Electrical Discharge Machining vs. ECM
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Both ECM and ECM are non-conventional machining methods; however, that one letter makes a big difference! EDM, or electrical discharge machining, relies on localized spark erosion to remove material, whereas ECM, or electrochemical machining, utilizes electrolysis to dissolve the metal locally. We will explore some of the other differences, similarities, and advantages of each below.
In addition to the metal removal method, there are some other fundamental process differences:
Working fluid: ECM uses a conductive electrolyte, most commonly NaCl-based or NaNO3. EDM utilizes a dielectric fluid, typically deionized water.
Power: ECM is a low voltage, but high current process whereas EDM is the opposite: high voltage and lower current.
Tooling: Although both processes are non-contact and typically utilize a custom shaped tool, EDM exhibits tool wear and ECM does not.
Non-contact process: the tool or electrode does not come into contact with the work piece. A small gap is maintained and flushed with the working fluid.
Electrical energy: Both processes require a power source, typically a pulsed DC power supply, to enable the metal removal.
Conductive materials: In general, both processes are limited to processing electrically conductive materials.
ECM - ADVANTAGES
The electrochemical machining process can be thought of as reverse electroplating; instead of adding material, metal is dissolved and carried away by a flowing electrolyte.
Non-thermal machining: No thermal-related stress means the material properties of the surface remain unchanged after ECM. This also means no heat-affected zone (HAZ) and no recast layer or other surface deposits.
Surface finish: The ECM process is capable of very low surface roughness values. The achievable results can be compared to electropolishing; however, shape formation is achieved simultaneously. ECM also doesn't require a finishing pass or finishing electrode.
Volume production: The lack of tool wear makes the ECM process well-suited for volume production. Although the initial development costs can be high, the return on investment can be quickly realized in production.
Process speed: ECM removes material continuously from all surfaces that are in close proximity to the electrode. Provided there is sufficient electrolyte flow and available electrical amperage, the ECM removal rate scales linearly with surface area of the electrode. For example, we could drill 1 hole at 1 mm/min or we could drill 100 holes at 1 mm/min (equivalent of 1 hole at 100 mm/min).
EDM - ADVANTAGES
The electrical-discharge machining process is much more common and can be found in many standard machine shops across the country. Therefore, it possesses two large advantages over ECM.
Low initial cost: Many years of process development and refinement have resulted in a process that is very well understood. As a result, the tool geometry can easily be designed and fabricated to support the EDM process with relatively low risk. This, in addition to the wide availability of equipment, drives the initial cost down.
Prototype quantities: Tangential to the low initial cost, EDM is well suited for low volume or prototype quantities. However, tool wear is continuous and as a result, it needs to be replaced on a regular interval. This does not prevent EDM from being used in production but does result in additional cost and time.
At Voxel we recognize that there are numerous ways to fabricate a part and that neither of these solutions is superior in all cases. Each and every application has unique challenges that may make it well-suited for a specific fabrication process. We are happy to discuss your application with you and determine the best manufacturing process to achieve your desired results.
This article is part of our ongoing “PECM vs. Competing Processes” series that compares PECM to other, popular machining processes. Find other articles in the series below:
CNC Milling vs. ECM
Electropolishing vs. ECM