Development of an original electromagnetic damping-controlled horizontal cutting mechanism for microwire-EDM

In this study, an original ‘electromagnetic damping-controlled horizontal cutting mechanism’ is designed and proposed for precisely controlling micro-scale wire-tension for cutting a microstructure array. The electromagnetic damper uses a set of three annular electromagnets equally distributed with their end-faces orientated toward a mild-steel disc. This arrangement is located at the front of the cutting mechanism. The cutting mechanism also consists of a set of microgroove rollers, a wire-electrode guide, and an auxiliary guide designed to suppress wire-wriggling and wire-swaying in order to deliver a tungsten wire of Ø13 μm diameter at a steady state over the long-term. Experimental verification is conducted on B-NPD (boron-doped nano-polycrystalline diamond), which possesses a high melting-point and high electrical resistivity characteristics, to establish the feasibility of cutting such difficult-to-machine materials. A 'one-cut one-skim' machining approach is used whereby the surface flatness and the dimensional accuracy of the slot-wall can be improved. Experimental results found that the wire feed-rate during the finish-cutting stage can be used at a rate greater than that of the rough-cutting stage. The resultant diamond microstructure array is of high-consistency and aspect-ratio at 1:22, demonstrating that the electromagnetic damping-controlled horizontal cutting mechanism can precisely and stably control the tension and running speed of the microwire.