Micro-EDM machinability of difficult-to-cut Ti-6Al-4V against soft brass

Abstract

In recent years, Ti-6Al-4V (titanium alloy grade 5) is found to be one of the most widely used materials for successful applications in aerospace, automotive, and biomedical industries because of its excellent mechanical and thermal properties, outstanding corrosion resistance, and low modulus of elasticity. However, the machining of Ti-6Al-4V by conventional machining processes has always been a challenge. This study will present a comparative experimental investigation on the micro-electro-discharge machining (micro-EDM) machinability of difficult-to-cut Ti-6Al-4V against easy-tomachine brass materials. As both materials are electrically conductive, they are machinable using micro-EDM process irrespective of their hardness. It was hypothesized that the machining performance as well as quality of micro-features would vary because of the significant differences in thermal and electrical properties of two materials. In this study, the machinability of the two materials was evaluated based on the quality of the micro-features produced by the micro-EDM. Both blind and through micro-holes and micro-slots were machined on brass and Ti-6Al-4V materials. The quality of micro-features was assessed based on the dimensional accuracy, surface finish, and profile accuracy of the features. In addition, the arrays of micro-features were machined and micro patterning was done in both materials to compare the mass production capability of micro-EDM process on those materials. It was found that the dimensional accuracy of the microfeatures on the Ti-6Al-4V was slightly inferior compared to those on brass due to significantly higher tool electrode wear during machining of titanium alloy. The machined surface of the micro-features in Ti-6Al-4V was found to suffer from resolidification of molten debris, whereas micro-features on brass was found to produce smoother surface finish. Both brass and Ti-6Al-4V materials were found to produce arrays of micro-features successfully, although the micro-features on Ti-6Al-4V had debris attached to the edge and surface. The study also investigated the causes associated with the challenges in micro-EDM of Ti-6Al-4V.

Process Fingerprint in Micro-EDM Drilling

“…The levels of the processing parameters were set so as to cover a wide process window. The selection was carried out according to the machine vendor’s recommendation and to previously reported experimental research involving a similar combination of tool and workpiece materials [4,22,25]. Table 1 is a summary of the experimental factors and their levels.…”

“…Lastly, the DOC and TR were used to evaluate the quality of the drilled holes, since these are the two parameters that are mostly considered for assessing the geometrical characteristics of micro-EDMed holes [4,5,31,32,33,34]. The DOC was computed as:DOC=Dout−Dt while the TR was calculated as:TR=Dout−DinH…”

“…Deionized water or hydrocarbon oil are commonly applied as dielectric medium. Tubular tools of brass or copper material are used to increase the drilling speed [3,4].…”

Material-Technology Index to evaluate micro-EDM drilling process

“…A micro-EDM machinability comparison between difficult to cut Ti-6Al-4V and soft brass was made in [15]. The machinability of the two materials was evaluated based on the quality of the micro-features in terms of dimensional accuracy, surface finishing, and profile accuracy of the features.…”

A Study of Electrochemical Machining of Ti-6Al-4V in NaNO3 solution

“…have used direct laser disposition to create Ti-6Al-4V aerostructures that are high in quality and performance, and tend to experience significantly reduced levels of strain 3 . M. D. Moses and M. P. Jahan made blind holes, micro-through-holes, and grooves in Ti-6Al-4V using micro electrical discharge machining (micro-EDM) 4 . Research by F. Z. Wang, J. Zhao, A. h. Li et al .…”