Efficient Electrical Discharge Machining Titanium Alloy by A Multiple Variable Adaptive Control System

Key words:  Electrical discharge machining  Adaptive control  Titanium Alloy  Multi-variable control.

Abstract:

In electrical discharge machining titanium alloys, the 1400-1600 ℃ melting points of titanium alloys require the input of sufficient discharge energy to melt and vaporize the titanium alloy. However, because of low thermo-conduction, the input energy easily raises the temperature of the gap liquid to a high enough level. Usually, the elevated temperature of the gap liquid resulted in a reduction of the gap breakdown strength, so that the liquid dielectric deionization after pulse discharging tends to be incomplete and causes occurrences of large arcing pulses, burning the workpiece surface and causing electrode wear. This contradiction hinders the machining of titanium alloy by electrical discharge machining (EDM). To solve this issue, this study thoroughly analyzed the factors influencing gap liquid breakdown strength during EDM and identified two key elements: gap distance and amount of chips left in gap. Based on this analysis, a solution was proposed, which involved the development of a multiple variable adaptive control system. This system adjusted the gap servo voltage in proportion to the gap distance to control the discharge types of pulses, regulated the electrode discharging time to the quantity of chips left in the gap in an electrode discharge time. By dynamically adjusting these two variables, the system maintained an optimal liquid breakdown strength, facilitating effective machining while preventing arcing in machining. Experimental validation confirmed that this multiple variable control system significantly enhanced the EDM process for titanium alloys, even under challenging conditions, demonstrating its practical utility.