If you are familiar with EDM (electrical discharge machining) you will know that this non-conventional material-removal process has gained considerable importance in recent years. Without it, machining parts with highly complex features would be very difficult, if not impossible. Its popularity rests not only on the advantages it offers, but also on its applications. Below we give a brief overview of this process and look at its main uses.
What is EDM?
EDM (electrical discharge machining) is a machining process that removes conductive material using thermal energy, generated by very short, precise and controlled electrical discharges (from 2 to 2,000 µs) between the tool (electrode) and the workpiece, in a dielectric fluid. What sets EDM apart from other machining processes is that it removes material without any physical contact with the workpiece (a distance of approximately 0.5 mm known as the “gap”).
There are 2 main types of EDM:
- Die-sinking EDM: machining of blind holes and shapes. The electrode has the shape to be machined into the workpiece.
- Wire EDM: machining of through holes and very complex contours. The electrode is a continuous wire that cuts through the workpiece.
Advantages of EDM
EDM has proved to be faster and more efficient than traditional machining methods, cutting production time and the associated costs, and it has become highly important in a large number of industries, above all because of the advantages it offers. The most significant are:
- It can handle all sizes and thicknesses (from tiny parts to very large components) as well as brittle and easily deformed materials. It also produces very complex shapes with minimal operator intervention.
- It is easy to automate thanks to the control program that manages the process, allowing operations to run in sequence – from roughing to finishing.
- The hardness of the workpiece material is not a factor, since the process vaporises the metal rather than literally “cutting” it. This is a major benefit with the very hard materials used in die making, or when working with materials of differing hardness or poor machinability. And because material removal takes place in the dielectric fluid, even highly flammable materials can be machined.
- The method produces parts with high-quality finishes within tight manufacturing tolerances.
In addition, each type of EDM has its own advantages. In wire EDM, for example, both internal and external cuts are possible, no prior machining of the electrode is required, and other steps such as hardening or clamping can even be dispensed with, which in turn helps shorten production time.
The main uses of EDM
EDM has always been associated with mould and die making. However, its usefulness goes further and extends to a range of applications. As a result, many industries benefit from this process, including medicine, aerospace, aviation, the automotive industry, watchmaking and jewellery, and the power industry, among others. Let us look at how it is applied in these fields.
Dies, moulds and prototypes
The very characteristics of EDM make it highly suitable for producing dies (for deep drawing, extrusion and coining), moulds (aluminium die casting, plastic injection, etc.) and for prototyping in industries where production volumes are relatively low (such as aerospace). In general, EDM gives mould and die makers the optimisation they need in their production chain to remain competitive.
Production of tools and complex components
EDM is extremely useful for producing very small, precise parts or microstructures, where conventional cutting tools could damage the workpiece through excessive pressure. It also makes it possible to work with highly complex geometries, even producing unique solutions such as watch mechanisms, orthopaedic prostheses or surgical instruments.
Deep-hole drilling
Drilling tiny (even microscopic) holes in very hard metals would be an impossible operation without EDM. From aviation to biomedicine, there is growing demand for smaller, deeper and more precise holes, produced as quickly and consistently as possible. For example, EDM is used to drill the edges of turbine blades in jet engines, which is essential to prevent them from overheating.