Ultrasonic welding
From Wikipedia, the free encyclopedia
Ultrasonic welding is an industrial technique whereby high-frequency ultrasonic acoustic vibrations are used to weld objects together, usually plastics, and especially for joining dissimilar materials. This type of welding is used to build assemblies that are too small, too complex, or too delicate for more common welding techniques. In ultrasonic welding, there are no connective bolts, nails, soldering materials, or adhesives necessary to bind the materials together.
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[edit] Process
For joining complex injection molded parts, ultrasonic welding equipment can be easily customized to fit the exact specifications of the parts being welded. The parts are sandwiched between a fixed shaped nest (anvil) and a sonotrode (horn) connected to a transducer is lowered down and a ~20 KHz low-amplitude acoustic vibration is emitted. When welding plastics, the interface of the two parts is specially design to concentrate the melting process. One of the materials usually has traditionally a spiked energy director which contacts the second plastic part. The ultrasonic energy melts the point contact between and the parts, creating a joint. This process is a good automated alternative to glue, screws or snap-fit designs, but it only has useful applications for small pieces such as watches, cassettes, toys, and medical tools. The chassis of an automobile or in welding pieces of a bicycle together, ultrasonic welding would traditionally have uneconomical prohibiting power usage.
Ultrasonic welding of plastics causes local melting of the plastic due to absorption of vibration energy. The vibrations are introduced across the joint to be welded. Ultrasonic welding of metals is not due to heating, but instead occurs due to high-pressure dispersion of surface oxides and local motion of the materials. Although there is heating, it is not enough to melt the base materials. Vibrations are introduced along the joint being welded.
[edit] History
Ultrasonic welding appeared in the mid 60's and is rapidly developing. In its infancy, only hard plastics could be welded because their properties were the only fitting—they were acoustically conductive and had a low melting point. Less rigid plastics such as semicrystalline plastics can be welded today.
[edit] Hearing issues
An inevitable by-product of ultrasonic welding is a blast of ultrasonic sound. It is widely accepted that most humans can hear ultrasonic noise as children but lose this ability around the late teens. A device known as the "Mosquito" which emits ultrasonic noise and is intended to break up groups of loiterers is being trialled in the UK, mostly outside shops and other places where youths gather. However, not all humans lose this ability so early and some never do. Persons who can "hear" ultrasonic sound would not be comfortable working in a factory or other environment where it is used.
[edit] External links
 Metalworking
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| Welding | |
| Arc welding: Shielded metal (MMA) | Gas metal (MIG) | Flux-cored | Submerged | Gas tungsten (TIG) | Plasma | |
| Other processes: Oxyfuel | Resistance | Spot | Forge | Ultrasonic | Electron beam | Laser beam | |
| Equipment: Power supply | Electrode | Filler metal | Shielding gas | Robot | Helmet | |
| Related: Heat-affected zone | Weldability | Residual stress | Arc eye | Underwater welding | |
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See also: Brazing | Soldering | Metalworking | Fabrication | Casting | Machining | Metallurgy | Jewelry |
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