**11. Joint and adaptation design (fit-up)**

LBW is in most cases without metal fillers. Therefore, to have an ideal laser weld, the edges must fit perfectly at the joint. If the distance between the weld surfaces is too great, there will not be enough melt to fill the gap and an undercut will be created on the weld surface. To create the desired weld, the gap distance must be very small. Normally it should not be more than 10% of the material thickness [3, 4, 6].
