System and method for welding two thermoplastic workpieces

A system for welding two thermoplastic workpieces, comprising:

• an ultrasonic tool;
• a support;
• and
• a cooling unit;
• wherein the ultrasonic tool is configured to generate mechanical vibrations with a frequency of between 20 kHz and 100 kHz,
• wherein a head of the ultrasonic tool faces the support such that a receiving region for the workpieces is formed between the head of the ultrasonic tool and the support;
• wherein the system is configured to clamp the workpieces together in the receiving region by the ultrasonic tool and the support when at least one attachment portion of the workpieces has a mutually opposite arrangement in the receiving region;
• wherein the ultrasonic tool is configured to introduce mechanical vibrations into the attachment portion of the workpieces to weld the workpieces in a joining zone;
• and
• wherein the cooling unit is configured to cool at least a part of the attachment portion of the workpieces and/or a cooling portion of the workpieces that directly adjoins the attachment portion using cooling liquid.