An inverse heat conduction method to determine the energy transferred to the workpiece in EDM process

Abstract

In this paper, an inverse heat conduction method is applied to estimate the amount of the energy (F c ) transferred to the workpiece during electric discharge machining (EDM) process. Embedded thermocouples which were connected to a four channel data logger were utilized to measure the temperature of a specific location on a rectangular workpiece during the EDM process. After temperature measurements were done, the 2-D heat conduction model of the workpiece and the Levenberg-Marquardt (LM) scheme were used to determine the energy transferred to the workpiece. This inverse procedure facilitates the determination of the heat energy at discharge-workpiece interface in EDM processes, which yet is a challenge for existing numerical models. The obtained results showed that the energy transferred to the workpiece varies with the discharge current and pulse duration from 5 % up to 45 %, which shows that the value of F c is a function of discharge current and pulse duration and that the fixed value of energy assumed in majority of the previous researches is not in accordance with real EDM conditions. Furthermore, the effects of machining parameters such as discharge current and pulse duration on F c were studied. It was evident that the F c has a direct but non-linear relationship with both discharge current and pulse duration, while discharge current has a higher impact on F c .

Modelling of single spark interactions during electrical discharge coating

“…It is evident that the values for Fv, predicted using the current model, are close to the experimental EDC data and in good agreement with other studies, including (Singh, 2012) and (Shabgard and Akhbari, 2016) (Figure 5), reflecting the incorporation of real processing conditions, such as the Gaussian distribution of the heat source, along with latent heat of fusion and the cermet material properties. However, it is noted that the modelling of EDC processes returns slightly higher values for Fv, as compared to EDM.…”

“…The high increase in fraction of energy transferred, for pulse-on conditions of 32 and 64 µs, was attributed to the drop in gap voltages, to 23 and 18 V, respectively. Overall, the values of Fv are in good general agreement with previous reports such as (Singh, 2012) and (Shabgard and Akhbari, 2016) , but are slightly higher, which probably reflects the differences in the EDC mechanisms of surface modification, as workpiece material is replaced / alloyed with tool electrode material, being distinct from material removal during EDM processing.…”

“…Figure 5a illustrates that an increase in current, from 2 to 19 A, for a fixed pulse-on time of 8 µs, having a low impact on Fv, and this is attributed to the instability of the heat source. Under conditions of short pulseon time, discharge occurs at very high frequency, resulting in inadequate time for conduction of energy and hence insignificant impact of current (Shabgard and Akhbari, 2016). Conversely, Figure 5b illustrates increasing Fv to the workpiece with increasing pulse-on time from 2 to 64 µs (for a fixed current of 10 A), being attributable to the effects of a relatively steady heat source with sufficient time for conduction.…”

“…Figure 5 Fraction of energy transferred to the workpiece, compared to literature (Singh, 2012) and (Shabgard and Akhbari, 2016) as function of increasing: a) current and b) pulse-on time.…”

“…Figure 2 Crater radius as a function of current and pulse-on time obtained experimentally (Table 1). Figure 5 Fraction of energy transferred to the workpiece, compared to literature (Singh, 2012) and (Shabgard and Akhbari, 2016) as function of increasing: a) current and b) pulse-on time.…”