Geometric improvement of electrochemical discharge micro-drilling using an ultrasonic-vibrated electrolyte

Abstract

Electrochemical discharge machining (ECDM) is a spark-based micromachining method especially suitable for the fabrication of various microstructures on nonconductive materials, such as glass and some engineering ceramics. However, since the spark discharge frequency is drastically reduced as the machining depth increases ECDM microhole drilling has confronted difficulty in achieving uniform geometry for machined holes. One of the primary reasons for this is the difficulty of sustaining an adequate electrolyte flow in the narrow gap between the tool and the workpiece, which results in a widened taper at the hole entrance, as well as a significant reduction of the machining depth. In this paper, ultrasonic electrolyte vibration was used to enhance the machining depth of the ECDM drilling process by assuring an adequate electrolyte flow, thus helping to maintain consistent spark generation. Moreover, the stability of the gas film formation, as well as the surface quality of the hole entrance, was improved with the aid of a side-insulated electrode and a pulse-power generator. The side-insulated electrode prevented stray electrolysis and concentrated the spark discharge at the tool tip, while the pulse voltage reduced thermal damage to the workpiece surface by introducing a periodic pulse-off time. Microholes were fabricated in order to investigate the effects of ultrasonic assistance on the overcut and machining depth of the holes. The experimental results demonstrated that the possibility of consistent spark generation and the machinability of microholes were simultaneously enhanced.

Hybrid micro-machining processes: A review

“…Vibration and magnetic field can be applied in combined hybrid processes to improve the performance of these processes. An ultrasonic-vibrated electrolyte in micro-ECDM enhances the machining depth by assuring an adequate flow of electrolyte for spark generation and chip removal in the gap between the tool and the workpiece [163]. Moreover, it is shown that the magneto-hydrodynamic convection induced by the magnetic field can effectively enhance electrolyte circulation, which contributes to higher machining performance.…”

Building micro and nanosystems with electrochemical discharges

“…The following strategies were explored so far: optimizing the tool-electrode shape, promotion of the electrolyte flow by tool-electrode motions (e.g., tool vibrations [51][52][53][54] and tool rotation [48,52,55,56]), electrolyte motion [57] and flushing of the micro-hole in function of the measured force exerted on the toolelectrode [53,58]. • Optimizing heat transferred to the work-piece: Controlling the heat generated can be achieved passively or actively.…”

“…This is achieved either by using small machining voltages [18] or by reducing the time during which the voltage is applied [58,60,63,64]. Another promising approach is to control the discharge location by using side insulated tool-electrodes [57,65].…”

Experimental Study of Micro Electrochemical Discharge Machining of Ultra-Clear Glass with a Rotating Helical Tool

“…A host of literature proved that electrolyte circulation plays an important role in machining performance. Many approaches to enhancing the electrolyte circulation in ECDM and wire ECDM have been proposed [23][24][25]. Fang used rotary helical electrodes in wire ECDM, which accelerated the cycle of the electrolyte [26].…”