pressure is the primary controller of melt layer thickness, and must be kept within an optimal range in order to produce quality joints. although pressure can vary between 0.5-20mpa across different materials and geometries, the tolerances for a given application are quite tight. too little pressure will prevent sufficient heat generation, while too much pressure can cause all of the molten material to squeeze out of the joint. both scenarios will result in a weak weld. pressure is controlled by the lifting table.