| dc.description.abstract | During electrochemical machining (ECM) processes, narrow processing inter-gap often lead to poor electrolyte renewal, inhibiting the removal of the metal oxides, bubbles, and heat generated during reactions. This can adversely affect the machining precision and surface quality of the workpiece, especially for complex structures such as rectangular groove with inner cylindrical structure. The flow field is uneven in the processing inter-gap of such structures, increasing the likelihood of direct collisions between the workpiece and the tool electrode and potentially causing damage to both the tool electrode and workpiece. To overcome these difficulties, this study proposes an approach entailing the combination of a pulse current with ultrasonic-vibration-assisted sidewall-insulated electrodes. The study then applied this approach to conduct electrochemical trepanning with tool sinking on SUS304 stainless steel round workpieces to create rectangular groove with cylindrical structure. The effects of various processing parameters, including the pulse frequency, machining current, power of ultrasonic vibration, and duty factor, on the workpiece quality, such as the diameter, height, and taper angle of the cylindrical structures, were measured through experiments.
The experimental results indicated that when the sidewall-insulated electrodes were used, ECM with tool sinking resulted in a smaller taper angle and better external appearance than did ECM with mask. For ECM with tool sinking, applying the combination of a pulse current with ultrasonic-vibration-assisted sidewall-insulated electrodes improved the uniformity of the flow field. Moreover, for the sidewall-insulated electrodes, ultrasonic vibration assistance caused rapid changes in the electrolyte pressure in the machining area. This resulted in pumping and cavitation effects, both of which disturbed the electrolyte, accelerating the circulation and renewal of the electrolyte within the inter-gap. This reduced the resistance within the machining area, thus significantly reducing both the taper angle and the flow marks at the bottom of the groove. The minimal taper angle 1.697° of the cylindrical structures was obtained with the following experimental parameter combination: Pulse frequency of 1000 Hz, machining current of 18.5 A, power of ultrasonic vibration of level 6, and duty factor of 50%. The taper angle of the cylindrical structures was 19.73% smaller than that obtained through ECM with mask. | en_US |