Ultrasonic welding

ULTRASONIC WELDING:

Ultrasonic welding is an industrial process whereby high-frequency ultrasonic acoustic vibrations are locally applied to workpieces being held together under pressure to create a solid-state weld.

Components of an ultrasonic-welding machine for making lap welds
Fig. 1 Components of an ultrasonic welding machine for making lap welds

The oscillation frequency generally ranges from 10 to 75 kHz, then also a lower or higher frequency can be employed for plastics, metals, and also especially for joining dissimilar materials.

The ultrasonic-welding process is versatile and reliable.

In most of the variety of metallic and nonmetallic materials, including dissimilar metals this process is used.

For the purpose to bind the materials together, there is not much need of connective bolts, nails, soldering materials, or adhesives in the ultrasonic welding.

It is used mostly for joining of plastics, for packaging with foils, and for the lap
welding of sheet, foil, and thin wire.

For the efficient operation, proper coupling between the transducer and the tip is needed.

When it gets connected to metals, a notable characteristic of this method is that the temperature stays well below the melting point of the involved materials.

So there is need to prevent any unwanted properties which may get created from high temperature exposure of the materials.

PROCESS OF ULTRASONIC WELDING:

Ultrasonic welding equipment can be easily customized to fit the exact specifications of the parts being welded.

The parts are connected between a fixed shaped nest (anvil) and a sonotrode (horn) and they both are connected to a transducer.

And then there is ~20 kHz low-amplitude acoustic vibration which gets emitted.

In ultrasonic welding of thermoplastics, the 15 kHz, 20 kHz, 30 kHz, 35 kHz, 40 kHz and 70 kHz are the common frequencies which are used.

For contacting the second plastic part there is one of the materials which has a spiked or rounded energy director.

For alternative to glue, screws or snap-fit this process is a good alternative.

For the purpose of welding metals, this process can also be used.

Due to the more power level requirements, this process would not be prefered easily for welding the chassis of an automobile or in welding pieces of a bicycle together.

COMPONENTS IN ULTRASONIC WELDING:

Basically all ultrasonic welding systems are composed of the same basic elements.

From converter or piezoelectric transducer, an optional booster and a sonotrode from all this the ultrasonic stack is made.

The all of three stack element are specifically tuned to resonate at the same exact ultrasonic frequency (typically 15, 20, 30, 35 or 40 kHz).

CONVERTER

By using piezo electric effect the converter converts the electrical signal into a mechanical vibration.

BOOSTER

For the purpose of modification of amplitude of the vibration mechanically the booster is used.

To clamp the stack in the press in standard systems the booster is used.

HORN OR SONOTRODE

Ultrasonic seam welding using a roller as the sonotrode
Fig. 2 Ultrasonic seam welding using a roller as the sonotrode

Takes the shape of the part, also modifies the amplitude mechanically and applies the mechanical vibration to the parts to be welded.

ADVANTAGES:

SPEED

It is one of the most exceptionally fast process than any other process.

The material to heat, weld and cool very quickly because of the transmission of high-frequency ultrasonic acoustic vibrations through the horn .

SAFETY

For the safety purpose ultrasonic welding equipment is extremely safe compared to any other welding techniques.

The ultrasonic energy is mostly focused on reducing the risk of dangers due to excess electrical energy.

RELIABILITY

Ultrasonic welding equipment will function with a high level of reliability after assembled and tested.

REDUCED MATERIAL COSTS

The ultrasonic welding process is very cost-effective in terms of material usage.

The process doesn’t use connective bolts, solder or adhesive material, so it helps to reduce material costs for the project.

Also ultrasonic welding is highly precise and produces high-quality joints, part scrapping is kept to a minimum.

The ability to minimize human intervention during and after the welding process also keeps labor costs to a minimum.

DISADVANTAGES:

MATERIAL LIMITATIONS

Ultrasonic welding is appropriate for many thermoplastics but isn’t ideal for all.

The materials on which this process is to be carried out requires lower moisture content.

SIZE LIMITATIONS

For producing large joints greater than 250 mm in length ultrasonic energy is not sufficient.

The transducer power output is not able to handle anything larger than that.

JOINT TYPE LIMITATIONS

This process can only be used on specifically designed joints, called lap joints, where parts directly overlap one another with a flat surface.

This technique is not better for the welding corner, butt, tee and edge joints.

HIGH INVESTMENT

Basic ultrasonic welding equipment is significantly more expensive than traditional welding equipment, and the costs only increase with the introduction of automation.

LEAD TIME

If you choose to add ultrasonic welding equipment into your manufacturing operations, you won’t be able to start churning out parts immediately.

All ultrasonic tooling setups must be custom-built for any part being welded, which requires fixture and process development as well as several rounds of testing and troubleshooting.

This means that new setups may not be used immediately and also that the new projects will have a slightly longer lead time.

APPLICATIONS:

IN COMPUTER ELECTRONICS INDUSTRY

For joining wired connections in the computer and consumer electronics industry, ultrasonic welding is mostly prefered.

Ultrasonic welding is also helpful for the connections in small, delicate circuits where traditional welding techniques may damage the part.

IN AUTOMOTIVE INDUSTRY

For the large scale applications in automative industry this welding is used.

With the help of this welding, door and instrument panels are typically assembled.

IN AEROSPACE INDUSTRY

This process is mostly preferred in the aerospace industry on the metals.

For the purpose to join thin, lightweight sheets of aluminum and other light metals this method is mostly preferred.

Air duct can be easily made with using this technique.

IN CONSUMER PRODUCT INDUSTRY

Because ultrasonic welding is most commonly used in thermoplastics and is easily automated, it is a common welding technique for a variety of consumer products, including toys and tools.

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