Modeling gas film formation in electrochemical discharge machining processes using a side-insulated electrode

Abstract

Electrochemical discharge machining (ECDM) is an effective spark-based machining method for nonconductive materials such as glass. The spark generation in ECDM processes is closely related to the electrode effects phenomenon, which has been explained as an immediate breakdown of electrolysis due to the gas film formation at the electrode surface. The initiation of the electrode effects is mainly influenced by the critical current density, which is dependent on several parameters such as the wettability of the gas bubble, surface conditions of the electrode and hydrodynamic characteristics of the bubbles. In ECDM processes, precise control of the spark generation is difficult due to the random formation of the dielectric gas film. In this study, a partially side-insulated electrode that maintained a constant contact surface area with the electrolyte was used for the ECDM process to ensure that a uniform gas film was formed. Visual inspections indicated that the side-insulated tool provides new possibilities for describing the exact geometry of a gas film by inducing single bubble formations. Experiment results demonstrated that ECDM with a side-insulated electrode immersed in the electrolyte generated more stable spark discharges compared to non-insulated electrodes. Microchannels were fabricated to investigate the effects of the side insulation on the geometric accuracy and the surface integrity of the machined part.

Micro-Hole Drilling on Glass Substrates—A Review

“…A major problem encountered with SACE is the limited flushing of the machined material at high machined depths which reduces both the machining speed and quality. Several methods were proposed to allow more localized flushing of the machining zone, including: Adjusting the tool shape: different tool shapes including tools with side insulation, flat sidewalls, and spherical ends proved to reduce the taper and overcut [ 102 ], enhance machining accuracy [ 103 , 104 , 105 ], and reduce the hole entrance diameter by up to 65% and the machining time by up to 83% for a 500 mm deep hole [ 106 ]. Tool rotation: results in smooth sidewalls ( R a down to 0.13 μm [ 95 ]) and reduced taper [ 96 ].…”

“…Adjusting the tool shape: different tool shapes including tools with side insulation, flat sidewalls, and spherical ends proved to reduce the taper and overcut [ 102 ], enhance machining accuracy [ 103 , 104 , 105 ], and reduce the hole entrance diameter by up to 65% and the machining time by up to 83% for a 500 mm deep hole [ 106 ].…”

Building micro and nanosystems with electrochemical discharges

“…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

“…Many scholars conducted further studies of UAECDM [12][13][14]. Han and Min proposed a method of using the side insulation tool and low concentration electrolytes to reduce undesirable over cutting [15]. Furutani concluded that the width, depth and surface roughness of grooves machined by electrochemical discharge milling increased with higher voltage [16].…”