It is amazing to see the shapes and assemblies that can be made from various types of plastics. An important technology for manufacturing many of these components is an ultrasonic plastic welder. But how do they work?
I came across the Branson Ultrasonic Horn Catalog found in the Branson Custom Tooling section on Emerson.com. An ultrasonic welder consists of a power supply, actuator, converter, booster, and horn. The power converter converts standard 60Hz low-frequency electrical energy into very high frequency (15, 20, 30, 40KHz) electrical energy.
From the catalog, here is the theory of operation.
The welding stand houses the converter, booster and horn in a rigid, column-mounted cabinet. A pneumatically activated carriage mechanism applies pressure to the part, and an electronic programmer controls ultrasonic exposure and clamping time.
The converter transforms electrical energy from the power supply into 15, 20, 30 or 40 kHz mechanical vibrations. The heart of the converter is a lead zirconate titanate electrostrictive element which expands and contracts at its resonant frequency when excited by electrical energy.
The ultrasonic horn, usually one-half wavelength long at a resonant frequency of 15, 20, 30 or 40 kHz, transfers mechanical vibratory energy from the converter to the work piece. In addition, the horn maintains the pressure necessary to form a weld once joint surfaces have been melted.
When a horn is vibrated at its resonant frequency, its two ends move in opposite directions, lengthening and shortening the horn. No longitudinal motion occurs at the horn’s center or nodal area, but stress concentration is greatest in this area.
Horn amplitude is measured as peak-to-peak displacement of the horn face. Amplitude is increased or decreased by changing the mass ratio of the horn or by altering the input amplitude. The ratio of a horn’s output amplitude to its input amplitude is called “gain.” The horn amplitude required for a specific application is dependent on the type of plastic, type of operation (e.g. welding, staking, etc.), part geometry, and joint design of that application.
Many types of horns are available to meet the requirements of the plastic welding application. The catalog outlines several basic horn types including Stepped, Exponential, Catenoidal, Rectangular or “Bar”, and Circular horns. Beyond these basic horns the catalog lists many others developed for development and special tooling.
Here’s a short 2:13 YouTube video, Branson GSX-E1 Ultrasonic Welder, which provides an overview and benefits of the Branson Ultrasonic Welding technology.
Visit the Branson GSX-E1 Ultrasonic Welder page on Emerson.com for more information on this advanced and intuitive flexible joining solution, designed to optimize and ensure quality welds.
