Compact ultrasonic actuators with low weight can be easily mounted on robot arms and are thus well suited for fast and low-energy joining of plastic parts. Pre-loading the pneumatic cylinder of the actuator saves time – up to 1 second per weld spot. This is particularly noticeable in applications with many weld spots.
Pre-loading means that the cylinder has already been extended via an intelligent pneumatic system when the weld tool gets in contact with the material. Therefore the machine can immediately start the welding process. The time saved in applications with many weld spots may be significant. The joining of acoustic foam for an engine compartment with up to 20 weld spots is an example that is more and more frequently realized by means of robots. In this case, time savings per application may amount to as many as 20 seconds.
It is also possible to use several ultrasonic welding systems within automation lines; this is referred to as multi-head applications. Herrmann Ultrasonics has specially developed the VE SLIMLINE product range for automation; the machines are available with frequencies of 20, 30, and 35 kHz and with outputs of up to 6200 Watt. The 35 kHz VE COMPACTLINE, which is even smaller, is mostly used for robot applications. In addition, Herrmann supplies the new HiQ control concepts that can be easily adapted to the complexities of the various joining applications. They are characterized by easy integration into the overall control architecture.
The high processing speed that is provided by ultrasonic welding makes it very attractive for mass production despite higher initial investment. During the process, the ultrasonic vibrations that are generated from electrical voltage precisely melt the plastic at defined joining points and create a homogeneous bonding. Cycle times of up to 60 cycles per minute can be realized, depending on the required weld times between 200 and 800 milliseconds. The cold weld tools do not require a heat-up phase and are ready for operation at any time without the need of maintaining a certain temperature level. Good and profound preliminary application consulting is crucial though. This is particularly applicable for component design in order to achieve best-possible focusing of the ultrasonic vibrations in the joining area.