Establishing the weld parameters for any given application is a condition of the material inputs and the process variations within those inputs. The more critical the weld parameters need to be controlled, the more critical it is to tcontrol the variations of the materials being bonded.
Like most processes there are ways to define material flow at the weld junction to influence the consistency of the weld, but every application is different. Except in cases requiring leak tight junctions, typical manufacturing inputs will generally satisfy the weld parameters to produce parts that are well within the print spec's.