Small scale laser processing (welding, scribing, surface modifications) is often called either micro or milliprocessing, depending on the size of the required features. The line between these is not always clear, though, since sometimes microprocessing is used to mean all kinds of small size machining. However, it is important to separate the so-called invisible surface modifications, most often meaning nanoprocessing, and visible milliscale processing that is still much more accurate and smaller than conventional laser cutting or welding. Perhaps contrary to the common sense, the precise milliscale machining has been more challenging to laser processing than nanomachining, because the material removal rate is very slow with micromachining laser system and their work areas tend to be limited.
Almost any laser can be used for small scale machining, but since the required power levels are low, the maximum powers are often few hundred watts on continuous wave lasers. For more accurate machining, pulsed lasers such as Nd:YAG-, Nd:YVO4- and fiber lasers are used. In this case the pulse properties like pulse duration, energy and repetition rate, become vastly more important than the “raw power” of the laser.
The most common applications for small machining are probably the laser spot welding of razor blades and hermetic welding of pace maker covers. Cutting of coronary stents is one of the newer applications. What is common with all of these is that the heat input has to be low, controlled and accurate. Practically speaking no other welding or cutting process could satisfy those requirements. One quite important application area is mould scribing, for example the small features in coin moulds can be easily scribed with laser marking systems. The disadvantages of such a system include quite high price (although precision machining centers are always expensive) and long machining time: larger products might take days or even weeks to fabricate depending on the material to be removed and the amount of it.
Laser engraving of HDPE by vaporizing