CASE STUDY

Ultrasonic Welding
Process Development

Developing a stable ultrasonic welding process for high-volume production

Stable Ultrasonic Welding

THE challenge.

Faltec Europe was tasked with developing an ultrasonic welding process capable of joining dissimilar plastics in a high-volume automotive application. The components involved were painted wheelarch over-fenders, requiring internal brackets to be securely fixed for strength and vehicle installation.

The challenge lay in the materials themselves. The outer shell and internal brackets were manufactured from different moulded components, each responding differently to heat, pressure and vibration. In addition, the process required a high number of welds to be completed simultaneously, with extremely tight dimensional tolerances across the entire part.

Early development revealed sporadic and inconsistent weld failures, including snapped weld tabs, heavy or incomplete welds, and misalignment. With failures presenting in different ways, it was initially unclear whether the root cause lay in material behaviour, part design, equipment performance or process control.

WHY IT MATTERed.

This was a high-volume production process, operating at approximately one part every 40 seconds across extended production hours.

For mass production to be viable, the welding process needed to be stable, repeatable and capable of delivering consistent results over time.

Any variability had the potential to disrupt production flow, impact quality and increase scrap. Establishing a robust process was therefore critical to both customer delivery and long-term manufacturing performance.

Technical
uncertainty.

Although Faltec had experience with ultrasonic welding, this application presented new levels of complexity:

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Welding dissimilar plastics that could not be directly fused
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A large number of simultaneous weld points on each part
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Sensitivity to minor dimensional variation in moulded components
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Equipment behaviour changing over time due to heat build-up and vibration

With failures occurring sporadically and without a clear pattern, identifying the root cause required a structured and methodical investigation across both equipment design and process parameters.

Technique

OUR approach.

The project focused on understanding and controlling the interaction between equipment design, process settings and part variation. Faltec worked closely with the equipment manufacturer to develop a bespoke ultrasonic welding system tailored to the application.

Key areas of investigation included:

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Temperature management, particularly how sonotrodes heated up during extended use
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Processing speed and actuator movement stability
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Applied pressure at each weld point
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Timing between actuator movement and ultrasonic activation
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Balancing and control of individual cylinders and springs

Given the scale of the system, this required targeted setting and tuning across approximately 60 cylinders and 100 individual sonotrodes.

Stable Ultrasonic Welding

Engineering
development and trials.

Multiple development routes were explored in parallel to isolate contributing factors and improve robustness, including:

Through iterative testing, analysis and refinement, the team identified the machining process used for the original mother block threads as the primary root cause of the weld failures. Modifying this process delivered a significant and sustained improvement in weld stability.

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Re-manufacturing critical welder components using titanium to increase durability
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Redesigning the shape of the mother blocks to influence ultrasonic frequency behaviour
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Adjusting operating frequencies and equipment settings
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Refining actuator speed, angle and motion control
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Re-manufacturing mother blocks with a modified threading process

Offering

The RESULT.

Over the course of several months, Faltec successfully established a stable and repeatable ultrasonic welding process capable of operating at full production volumes.

The final solution combined redesigned equipment components with tightly controlled process parameters, delivering consistent weld quality across long production runs. The process is now fully embedded in mass production, supporting uninterrupted output and meeting both functional and quality requirements.

What this
demonstrates.

This project highlights Faltec Europe’s ability to:

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Diagnose complex manufacturing issues where multiple variables interact
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Work collaboratively with equipment suppliers to develop bespoke solutions
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Apply structured engineering thinking to achieve stable, high-volume production
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Translate development learning into repeatable, production-ready processes

It also reinforces Faltec’s approach to advanced manufacturing: practical, data-led and focused on long-term reliability rather than short-term fixes.

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