Innovative ultrasonic welding machines provide many benefits

by Kurt Fugal

Ultrasonic welding machines’ quick, clean process uses high-frequency vibrations and pressure instead of heat to melt and weld plastics, which provides many benefits.

Ultrasonic welding, perhaps the most rapidly developing field in the industry, uses high-frequency vibrations – not heat – to weld plastic pieces together. Ultrasonic welding machines are used to join small- and medium-sized pieces of plastic by creating frictional heat that melts the plastic together. Once the vibrations stop, the plastic immediately cools and solidifies.

Among the benefits of ultrasonic welding are that it’s quick, repeatable and does not use any “consumables,” or additional materials. There are no screws, nails, bolts, soldering materials, glues or other adhesives necessary. The finished pieces come out strong and clean – in fact, ultrasonic welding machines can also create hermetic seals. Plus, because no heating is involved, no ventilation system is required.

It is through pressure and high-frequency mechanical vibrations (15 kHz to 40 kHz) that plastic is melted into a solid-state weld. Most preferred ultrasonic welders run at 15 kHz, 20 kHz, 30 kHz and 40 kHz frequencies.

To begin the process, two thermoplastic pieces with similar melting points are placed in the ultrasonic welding machine. Next, high-frequency vibrations are applied directly to the joint that is being welded. Because the vibrations are limited to the joint, only the joint – not the base material – is melted. Once the plastic is melted, the vibration is stopped, pressure is applied, and the pieces are melded together. The entire process is so fast and efficient, weld times can be less than a second long.

The growing number of industries relying on ultrasonic welding machines includes the automotive, cosmetic, computer, domestic appliance, toy, medical, electronics, textile, packaging and food industries. In the medical industry, ultrasonic welding is often used because the process can ensure that no parts are contaminated by outside substances. In fact, products processed with ultrasonic welding machines may be used for “clean rooms” in hospitals. The most common use of ultrasonic welding is in the packaging and food industries where, again, the contaminant-free, clean process is of paramount importance.

The roots of the ultrasonic welding industry go back to the late 1940s, when ultrasonic waves were first used, mostly for cleaning. Then in the 1950s, ultrasonic welding was first introduced for plastics and metals. It was in 1965 that ultrasonic welding was patented by two men, Robert Soloff and Seymour Linsley. The toy industry was the first to embrace the innovative welding process; and now, there are a growing number of uses every year.

Today, ultrasonic welding is considered the leading assembly method for rigid thermoplastics. Models of ultrasonic welding machines include: ultrasonic hand guns; bench-top integrated ultrasonic welders; automation ultrasonic actuator heads and modular power supplies; and closed-loop process controls, like energy welding, distance welding, time welding, force welding, automatic frequency tuning and variable-amplitude output control. There are microprocessor and standard-time models available, as well as tools of the trade, like ultrasonic horns, fixtures, converters and boosters for all makes, models and brands of ultrasonic welders.

In today’s competitive ultrasonic-welding-machine market, it is important to find a plastic assembly solutions provider with top-notch service and technical support, and a company that meets each customer’s individual needs. For superior solutions, check out Plastic Assembly Systems at

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