Optimal Design of AM Support Structures for EDM Removal from Build Plate

Abstract

Abstract Wire electric discharge machining (wire EDM) is a non-traditional material removal method that is commonly used in additive manufacturing (AM) applications to efficiently remove AM metallic parts from their build-plates. However, a persistent problem in wire EDM of AM parts is wire breakage which leads to longer machining time, challenges in rethreading wire, and wasted material, decreasing efficiency. This is the first reported study on wire EDM strategies to mitigate the two main causes of this issue in AM applications: intermittent workpiece thickness (i.e., support structures) and trapped metal powders. When AM metallic parts are made using a powder bed fusion (PBF) process, pockets of non-fused powder can become trapped in the part and supports. This powder creates a non-uniform cutting path which leads to wire breakage. Additionally, the interrupted cuts and nonuniform support thickness result in interactions between wire and AM support design that is currently not well understood. This study investigates the effects of various AM support structures on EDM wire breakage and overall machining time by understanding the effects of three critical EDM process parameters (voltage, wire feed rate, water flushing rate) on the machinability of 316L SS AM builds. In addition, the effect of heat treatment cycles on wire EDM machinability of AM parts with entrapped powder is investigated. The results of this study show that reducing the wire EDM voltage eliminates wire breaking, and that thicker supports provide steadier cutting conditions for the wire.