Vibration welding, is a form of frictional welding where force is applied to two pieces of a material so that they are pressed together extremely tightly. They are then rubbed together rapidly, creating heat and a molten weld pool forms that penetrates into the weld joint.
The weld is allowed to cool while pressure is maintained to keep the pieces bonded together. Once cooled, a particularly strong weld is formed without introducing any other substances into the process.
Linear friction welding is virtually synonymous with vibration welding, though there are other kinds of friction welding such as angular friction welding. In addition, vibration welding can be confused with other processes that utilize vibration in the process of creating a weld, such as ultrasonic welding where the vibration is created through sound instead of rubbing the pieces together.
In vibration welding there are no welding torches used, no welding wire needed, and no hands-on, manual interaction between the welder carrying out the work and the materials being welded. The process is completely automated.
Advantages of Vibration Welding
Vibration welding is used on nearly all thermoplastics, and can handle medium to large pieces such as automobile bumpers.
While the moisture content of the materials can be a concern for vibration welding, it can weld materials with a higher moisture content than ultrasonic welding. In fact, vibration welding is better suited to tolerate surface contaminants and mold since these are cleared away during the vibration process and therefore very little if any prior preparation needs to be done before joining the materials.
In addition, the melted area between the two materials is not exposed to any air. This is critical for materials that are susceptible to thermo-oxidative degradation.
How Vibration Welding Works
During the vibration welding process, two materials are pressed together with a significant amount of force. One material is held in place, while the other is moved back and forth (“reciprocating motion”) by either an alternating electromagnetic or hydraulic linear motion generator. This motion generator moves one material, while the other remains fixed so that heat is generated and a weld pool is formed.
When the weld has penetrated into the materials sufficiently, the materials are quickly returned to their final position so that the weld can cool. This process is quite rapid and generally takes less than 15 seconds.
Applications for Vibration Welding
Vibration welding was developed in 1960 by an American company called Sonobond Ultrasonics. This welding process has not changed significantly through the years aside from a few subtle improvements. While many industries use vibration welding, it is critically important for the aerospace and automotive industries because of the very low cost and high quality of vibration welding.
In the Aerospace industry many parts are made from aluminum because aluminum is a soft alloy that has strong tensile strength and can withstand the high temperatures created during the vibration process. A clean, strong vibration weld is naturally ideal when welding parts onto an airplane.
Sheet gauge steel and stainless steel are also common metals used for vibration welding. Advanced technology industries where large quantities of secure welding must be done also prefer this process, though it can also be used in smaller jobs such as welding the arms of eyeglasses onto the hinges on the frames.