Effect of process parameters on formability in two-point incremental forming-machining of planar and twisted AA5083 blades

The deformation machining process (DMP) involves machining and incremental forming of thin structures. It can be applied for manufacturing products such as curved-surface blades without using 5-axis computerised numerical control machines. This work presents the effect of tool diameter and forming temperature on spring-back and dimensional accuracy of a simple fabricated part. The results of the first phase of the study are utilised to design the fabrication process of a curved surface blade. A feature-based algorithm is used to design the tool path for the forming process. The dimensional accuracy of the final product is improved through warm forming, two-point incremental forming, and extension of the bending zone to the outside of the product edges. The results show that DMP can be used to fabricate complex curved-surface workpieces with acceptable dimensional accuracy.

Investigation of the microstructure and thermo-mechanical properties of functionally graded materials fabricated by the vibrating centrifugal solid particle method

In this research, SiC/Al A413.1 functionally graded materials (FGMs) were fabricated by the vibrating centrifugal solid particle method (VCSPM), and the effects of the SiC particles on the microstructure and thermo-mechanical properties of an A413.1 aluminium alloy were investigated. The benefits of a vibration during centrifugal casting of FGMs are illustrated. After designing and fabricating the centrifugal casting machine, cylindrical FGM specimens were produced using the centrifugal solid particle method (CSPM) and VCSPM. This study used SiC particles with an average particle size from 50 to 62 μm as reinforcements to fabricate A413.1-10 wt% SiC functionally gradient composites at three annular mould speeds (900–1500 and 2100 rpm) and with or without a vibration of the mould. The Brinell hardness was measured; the yield strength (YS), ultimate tensile strength (UTS) and Young’s modulus (E) were determined by tensile testing; the density was determined by the Archimedes method; and the thermal expansion coefficients were measured with a dilatometer. A comparison of the samples produced by the conventional method and VCSPM shows a significant reduction in the porosity and an increase in the distribution gradient of the reinforcing particles for the VCSPM case. It can be concluded that in both processes, the mechanical and thermal properties improved in most cases by moving from the inner radius to the outer radius because of the movement of particles towards the outer radius from the centrifugal force. The results also show that the use of a vibration dramatically increased the rate and speed of migration of gas bubbles towards the inner radius, and the mechanical properties (hardness, YS, UTS and E) improved by moving from the inner to outer radius due to an increase in the percentage of silicon carbide particles. Upon increasing the velocity and using the VCSPM, the slope of these changes becomes steeper than those for the vibration-free mode and at low rotation speeds.

Electrochemical trepanning of blades made of Inconel 625

In the aerospace field, difficult-to-machine materials are used widely to improve engine performance. As a nickel-based material that performs well in all aspects, Inconel 625 is used for the blisks of aircraft engines, and electrochemical trepanning (ECTr) is used widely to fabricate such blisks because of its unique advantages regarding ruled surface parts. In this study, to investigate the performance of Inconel 625 in ECTr, measurements were made of the electrochemical characteristics firstly, specifically the anodic polarization curve and the actual volumetric electrochemical equivalent curve. Then, via dynamic electric-field simulations, the processes for forming Inconel 625 blades using ECTr were examined under direct voltage (DV) and pulsed voltage. The contours and current density distributions of formed blades at different times were obtained under different duty cycles. With decreasing duty cycle, the forming accuracy improved gradually and the stray current was reduced. To verify the simulation results, ECTr experiments with Inconel 625 were performed under different voltage conditions. With DV and 90% and 80% duty cycle, the taper angles of the machined blades were 7.784°, 6.278°, and 5.191°, respectively, and the surface roughness ( Ra) values were 0.95, 0.81, and 0.72 μm, respectively. With DV, there were obvious flow marks and gullies on the microscopic surface. With decreasing duty cycle, stray corrosion was reduced effectively and the state of the flow field was improved. Overall, the simulation results were verified effectively.

Performance assessment of energy efficient and eco-friendly turning of Nimonic C-263: A comparative study on MQL and cryogenic machining

Nimonic C-263 is predominantly used in the manufacturing of heat susceptible intricate components in the gas turbine, aircraft, and automotive industries. Owing to its high strength, poor thermal conductivity, the superalloy is difficult to machine and causes rapid tool wear during conventional machining mode. Moreover, the unpleasant machining noise produced during machining severely disrupts the tool engineer’s concentration, thereby denying a precise and environment friendly machining operation. Hence, close dimensional accuracy, superior machined surface quality along with production economy, and pleasant work environment for the tool engineers is the need of an hour of the current manufacturing industry. To counter such issues, the present work attempts to compare and explore the machinability of two of the most popular machining strategies like minimum quantity lubrication (MQL) and cryogenic machining process during turning of Nimonic C-263 work piece in order to achieve an ideal machining environment. The machining characteristics are compared in terms of surface roughness (SR), power consumption (P), machining noise (S), nose wear (NW), and cutting forces (CF) to evaluate the impact of machining variables like cutting speed (Vc), feed (f), and depth of cut (ap) with a detailed parametric study and technical justification. Yet again, an investigation is conducted to compare both the machining strategies in terms of qualitative responses like chip morphology, total machining cost, and carbon emissions. The study revealed that cryogenic machining strategy is adequately proficient over MQL machining to deliver energy proficient and gratifying work environment for the tool engineers by reducing the cost of machining and improving their work efficiency.

Fabrication of hydrophobic surfaces on Titanium using Micro-EDM exhibiting antibacterial properties

Microbial contamination on medical assistive devices has been the major challenge for biomedical industries. The present work is focused on producing patterned surfaces on commercially pure Titanium (cp-Ti) using Micro-Electrical Discharge Machining (Micro-EDM) technique, and the feasibility of patterned surface in restricting bacterial growth. Geometrical patterning in form of micro-holes have been produced on cp-Ti biomaterials with Micro-EDM in two forms, one with 20 µm inter-distance forming a dense pattern and the other with 60 µm inter-distance forming a sparse pattern. The patterned surface establishes the degree of hydrophobicity as 130° and 106° for densely patterned and sparsely patterned surfaces respectively. Further, the effect of bacterial adhesion over the textured cp-Ti surfaces are challenged with model bacteria gram negative Escherichia coli (e.coli) in Luria broth (LB) agar media. The Colony Forming Unit (CFU) count obtained for densely patterned surface compared with that of non-patterned surface reflects 90% reduced bacterial growth. The instances of pattern formation and bacterial growth have been observed with Scanning Electron Microscopy. The enhanced material properties with micro-patterning that combat microbial activities on the biomaterial surface proves its efficacy in adoption for biomedical applications, with significant reduction in bacterial contamination on medical devices or implants, leading toward reduced healthcare risks and issues related to bacterial infections on the biomaterials.

A novel prognostics solution for machine tool sub-units: The hydraulic case

A novel prognostic approach was developed and applied to a machine tool hydraulic unit. Three components were considered: pump, sensor and valve. The proposed methodology exploited a digital twin of the system to perform simulations of the healthy and faulty machine. The digital twin was properly validated through experiments. This approach dealt with the need to carry out time-consuming and expensive experimental campaigns, that is, run-to-failures – not affordable in many industrial applications. The diagnosis module was trained on digital twin simulations and fulfilled the fault detection, isolation and quantification phases. The challenge related to the variability of the operating conditions of the machine was addressed through a robustness analysis of the methodology. The solution successfully dealt with both stationary and non-stationary working conditions. A dedicated classification model was designed for each faulty component, maximising the associated classification rate. The testing procedure consisted of the application of a 10-fold cross-validation to compute the mean classification rates for stationary and non-stationary working conditions. Diagnosis performance results were excellent for the pump, whereas they were lower for the sensor and valve, reaching 79.75% and 74.93% accuracy respectively for the most challenging working cycle. The prognosis directly exploited the output of diagnostics, allowing for experimental effort reduction. Prognosis predictions were built starting from the updated health status provided by the diagnosis output. In order to test the prognosis module, mean and standard deviation of the prediction errors (less than 1.176%) were computed through a Monte Carlo approach. The conceived methodology allowed one of the critical goals of prognostics to be handled: the Remaining Useful Life probability density function estimation.

Kinetostatic analysis, manufacturing, and experimental application of a press machine based on Stephenson II mechanism

Press machine tools are often used in important industrial establishments, such as automobiles, aerospace, and aviation; these machine tools must be produced with high precision. Therefore, studies related to improving press tools and enhancing their precision are being conducted. In this study, a press machine tool based on the Stephenson II mechanism is proposed. Compared to that of conventional crank presses, this mechanism increases the slider balance using a ternary link and unique connecting rods. Thus, the slider precision can be improved with a small addition to the mechanism, and load transmission can be ensured in a balanced manner. To test the contribution of the mechanism, dynamic analysis is performed using the kinetostatic method, and the dynamic data of the mechanism are obtained. Subsequently, a press machine prototype is designed and manufactured. The experimental results are verified against the theoretical results, confirming that the proposed press machine tool based on the Stephenson II mechanism has better characteristics than those of the conventional press machine owing to the favorable distribution of forces on the slide and lower reaction to the slide guides.

A Legorization method based on 3D color printing trajectory

In this paper, a Legorization method which can reconstruct LEGO model with complex internal and external structures from 3D color printing trajectory is proposed. Different from voxelization methods, by combining advanced adaptive slicing algorithm with building “high-resolution” regions with thin plates, the reconstruction accuracy of initial LEGO units can be guaranteed. Furthermore, the tree structure is employed for automatically generating support structures which can be converted into LEGO support structures. By adopting split assembly appropriately and implementing combination of these parts accurately, the reducing supporting structures can be further simplified. In order to optimize the Legorization scheme, a machine learning method is used to guarantee the quality and efficiency of the reconstruction work. Complex LEGO models are provided to demonstrate the effectiveness of the proposed method.

A new geometry definition and generation method for a face gear meshed with a spur pinion

The conventional tooth surface of a face gear is difficult to manufacture, and the cutter for the face gear cutting is not uniform even though the parameters of the pinion mating with the face gear slightly change. Based on the analysis of the geometry features of the tooth surface, a new developable ruled surface is defined as the tooth flank of the face gear, for which the most important geometry feature is that the flank could be represented by a family of straight lines, hence it could be generated by a straight-edged cutter. The mathematical models of the new ruled tooth surface, the cutter and the generation method are presented, the deviation between the ruled surface and the conventional surface, the correction of the ruled surface to reduce the deviation are investigated through numerical examples. The manufacturing process is simulated by VERICUT software, and the results demonstrate that even when the principle deviation is added to the machined deviation, the absolute deviation is on the micro-scale. The meshing and contact simulation shows that the new surface could obtain good meshing performance when the number of face gear teeth is greater than three times the number of pinion teeth. This research provides a new method for manufacturing face gears.