What Are the Advantages & Disadvantages of Ultrasonic Welding?

Joining molded plastic parts can be a difficult task. Adhesives, bolts and solder are only so effective and often result in ugly joints that need reworking. The best way to get around these issues is with a method called ultrasonic welding.

Ultrasonic welding is often the best choice for welding molded plastic parts. Using high-frequency ultrasonic acoustic vibrations, ultrasonic welding effectively joins materials in a way that is quick, safe and reliable. As a result, many industries choose to use ultrasonic welding for their thermoplastic applications. While not appropriate for all applications, if your manufacturing company works with thermoplastics, it is important to know what ultrasonic welding is, what its advantages and disadvantages are and how your company may benefit from implementing ultrasonic welding in your operations.

What Is Ultrasonic Welding?

Ultrasonic welding, also known by the acronym USW, is a welding technique that uses ultrasonic vibration to weld two parts together. Instead of using heat, the process of ultrasonic welding uses ultrasonic frequency mechanical vibration energy on the workpiece, causing the material to deform and create a solid-state weld. The process works as follows:

Setup: The two pieces to be joined are assembled in the fixture. The fixture, also known as the anvil or the nest, holds these parts in place during the welding process.
Horn contact: When the two parts are placed, the horn, also known as the sonotrode, is placed in contact with the upper part of the piece, pressing down toward the fixture. The horn is the part that transmits the mechanical vibration to the two pieces to be welded.
Pressure applied: When the horn and the parts are placed, the pressure is applied to the setup using a pneumatic or electric driven press.
Weld time: Upon applying pressure, the horn is vibrated vertically at a high frequency and transmits the mechanical vibration energy to the two pieces in the fixture. The frequency can be between 15 and 70 kilohertz (kHz) and is most commonly 20 kHz. The mechanical vibration generates heat energy at the contact point between the parts of the workpiece, causing them to melt and fuse.
Hold time: After the weld time has elapsed, the vibration stops, and the system maintains pressure on the two pieces, causing them to fuse together and form a strong weld.
Retraction: As soon as the weld has cooled and solidified, the pressure is released, and the horn is retracted, allowing the welded part to be removed from the fixture.

The ultrasonic welding process is most commonly used to weld thermoplastics but may also be used on certain types of metals. Some metals that can be welded using ultrasonic energy include gold, silver, copper and aluminum. Ultrasonic vibration is particularly effective at welding dissimilar materials and is favored for its ability to join parts without bolts, solder, nails or adhesives.

Applications of Ultrasonic Welding

Ultrasonic welding is valued in many industries for its ability to create quality welds without direct application of heat. Some of the industries that most commonly make use of the ultrasonic welding process include the following:

Computer electronics industry: In the computer and consumer electronics industry, ultrasonic welding is used to join wired connections. It is also used to create connections in small, delicate circuits where traditional welding techniques may damage the part. Ultrasonic welding is commonly used to create parts for microcircuits, computer disks, capacitors and flash drives.
Automotive industry: In the automotive industry, ultrasonic welding is commonly used in large scale applications. For example, door and instrument panels are typically assembled using ultrasonic welding. Many electrical components, such as engine components, are also commonly made using this technique.
Aerospace industry: In the aerospace industry, ultrasonic welding is most often used on metals. This method is typically used to join thin, lightweight sheets of aluminum and other light metals. Most commonly, air ducts are made using this method of welding.
Medical industry: Ultrasonic welding is popular in assembling medical equipment such as filters and pipettes. The reason it is so popular is that ultrasonic welding doesn’t introduce contaminants or degradation to the weld, making it ideal for creating filters including anesthesia, arterial, blood and gas filters. Many plastic-based textiles for the medical industry are also assembled using ultrasonic vibration, including sterile garments like face masks and hospital gowns.
Packaging industry: Ultrasonic welding is often used to weld together parts of packages to create a complete barrier, especially around substances that may be more sensitive to heat. For example, ultrasonic welding is often used to package heat-sensitive foods. Some examples of applications of ultrasonic welding in food packaging include blister packs, candy wrappers, frozen food packaging and beverage containers. It is also used to package explosives, fireworks and heat-reactive chemicals.
Consumer products 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.

Because of the ability of this process to weld notoriously difficult materials reliably and with little damage or application of excess materials, many industries have found several ultrasonic welding uses within their operations.

Advantages of Ultrasonic Welding

Ultrasonic welding has found widespread popularity across a range of industries for its ability to be used on thermoplastics and other materials. However, there are many other reasons that ultrasonic welding may be preferable as compared to other welding and joining techniques. Some of these advantages of ultrasonic welding are explained in more detail below:

Speed: One of the most significant advantages of ultrasonic welding is the fact that it is an exceptionally fast process. The transmission of high-frequency ultrasonic acoustic vibrations through the horn allows the material to heat, weld and cool very quickly. In many cases, the welding process takes a few seconds at most, allowing for high throughput and short turnaround times.
Safety: Using ultrasonic welding equipment is extremely safe compared to other welding techniques. The ultrasonic energy is highly targeted, reducing the risk of dangers due to excess electrical energy. Additionally, the heat produced is minimal, localized and quickly dissipated, minimizing the thermal impact on the material and reducing the chances of excess heat damaging any surrounding equipment.
Reliability: Once assembled and tested, ultrasonic welding equipment will function with a high level of reliability. The process can even be automated so that thousands of parts can be welded reliably with minimal human intervention. As a result of this reliability, equipment failures and faulty welds are of minimal concern.
Joint quality: Ultrasonic welding produces a very clean and precise joint. When used properly, ultrasonic welding equipment produces no plastic flash or deformation, resulting in a clean, nearly invisible seam that requires no touch-up work.
Flexibility: Ultrasonic welding can be applied to a variety of materials and parts. Thermoplastics and several metals can be welded using this technique, and it is especially useful in welding dissimilar materials. Additionally, ultrasonic welding can weld thin to thick material combinations.
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, because 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.

These advantages of ultrasonic welding make it an ideal choice for many industrial applications, especially those that involve a high volume of plastic parts.

Disadvantages of Ultrasonic Welding

While ultrasonic welding offers several advantages, it is not an ideal welding procedure for all applications. There are several drawbacks to this method of welding that may pose a problem for certain types of manufacturers. Some of these disadvantages are detailed below:

Material limitations: Ultrasonic welding is appropriate for many thermoplastics but isn’t ideal for all. The ultrasonic welding process requires a lower moisture content in the materials that it welds. Materials with high moisture content require vibration welding, which is an entirely different technique. Exceptionally strong, hard thermoplastics are also more challenging to handle using this technique.
Size limitations: While ultrasonic welding is highly useful for many thermoplastics and specific types of metals, it is not appropriate for all applications involving these materials. First of all, ultrasonic energy is not enough to produce large joints greater than 250 mm in length. The power output of the transducer is insufficient to handle anything larger than that. Additionally, thick materials are not easily vibrated using mechanical vibration energy, making ultrasonic vibration an ineffective welding technique for thicker materials.
Joint type limitations: Ultrasonic welding can only be used on specifically designed joints, called lap joints, where parts directly overlap one another with a flat surface. Corner, butt, tee and edge joints cannot be effectively welded using this technique.
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 ultrasonic welding setups may not be used immediately and also that new ultrasonic welding projects will have a slightly longer lead time.
Custom tooling: As part of the custom building needs of ultrasonic welding, custom tooling is needed for every new project for an ultrasonic welding application. Fixtures for parts must be made to perfectly fit workpieces, meaning that high-quality CNC tooling is a necessity. This may not be a problem for full-service shops with CNC tools and toolmakers on hand, but it may be an issue for smaller companies with greater space and labor limitations.
High investment: Basic ultrasonic welding equipment is significantly more expensive than traditional welding equipment, and the costs only increase with the introduction of automation. Trying to cut costs by going with less expensive machines isn’t a valid option, either — inexpensive machines rarely offer any feedback or automation options and may be less reliable due to lower-quality equipment. If your company chooses to go with ultrasonic welding, your best option is to invest in high-quality ultrasonic welding equipment with process monitoring, automation options and a proven record of quality performance.

It is important to mention that ultrasonic welding is still an option for companies that can’t afford equipment of their own. While ultrasonic welding isn’t the best option for all applications, smaller companies that could benefit from the process can work with production companies that specialize in ultrasonic welding techniques.

Choose Global Electronic Services for Ultrasonic Welder Repair

Ultrasonic welding offers many advantages to manufacturers that serve industries where thermoplastic welding is in high demand. Between the quality and cost savings of ultrasonic welding, it’s a highly effective welding method, especially for companies with in-house CNC tooling. However, when you’re working with ultrasonic welding or are considering implementing ultrasonics into your manufacturing operation, you need an experienced repair service to help keep your ultrasonic welding equipment running smoothly. That’s where Global Electronic Services can help.

Global Electronic Services is a leader in electronics repair across a wide range of manufacturing industries. We’re can provide comprehensive repairs, replacements and maintenance for your ultrasonic equipment to help you increase uptime and improve reliability. Global has been repairing and maintaining ultrasonic equipment for businesses located around the world for decades, and we can do the same for your organization. Our certified staff is dedicated to quality service, and we thoroughly inspect and evaluate each piece of equipment before returning it to you. Whichever brand of ultrasonic equipment your work with, you can trust us for quick and reliable repair services.

On top of the quality of our work, Global Electronic Services offers speed, with a five-day turnaround time and a free one-to-two-day rush service. We also provide 24/7 access to real customer service and support professionals to keep you updated on the status of your repairs. If that wasn’t enough, our 18-Month, In-Service Warranty will give you peace of mind.

You’d think that with our dedication to quality and service that our repair options would blow your budget. The reality is that our repair services are designed for affordability. We guarantee that no matter a qualified competitor’s price, ours will beat it by at least ten percent.

See why Global Electronic Services’ customers are our customers for life. If your company is interested in partnering with a quality ultrasonic welder repair service, contact us for more information about our experience repairing ultrasonic welding equipment and to get a free, no-obligation quote.