A method of welding two parts of a medical device is provided, comprising the steps of providing a first part having an internal surface with a provided welding seam and providing a second part having a joining portion comprising an external surface with an opposite welding seam, wherein at least one of the first and the second part has one or more tensioning members that are configured to interact with the surface of the other one of the first and second part to create a normal force between the welding seam of the first part and opposite welding seam of the second part, and comprising the step of inserting the joining portion of the second part inside of the first part locating at least on welding location and comprising the step of delivering at least one pulse of laser beam energy, each pulse being directed to the welding location.