Key Engineering Materials Vol. 1010

Abstract: Rolled titanium alloy has been widely applied to components in aerospace industry. The cutting force and the quality of hole are studied in drilling of countersunk hole of rolled titanium alloy with the crystallographic anisotropy. The periodical changes in the cutting force were observed in drilling of rolled titanium alloy, whereas in drilling of carbon steel, the cutting force increases without periodical changes due to isotropic material. The cutting force depends on the cutting direction angle, defined as the relative angle of the cutting direction with respect to the workpiece coordinate system. When the cutting direction is parallel to the rolling direction, the cutting direction angle is denoted as 0°, and when it is perpendicular, the cutting direction angle is denoted as 90°. The cutting force becomes stable around a cutting direction angle of 0°, while high frequency vibrations are observed in the cutting force around a cutting direction angle of 90°. The countersunk angle and the surface finish depend on the cutting direction angle. The cutting forces, then, are analyzed using an analytical force simulation. A three-dimensional chip flow is interpreted as a piling up of orthogonal cuttings containing cutting velocities and chip flow velocities. The cutting force is predicted by the determined chip flow model, where the chip flow direction is determined to minimize the cutting energy. The changes in the shear plane cutting model of rolled titanium alloy are discussed in the simulation. These findings provide better understandings of the effect of anisotropy in drilling to improve the quality of countersunk holes.

Abstract: Adaptive feed-rate controlled (AFC) drilling has been proposed as a high-quality and highly efficient drilling method for thermoplastic resins. The feed rate of the drill tool is controlled by the load in the thrust direction during AFC drilling. In the early stages of AFC drilling, the drill feed rate is extremely low, followed by a sudden increase in the drill feed rate. Experimental investigations revealed that the temperature near the drilling point had a dominant effect on the position at which the drill feed rate transitioned from low to high. The feed-rate transition temperature was approximately 150 °C for PA6. Therefore, the feed-rate transition position accelerated as the spindle speed increased, which significantly affected the cutting temperature. After the feed rate transitioned to a higher speed, drilling progressed at a constant rate. Additionally, the temperature of the drilled hole was generally constant regardless of the hole depth. One of the applications in which AFC drilling is expected to be superior is the drilling of different stacked materials. The effectiveness of AFC drilling was examined and compared with general constant-feed drilling for a stacked material of PA6 and carbon-fiber-reinforced thermoplastics. When the drilling efficiency was aligned, the maximum thrust force during AFC drilling was suppressed to less than 50% of that during general constant-feed drilling. Furthermore, the finished inner surface of the drilled hole was better after AFC drilling.

Abstract: Laser machining has become an excellent choice for cutting thin metal substrates due to its ability to deliver high-quality cuts with minimal material waste and fast processing times. In this research, a Nd: YAG nanosecond laser was studied for cutting a hole of a thin electrical steel, with a thickness of 0.1 mm. The trepanning technique was targeted for cutting a circle with a diameter of 1 mm. The three process parameters: laser power (P), scanning speed (v), and pulse frequency (f) are examined to evaluate their influences on the four cutting qualities of the heat affected-zone (HAZ), height of recast layer (H_R), width of recast layer (W_R) and error of diameter (E_D). Each process parameter is elected with three levels and a total of 27 experimental datasets are achieved. Based on the experimental results, the preference selection index (PSI) method was used to determine a set of process parameters through the best cutting multi-quality. Through implementing the PSI calculation, the result shows that the best quality is found by the qualities of HAZ = 82.1 µm, H_R = 17.4 µm, W_R = 24.2 µm and E_D = 14 µm at process parameters of P = 9 W, v = 600 mm/s, and f = 30 kHz.

Abstract: Cubic-machining is proposed as a new accuracy evaluation method for 5-axis machining centers. The cutting tool posture, toolpath and workpiece size in each zone are being studied. In this study, cubic-machining on two types of vertical type 5-axis machining centers with different rotational table configurations is simulated to evaluate the effect of structure errors between each axis on the machined surface. The B-axis rotational table configuration is defined as W/CBY0XZ/T for both models. The simulation results on the top surface of cube show that the effect of structure error between the B-Y axes on the tilting table model with tilted B-axis appeared than that on the trunnion table model as machining error. In the tilting table model, the positions of the B-axis coordinate system and the workpiece coordinate system are far apart in the Y and Z directions due to the inclination of the B-axis. Therefore, the structure error between the B-Y-axes acts in the direction of shifting the table up and down, resulting in larger machining errors. On the other hand, the superposition of structure errors except between the B-Y axes is common to both models, and it is confirmed that a similar evaluation could be made by taking the difference between the reference surface and the other surfaces. However, the eight machined surfaces except the reference surface have a tool posture symmetrical to the C-axis, making it impossible to compare the height differences between these surfaces. On the side surface of cube, the tool posture with a large change in the B-axis control value resulted in significant height differences between the respective machined surfaces. It is confirmed that tool postures with varying B-axis control values can lead to the identification of structure errors.

Abstract: This study investigated the characteristics of a microtool used in electrochemical microdrilling under conditions with and without magnetic field assistance. The experimental results indicated that charged ions and the direction of bubble movement were affected by the Lorentz force under the condition with magnetic field assistance, forming a vortex to promote electrolyte renewal. Reaction products and heat generated by the machining process were effectively discharged. The zone affected by stray current corrosion and microhole expansion were also reduced.

Abstract: In this paper, the effect of the constant number of simultaneous cutting edges was verified for high-precision machining of a corner radius. To verify the effect of the constant number of simultaneous cutting edges, we measured the size of corner radius at several locations using a coordinate measuring machine which can measure 3D. As a result, it was found that percentage of remaining cutting volume was reduced by keeping the constant number of simultaneous cutting edges. Furthermore, surface photograph was also measured to investigate the influence of number of cutting flutes.

Abstract: As 3D printing technology continues to advance, it offers unprecedented opportunities to manufacture complex components such as gears. This study investigates the influence of various variables associated with 3D printing, particularly using the fused deposition modeling (FDM) method, on the surface finish of gears. Additionally, it outlines future research directions aimed at understanding how surface finish behavior correlates with wear resistance. The research begins with an in-depth analysis of the key variables involved in 3D printing gears using the FDM technique. These variables include extrusion temperature, printing speed and layer height. By systematically varying these parameters, the study aims to find their individual and collective effects on the surface finish of 3D printed gears. Experimental tests are carried out to evaluate the impact of each variable on the quality of the surface finish. Parameters such as surface roughness, uniformity of material deposition and layer adhesion are meticulously evaluated. The results demonstrate that variables such as extrusion temperature and layer height exert a significant influence on gear surface finish, while printing speed may have less pronounced effects. In summary, this study highlights the importance of understanding how various 3D printing variables affect gear surface finish and wear behavior. It identifies future areas of research that could provide a better understanding of these phenomena and lead to significant advances in the manufacturing of 3D printed gears.

Abstract: Additive manufacturing (AM) has revolutionized complex component fabrication. Wire arc additive manufacturing (WAAM) uses an electric arc to deposit material layers, offering cost-effectiveness and speed. Inconel-625, known for its wear resistance, is widely used in marine and high-performance applications. This study examines post-heat treatment effects on WAAM-fabricated Inconel-625's slurry erosion behavior. WAAM deposits Inconel-625 layer by layer, characterized for microstructure and mechanical properties. Controlled post-heat treatments at 1100°C for 2 hours (water quenched, furnace cooled) enhance material properties. Specimens undergo slurry erosion tests under varied conditions: impact velocity (20, 30, 40 m/s) and strike angle (30, 60, 90°). Results show improved wear resistance with water quenching at 1100°C, while erosion intensifies with higher impact velocities. The influence of strike angle on slurry erosion varies between treated and untreated specimens. FESEM imaging reveals erosion mechanisms, with ductile failure at lower strike angles for as-built WAAMed Inconel 625, contrasting with brittle failure post-water quenching at 1100°C. This study informs engineers and designers aiming to enhance AM component performance in erosive environments, contributing to understanding manufacturing processes, heat treatment, and material performance in additive manufacturing.

Abstract: This study evaluates the effect of the vibration assisted ball burnishing method on surface integrity of maraging C300 steel surfaces printed by additive manufacturing with Selective Laser Melting (SLM) technology. The analysis contemplates variations in tool preloads and applied force. The analyzed C300 material is based on the as-built (AM), machined (M) and vibration assisted ball burnishing (VABB) states. Surface roughness was evaluated to assess topographical conditions both before and after the burnishing process. Microstructure and mechanical deformation were analyzed by Scanning Electron Microscopy (SEM) technique to examine the stresses generated by compression effect. It was found that forces in the range of 180 to 220 N reduce the roughness Sa value by up to 59% with respect to the M finish and up to 97% with respect to the AM finish. Furthermore, burnishing parameters significantly vary the final quality of the surfaces depending on the initial state of the surface and the conditions of the material.