The presented publication is focused on increasing the productivity and efficiency of machine production of precision holes. Considerable attention was paid to the influence of the pre-preparation and drilling technology on the quality of the reamed hole. The material selected for machining was chromium-molybdenum steel 42CrMo4 QT. The cluster analysis is implemented to evaluate the experimental results obtained by measuring the cylindricity and surface roughness of the drilled and reamed holes. The factor of hole pre-preparation technology was selected in two quality levels, and the factor of drilling technology in four quality levels. The constant factors were carefully controlled during the experiment, i.e., other possible influences were excluded or minimised. Under constant cutting conditions, the experiment of the subject machining process was carried out. The cutting process parameters investigated were the cylindricity and the roughness of the machined surface Ra. The novelty and contribution of this research lie in confirming the assumption that drilling technology influences hole quality primarily, whereas hole pre-preparation technology has a secondary effect.

The key to proper implant integration in bone replacement is to orchestrate the complex interactions between materials and tissues. Moreover, due to the rapid demographic shift towards aging societies and the increase in elderly and osteoporotic patients, it is of great importance that implant materials are osteointegrative in not only healthy but also compromised bone tissues. Here, titanium (Ti) scaffolds were subjected to shifted laser surface texturing (sLST) using a nanosecond pulsed laser to create an open pore macrotopography with micro-and nano-Ti droplets. In contrast to conventional laser texturing, which leads to high heat accumulation; in sLST, the frequency of laser pulses is low, allowing for resolidification, thereby creating a surface with abundant coverage micro-/nanodroplets. The main objective was to compare the cellular responses of human mesenchymal stromal cells (hMSCs) on sLST-textured Ti surfaces (LT-Ti) for the first time with standard sand-blasted, acid-etched surfaces (SLA-Ti). In-depth analyses of cell survival, proliferation, shape, mineralization, and gene expression were performed. Cell survival/proliferation was found to be similar on both surfaces; however, SEM imaging revealed differences in hMSC morphology. On LT-Ti, cells adopted well-rounded shapes, whereas on SLA-Ti they assumed more planar shapes. Bulk RNA sequencing performed after short-term culture on both surfaces disclosed expression changes in genes such as DUSP6, TNFSF12-TNFSF13 and SULT1A4. Remarkably, the osteogenic differentiation capacity of hMSCs was significantly enhanced on LT-Ti compared to SLA-Ti. Furthermore, aged/osteoporotic donor cohorts showed significantly enhanced matrix mineralization on LT-Ti. In conclusion, our novel results demonstrate that sLST-Ti surfaces are safe, highly biocompatible, can rescue patient-cohort-specific mineralization behavior, and therefore hold great potential for the development into next-generation implants, which are suitable for both the elderly and bone-compromised populations.

Additive and coating technologies, such as high-velocity oxy-fuel (HVOF) thermal spraying and direct metal laser sintering (DMLS), often require extensive post-processing to meet dimensional and surface quality requirements, which remains challenging for nickel-based superalloys such as Inconel 718. This study presents the design and topology optimisation of a cutting tool with a linear cutting edge, capable of operating in turn-milling or turning modes, offering a viable alternative to conventional grinding. A non-optimised tool served as a baseline for comparison with a topology-optimised variant improving cutting-force distribution and stiffness-to-mass ratio. Finite element analyses and experimental turn-milling trials were performed on DMLS and HVOF Inconel 718 using carbide and CBN inserts. The optimised tool achieved significantly reduced roughness values: for DMLS, Ra decreased from 0.514 ± 0.069 µm to 0.351 ± 0.047 µm, and for HVOF from 0.606 ± 0.069 µm to 0.407 ± 0.069 µm. Rz was similarly improved, decreasing from 4.234 ± 0.343 µm to 3.340 ± 0.439 µm (DMLS) and from 5.349 ± 0.552 µm to 4.521 ± 0.650 µm (HVOF). The lowest measured Ra, 0.146 ± 0.030 µm, was obtained using CBN inserts at the highest tested cutting speed. All improvements were statistically significant (p < 0.005). No measurable tool wear was observed due to the small engagement and the use of a fresh cutting edge for each pass. The resulting surface quality was comparable to grinding and clearly superior to conventional turning. These findings demonstrate that combining topology optimisation with a linear-edge tool provides a practical and efficient finishing approach for additively manufactured and thermally sprayed Inconel 718 components.

This study investigates the influence of tool geometry and cutting parameters on thrust forces and process stability during the drilling of 90MnCrV8, a hard and wear-resistant tool steel. The objective was to identify the dominant and interactive effects of feed per revolution (f_rev), nominal tool diameter (D), cutting speed (v_c), and geometry angles (ε_r, α_o, ω_r) on the thrust force (F_f). Experimental data were evaluated using analysis of variance (ANOVA) to determine statistical significance and effect size (η²), supported by theoretical models by Kienzle, Merchant, Oxley and Zorev to explain observed physical trends. Feed per revolution had the most decisive influence on thrust force (η² = 0.690; p < 0.001), followed by tool diameter (D; η² = 0.188). Geometric parameters showed secondary yet significant effects, mainly on stress distribution and chip evacuation. The interaction between D and f_rev produced a multiplicative force increase, while the combination of f_rev and helix angle (ω_r) reduced friction at higher feeds. Cutting speed had a minor effect (η² = 0.007), suggesting limited thermal softening. The findings confirm that drilling hard steels is primarily governed by the energy of plastic deformation.