The cost of ultrasonic and thermal assembly equipment is comparable in the high-end, high-volume production environment, said Crawford. “Thermal assembly has some lower-end, lower-volume options that are much less expensive than ultrasonic equipment,” said Crawford, but one also must take into account machinery options and features for both technologies.
Regarding tooling, Crawford notes that ultrasonic technology for multi-point heat staking is usually more expensive because of the complexity of the horns and materials required. “Ultrasonic multi-point heat staking has some additional limitations that thermal assembly does not,” he added. Notably, heat stake points must all be on a single plane and typically all posts must be the same size and shape to achieve consistent assembly results. Thermal assembly tooling typically is the least expensive. “Thermal heat staking tooling has the widest range of use and achieves the best results in overall assembly performance,” said Crawford.
On the maintenance front, Crawford noted that ultrasonic multi-point heat staking is usually fairly easy to maintain, but has special cleaning requirements, as the horns typically are made from stainless steel or titanium. Thermal assembly tooling is easier to maintain, but that is “directly related to the quality of the tooling,” stressed Crawford. “Higher-end tooling using better materials and coatings makes maintenance easier and less frequent.”
So, given these advantages, why don’t manufacturers of medical wearables shift en masse to thermal assembly methods? It’s partly inertia and partly a lack of awareness. Adhesives and ultrasonic technology are the most common methods currently used, and many medical device manufacturers simply don’t have experience using thermal assembly processes, according to Crawford. But the tide may be turning. “Customer studies on comfort and feel have led medical device manufacturers to replace their existing ultrasonic processes with thermal assembly for welding the adhesive patches onto wearable devices [to achieve] a more comfortable user experience,” said Crawford.
The next rendezvous for plastics professionals and the medical device supply chain happens in Cleveland, OH, on March 7 and 8, 2018. UBM America’s newest design and manufacturing trade show and conference, Advanced Design & Manufacturing (ADM) Expo showcases five zones—medical manufacturing, plastics, packaging, automation and robotics, and design and manufacturing. A full slate of conference sessions will explore innovations in advanced manufacturing. Go to the ADM Cleveland website to learn more and to register to attend.