**3.5 Appearance, precision, and cleanliness**

Since there is no need for filler metals in LBW, it provides an excellent welding quality and clean processing, so that it gains attention especially in the medical engineering industry where the quality of medical devices and components is very important.

The feature of weld optics focuses the beam down to a spot size range of 200-300 μm. On the contrary, larger spot sizes are rarely used, when low-shift welding

### *Laser Welding DOI: http://dx.doi.org/10.5772/intechopen.102456*

is desired. However, large weld spots are not beneficial since they require higher overall energy and a larger heat input rate. The weld heads function with a collinear chargecoupled device (CCD) camera. Different focal planes of the beam are corrected in the visible and infrared spectra. During this modification process, a sharp CCD image indicates the proper adjustment of the weld head to its correct focal position. Moreover, a projected crosshair is centered to the position of the weld spot to be perfectly superimposed with the beam (**Figure 5**). Thus, machine vision algorithms are employed for automated precise adjustment of the welding optics to desired coordinates so that the beam is exactly irradiated to the gap between the workpieces to be joined.

To keep the power density constant, LBW should be always carried out using the waist of the beam with an accuracy of 10 μm. If the irradiated beam is not focused, the power density rapidly increases and causes an uneven weld pool. Since the strength of the contact between the joining surfaces is one of the key parameters of low-shift welding, the welding design should be consistent with this parameter. To adjust cylindrical parts to the most parallel state, a dome-shaped air bearing is used. A preset force moves the parts in contact with each other, which are self-adjusted as floating on an air bearing. When the surfaces are positioned parallel to each other, the angular position is fixed to activate the alignment. Predetermined offsets can compensate for the predicted weld shift in a planar setup. By optimizing the tolerance of the parts, the accuracy of the offset can be improved.

If a welded component shifts during the nano-welding process, additional employment of the weld energy in an opposite direction bends the workpiece back into the desired location. During this process, the effect of the unavoidable shrinkage is exploited. Careful experimenting should be carried out to determine the proper power and time of the corrective pulse. This procedure is known as laser-induced micro-adjustment (LIMA). Forming nanostructured weld joints requires a weld design, which is optimized for LBW. The LBW system has to consider the specific aspect ratio of the workpiece. To obtain an optimal result, it is suggested that the nanostructure designer and the manufacturer of the welding system work together from the beginning.
