Search

As a typical non-traditional machining method, reciprocated traveling wire electrical discharge machining (RT-WEDM) has been widely used in mold and die manufacturing industry. However, at present RT-WEDM still suffers from the problem that a large portion of molten material remains in a molten pool after a discharge, due to a relatively long discharge duration. This phenomenon limits the improvement of material removal efficiency and resulting in a thicker recast layer. To facilitate the expelling of the molten material in RT-WEDM, a two-stage discharge current regulation method is proposed in this study, which includes oscillating-current regulation (OCR) during discharge duration and explosive-current regulation (ECR) right before the end of the discharge. A pulse power generator with discharge current regulation modules is developed, and the control principle for generating an oscillating current and an explosive current is elaborated. Regulation parameters are determined based on an analysis of discharge plasma behavior. Both single-pulse discharge experiments and consecutive-pulse machining experiments are carried out to verify the effect of the proposed two-stage regulation method. The results show that the material removal rate (MRR) has been increased by 16.5% and the average thickness of recast layer on the workpiece surface has been reduced by about 15%. [ABSTRACT FROM AUTHOR]

Fast electrical discharge milling (fast ED-milling) has become a promising technology in the manufacturing industry for machining complex structures such as diffuser-shaped film cooling holes. However, the mechanism of the efficient removal of materials in this technology is not yet fully understood. To gain a further insight into this matter, an experimental investigation on the morphology of discharge craters including the absolute material removal volume per discharge, material residual volume per discharge, and directionality, is firstly carried out. The obtained results imply that a high-pressure inner flushing can significantly promote the expelling of molten material from a molten pool and is a fundamental reason why fast ED-milling can be of higher machining efficiency than regular ED-milling. To explore the mechanism behind, a novel thermal-fluid coupling model is developed to simulate the evolution process of the molten material under the effect of a flow field. The results of numerical simulation show that during a discharging, the molten material moves along the workpiece surface towards the outlet of a gap channel and solidifies at the side of a crater that is away from the electrode center. Another interesting finding is that an inappropriately high flushing pressure can result in a low machining efficiency because the severe heat convection will consume a large part of the heat generated by a discharge. This well explains the phenomenon that occurred during the experimental investigation. [ABSTRACT FROM AUTHOR]