Laser Polishing

Abstract

A new approach to polish metallic freeform surfaces is polishing by means of laser radiation. In this technology a thin surface layer is molten and the surface tension leads to a material flow from the peaks to the valleys. No material is removed but reallocated while molten. As the typical processing time is 1 min/cm² laser polishing is up to 30 times faster than manual polishing. Reducing the roughness by laser polishing is achieved for several different materials such as hot work steels for the die and molding industries or titanium alloys for medical engineering. Enhancing the appearance of design surfaces is achieved by creating a dual-gloss effect by selective laser polishing (SLP). In comparison to conventional polishing processes laser polishing opens up the possibility of selective processing of small areas (< 0.1 mm²). A dual-gloss effect is based on a space-resolved change in surface roughness. In comparison to the initial surface the roughness of the laser polished surface is reduced significantly up to spatial wavelengths of 80 microns and therefore the gloss is raised considerably. The surface roughness is investigated by a spectral analysis which is achieved by a discrete convolution of the surface profile with a Gaussian loaded function. The surfaces roughness is split into discrete wavelength intervals and can be evaluated and optimized. Laser polishing is carried out by using a special tailored five-axis mechanical handling system, combined with a three axis laser scanning system and a fibre laser.

Microstructure and Residual Stresses of Laser Structured Surfaces

“…A 3D laser scanning system enables fast, threedimensional deflection of the focused laser beam on the work-piece surface. The setup is described in detail in [3,4,5]. The principle of the process is shown in Fig.…”

Laser Finishing of Ti6Al4V Additive Manufactured Parts by Electron Beam Melting

“…Nicoletto et al [12] studied the influence of roughness and morphology on the fatigue life of Ti alloy components produced with different orientations, using either a laser or an EBM system. Thus, the finishing of the AM parts is an important issue; different techniques can be adopted, such as abrasive fluidized bed [2], laser treatment [13][14][15][16], and chemical polishing [17][18][19]. Laser treatments offer some advantages compared to the other aforementioned techniques, such as absence of any mechanical contact due to the lack of tools which lead to a no wear high accuracy and high repeatability.…”

Micromachining of Transparent Biocompatible Polymers Applied in Medicine Using Bursts of Femtosecond Laser Pulses

“…While the material is in the liquid state it is pulled in the directions where the surface tensile force is strongest, meaning that it is pulled mainly into various valleys and cavities, hence the surface roughness after solidification may get smaller if the correct laser heating parameters are found. In addition, this process results in a combination of remelting of a thin surface layer smaller than 5 µm and vaporization of micro edges [ 26 , 27 , 28 , 29 , 30 ], see Figure 2 A. Using laser radiation, it is possible to enhance the surface quality of many different materials such as metals, plastics, ceramics, glasses, etc.…”