## 1 Introduction
An innovative finishing method for the internal surfaces of complex tubular structures made from Inconel 718 and fabricated using SLM technology was proposed by [PERSON] et al. [7]. The developed approach integrates rotational motion with linear vibration in the presence of a magnetic field, enabling precise control of the magnetic abrasive action within narrow gaps between two concentric tubular layers. The process facilitated uniform material removal from both the outer surface of the inner tube and the inner surface of the outer tube. The initial surface roughness of -7 \(\upmu\)m Ra was reduced to below 1 \(\upmu\)m Ra, and in the best case, to as low as 0.21 \(\upmu\)m Ra. Microstructural analysis confirmed the removal of the top layer containing coarser dendritic cells, which translated into an increase in nanohardness and a reduction in residual stresses without inducing substructural damage. The theoretical model of material removal developed in the study was successfully validated experimentally, showing good agreement under various processing conditions. The combined use of rotational and vibrational motion was identified as the most effective configuration, yielding a superior surface finish and enhanced material removal rates. The issue of surface quality improvement in additively manufactured 316L stainless steel samples was further addressed by [PERSON] et al. [8], who focused on the relationship between surface inclination angles and the effectiveness of MAF. The authors produced seven samples with varying inclination angles (0-90\({}^{\circ}\)) using an EOS M290 printer while maintaining constant printing parameters to eliminate confounding variables influencing surface quality. The study revealed that initial surface roughness increased with an inclination angle of up to 60\({}^{\circ}\), then decreased, which was attributed to the interplay between the stair-stepping effect and the presence of partially melted particles. MAF polishing led to a significant improvement in surface quality, achieving a maximum Ra reduction of 75.7% (for the 0\({}^{\circ}\) sample). Furthermore, the average reduction in peak height (Rp) was twice that of valley depth (Rv), indicating the preferential removal of surface asperity peaks. A theoretical model was proposed to account for the influence of initial surface roughness on the indentation depth created by abrasive particles and hence on overall material removal. The model showed good agreement with the experimental data. Microhardness testing revealed no significant differences among samples with different inclination angles, ruling out mechanical property variations as a factor influencing polishing efficiency. This study confirms the viability of MAF as a flexible surface finishing technique for complex AM geometries, emphasizing that process parameters should be tailored based on the local initial roughness conditions. While the previous study highlighted the adaptability of MAF to various build orientations in metals, further research has expanded its application to non-metallic materials using hybrid polishing mechanisms. [PERSON] et al. [9] addressed the development of a finishing process for zirconia ceramics fabricated via stereolithography (SLA). They proposed an innovative technique called A-MFAF (alternating-magnetic field-assisted finishing), which utilizes a specially designed magnetic field generator composed of a magnetic column and a rectangular pole, enabling dynamic regulation of the magnetic field within the machining zone. The process employs a novel abrasive medium termed MSTF (magnetorheological shear thickening finishing), consisting of PEG 200, SiO\({}_{2}\), iron particles, and SiC. This combination facilitates the synergistic effects of magnetorheological and shear thickening mechanisms (MRST). The study demonstrated that the use of MSTF reduced the surface roughness from Ra = 1.79 \(\upmu\)m to 89 nm and Sa from 5.45 \(\upmu\)m to 109 nm. Optimal finishing results were achieved with a working gap of 0.6 mm and a rotational speed of 700 rpm.