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Delamination is one of the major damages associated with drilling carbon fiber-reinforced plastics (CFRP), Peel-up and Push-out are two recognizable delamination mechanisms, while drilling without using a back-up plate under the workpiece complicates the delamination mechanism even more. Minimizing delamination is dependent on many factors such as cutting parameters, geometry and type of drill bits used. The objective of this study is to present a new approach to measure the equivalent adjusted delamination factor ( F e d a ) when drilling unidirectional CFRP laminates without using a back-up plate and comparing it experimentally and numerically with conventional delamination factor ( F d ) and adjusted delamination factor ( F d a ). A polycrystalline diamond (PCD) twist drill and a special diamond coated double point angle drill was used for drilling in this study. The 3D finite element model was developed in ANSYS-Explicit to simulate the drilling process using the ply-based modeling method instead of a conventional zone-based concept. Experimental drilling validation process was implemented by utilizing a CNC machining center. Results show that the F e d a obtained is suitable to estimate the drilling induced damages, damage analysis shows that good agreements were obtained from the experiments and finite element method (FEM) simulation, while the special diamond coated double point angle drill seemed to provide a better hole quality, and drilling induced damage is highly affected by feed rate which is considered one of the important parameter.

Electrical discharge machining (EDM) is one of the most widely used non-conventional methods to machine electrically conductive materials in the manufacturing industry because of its strong capability in machining difficult-to-cut materials irrespective of their strength and hardness. Electrical discharge drilling (EDD) is an important variant of EDM. Due to the limitation of conventional drilling processes, special holes, particular those with high aspect ratios on hard-to-cut materials, can only be drilled by EDD. Extensive research has been carried out to improve the efficiency and quality of the EDD process by using different approaches, such as assisted EDD and powder-mixed EDM drilling aiming to improve the material removal rate (MRR), tool wear rate (TWR), surface quality and accuracy. This paper provides a comprehensive review of the EDD process. Different methods were compared; the advantages and disadvantages of each process were summarised; state-of-the-art technologies and the latest development were introduced, and research trends and new directions were presented.

The significant amount of heat and friction generated in machining Ti-6Al-4V affects the cutting performance and results in serious problems such as severe tool wear and poor surface quality. Graphene oxide (GO) nanoparticles have excellent thermal conductivity and high lubrication capability and have emerged as a promising solution to the heat and tribology issues. As an additive material, GO nanoparticles mixed in base fluids may lead to significant increase in thermal conductivity and lubrication capability, which in turn, could result in smaller cutting forces and lower cutting temperature in the cutting zone. This paper presents new models of using GO nanofluids in turning processes which can accurately predict the change in cutting temperature and cutting forces. The cutting temperature model was created by considering the thermal conductivity and specific heat of the GO nanofluids along with their heat transfer coefficient and friction coefficient, whereas the cutting force model was developed by taking into account friction, tool geometry and the friction coefficient associated with the thermal properties of nanofluids.

In thin-wall milling processes, the interactions between cutting loads and the displacement of the thin-wall part lead to varying tool-workpiece engagement boundaries and undesired surface form errors. This unavoidable issue becomes more severe in the machining of titanium alloys due to their poor machinability caused by the low thermal conductivity, high strength and high chemical reactivity. This paper presents a new predictive model to calculate the cutting-induced thermal-mechanical loads and workpiece deflection in milling Ti-6Al-4V thin-wall components. The cutting heat sources and the development of tool flank wear were considered in the modelling process to improve the prediction accuracy. The cutting loads were modelled analytically and calculated using an efficient iterative algorithm, and the deformation of the thin-wall part was simulated through a finite element model. A series of cutting experiments were conducted under various cutting conditions to validate the predicted results. Both the cutting forces and thin-wall displacement were recorded to examine prediction accuracy, and good agreements have been achieved between the measured results and simulated outcomes. The predicted cutting forces in the radial, feed and axial directions are within errors of 14%, 10% and 5%, respectively, concerning the experimental values. Meanwhile, the maximum predicted deformation errors at the initial, middle and end portions of the workpiece are less than 20%.

This paper presented a new electrical discharge machining (EDM) method using powder mixed effects formed by the graphene–water dielectric to improve the machining performance in processing titanium alloy. Theoretical and simulation models were developed to analyze the effects of graphene bubbles on discharge breakdown characteristics and the plasma channel. To validate the theoretical model, single-pulse experiments were conducted by analyzing the shape and dimension of single-discharge craters. Comparative and exploratory experiments were carried out to investigate the erosion characteristics of the new machining approach. Experimental results show that graphene bubbles could affect the erosion characteristics and improve the machinability of titanium alloy. The material removal rate was increased by 28% and surface roughness was reduced by 55%, whereas relative electrode wear was reduced by 43% compared to traditional EDM processes.

Electrical discharge machining (EDM) is a non-conventional machining process which has been widely used to machine difficult-to-cut materials. However, the efficiency of EDM hole making processes is low, and the quality of drilled holes is a concern especially when machining deep blind holes due to the poor removal of debris in the discharging gap. In this study, a new strategy based on shape modification of the electrode was developed to address this issue by indirectly changing the flow of dielectric. The electrodes of five different shapes with identical machining area were applied to improve the debris removal during the machining process. The effects of various electrode profiles on the machining performance were investigated. Machine time, material removal rate (MRR) and electrode wear rate (EWR) were used to evaluate the machining performance. The computational fluid dynamic (CFD) software Fluent was used to simulate the flow of dielectric caused by different electrode profiles. The results show that, compared with the straight electrode, the maximum effective cutting depth of curved electrodes and long-curved electrodes increased 13.793% and 132.184%, respectively, and the MRR of stepped electrodes was significantly higher after the machining depth reached 2 mm and 4 mm for electrodes with the working length of 2 mm and 4 mm, respectively. The surface roughness was identical for holes machined by all types of electrode. However, obvious carbon adhesion can be observed at lower cutting depth for straight electrode, followed by curved and long-curved electrodes.

Wire electrical discharge machining (EDM) is the most important approach to cutting difficult-to-machine materials and components with complex shapes in the manufacturing industry. However, the multiple demands for high material removal rate, high surface quality, and low energy consumption require contradictory working conditions and restrict the further improvement of the performance of WEDM. This paper introduced a novel powder-mixed multi-channel WEDM method using the multi-channel discharge effect to meet the conflicting requirements. The multi-channel discharge effect utilizes the equipotential characteristics of the semiconductor powder mixed in the dielectric to disperse discharge energy and therefore provides a feasible solution to resolve the above contradictions. New working principles and machining mechanisms were discovered and verified by the simulation and experimental results. Comparative experiments show that the new powder-mixed multi-channel discharge WEDM method significantly reduced surface roughness and thermal defects while maintained a similar material removal rate as conventional WEDM.

Owing to its ultra-hardness, polycrystalline diamond (PCD) is ideal for the machining of difficult-to-cut materials. According to ISO 3685, flank wear is the main factor that leads to tool rejections. In this study, a new theoretical model was developed by considering both abrasive and adhesive wear in order to investigate the process and mechanism of flank wear of cutting tools made of different PCD materials. The width of flank wear (VB) was calculated by solving the differential equation formulated to describe the rate of flank wear and its relationship with cutting parameters and the properties of tool and workpiece materials. To validate the analytical model, a series of cutting experiments were conducted by turning titanium alloy Ti6Al4V with customized tools made of three types of PCD materials. Morphological characteristics of worn areas were analyzed after each cutting test to investigate the wear process and mechanism. It was found that the wear mechanisms of three different types of PCD tools were different. Calculation outcomes matched experimental results when tools made of CTB002 and CTB010 were used. Obvious deviation was found when the tool made of CTM302 was used due to the occurrence of large-scale fracture of tool tip in the cutting passes.

Laser–electrochemical hybrid machining (LECM) is promising in the processing of thin-wall parts, which avoids problems such as the weak stiffness of structures and thermal defects. However, while most studies focus on precision machining via LECM, few investigate the potential of this technique in macro-area processing. In this paper, the synergistic effects on the coupling of thermal field and electrochemical field on bulk material removal mechanisms in the LECM of additively manufactured Ti6Al4V are comprehensively analyzed experimentally and theoretically. According to the experimental results, LECM improved the material removal rate (MRR) by up to 28.6% compared to ECM. The induction of the laser increases local heating, accelerating the temperature rise of the electrolyte, eventually promoting the electrochemical reaction. The hydrogen bubble flow promotes overall heat convection between the electrode and workpiece, which facilitates the removal of the facial precipitates and increases the efficiency of electrochemical dissolution. Higher voltages and laser powers promote the formation of hydrogen bubble flow; meanwhile, they also aggravate laser energy scattering, limiting the overall machining efficiency. Additionally, laser irradiation causes the ablation and rupture of hydrogen bubbles, which weakens the bubble flow effect and ultimately decreases the material removal efficiency. This study reveals the underlying mechanisms of the joint effects of the laser field and electrical field in LECM, and the findings can provide valuable insights for the optimization of LECM parameters in industrial applications.

The increasing utilization of hard-to-cut materials in high-performance sectors such as aerospace and defense has pushed manufacturing systems to be flexible in processing large workpieces with a wide range of materials while also delivering high precision. Recent studies have highlighted the potential of integrating industrial robots (IRs) with electric discharge machining (EDM) to create a non-contact, low-force manufacturing platform, particularly suited for the accurate machining of hard-to-cut materials into complex and large-scale monolithic components. In response to this potential, a novel robotic EDM system has been developed. However, the manual programming and control of such a convoluted system present a significant challenge, often leading to inefficiencies and increased error rates, creating a scenario where the EDM process becomes unfeasible. To enhance the industrial applicability of this robotic EDM technology, this study focuses on a novel methodology to develop and validate a digital twin (DT) of the physical robotic EDM system. The digital twin functions as a virtual experimental environment for tool motion, effectively addressing the challenges posed by collisions and kinematic singularities inherent in the physical system, yet with proven 20-micron EDM gap accuracy. Furthermore, it facilitates a CNC-like, user-friendly offline programming framework for robotic EDM cutting path generation.