Jointing pressure too low: lack of mixing of join partners

Jointing pressure too high: too much plastified material is pressed into the welding beads. This leads to a clash of colder layers and thus to an insufficient mixing and a reduction of strength. In addition, the excessively high pressure leads to inadmissibly high shear deformations, which, in turn, lead to increased residual stress in the welding seam, which may reduce the strength considerably.