The current signal in spark-assisted chemical engraving (SACE): what does it tell us?

Abstract

Spark-assisted chemical engraving (SACE) is a promising micro-machining technology for the low-cost machining of holes and channels in non-conducting materials, such as glass and some ceramics. Despite the complexity of SACE due to the interdependency of thermal, electrochemical and mechanical effects, the key data of the machining process can be obtained from only a few signals. Possible process surveillance signals are analysed and discussed. In particular, the current flowing between the electrodes is analysed. It is shown that various information can be deduced from it, such as qualitative indications of the local electrolyte temperature, differentiation between machining and non-machining and the distinction between the presence and absence of a gas film. However, so far no direct link between the current and the instantaneous material removal rate could be found. Experimental results are presented and the possibility of active process control based on current measurement is discussed.

Characteristics of the Arcing Plasma Formation Effect in Spark-Assisted Chemical Engraving of Glass, Based on Machine Vision

“…The results indicated deviations in the diameter of the machined contour and the thermal-affected region of approximately 3.7% and 2.7%, respectively. The experimental results indicated good agreement with those obtained by extant studies [ 18 ]. In reference [ 18 ], Wüthrich et al indicated that deviations of the micro-holes with a mean diameter of a few hundred microns typically corresponded to approximately 20% of perfect circular contour.…”

Experimental Study of Tool Wear in Electrochemical Discharge Machining

“…As can be seen from Figure 8, the average current of spark discharge shows a trend to decrease slightly and then increase as the voltage increases. According to the research of Wüthrich et al [27], it is known that in the process of electrochemical When the cathode has loss after 200 s of machining, it can be seen from Figure 7 that the gas film formation time generally shows a decreasing trend, but the reduction is not significant. Zhang et al [26], in their conclusion, stated that the critical voltage also increases with the increase in the diameter of the tool electrode.…”

“…The trend in the gas film formation time before and after machining is consistent. From another perspective, according to Wüthrich et al [27], the gas film formation time is related to the time required by the local heating of electrolyte, which also depends on the resistance between the electrodes (local temperature of the electrolyte). At high voltages, the spark discharges become more intense, and the conductivity of the electrolyte is enhanced with the increase in the local temperature of the electrolyte, leading to the decrease in resistance between the electrodes.…”

“…As can be seen from Figure 8, the average current of spark discharge shows a trend to decrease slightly and then increase as the voltage increases. According to the research of Wüthrich et al [27], it is known that in the process of electrochemical discharge, the current of the electrochemical reaction is much higher than the spark discharge current. When the voltage is low, the system has not entered the spark state of stable discharge, and the spark discharge is mixed with the electrochemical reaction.…”

Characterization and modeling of 2D-glass micro-machining by spark-assisted chemical engraving (SACE) with constant velocity

“…The machining takes place in an electro-chemical cell where the cathode is used as a tool and the anode as a counter-electrode. When a voltage higher than a critical value, called critical voltage, is applied, bubbles grow so dense on the tool electrode that they coalesce into a gas film; this has been identified as one of the key parameters for machining repeatability [3]. Electrical discharges take place between the tool electrode and the electrolyte.…”