A methodology for precision manufacture of a nozzle using hybrid laser powder-bed fusion: A case study

Abstract

This paper presents a methodology for precision manufacture of a nozzle using the hybrid laser powder-bed fusion (L-PBF) technology. A new distortion predictive model for hybrid L-PBF was developed using finite element techniques. The model was validated against experimentally measured distortion using optical scanning. The validated model was utilised to mitigate distortion by applying additional stiffeners to the nozzle geometry where the distortion was reduced by 60% to acceptable tolerance of ± 200 µm. Micro-milling trials were conducted to identify optimum cutting parameters delivering high material removal rates while maintaining the average surface roughness of less than 1 µm. Finally, a nozzle with reduced distortion and desirable surface finish was manufactured, which has been used in industrial research context for process and product development of food products.

Benchmarking of 316L Stainless Steel Manufactured by a Hybrid Additive/Subtractive Technology

“…Relative to the as-built surfaces (having average values for Ra and Sa of 11.4 µm and 14.9 µm, respectively), these Ra and Sa values after the in-envelope micro-milling of the 316LSS surfaces were more than an order of magnitude lower and similar to finish qualities achievable on polished surfaces [47,48]. It is noteworthy that Afazov et al [21] reported minimized Ra values between 0.55 µm and 0.65 µm when using optimized milling parameters on an out-of-envelope system (i.e., Kern Evo Ultra-Precision CNC Machine) to machine 316LSS samples as-built using a Matsuura LUMEX Avance-25 system. The comparable roughness attained in the present study demonstrates the good capability, processing flexibility, and high efficacy possible with in-envelope hybrid processing.…”

“…Relative to the as-built surfaces (having average values for Ra and Sa of 11.4 µ m and 14.9 µ m, respectively), these Ra and Sa values after the in-envelope micro-milling of the 316LSS surfaces were more than an order of magnitude lower and similar to finish qualities achievable on polished surfaces [47,48]. It is noteworthy that Afazov et al [21] reported minimized Ra values between 0.55 µ m and 0.65 µ m when using optimized mill- For the as-built vertical side-wall surfaces, the roughness parameters (Table 1) showed a minor dependence on the laser power over the process window studied in this work, namely with the contour E density ranging from 19.0 J•mm −3 to 45 J•mm −3 . The surface roughness on the as-printed vertical side-walls exhibited Sz values of 144.77 µm and 106.4 µm, respectively, at the lowest and highest conditions of 160 W (19.0 J•mm −3 ) and 380 W (45 J•mm −3 ).…”

“…To date, Avegnon et al [20] additively built 316LSS using a hybrid machine but undertook out-of-envelope milling to study the effectiveness of energy consumption as a process signature that could be correlated with the microhardness. Afazov et al [21] used an A/SM machine for building 316LSS, but also investigated machining parameters out-of-envelope, using a stand-alone micro-milling center to assess the impacts on the material removal rates and the surface roughness. By contrast, Ahmad and Enemuoh [22] examined the influence of LPB and in-envelope micro-milling parameters on energy consumption during A/SM and developed an analytical model for the processing of 316LSS, but without considering the efficacy of the parametric set on the part quality and performance.…”

Metal powder bed fusion process chains: an overview of modelling techniques

“…Little research has been conducted into modelling hybrid LPBF and micro-milling. Afazov et al [115] used the inherent strain approach for modelling LPBF and further developed the inclusion of the micro-milling process. The material removal process was modelled by deactivating elements form the stiffness matrix, in a similar fashion to the modelling of conventional machining.…”

“…Modelling of hybrid LPBF for a stainless steel 316 component. The figure shows a comparison of experimentally measured surface deviation from the nominal geometry and that predicted numerically[115]. Units in mm…”