Rationalizing requirements for gaps, surface offsets and edge radii in miniature laser welded components

In an ideal world, laser welds would always be made on perfect parts allowing no pre-weld gap, edge rounding or surface level offset. In the real world however, such deviations are not only unavoidable, but are subject to the cost/schedule/performance constraint when piece part dimensional tolerances are decided. In this work we collect recommendations from a variety of sources and try to rationalize how and why they work. We will look at common laser weld geometries: edge, butt, and lap, and discuss how the part deviations from ideality interact with the beam to determine the resulting size and character of the weld. With the aid of simple geometrical and energy arguments and finite element calculations employing level set methodology we will try to understand the physics of the weld variations that were found to result in practice.