the boss into a rivet-like head, trapping the PCB.