A tongue-and-groove joint provides internal and external flash containment and is good for a strong hermetic seal. (Image courtesy of Emerson Automation Solutions)
Ultrasonic plastic welding is an effective, repeatable and reliable joining method for a range of thermoplastic materials. It is used in an ever-increasing number of applications worldwide, for everything from medical devices and implants to consumer products.
But like any other joining or product assembly technology, it is essential to get the basics right to avoid pitfalls or unexpected difficulties. Fortunately, the benefits and the potential pitfalls of this still-growing technology are well-understood and can be easily avoided by thinking ahead and working closely with your ultrasonics supplier to address five key considerations:
1. Part design (e.g. geometry, joint design, wall thickness)
A chisel-step joint allows for thinner walls than standard energy director and is good for structural welds. (Image courtesy of Emerson Automation Solutions)
Avoid design pitfalls by engaging early with application experts about the details of part design. Among the most critical aspects of design for ultrasonically welded parts are part geometry and joint style. For example, if hermetic sealing is essential for product performance, consider using tongue-and-groove joints rather than chisel-step or other joints. Adding texturing or “energy directors” on part surfaces further enhances joint reliability and manufactured part quality.
2. Material selection
Ultrasonic welding works extremely well with a range of thermoplastics, but some are incompatible with each other or with the process, so choose with care. Once you’ve selected material types for part design, ensure that your supply chain can manufacture (e.g. injection mold) tight-tolerance parts consistently. In the event that a material is adapted or changed, it’s good to reevaluate the process with the help of your ultrasonic supplier, since weld parameter changes or even equipment changes may be required. Because weld quality and strength tie closely to part design and materials, recognize that even small changes can have significant effects on the joining process.
3. Actuation technology
Next, select the right actuation technology based on your application needs, production targets and budget. This selection is especially important for medical or electronics manufacturers whose product designs use delicate or miniaturized components with high regulatory and traceability requirements. Conventional pneumatic actuation technology relies on relatively high levels of downforce to actuate the welding process and can be too strong for thin-walled or delicate parts. They need a technology that offers much more sensitive resolution at low levels of actuation and weld force.
For these manufacturers, an electromechanical actuation system provides a much finer degree of resolution at very low levels of actuation force. This type of system provides the superior stability and control needed to repeatably join small and delicate parts.
4. Equipment adaptability
To keep pace with evolving production requirements, choose a welder that offers modularity and adaptability. Emphasize modular systems available with short lead times that can be manually operated on a benchtop or fully automated when increased production speeds are required. Demand easy and intuitive controls that can establish and maintain consistent process quality, automatically adjust to manage minor variations, and collect the required part and traceability data.
5. Global support
Finally, look for global support, including advice and recommendations that help shape your product design, reduce labor costs for training and production, minimize downtime and maintenance requirements, and enable you to adapt when supply chain, vendors or manufacturing requirements change.
Tarick Walton is global product manager for Emerson and is the lead for the company’s for Branson product development, product launch and strategic support of portfolio price, sales and performance across the ultrasonic market.
Mike Diker is Emerson’s applications supervisor, leading a team of engineers specializing in Branson technologies.
Although ultrasonic welding is a powerful and adaptable joining technology, it’s not ideal for every application. However, by accentuating the positives of product design, materials, actuation technology, adaptability and global support, manufacturers can make smarter choices about when and how to apply it to produce attractive, innovative, and high-quality products.
The opinions expressed in this blog post are the authors’ only and do not necessarily reflect those of Medical Design and Outsourcing or its employees.
Tarick Walton & Mike Diker, Branson Ultrasonics at Emerson
