The ECM 500 from Electrosion enables more aerospace parts to be made with electrochemical machining

The use of electrochemical machining (ECM) in the aerospace industry is well known for applications such as blades and blisks, but it requires considerable skill and experience to produce a viable electrode. The ECM 500, developed by Electrosion, based in Barnsley UK has resolved this problem and enables the technology to be easily applied to a much wider range of applications, thanks to its revolutionary Impulse technology.

ECM uses electrolytic principles to erode the workpiece, dissolving the waste material in the sodium nitrite electrolyte. The advantages are speed, accuracy, surface finish, zero electrode wear and the ability to cut any metal irrespective of its hardness. The main disadvantage, up until now, has been the wide gap required between the electrode and the job to achieve sufficient electrolyte flushing. This has made it difficult or impossible to machine fine detail and has made electrode design complex, as its shape can be significantly different from that of the finished part. The new Impulse technology on the ECM 500 overcomes this limitation by oscillating the electrode and pulsing the current simultaneously. The result is that electrode gaps down to 10 microns can be used and, because the shape of the electrode is now identical to the finished part, it makes it easy to produce intricate shapes. Steve Duffield, Managing Director of Electrosion said, " The ECM 500 can achieve material removal rates of 1000 mm3/min and routinely produce surface finishes of 0.1 Ra and, with care, 0.03 Ra."

Compared with EDM, ECM is 100 times faster. Furthermore, a feature of ECM is zero electrode wear, which means that the ECM 500 only requires one electrode to cut multiple parts or cavities, saving the cost and time involved in producing the roughing and finishing electrodes required for EDM.

The ECM 500 can erode the hardest and most difficult to machine materials, including tungsten carbide and titanium, at low temperature, without any load on the part. For aerospace designers and manufacturers there are considerable benefits, as the process does not introduce any stress into the part, and difficult to reach features, which can only be reached with a very long tool, can be accurately and repeatedly machined without electrode wear or deflection. The new capabilities for eroding fine detail will allow engineers to economically apply the advantages of ECM to a much wider range of parts, enabling designs to be optimised using harder materials where appropriate, without having to consider the limitations of manufacturing methods.

Fuzzy logic principles in the control system on the ECM 500 have made the machine easy to operate and suitable for a production environment. Technology in the control adjusts the settings to suit each material and job, eliminating the need for highly skilled workers. Steve Duffield added, "With the ECM 500 we have simplified the process and overcome the associated limitations, making it a method of manufacture that can be used for many different applications. It is particularly beneficial for fragile parts made from exotic materials, which are difficult to machine in any other way. Now that we can produce intricate shapes, ECM can become a mainstream production method and aerospace designers and manufacturers will have much more freedom to make complex parts which would have previously been very costly or impossible to produce."