Real time measurement of the electrode wear amount is almost impossible because the EDM conditions, together with material type and hole shape, affect the electrode shape causing different machining situations and different electrode wear. Thus, an estimation model is more preferable rather than real time measurement. Consequently, the electrode wear model in Eqs. (2) and (4) requires adjustment.
Considering that the EWR of the current hole machining is not influenced by the electrode wear history, but only the previous electrode shape (same as memory less property of stochastic), the estimation model can be compensated by using the discharge time (Ts) until the (n−1)th hole machining and machining time (tm) for the current hole (nth). In other words, the EWR of the (n+1)th hole is estimated by using Eqs. (7) and (8) and the estimation model is compensated again for the EWR of the (n+2)th hole.