Manufacturing Processes - ECM Electrochemical Machining Process
ECM & ECDM Electrochemical Machining
This book presents an unconventional and largely unknown technology, which is able to micro-machine at relatively low cost glass, polymers and other materials. This process is called Spark Assisted Chemical Engraving (SACE), or Electro Chemical Discharge Machining (ECDM).
Electrochemical Machining ECM
Electrochemical Machining fits in the category of machining as a manufacturing process. It involves removal of material from a workpiece using electrolysis. This is achieved by connecting the workpiece and the electrode to an electrical power supply. Similar to electrical discharge machining the material for this process to work has to be electrically conductive, but unlike electrical discharge machining the workpiece and electrode are immersed in an electrolyte fluid as opposed to a dielectric fluid.
Electrochemical Machining Advantages
The main advantage of electrochemical machining is that it can be used to machine extremely hard materials with no stressing. This is due to the absence of physical contact and heat. You will notice that there are many similarities between electrochemical machining ECM and electrical discharge machining EDM and consequently the advantages for both are also very similar, but ECM does have some distinct advantages over EDM.
Advantages over EDM
- thin section and fragile parts can be machined (no stress involved)
- its faster than EDM
- There is no tool wear with ECM,
- There is no heat involved
- Tool can be made from soft electrode materials such as copper which is very easy to machine
Electrochemical Machining Disadvantages
The main disadvantage of electrochemical machining is that the process is not particularly environmentally friendly. Not only is it a high energy process but it also produces a chemical sludge that needs to be disposed of. In addition to that the equipment used has a tendency to become corroded so requires frequent maintenance.
In terms of cost, equipment is also more expensive than standard machinery and equipment.
Electrochemical Machining Process
The process involves removing any electrically conductive material using anodic dissolution of the workpiece in a stream of electrolyte. The electrolyte separates the workpiece which is the positive anode side (+ve) from the tool electrode which is the negative cathode (-ve) side. The feed rate of the tool is then matched to the dissolution rate of the workpiece with removal rate being governed by Faraday's law which in practice means it is limited by the current and the electrolyte used. Features machined into the workpiece are a mirror image of the tool and the quality of the machined finish is inversely proportional to the rate of material removal.
Because there is no tool wear whatsoever, the tool can be made to any required shape out of a soft material such as copper.
It is common practice to load several electrodes into one tool holder in order to machine complex components with multiple cavities. The process can be duplicated very easily due to the fact there is no tool wear. It is a simple case of changing out the workpiece and running the program again. However compared to standard machining the cycle times would be considered quite long, but this is somewhat offset by the faster setting up times involved and the lack of tool wear.
ECM Electrochemical Machining
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