The Guide To Ultrasonic Welding Machines & Tooling - Xfurth Ltd

A big determining factor is the type of components you are working with and the integrity of weld you need to achieve. Ultrasonic welding can comfortably create airtight hermetic seals and form strong bonds between thin walled parts. This makes it a superior choice to other welding techniques when dealing with fragile components. 

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You can also reliably weld internal surfaces. Some ultrasonic welding machines can handle multi-level or curved joints, but this very much depends on the component. If in doubt we recommend you chat with us about your project requirements before making an investment. The same applies if you require multiple parts per weld cycle. Some ultrasonic welders can do this, but it is part dependent.

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How Ultrasonic Welding Machines Work

Ultrasonic welding uses high frequency vibrations to raise the temperature of a join in a very short amount of time. These localised vibrations create a linear friction which coupled with an applied force create a molecular bond at the weld joint.

How Long Does It Take?

Once the required vibrational frequency is reached, the pressure can be gradually released and the cooling process begins, thereby solidifying the material and forming the weld. The time this takes varies on the size of the component, type of weld and material, however ultrasonic welding is a relatively fast method. Some welds can form in as short a time as 0.25 seconds. A complete welding cycle is usually completed between 3 - 5 seconds including actuation, welding and cooling. The weld cycle and bond strength can be controlled by varying the amplitude of the tooling, length of weld time and the pressure which is applied. Adjusting these three factors gives users a great deal of precision over the end result.

There are many designs and combinations of ultrasonic welding machine to match the needs of different industries. However, each of them has the following six main elements in common: 

The Power Supply / Generator

The power supply transforms a low frequency, 50 to 60 kHz electric current to a high frequency, 20 to 40 kHz electric current. The application usually dictates which frequency is required. Most British manufactured ultrasonic welders fall into the 20 to 40 kHz range, but some can be as high as 15 kHz. Generally the higher the frequency, the smaller the tool, and the lower the wattage produced by the generator. For example, a 40 kHz is usually 800 watts, 20 kHz can be as high as 5,000 watts.

The Transducer / Converter

The transducer, or converter, transforms the high frequency electric current into high frequency ultrasound vibration.

Booster

These ultrasound vibrations, on their own, are not particularly strong; so they require a booster to increase their strength and intensity. We often refer to the output in mechanical movement as amplitude, which is measured in microns.

Sonotrode / Horn

The sonotrode, or horn, delivers the ultrasound onto the welding material. The horn applies pressure to the material and vibrates vertically at a rate of 20,000 to 40,000 times per second (depending on the frequency used). It is this vibration that creates the linear friction that causes the weld joints to melt and bond together. The components are held in place by the anvil.

Anvil / Nest

The anvil is the platform on which the two components are stacked, to hold the components together at the correct pressure in order to achieve the required weld.

Pneumatic Head Cylinder / Actuator

As the welding process requires pressurising to ensure a strong weld is created, the complete welding stack is mounted to a pneumatically driven slide, which enables the tooling to contact the components to be welded, and then 'lift off' after welding, allowing the operator to remove the welded component from the nest. Usual welding pressure is between 1.5 - 3 bar.

Once the required vibrational frequency is reached, the pressure can be gradually released and the cooling process begins, thereby solidifying the material and forming the weld. The time this takes varies on the size of the component, type of weld and material, however ultrasonic welding is a relatively fast method. Some welds can form in as short a time as 0.25 seconds.

A complete welding cycle is usually completed between 3 - 5 seconds including actuation, welding and cooling. The weld cycle and bond strength can be controlled by varying the amplitude of the tooling, length of weld time and the pressure which is applied. Adjusting these three factors gives users a great deal of precision over the end result.

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How To Choose An Ultrasonic Welding Machine

No two ultrasonic welding machines are exactly alike. At Xfurth we have manufactured many bespoke models over the years, developing a group of features to provide you with excellent reliability, stability and ease-of-use. Our ultrasonic welding machines can be used for various welding functions, including component welding, riveting, swaging, inserting, spot welding and de-gating.

Elements

All ultrasonic welding machines will have the standard elements we explained in an earlier section. This covers a broad spectrum of functions and levels of quality, however when shopping around for an ultrasonic welding machine, pay attention to whether the manufacturer can supply the following elements:

As a standard all our bench mounted machines feature:

• Flexibility with working frequency. This means the same machine can be used to weld components in either 20 to 40 kHz with only the ultrasonics having to be changed
  
  
• A wide power range. Our machines are available from 400 to 5,000 W in output
  
  
• Proportional valve as standard helping to achieve a consistent pressure throughout the welding process
  
  
• Full monitoring of up to 5 weld conditions, including power, energy, time position and collapse
  
  
• Solid Aluminium H frame construction for maximum stability
  
  
• Modern control systems with touchscreen interface and weld programme memory (our machines can store up to 99 programmes)
  
  
• Downloadable or streamed weld monitoring data  
  
  
• Option of rocking or sliding table
  
  
• Fixed guarding as a standard on all machines for increased safety and acoustic noise reduction
  
  
• A rigid dovetail head assembly encouraging greater stability, which can be an issue with cheaper units
  
  
• British designed and manufactured machine
  
  
• Festo pneumatics and B&R HMI
  
  
• A 24 month warranty on the machine
  
  
• A variety of standard options such as part sensing and ejection, linear encoder and bar code reader

Cost

Costs can range from £12,000 upwards depending on the size and specifications. Ultrasonic welders vary from 'standard bench mounted machines’ to purpose built machines. However, at Xfurth even our ‘standard’ machines have everything you'd expect from a higher end model. 

Whilst a second hand, or a machine purchased from the Far East, may initially cost less - sometimes this short-sighted approach will end up costing you far more in the long run. When it comes to ultrasonic welders it is well worth paying for quality, as this will yield you a more reliable, productive machine with the expected high level of process control.

There are plenty of cheap ultrasonic welders on the market which, on the surface, resemble a better made model, however these types of units frequently develop faults and welding errors that can cost operators a lot of money and lost productivity. When investing this amount of money in an asset, we believe it makes sense to choose a British built and designed ultrasonic welding machine.

What To Look For In A Machine

So how do you tell a low quality, cheaply built machine from a high quality welder?

The first thing is rigidity. A high quality welding machine will be fully stable when activated. Cheaper grade machines can vibrate and bow under welding pressure. This generates inconsistent movements leading to poor weld quality. 

The second thing is control. Are you able to load and store welding programmes as well as have full traceability on your manufacturing? This is very important for any ISO accredited business, as well as companies in the medical or automotive industries. We believe in being able to fully utilise process control on our machines, so even our standard machines have the facility to download or stream to a computer to ensure all your data is fully traceable.  

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Ultrasonic Tooling

Ultrasonic tooling involves manufacturing sonotrodes and fixtures for ultrasonic welders, these are usually job specific and are designed to meet the requirements of your application. Our team of design engineers can create any fixture or sonotrode you need to work with any brand of ultrasonic welding machine. We can also manufacture ultrasonic tooling in all frequencies.  This is all manufactured on-site at our Luton factory, where we have a fully operational tool room.

Design

The design of your tool is critical to achieve its desired outcome. To do this we start with an understanding of the looked-for characteristics of your end product and work backwards from there. Based on the part size, material, shape and weld integrity for your component, we will design you a custom tool that achieves your result in the fastest, most energy efficient and cost effective way possible.

Materials

Ultrasonic tools are made from metal, either Aluminium, Titanium, or hardened steel being the most common. There is a cost difference between the material choices due to manufacturing time and material cost, but more importantly the chosen material for your sonotrode is dependent on the application or the material you are welding. 

For instance, when choosing glass filled Nylon as a material for bonding, then you will most likely require hardened steel tooling as the glass will be abrasive and wear the tooling very quickly if it is made in a softer metal alternative. 

We can create any type of custom tool for your welder:

Sonotrodes  /  Horns: As the operational end of an ultrasonic welder, bespoke sonotrodes are frequently required to achieve the specific weld strength and cycle required by your application. At Xfurth we have many years’ experience manufacturing sonotrodes for ultrasonic welding machines.

With our CNC equipped tool room, we have the capability to manufacture sonotrodes in Aluminium, Titanium and hardened steel. As we keep a large stock of material we can usually manufacture your tooling within a very short lead time. Full technical advice and support is also available for existing tooling. 

Boosters: We manufacture a range of standard boosters, available in various ratios. The actual ratio required for a particular application will vary. We will be pleased to provide technical advice on request. Standard boosters have threads to match the transducer on the input end, with a matching thread on the output. Special components with different thread sizes are also available, as are adaptor studs.  

Location Nests: Component nests and location fixtures can be supplied in machined or cast design to suit your assembly, and if required can incorporate pneumatic clamping and part ejection.

Cost

Ultrasonic tooling can cost anything from a few hundred to a few thousand pounds, depending on the material you need, the size and operating frequency.

Durability

The biggest costs that an ultrasonic welding machine incurs over its lifetime are replacement tools, especially if these are non-standard parts. In the long term, you can expect tooling to last hundreds of thousands of cycles. However, if tooling fails, this can usually occur with no discernible warning. 

At Xfurth, we can turn around and prioritise your tooling breakdowns to ensure you are up and running in a matter of days. Even the issues listed above can be overcome with the right design strategy. At Xfurth we have extensive experience of creating custom tooling that stands the test of time.

Simply get in touch by calling 436 000 to discuss your application with one of our engineers.

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Why Choose Xfurth?

After reading this guide, we hope we have given you enough information to decide whether ultrasonic welding is the right choice for your application. If you would like to find out more about taking the next steps, this final section shows you what to do and what our sales process looks like.

A quick Google search will find you a number of ultrasonic welding machine suppliers, so why choose Xfurth for your equipment and tooling requirements? Our answer to this is simple. When you are investing a large sum of money in a precision piece of equipment, surely it makes sense to deal directly with knowledgeable engineers, rather than salespeople.

This isn’t to say that there isn’t some great kit out there – there is. Nevertheless most places that sell ultrasonic welders don’t make the equipment themselves. They are only distributors or agents in the UK, not manufacturers. 

Furthermore, a distributor has an inventory of products which they need to sell to make a profit. So when their salespeople are listening to your requirements, they’ll be thinking of ways in which their current stock matches your requirements. They will inevitably suggest the product as the solution. It is unlikely to be a perfect fit.

This is the opposite of the approach that we take. As we are a manufacturer ourselves, we design equipment to exactly meet our customer’s applications. We listen to your requirements and then use our expertise, knowledge and engineering experience to custom design the perfect ultrasonic welding machine for your business.

This is the Xfurth way of doing things.

Purchase Or Hire?

For long term production or larger projects, the most cost effective approach is to purchase a machine. This is a one time investment that will soon recoup its costs in terms of efficiency and productivity. We also provide on-tap expert technical advice, training, installation and ongoing support as part of the price.

If you only have a short term requirement or a limited budget, we also have a pool of machines we can rent you for the duration of your project. If this is something that interests you, please get in touch by calling 436 000.

Investing In An Xfurth Ultrasonic Welding Machine

If you are interested in purchasing an ultrasonic welding machine from Xfurth, the first step is to make an initial enquiry by , or through our website landing page. Full details of how to get in touch are given below.

At this stage, the more we know about your project, the better we will be able to help you. So please provide us with CAD data, expected production volumes, required weld integrity and material selection (if this information is available). Once you’ve told us about your project, we can get the ball rolling by arranging your Feasibility Study. 

A lot of manufacturers charge a fee for this service, but at Xfurth we offer the Feasibility Study free of charge to all potential customers. The Feasibility Study includes a face-to-face meeting at your premises, where we provide consultancy on your project, including a review of your technical drawings, CAD data and product requirements. We can advise you if ultrasonic welding is the right solution for you and suggest a design, or if an alternative welding technique is better suited.

We may recommend some CAD changes as part of our consultancy. If so, we can revisit your data once you have made the required changes.

On receiving your order we will produce a timing plan for the project, carry out first product trials and second acceptance trials if required.

Are you interested in learning more about Ultrasonic Welder? Contact us today to secure an expert consultation!

Once ready, we will install the equipment at your premises and provide your team with full training on its use and maintenance. We can conduct training on-site at your location or at our facility in Luton, depending on what works best for you.

After installation and training, you can continue to benefit from our first class UK based after sales and technical support service.

Claim Your FREE Feasibility Study

We undertake all Feasibility Studies free of charge, talking through and discussing design changes until you are completely happy with your welding solution. This expert consultancy service is provided with no obligation to purchase. 

It is important to us that you make the right choice for your application and you get a machine that meets all your requirements.

To request a Feasibility Study, please click below:

You can also call us on 436 000

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reference

Ultrasonic welding (USW) is a solid-state welding process where two components are joined by applying high-frequency oscillatory shear stresses while under modest clamping force. This procedure, which is frequently employed in lap welding (as shown in Fig. below), breaks off surface coatings and permits close contact between the components, forming a strong metallurgical bond. Heat is produced at the interface by friction and plastic deformation, but the temperatures stay much below the melting point, negating the need for shielding gasses, fluxes, or filler metals.

In USW, a sonotrode that is attached to an ultrasonic transducer transmits the oscillatory motion to the upper workpiece. This device transforms electrical energy into high-frequency vibratory motion, with amplitudes of 0.018 to 0.13 mm (0.–0.005 inches), and a frequency range of commonly 15 to 75 kHz. The surfaces are not significantly plastically deformed since the clamping pressures utilized are substantially lower than in cold welding. Welding times are typically shorter than a second.

Copper and aluminum are among the softer materials that ultrasonic welding works best on. Harder materials erode the sonotrode more quickly. The best workpieces are small, usually less than 3 mm (1/8 inch) in welding thickness. Soldering is not required when using this technology for wire terminations and splicing in the electrical and electronics sectors. Additionally, it is employed in the welding of solar panel tubes to sheets, the assembly of small parts, and the assembly of aluminum sheet-metal panels.

Welding Process

The following describes the general operation of the ultrasonic welding process:

-Material Preparation: Place the plastic components on the welding stack of the machine in a lap joint configuration.

-Production of High-Frequency Electricity: Standard electricity (50–60 Hz) is transformed into high-frequency electricity (20–40 kHz) by the generator.

-Conversion to Ultrasonic: The vibrations are amplified by the booster after the transducer converts the high-frequency electricity into ultrasonic waves.

-Welding: Ultrasonic vibrations are directed onto the assembled parts by the welding horn, also known as a sonotrode. The press is used by the operator to provide pressure. The operator extracts the welded components and retracts the horn after welding.

Ultrasonic welding machine components

Ultrasonic welding machines are made up of different parts, each with a specific function. Here are some key parts found in all types of ultrasonic welding machines:

Generator

The generator converts electrical power into the required high frequency and voltage at a resonant frequency. A microprocessor that manages the welding cycle and enables essential communication via the user interface is also a part of it.

Machine Press

The machine press secures the welding assembly and applies the necessary force to maintain the joint. It is equipped with a pressure gauge and regulator, enabling the operator to adjust the force applied to the system.

Welding Stack

The transducer, booster, and welding horn are all part of the welding stack and are fixed to the press in the middle of the booster. The ultrasonic vibrations are produced by this assembly, and in order to guarantee excellent welded seams, their frequency must nearly match that of the generator.

Transducer

A transducer, sometimes referred to as a converter, converts electrical energy with a high frequency into mechanical vibrations. It is made up of many ceramic piezoelectric discs sandwiched between two titanium blocks. In addition, a thin electrode made of metal is positioned in between the piezoelectric discs.

Booster

The booster has two main purposes. It delivers the vibrations to the welding horn after amplifying them through contraction and expansion. It also serves as a foundation for the welding stack on the welding press.

Welding Horn

A welding horn, typically made of aluminum or titanium, transmits vibration to the welded part.  Although aluminum works well in low-volume applications, it wears rapidly. In order to counter this, the majority of welding horns include hardened tips, which improve performance and longevity under heavy usage.

Support Tooling

Support tooling acts as the foundation of the machine by supporting its lower component while it is being welded. In order to provide stability and accuracy, it is made to fit the workpieces' curves.

Welding parameters

Ultrasonic welding is a highly effective method of joining materials, usually metals or polymers, by using high-frequency vibrations. The force applied perpendicular to the vibration direction, vibration amplitude, and vibration duration are the three main technological factors that affect the effectiveness and quality of ultrasonic welding. Comprehending and managing these variables is essential to attaining ideal welds.

Vibration Duration

The time that ultrasonic vibrations are applied to the materials to be connected is known as the vibration duration or weld time. This length is typically less than one second for the majority of welding operations. Nonetheless, if a weld requires more energy, the vibration length needs to be raised while maintaining the same values for the other parameters. The following formula determines the energy required for a welding cycle:

where �� is the energy in joules, �� is the power in watts, F is the force in newtons, �� is the amplitude in micrometers, �� is the frequency in hertz, and Δ�� is the cycle time in seconds.

Vibration Amplitude

The longitudinal extension and contraction of the welding tool are measured by the ultrasonic vibrations' amplitude, which varies between 5 and 35 micrometers. This is an important amplitude because it matches the welding surface's friction distance. It takes less time to input the same amount of energy when the amplitude is increased because more power is needed to keep the vibration going. Amplitude profiling or stepping, as it is called, is made possible by the state-of-the-art ultrasonic equipment during the welding cycle. Since it strengthens the bond and avoids tool trapping, this method is very helpful for welding alloys like aluminum.

Force Perpendicular to the Vibration Direction

A key factor in the ultrasonic welding process is the force applied perpendicular to the vibration direction. The required mechanical stress on the welding zone is created by this force, which is produced by a pneumatic cylinder. The following describes the performance criteria for vibration creation and maintenance:

where Smh ​ is the cross-sectional area of the pneumatic cylinder in square meters, pℓ​ is the compressed air pressure in pascals, and η is the mechanical efficiency. As the pressure increases, the mechanical load increases, requiring more power to sustain the vibration.

Process variants

In ultrasonic spot welding, the oscillating motion is transmitted from the overlapped inserts to the thinner materials (ranging from 0.005 to 3 mm). The sonotrode, applying force to compress the pieces, creates a welded bond that vibrates with the workpiece. It's crucial that there is relative movement between the workpieces, not between the sonotrode and the upper workpiece. This method can connect sheets or wires of varying material qualities. Ultrasonic welding, a form of continuous spot welding, produces welded joints between overlapping thin sheets positioned between the sonotrode and the anvil. During the process, three vibration units provide alternating motion around the axis of the tubular sonotrode, forming a seam of consistent size and shape with its tubular front surface.

Types of Ultrasonic Welding

Both metals and polymers, which have different material compatibilities are frequently joined via ultrasonic welding.

Ultrasonic Plastic Welding: For thermoplastics like polyester, ABS, and polycarbonate, ultrasonic plastic welding is the best method. Properties like hardness and moisture content should be taken into account. But it isn't appropriate for plastic polymers like polyamide and PVC.

Ultrasonic Metal Welding: This technique is effective for joining metals, including alloys made of copper, silver, brass, nickel, gold, and aluminum. This method works best with thin, small-diameter metals, which makes it ideal for sensitive uses.

Advantages of Ultrasonic Welding

Because ultrasonic welding uses indirect heating techniques, it improves aesthetics without sacrificing functionality, setting it apart from conventional sheet metal welding and non-welding methods. These are its main benefits:

Speed: High-frequency ultrasonic vibrations produced by ultrasonic welding swiftly weld suitable pieces, ensuring a quick production process. Short turnaround times and high throughput are the results of this.

High Level of Safety: Less operational risk is created by the indirect heat application. The welded connections and surrounding materials are shielded from damage by the localized and fast dissipation of the heat generated.

Reliability: The machinery is dependable and has few malfunctions and failures. Automation further minimizes operational and human error, saves operating expenses, and enhances the quality of welded joints.

Suitable for Dissimilar Materials: Another important aspect of plastic welding is that this procedure works well for joining disparate materials together. When joining dissimilar plastics, ultrasonic welding does not need the development of molecular bonds, in contrast to other plastic welding techniques.

Disadvantages of Ultrasonic Welding

There are a number of disadvantages to ultrasonic welding. It is inappropriate for hard and moisture-containing plastics, to start with. This method has trouble with thermoplastics with high moisture content and strong polymers like polypropylene. Furthermore, the transducer's limited range of 100-150 mm means that it is unable to weld pieces with joints greater than 150 mm. Part size is another constraint. The fact that melting thick materials takes a lot of energy makes them troublesome as well.

The expensive initial outlay is yet another major disadvantage. For organizations, ultrasonic welding equipment requires a significant financial investment due to their high cost, which rises with automation. Additionally, this method is limited to lap joints, which are formed of sections that overlap one another on a level surface. Other joint types, such as corner, butt, tee, and edge joints, shouldn't use it. When choosing whether ultrasonic welding is the best technique for your application, keep in mind that these drawbacks limit its versatility in comparison to other welding techniques.

Applications of Ultrasonic Welding

Ultrasonic welding is a valuable technique that finds uses in a wide range of industries, particularly in the fabrication of consumer and industrial goods. It's utilized to make vital medical supplies like anesthesia filters, blood and gas filters, and face masks. This method is perfect for medical devices since it guarantees low-cost, high-quality joints in parts composed of different medical polymers, like ABS and polyethylene.

To create components like instrument panels, door panels, and steering wheels, the car industry uses ultrasonic welding to fuse plastic. In addition to its low capital costs, automation, quick cycle times, and flexibility, the process is preferred because it uses indirect heat, which does not cause damage to the workpiece.

Because of its accuracy, speed, and high-quality joints, ultrasonic welding also helps the aircraft sector.

In the same way, the electronics sector uses ultrasonic welding to join wires and put together electric motors, capacitors, storage media, and delicate circuits. Because of its accuracy and dependability, it is perfect for creating tiny, complex electrical components.

References

Groover, M.P., . Fundamentals of Modern Manufacturing: Materials, Processes, and Systems. 4th ed. Hoboken, NJ: John Wiley & Sons, Inc.

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