Abrasive waterjet cutting is a well-established non-conventional technique for the processing of difficult-to-cut material and rendering of various complex geometries with high accuracy. However, as in every machining process, it is also required that high efficiency and productivity are achieved. For that reason, in the present study, the effect of performing the machining process by multiple passes is investigated, and the evaluation of this approach is performed in terms of total depth of penetration, kerf width, kerf taper angle, mean material removal rate, and cutting efficiency. In the case of multiple passes, the passes are performed in the same direction with the traverse speed adjusted accordingly in order to maintain the total machining time constant in each case. From the experimental results, it was found that the effect of multiple passes on the kerf characteristics, mean material removal rate, and cutting efficiency depends on the process conditions, especially regarding the depth of penetration, and it is possible to achieve significantly higher efficiency by the multi-pass cutting technique when the appropriate process conditions are selected.

Abrasive Waterjet Machining (AWJM) is considered a viable alternative to conventional machining processes, due to its capability of rendering even complex features on parts with high productivity. However, it is currently also important for manufacturing processes to comply with the various aspects of sustainability, by putting emphasis on the environmental dimension apart from the economic. Although AWJM generally is considered an inherently environmentally friendly process, it is required that thorough experimental studies be carried out to evaluate the sustainability of AWJM under various conditions. In the present work, AWJM experiments under various conditions were conducted on a Ti-6Al-4V workpiece in order to determine the optimal conditions leading to a high degree of sustainability in this process based on several indicators. The experiments were carried out using glass beads, which act as an eco-friendly abrasive. After the basic outcome of the experiment was analyzed to determine the correlations between process parameters and depth of penetration, kerf width, and kerf taper angle, sustainability analysis with the aid of Grey Relational Analysis (GRA) was conducted. The optimum solution provided a sufficiently high score regarding both the economic and environmental dimensions of sustainability.

Safflower oil is a very valuable product for the body and human health. It is rich in macro- and microelements, vitamins and minerals, and also has antioxidant properties. The primary purification of safflower oil is an important stage of its production and directly affects the quality of the final product and its storage ability. Purifying safflower oil using a combination of filtration and sedimentation processes in an experimental cone-shaped centrifuge is a new direction in its processing. The purpose of this study was to determine the effects of flax fiber as a filter material for safflower oil. The Akmai variety of the safflower was tested. The results showed that the quality indicators of safflower oil before and after filtration through flax fiber are different. The amount of unsaturated fatty acids such as oleic (18.31 ± 0.874%) and cis-linoleic acid (82.52 ± 1.854%) increased, as well as the content of arginine (2.1), tyrosine (0.57), methionine (0.4), cystine (2.5), tryptophan (2.6), and other amino acids (in oil g per 100 g of protein). The increase in the total amount of phenols (322.12 ± 6 mgEAG/kg of oil) was observed, which directly caused the higher antioxidant activity (42.65 ± 8%) of the safflower oil. These results demonstrate that flax fiber can enrich safflower oil. To find the optimal conditions for safflower oil centrifugation in a cone-shaped sedimentary-filtering centrifuge, the thickness of the flax fiber and the distance between the inner and outer perforated filter rotor were tested. It was found that the optimal and effective thickness of the flax fiber is 1.5 × 10⁷ nm, while the thickness of the sediment is 0.5 × 10⁷ nm.

Non-conventional machining processes offer significant advantages over conventional ones, especially in terms of the productivity, cost, and surface integrity of the produced parts due to their higher flexibility. Abrasive waterjet machining, in particular, constitutes an ecologically friendly process with a negligible thermal impact on a workpiece, and it has considerable capabilities for obtaining the desired outcome by regulating some of its numerous parameters. Among these parameters, the abrasive type is particularly important due to its hardness, mesh size, and shape, which lead to considerable deviations on the obtained depth, kerf characteristics, and productivity. Thus, in this work, a comprehensive comparison is conducted on the use of garnet and silicon carbide particles for the slot milling of the Ti-6Al-4V alloy under different conditions. The capabilities of both abrasive materials are evaluated by statistical analysis regarding the depth of penetration, kerf width, kerf taper angle, and material removal rate (MRR), which are obtained under the same process conditions. Finally, a multi-objective optimization based on grey relational analysis (GRA) is performed for several different practical cases. It was found that, although silicon carbide is more efficient in optimizing individual process outputs, the use of a garnet abrasive can lead to considerably better trade-offs between two or more objectives of the machining process.

The current scientific literature lacks an adequate description of hardware used to machine timber. Traditional woodworking and metals fabrication consists of tungsten carbide (TC) inserts. In this work, the authors investigate the influence of cutting tool geometry on the resulting surface roughness of timber samples. A variety of wood types were used in these studies to provide broad information on the correlation between the cutting tools used and resulting surface morphology. The cutting tools were prepared on a computer numerical control (CNC) lathe and roughness average (R_a) and average maximum peak to valley height of the profile (R_z) parameters were measured by contact stylus. The tip radius of the TC inserts used was determined to be the most significant factor that impacted R_a and R_z. In summary, we found that the tip radius of the TC insert was inversely proportional to the roughness level, indicating that a flatter TC insert cutting end results in a smoother wood surface.

This research examines the effect of trochoidal milling strategy parameters, namely cutting speed (Vc), feed per tooth (fz) and trochoidal step (Ptr) on arithmetical mean height (Sa), maximum height (Sz) and the functional volume parameters, namely peak material volume (Vmp) and core material volume (Vmc). As a working material for trochoidal milling, the AA 6082 aluminium alloy was selected. By assigning three levels for machining parameters, an L9 Taguchi orthogonal array was adopted to design and conduct the experiments. The effects of trochoidal milling parameters on the responses were examined through analysis of variance (ANOVA), contour plots and 3D topographic analysis maps. Reliable regression models were generated to correlate the independent variables with the surface quality responses. The results revealed that significant differences are indicated regarding the hierarchy effect of trochoidal milling parameters on surface and functional volume indicators. For arithmetic mean height Sa, feed per tooth is the dominant parameter, followed by trochoidal step and cutting speed. Maximum height Sz exhibits a different hierarchy in terms of the main effects of cutting parameters. Cutting speed has the most significant effect followed by feed per tooth and trochoidal step. The dominant parameter for peak material volume Vmp is feed per tooth, followed by trochoidal step and cutting speed. In the case of core material volume Vmc, the feed per tooth is the most significant milling parameter, followed by the effects of trochoidal step and cutting speed.