Experimental Analysis of Process and Laser Parameters in Laser Marking

Laser marking is a relatively new process to produce a mark on a product by the energy of a laser beam, mostly for the purpose of product identification and traceability. Compared to other techniques such as ink-marking, mechanical engraving and electro-chemical methods, laser marking has many advantages. In this study, laser marking is done with the laser of a standard RP/RM machine, i.e. a selective laser melting machine. This makes laser marking especially suited for marking parts produced by laser RP/RM techniques. On the other hand, the major difficulty in the process is the number of parameters and their complex relations which have not yet been investigated thoroughly. In the current study, the influences of scan speed, laser pump current (laser power) and pulse frequency of a Q-switched Nd:YAG laser on the mark qualities were investigated by single-factor experiments on stainless steel parts. It was found that these parameters substantially affect mark width, depth and rim formation which is caused by the expelled molten material due to the recoil pressure during the marking process. In order to investigate the influence of cross interactions, a design of experiment methodology was used to evaluate the effects of the same parameters on the success of the laser marking process in terms of removed material and clarity of the mark (visibility, sharpness, etc.).