During the production of a component, it may be necessary to join two or more pieces. This union can be carried out by welding the two pieces, with or without material or glue. The choice between the different technologies is carried out in relation to the materials used and of the result to be reached in terms of mechanic and hydraulic resistance, and also in terms of shocks given to the product in process. The range of technologies available is so vast that it requires expertise to choose, and then confirmed by laboratory tests before defining the method to be applied in production.