By thinking through the ultrasonic welding process, you can avoid the pitfalls and maximize results.
Tom Hoover, Emerson
Ultrasonic plastic welding is an effective, repeatable, and reliable joining method for a range of medical-grade polymers. It is used in an ever-increasing number of medical applications worldwide, in the manufacture of everything from analytical and drug-delivery devices to surgical instruments, filters, and consumables — even disposable medical apparel.
Like any other joining or product assembly technology, it is essential to get the basics right to avoid potential pitfalls or unexpected difficulties. Fortunately, 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 “accentuate the positives” in five areas:
- Part design, geometry, joint style, and surface finish.
- Material compatibility.
- Actuation technology.
- Global resources and support.
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 the performance of a medical product, consider use of 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.
Ultrasonic welding works extremely well with many medical-grade thermoplastics, but some are incompatible with the process. Once you’ve selected material types for a part design, ensure that your supply chain can manufacture parts consistently. Should a material be adapted or changed, weld parameter changes or even equipment changes may be required.
Because weld quality and strength tie closely to part design and materials, realize that even small changes can have significant impacts on the joining process. However, once you “dial-in” a process with the right ultrasonic welding equipment and weld parameters, you should enjoy outstanding repeatability and process control. Welded joints immediately bond into a cohesive assembly — no curing or setup time is required.
Next, select the right actuation technology based on your application needs, production targets and budget. This selection is especially important for medical device applications that rely on the use of delicate or miniaturized plastic parts, electronic components or other components with significant regulatory and traceability requirements.
The pneumatic actuation technology used on conventional ultrasonic welders relies on relatively high levels of downforce to actuate the welding process and can be too much for thin-walled or delicate parts. These parts need a technology that offers much more sensitive resolution at low levels of actuation and weld force.
Modularity and 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 set up rapidly, then 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, capture event logs and weld history for 21 CFR Part 11 compliance, and store required part and device traceability data.
Finally, look for global support, including advice and recommendations that help shape your medical product designs, reduce labor costs for training and production, minimize downtime and maintenance requirements, and enable you to adapt when the supply chain, vendors, or manufacturing requirements change.
Though ultrasonic welding is a powerful and adaptable joining technology, it’s not ideal for every medical application. However, by accentuating the positives of product design, materials, actuation technology, adaptability, and support, manufacturers can make the smartest choices about when and how to apply ultrasonic welding to produce attractive, innovative, and high-quality medical devices and products.
Tom Hoover has been a senior medical market manager for assembly technologies at Emerson since 2010. He has experience in all aspects of medical device product development and regulatory compliance.
The opinions expressed in this blog post are the author’s only and do not necessarily reflect those of Medical Design and Outsourcing or its employees.