What is ultrasonic welding, and which are some scenarios where its use is reasonably necessary?
Welding is one of the most effective ways of joining two materials. Unlike other joinery alternatives, such as riveting, it primarily helps create a permanent bond because it applies heat energy.
We also have numerous welding techniques, and ultrasonic welding is one of the most popular methods. So what is it all about? Check out our guide for more revelation into this topic.
What’s Ultrasonic Welding
Usually abbreviated USW, this joinery method utilizes high-frequency ultrasonic vibrations to create a bond between two parts.
While it is primarily a welding method, it is unique because it applies indirect heating in creating joints.
One of the primary applications of the technique is in the joinery of metal surfaces with a thin cross-sectional area.
Other uses include in joinery of the following materials:
- Combining thermoplastics
- Welding unalike materials
The fundamental upside of ultrasonic welding is that it guarantees a perfect bond that would otherwise be impossible using other techniques.
It is especially critical in the joinery of plastics, whereby the method creates bonds without melting the materials.
Main Parts of Ultrasonic Welding Machine
An ultrasonic welder apparatus.
Before we analyze the ultrasonic welding process in detail, let us first check out the core components of this process.
Generator
Also commonly known as an ultrasonic generator, it is the electrical component that creates ultrasonic waves.
The system transforms its supplied electrical power into a resonating wave with a significantly high frequency.
What stands out in this part is the microprocessor which is pertinent in welding cycle control.
It is also imperative to set up a specific welding job’s requisite frequency and other specifications.
Machine Press
Welding is all about bringing two parts together to create a permanent bond, and this is primarily what a machine press does.
Like any other press, it applies significant pressure to the two different materials allowing them to merge into one.
It, therefore, works in tandem with the ultrasonic wave to facilitate the bonding.
Also noteworthy is that it features a pressure gauge, which is imperative in controlling the applied force.
Welding Stack
It’s the system responsible for the actual welding. It features three main parts:
- Transducer
- Welding horn
- Booster
As its name suggests, an ultrasonic stack delivers the vibrations which facilitate the merging of the parts.
It is noteworthy when using a welding stack to ensure its frequency is close to that of the signal generator, as this is cardinal to creating efficient and quality welds.
Piezoelectric Transducer
Like other typical transducers, this component is built to convert energy from one form to the other.
It changes the electrical signal into a mechanical vibration (ultrasonic waves) necessary for welding.
Its main parts include numerous piezoelectric ceramic discs sandwiched between titanium plates.
Also, the transducer features a thin metal electrode at the center of the ceramic discs to facilitate the energy form conversion.
Booster
The basis of ultrasonic welding is high vibrational energy acting upon compressed materials. Therefore, the booster, in this case, is cardinal in heightening mechanical vibrations.
Also, it is the base materials that form the foundation of the welding base stack.
Welding Horn
It is the last contact line between the ultrasonic vibrations and the welded materials.
Among the most common materials that make up the ultrasonic horn include titanium and aluminum.
Nonetheless, because of the significantly excessive force the welding horn applies on the materials, it should be primarily hard.
Hence, where it’s made of aluminum (soft material), the ends are hardened with another material to sustain the high pressure.
Support Tooling
Finally, this is the part that houses the lower end of the welding apparatus. It’s made of sturdy material to guarantee stability during ultrasonic welding.
How Does Ultrasonic Welding Work
Ultrasonic machine.
Here are the basics of an ultrasonic welding apparatus in merging two parts. In our guide, we’ll explain how to combine two plastics.
- First, the welder sets up the two materials to be combined on the welding stack primarily as overlapping parts with the ends on top of each other.
- Next, switch on the ultrasonic signal generator prompting the device to convert its supplied High-Frequency Electrical Energy to a higher frequency. This converter then transfers the high-frequency electric signals to mechanical vibrations (ultrasonic waves).
- Finally, the welding horn redirects these vibrations onto the parts you’re combining. Notably, at this time, the machine press has compressed the two parts together to facilitate the merging.
- After the combination ends, the system retracts the welding horn, leaving you with a perfectly clean joint design.
Types of Ultrasonic Welding
A Welded Pipe.
Fundamentally, ultrasonic welding is vital in joining two plastics or two metals. It brings us to the two primary modes of ultrasonic welding.
Ultrasonic Metal Welding
It is critical in combining metals with other compatible metals and works best for metal pieces featuring a thin profile.
Some of the common metals that you can merge with this technology include the following:
- Nickel
- Aluminum
- Silver
- Brass
- Copper
- Gold.
Ultrasonic Plastic Welding
It is the primary welding method for combining plastic materials such as:
But, while it is perfect for these thermoplastic materials such as those listed above, it doesn’t make great joints for plastic polymers.
Hence, avoid using it on polyamide and PVC plastics.
Material Selection Considerations
Plastic polypropylene.
When combining parts using the ultrasonic welding method, you need to pay attention to the following features:
Shape
Ideally, it would be best if you worked with shapes that are easy to overlap, as this is the basis of creating a perfect ultrasonic solder joint.
Moisture Content
Moisture is a big enemy to great joints. Hence, always ensure no moisture between the parts you intend to weld for the best results.
A blower would be handy in removing any moisture before laying the materials on the welding stack.
Hardness
This feature applies explicitly to plastics. For a seamless merging experience, limit the processes to soft plastics.
Hard plastics such as polycarbonate and polypropylene cannot combine effectively via ultrasonic welding.
Material Thickness
It’s essential only to use thin material that measures between 0.38mm and 3mm as they are the easiest to bond.
The logic behind this is that thick parts have more molecular bonds that necessitate a large energy output to break.
This will be impossible using the typical ultrasonic welding systems, so the joint quality in such parts will be poor.
Materials Similarity
While the technique can combine even dissimilar materials, it’s ideal for metals or plastics of the same family.
Similar materials share chemical bonds; therefore, merging them would take lesser effort and more strong and durable bonds.
If you want to combine dissimilar materials, high heating above 40 degrees Fahrenheit is necessary.
Another condition is that they must feature similar molecular structures. Otherwise, they will not merge.
Advantages of Ultrasonic Welding
Plastics Manufacturing Factory.
Here are the top reasons why ultrasonic welding is remarkably better than other alternatives like riveting and sheet metal welding.
It is Fast
It is one of the fastest welding techniques making it highly significant in making joints for industrial operations.
Therefore, you’ll most likely find it applied in mechanical assembly uses where the aim is to generate massive volumes within short timelines.
High Reliable
Manufacturers with automation capacity can significantly reap big profits with this method as it can create massive volumes of joints without the rest of the system faults.
Also, the joint quality for materials welded via this technique is top-notch.
Further, the machines applied in the method barely break down or require frequent maintenance.
Therefore, this is one of the most highly reliable joint-making methods.
Facilitates Dissimilar Materials Welding
No other method can allow the perfect bonding of two different types of materials than ultrasonic welding.
Hence, initiating the combined materials’ vibration starts the mechanical bonds’ breakage, which is pertinent in the joinery process.
No Consumables
The initial cost of setting up a quality ultrasonic system can be high, but once everything is up and working, the rest is free of charge.
The method requires no consumables such as rivets and soldering materials, which are mandatory for other joinery techniques.
This significantly reduces the costs of its application.
Disadvantages of Ultrasonic Welding
Limited to Lap Joints
Earlier, we cautioned that this method’s best type of joint is a lap joint, which makes it unsuitable for tee, corner, and edge joints.
Basically welding types
High Set-up Costs
You must spend top dollar setting up an efficient ultrasonic welding plant. Thus, it is almost out of reach for small-scale welders.
Also, setting up the initial system assembly costs is high if you opt for automation.
The best part of this is that mostly, these are one-off tooling costs that you don’t have to incur again once the setup is complete.
Material Compatibility Limitation
Although it’s the perfect joiner technique for plastics, it doesn’t guarantee the combination of moisture-containing material.
Thus, we cannot use it for thermoplastics with a relatively high moisture level.
Also, the method is unsuitable for welding hard plastics.
Size Limitation
Any material thicker than 150mm cannot be merged using ultrasonic welding technology primarily because of two factors:
- First, there’s the transducers’ size limitation. Its capacity is limited to producing vibrations for 100 to 150 mm materials hence limited to handling material of this thickness range.
- Also, combining thicker materials will require more ultrasonic energy, which may make the process uneconomical in the long run.
Common Applications of Ultrasonic Welding
- It is useful in the medical industry, primarily connecting parts such as gas filters, hospital gowns and face masks. Also, the capacity of the method to weld dissimilar parts comes in handy in manufacturing medical plastics.
- The method is also prevalent in the automotive industry in fabricating parts like the steering wheel and door panels. It is particularly popular because of its capacity to create excellent joints that barely distort the workpiece’s structure.
- It is the best technique for making wired connections in the electronics industry. Its joint quality is so perfect that it is useful in connecting intricate parts such as capacitors.
- Finally, aerospace industry manufacturers use the method in the welding process for dissimilar make-up parts.
Summary
Welding doesn’t have to involve direct heating necessarily. Excellent techniques such as ultrasonic welding are more effective yet require no heat input.
We hope you now have this process’s basics from our guide. The method has some limitations, but its excellence in making excellent bonds is unmatched.