Multi-Cycle Process Signature of Laser-Induced Thermochemical Polishing

Abstract

Laser-induced thermochemical polishing (LCP) is a non-conventional processing technique that uses laser radiation to smooth the surface of self-passivated metallic parts by initiating a localized anodic material dissolution. This technology can be used to selectively micro-polish without the need for masking or thermal and mechanical stress. However, there is still a lack in understanding the surface quality depending on the applied laser machining parameters. This paper takes up the concept of Process Signatures and interprets the surface smoothing as result of multiple, recurring internal material loads of a constant energy amount. The laser-induced thermal impact is identified as the relevant internal material load and is correlated with the surface roughness. This derives an empirical-based functional relation as multi-cycle Process Signature. The experiment results show an exponential decay in surface roughness with increasing cycle loads for titanium, Ti6Al4V, Nitinol, Stellite 21, and metallic glass. The Process Signature of LCP is a solution to a differential equation with respect to the cycle loads. The paper demonstrates how the multi-cycle Process Signature helps determine suitable machining parameters to predict the surface roughness, as well as to scale the polishing rate.

Change of Oxidation Mechanisms by Laser Chemical Machined Rim Zone Modifications of 42CrMo4 Steel

“…These rim zone properties are determined by the mechanical, thermal, thermo-chemical or chemical loads of the applied manufacturing process. The laser chemical machining (LCM) of metals is used for manufacturing difficult to machine materials and surface finishing [ 2 , 3 ]. Thermo-chemical loads which occur during LCM typically result in a change of roughness, residual stresses and surface chemical composition [ 4 , 5 ].…”

“…In this process, the laser beam is moved over the workpiece surface at high velocities by a scanner. The scan velocities can vary between 1 and 20 mm/s [ 3 ]. Electrolyte boiling [ 10 ] and the resulting bubbles are recognized as disturbing influencing variables for laser chemical processing.…”

Product Fingerprints for the Evaluation of Tool/Polymer Replication Quality in Injection Molding at the Micro/Nano Scale

“…The concept is equivalent to the evaluation of "Process or Manufacturing Signatures" [11], which similarly describes geometrical product variations depending on a given process condition. This method was adopted in the quality assessment of several manufacturing technologies such as milling [12], micromilling [13], grinding [14], laser polishing [15], additive manufacturing [16], and recently in replication technologies [17,18]. In [17] and [18], the replication fidelity of micro and nano structures, as well as sub-µm surface roughness, was found by measuring the IM insert and the plastic product in mirrored areas, finding a direct comparison of the features, and quantitative estimation of replication fidelity as the dimensional ratio between plastic and mold geometry.…”