Welding by time is a method of controlling the duration of ultrasonic energy applied during the welding process. In this method, the ultrasonic generator is programmed to deliver a specific amount of energy to the parts being welded, based on the length of time that the ultrasonic horn is in contact with the joint.

During the welding process, the ultrasonic horn is brought into contact with the parts to be welded, and the generator delivers a burst of high-frequency energy to the joint. The duration of this burst is determined by the welding time setting, and is typically in the range of a few tenths of a second to a few seconds, depending on the size and complexity of the joint.

Welding by time is a common method of controlling the welding process in many ultrasonic welding applications, as it allows for precise control over the amount of energy delivered to the joint, and can be used to optimize the welding process for a wide range of materials and part geometries. However, it is important to note that welding by time alone may not be sufficient to ensure consistent, high-quality welds, and other factors such as pressure, amplitude, and tooling design must also be carefully controlled to achieve optimal results.