Wire Electric Discharge Machining (wire-EDM) is a non-traditional machining process. Controlled electric sparks are successively used to vaporize part of a workpiece along a programmed path in order to machine a desired part. Because there is no tool that comes in direct contact with the workpiece, it is possible to machine thin, delicate parts. This thesis was designed to observe and analyze the differences in cutting capabilities for a conventional wire-EDM machine when cutting thin-walled sections from five commonly used metals utilizing a variation of roughing and finishing passes. The five metals that were used in this study are: Aluminum 6061 T6, Yellow Brass SS360, 420 Stainless Steel, D2 Tool Steel at 25 to 30 RC, and D2 Tool Steel at 60 to 65 RC. The thin-walled sections were constrained on each end by the parent material to which they remained attached, and they ranged in thickness from 0.05 millimeters (0.002 inches) increasing incrementally by 0.05 millimeters (0.002 inches) until they reached a thickness of 0.30 millimeters (0.012 inches). A Sodick AQ325L wire-EDM machine was employed to perform the machining. It was observed that differences exist in the capabilities of cutting thin-walled sections from the five different metals. This could be both observed visually through inspection and statistically through the analysis of each data set obtained by measuring the resultant thickness of each section. It was also observed that differences exist for the same material while utilizing the variations of cutting parameters: a roughing with no finishing passes, a roughing with one finishing pass, and a roughing with three finishing passes. Thus both the material properties and the cutting parameters play a significant role in determining the capability of cutting thin-walled sections with a wire-EDM machine.

Fir tree root forms are one way to retain turbine blades in turbine disks. These features are ruled surfaces that span the entire thickness of the disk and are usually machined by broaching. With increasing use of new heat resistant and difficult-to-machine materials, mechanical machining methods exhibit severe problems with tool wear and surface integrity. To mitigate these problems, thermal material removal processes such as Wire Electrical Discharge Machining (WEDM) are being considered in the aerospace industry. Developments in turbine design have led to a root form geometry in the form of an arc across the thickness of the disk in order to decrease the contact stress by increasing the contact area between blade and disk. A curved surface such as this cannot be produced by conventional WEDM as it is not a ruled surface. A novel WEDM process is being developed where an arc shaped curve is formed from an axially moving wire to allow for the production of such curved surfaces. / Thesis / Master of Applied Science (MASc) / Turbine blades are attached to turbine disks with specially shaped, straight slots called Fir Tree Root Forms (FTRF) that can be cut with broaching tools. Broaches wear out quickly because the disk is made of very difficult to cut material and the aerospace industry is starting to use Wire Electric Discharge Machining (WEDM), instead of broaching, to cut these slots since it can easily cut the material used. New turbine disk designs have curved slots, which can not be cut with a straight broach or wire, and a new process is therefore being developed which uses an arc-shaped wire to cut the desired curved shapes.