Abstract This study presents an experimental investigation to improve Selective Laser Melting (SLM) regarding aspects such as surface roughness, density, precision and micro machining capability by employing secondary processes such as Selective Laser Erosion (SLE) and laser re-melting. SLM is a layered additive manufacturing technique for the direct fabrication of functional parts by fusing together metal powder particles. Laser re-melting, applied after each layer or only on the top surfaces, is used to improve the roughness and density while SLE, a subtractive process, is combined with SLM to improve the precision and micro machining capability.

Manufacturing by Combining Selective Laser Melting and Selective Laser Erosion / Laser Re-melting (Productie door het combineren van selectief laser smelten en selectief laser eroderen / laser hersmelten)

Recent progress and perspectives in additive manufacturing of magnesium alloys

3D printing (3DP) of polymers using fused filament fabrication (FFF) is not yet massively adopted in industrial environments due to shape accuracy and surface integrity limitations. However, the FFF process combined with laser processing (hybrid manufacturing) or other precision machining processes is under investigation nowadays and is a promising combination for high quality 3DP final parts. This work investigates the effects on the dimensional accuracy and the surface roughness of process parameters, during low power CO2 laser cutting (LC) of thin acrylonitrile butadiene styrene (ABS) plates manufactured with the FFF process. Even though LC is highly flexible and the quality of the machined surfaces is versatile, certain problems are associated with LC, such as the kerf angle formation and the surface texture quality, which need optimization in respect to the LC parameters. The full factorial design methodology is adopted, having four parameters as input, i.e., stand-off distance (SoD), raster deposition angle (RDA), laser speed (LS), and laser power (LP), and kerf geometry characteristics as output, i.e., kerf widths (upper, middle, and down; Wu, Wm, and Wd), kerf angle (KA), and average and max height surface roughness (Ra and Rt). The statistical analysis is used to investigate the relations between the input and the output parameters. Seventy-two independent experiments were utilized. The analysis of variances (ANOVA), the interaction study, and the quadratic regression models (QRM) were adapted to fit the input with the output parameters, optimize the process KA close to 0°, and minimize the Ra close to 0 μm. The optimum parameter values (7.5 mm SoD, zero RDA, 14.4 mm/s LS, and 105 W LP) are validated by seven independent experiments, which show that only the Wu and Ra predicted values are close to the actual values following the ANOVA analysis and the mean average percengtage error (MAPE) index.

Laser cutting of 3D printed acrylonitrile butadiene styrene plates for dimensional and surface roughness optimization

An overview of modern metal additive manufacturing technology

Additive manufactured magnesium (Mg) alloys have widespread applications in the medical industry as orthopedic implants and biomedical stents, and in the transportation/automotive industry due to their status as the lightest structural metallic alloys. The printability of Mg alloys is challenging due to the high oxidization rate, rapid evaporation, and susceptibility to gas trapping. Accordingly, there might be many defects in the as-built parts such as cracking and delamination, porosity and lack of fusion, residual/thermal stresses and distortion, inhomogeneous/columnar microstructure, anisotropy in mechanical/physical properties, inclusions, and non-equilibrium phases formed during solidification. The removal of these defects has a great practical significance, where the post-processing heat treatments without altering the geometry of the parts are often sought in this regard. Accordingly, the present overview article focuses on and critically discusses the recent progress/advances in the application of hot isostatic pressing (HIP), solution annealing (solutionizing), and aging/precipitation heat treatment for the modification/homogenization of the microstructure and improvement of mechanical/functional properties of Mg alloys for the first time. The main fabrication methods are selective laser melting (SLM) from the category of powder bed fusion (PBF) processes, as well as wire and arc additive manufacturing (WAAM) from the category of directed energy deposition (DED) processes. Moreover, the adaptation of the friction stir processing (FSP) technology into additive manufacturing for grain refinement via dynamic recrystallization (DRX) and defect/pore closure (due to the elevated-temperature thermomechanical processing effects), combined severe plastic deformation (SPD) and thermal post-processing, hybridization of additive manufacturing for Mg alloys, and future prospects have been summarized. 

Post-processing heat treatment of lightweight magnesium alloys fabricated by additive manufacturing: A review

Despite the rapid growth in the past decade, the industrial adoption of additive manufacturing has not still been achieved due to certain limitations. A recent trend to alleviate its inherent drawbacks is to integrate additive manufacturing with secondary production techniques. Indeed, hybrid additive manufacturing solutions may help overcome the current barriers to today’s production systems by making use of the combined merits of merging technologies. This paper presents a comprehensive review of the current state-of-the-art in the field, covering the following three key aspects of the subject: (i) advances in the hybridization of additive manufacturing processes, (ii) developments in process planning for integrated technologies, and (iii) insights into the hybrid additive manufacturing industry. The main objective of the paper is to classify the latest knowledge for the researchers, along with highlighting challenges and future research directions in this field.

Mecid Uğur Dilberoğlu

Papers

Current trends and research opportunities in hybrid additive manufacturing