Ultrasonic Welding Robot: From Toy Presses to ABB Cells

An ultrasonic weld often takes less than a second. A horn vibrating tens of thousands of times a second presses two parts together, and with plastics the joint melts at the contact point and sets, with no screws, glue or solder. For decades that horn sat in a fixed press. An ultrasonic welding robot carries the horn to the part instead, so one cell can handle several different parts. This post follows the process from its discovery in the 1960s and the first presses to robot cells in car plants, today's work on cables, batteries and medical parts, and where ABB robots fit, including one real ABB project in China.

Ultrasonic welding of thin foils at the Essen welding fair in 2005, with the sonotrode rolling along the seam. Photo: NearEMPTiness / Wikimedia Commons (CC BY-SA 3.0)

From a tape dispenser to the first ultrasonic press

The plastic method was found by accident. Robert Soloff was a lab manager at Branson Instruments, where ultrasonic probes welded thin plastic films into bags and tubes. Working near a plastic tape dispenser, he found that the probe could weld a whole joint in one go, and he went on to build the first ultrasonic press. The patent for welding rigid thermoplastic parts this way was awarded to Soloff and Seymour Linsley in 1965, and Soloff later founded Sonics & Materials. The toy industry was the first to use the technology, and in 1969 the first car made entirely of plastic was assembled with ultrasonic welding.

A worker at a plastics press in the factory at kibbutz Mishmar Ha'emek, 1964. Photo: Willem van de Poll / Nationaal Archief via Wikimedia Commons (CC0)

For the next decades the process lived in presses. A typical machine has a pneumatic or electric press to hold the parts, a nest or anvil underneath, and a stack made of a piezoelectric converter, an optional booster and a horn shaped to fit the part, driven by a generator tuned to the stack, usually at 15, 20, 30, 35 or 40 kHz. With plastics a feature called an energy director melts at the contact point; with metals the bond forms under pressure without melting the base metal. The weak point was variety. At Huaxiang in China, plastic trim was welded on special machines or by hand, and in the UK Linecross used handheld units whose results depended on the operator.

An ultrasonic welding machine of the press type, made by Herrmann Ultraschall. Photo: Herrmann Ultraschalltechnik / Wikimedia Commons (CC BY-SA 4.0)

Robots changed that by carrying the stack. Huaxiang Group in Ningbo, a large supplier of car interior and exterior trim, had ABB robots on all its plastics lines from 2002. ABB then built it a complete robotic ultrasonic welding cell with an IRB 2400 robot, an ultrasonic welding machine and a positioner. The welding head sits on the robot's sixth axis, and the robot drives it along A and B column trim for Ford and Audi. According to ABB's 2007 case study, output rose from 50 to 300 sets a day, and one line could serve two to five car models a month with a single equipment investment.

ASEA and ABB robots in the ASEA Historical Collections in Västerås, Sweden, including the IRB 6, IRB 2000 and IRB 3000. Photo: Dependability / Wikimedia Commons (CC BY-SA 4.0)

Robot-held horns for car trim, cables and clean rooms

Other interior suppliers use the same idea. Telsonic says that where parts have complex shapes or many variants, the best answer is often to mount the ultrasonic unit on a six-axis robot. Its UK customer Linecross had welded parts for years with handheld 35 kHz Telsonic units, and in 2017 it installed a KUKA robot carrying a Telsonic converter and sonotrode on its wrist, with ambient and chilled air cooling so it can weld polymers again and again at high amplitude. The cell does three-dimensional spot welding and staking on consoles, seat frames and under-trays, mostly in glass-filled nylon. ABB lists ultrasonic welding of plastic parts among its robot solutions for car interiors.

A KUKA robot carrying a Telsonic ultrasonic converter and sonotrode in the Linecross cell for car parts, 2017. Photo: Telsonic

Metals are the other half of the story. Ultrasonic welding joins the copper, nickel and aluminium foils and meshes inside batteries, and it is used on wire harnesses. A study in Scientific Reports, reported on 23 October 2026 and led by X. M. Cheng, modelled ultrasonic welds between copper and aluminium cables and found that stress builds up at the edges of the aluminium wires, which cuts the area that carries the load. With the best gap volume inside the joint, the modelled weld reached 398.6 newtons at a welding energy of 300 joules. The machines keep changing as well: Emerson made its Branson Polaris ultrasonic welding platform, launched in spring 2026, the headline of its stand at Fakuma 2026 in Germany.

Ultrasonic converters, the piezoelectric part of the welding stack. Photo: Herrmann Ultraschalltechnik / Wikimedia Commons (CC BY-SA 4.0)

Medical parts suit the process because it adds no contaminants and can run in clean rooms, and filters, IV catheters and masks are all welded this way. No source shows an ABB robot holding an ultrasonic horn on a medical line, so that is a possibility, but ABB arms already work in such rooms. At BBS Automation in Blaichach, Germany, an ABB IRB 7600 stands in an ISO Class 6 cleanroom used to make sophisticated components. Array Plastics in Barcelona, whose specialities include ultrasonic and vibration welding, runs an IRB 1200 and two IRB 1600 robots to unload injection moulding machines, and ABB offers ultrasonic welding among its application packages for plastics.

A field service engineer works on an ABB IRB 7600 robot in an ISO Class 6 cleanroom at BBS Automation in Blaichach, Germany, 2023. Photo: Clemenspool / Wikimedia Commons (CC0)

Smaller batches, smarter welds and what still limits the robots

Car makers now place small orders for many models instead of big orders for one, as ABB's Huaxiang case study put it, and that favours cells that weld many part types. Huaxiang's cell already switched between car models, and Linecross chose a robot that works between two workstations with smart fixtures, so one part type can be welded while the other station is loaded and unloaded. Process data will matter more as metal welds go into batteries and power cables, since studies like Cheng's tie joint strength to welding energy and the gaps left inside the joint. Robot paths for a cell like this can be planned and checked in RobotStudio before the first part is welded.

The vision-guided ABB IRB 1600 in Limac FormPlast's moulding cell in Sweden. Photo: ABB

At home, ultrasonic welds are easy to miss. The process seals blister packs, food and drink containers and butane lighters, and it assembles flash drives with cycle times under 300 milliseconds. Toys were its first market, and masks are welded the same way, a line of work we covered in our post on face mask manufacturing. The robots stay in the factory, and what reaches kitchens, medicine cabinets and toy boxes is the welded product. Telsonic's argument for its robot cell is that the robot never misses a weld, which is the consistency those everyday products depend on.

Blister packs of tablets; sealing blister packs is one of the packaging uses of ultrasonic welding. Photo: Tarasna0922 / Wikimedia Commons (CC BY-SA 4.0)

Money comes first. At Huaxiang the case for the robot was that one investment served two to five car models a month. Heat is a limit too, which is why the Linecross cell needs ambient and chilled air cooling to keep welding polymers at high amplitude, and metal joints bring their own weak spots, such as the aluminium wire edges in Cheng's study. Then there are skills, because somebody has to set up each new part. At Array Plastics, ABB's graphical wizard let regular engineering staff program loading and unloading without special training, and ultrasonic cells will need that kind of help as well.

An 18 gauge IV catheter with its protective sleeve and cover, one of the medical parts made with ultrasonic welding. Photo: Intropin / Wikimedia Commons (CC BY-SA 4.0)

Innovation

AI solutions for effortless ABB robot control.

Automation

Robotics

ceojohntran@chatwithrobot.net

+84905311611

© 2025. All rights reserved.

qtran1215@gmail.com