What is the main difference between Wire EDM and Sinker EDM?
Wire EDM uses a thin, consumable wire as the electrode to cut through the workpiece, ideal for through-cut profiles and intricate 2D/3D contours. Sinker EDM (also called Ram EDM) uses a pre-shaped electrode, often made of copper or graphite, that is lowered into the workpiece to create a cavity, blind holes, or complex 3D shapes. Wire EDM is like a precision bandsaw, while sinker EDM is like a stamping or molding process using sparks.
How thick of a material can Wire EDM cut?
Wire EDM machines can typically cut materials up to 150mm (approximately 6 inches) thick, and some specialized machines can handle even greater thicknesses. The practical limit depends on the machine’s power, the wire’s ability to flush debris from the cut, and the material type. For very thick cuts, the process may require multiple passes or slower cutting speeds to maintain accuracy and surface finish.
Does Wire EDM leave a burr?
One of the hallmark benefits of wire EDM is that it is a non-contact thermal process. Since there is no physical cutting force, it virtually eliminates burrs. The finished edges are typically smooth and ready for use, though a slight recast layer may be present and can be removed with light secondary finishing if required for the application.
What is the typical surface finish from a Wire EDM cut?
The as-cut surface finish from wire EDM is generally very good, typically ranging from 16 to 64 microinches (Ra). The finish can be controlled by adjusting the power settings and the number of cutting passes. A “skim cut” or finishing pass at a lower power setting can significantly improve the surface finish, often eliminating the need for additional post-processing.
What is the “kerf” in Wire EDM?
The kerf is the width of the material removed by the cut. In wire EDM, the kerf is slightly larger than the diameter of the wire itself due to the spark gap. Standard wire diameters range from 0.004″ to 0.012″, with corresponding kerf widths. This must be accounted for in the toolpath programming, as it affects the final part dimensions.
Can Wire EDM cut non-conductive materials like plastic or ceramic?
No. Wire EDM relies on electrical conductivity between the wire and the workpiece to generate the cutting sparks. It cannot process insulating materials like plastics, ceramics, or glass. For these materials, other processes like laser cutting, waterjet cutting, or conventional milling must be used.
How accurate is Wire EDM machining?
Wire EDM is renowned for its high accuracy. Typical tolerances can be held within ±0.0002″ (±0.005mm) for many applications, and even tighter tolerances are achievable with precise machine calibration and optimal cutting conditions. This makes it suitable for producing stamping dies, precision gears, and medical components.
Is a start hole always required for Wire EDM?
Nearly always. The wire must be threaded through the workpiece to begin an internal cut. This requires a pre-drilled start hole, which can be made using a small hole drilling EDM machine or a conventional drill. Cutting can only begin from the edge of the material if the profile is open to the outside.
What are the main limitations of Wire EDM?
The primary limitations are that it only works on electrically conductive materials, it is generally slower than milling for simple shapes in soft materials, and it requires a start hole for internal features. The process also removes material, so it is not suitable for adding material or for repairs.
How does Wire EDM affect the material’s properties?
Because it is a thermal process, a very thin layer on the cut surface, known as the “recast layer” or “white layer,” is rapidly melted and re-solidified. This layer is typically harder and more brittle than the base material. For most applications, this layer is negligible and does not affect performance, but for highly stressed cyclic-load components, it may need to be removed via post-processing.