Sonic Welding

Plastic injection mouldings often need to be machined or assembled with other components to arrive at the final product. There are several methods of joining plastic available but sonic welding provides a quick, clean and efficient method of welding plastic parts together with a strong and permanent bond. There are a number of different friction welding methods: Ultrasonic welding, Vibration welding and Spin welding. All these methods work on the same simple principle of creating friction to create heat to melt the plastic at the joint.

Ultrasonic Welding is the most popular method and uses ultrasonic energy to create surface and intermolecular friction thus generating heat and in turn forming a weld. Ultrasonic welding is suitable for most thermoplastics. Amorphous polymers are generally ideally suited, semi-crystalline polymers, on the other hand, are generally more difficult to weld ultrasonically.

The suitability of a thermoplastic for ultrasonic welding depends on its ability to transmit high frequency vibration. This means that rigid materials are better than flexible ones. Melting behaviour is also important. Materials that melt over a broad temperature range and solidify gradually work best. The table shows the quality of weld to be expected when joining a particular thermoplastic to itself under optimum conditions. A near-field weld is one where the joint interface is within about 6mm of a welding horn tip contact point; anything else is far-field. Far-field welding is much less effective because of energy losses within the material.

The table below shows the ease of welding for different materials

Material

Ease of Welding

Near-Field

Far-Field

ABS

Excellent

Good

Acetal

Good

Fair

Acrylic

Good

Good to Fair

Fluoropolymers

Poor

Ineffective

PC/ABS

Excellent to good

Good

Polyamide (Nylon)

Good

Fair

Polycarbonate

Good

Good

Polyester Thermoplastic

Good

Fair

Polyethylene

Fair to Poor

Poor

Polypropylene

Fair

Poor

Polystyrene(General Purpose)

Excellent

Excellent

Polystyrene (High Impact)

Good

Good to Fair

Polysulphone

Good

Fair

PPO

Good

Good

PPS

Good

Fair

Rigid PVC

Fair to Poor

Poor

At Rutland Plastics, we have the expertise, flexibility and facilities to add the finishing touches required. Sonic welding is just one of the additional services we offer. We are also able to provide machining, gluing and multi-component assembly in addition to our full range of plastic injection moulding services.

Free design guide

Rutland Plastics has produced a free Design Guide to help you with all aspects of designing for plastic injection moulding.
Download free guide

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We can provide advice and quotes on anything from a simple sketch to a 3D computer model. Most drawing formats can be handled although we find STEP, Parasolid and DXF translate most successfully.

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