A novel flushing technique to improve micro-EDM dressing process stability: assessment through analyzing debris evacuation

This paper aims to develop an efficient debris-flushing technique for micro-EDM dressing to improve its process stability by providing a rotation to the dielectric medium. A setup was developed in-house in this regard to impart rotation to the dielectric medium at various speeds. To evaluate the efficiency of this flushing approach, the micro-EDM dressing process stability was assessed by monitoring and analyzing debris expulsion in real time with the aid of a high-speed photography and image processing technique on an immerging Ti6Al7Nb biomedical material. The process stability was appraised by monitoring and quantifying the (a) normal and arcing pulses % with the help of a developed pulse discriminating system and (b) the workpiece retraction captured in real time by a laser triangulation displacement sensor for the whole duration of machining. Additionally, the physics behind debris exclusions captured through high-speed photography under dielectric rotation was understood by analyzing the debris flow behavior in the discharge gap using a COMSOL Multiphysics model. The results show that the proposed flushing approach was capable to improve the micro-EDM dressing process stability significantly in comparison to no dielectric medium rotation case. The debris evacuation results were also found in good agreement with the process stability results. From the comparison, it was found that as high as ~17% more normal pulses with a reduction in spindle retraction height by more than 98% were achievable at the highest dielectric rotational speed in comparison to the no rotation condition.