PECM: What You Need to Know About Pulsed Electrochemical Machining
What is electrochemical machining?
We authored a three-part series with American Machinist to introduce PECM.
Electrochemical machining (ECM) or pulsed electrochemical machining (PECM) are material removal methods that fall under the non-conventional manufacturing category. PECM is a newer, more precise variant of ECM that utilizes a pulsed power supply, but the fundamentals remain the same. Unlike many other manufacturing processes, such as EDM, no contact exists between the tool and the work piece. Material in the very close proximity of the tool is dissolved by an electrochemical process and the by-products are flushed away with a flowing electrolyte. The resultant part takes on the shape that is an inverse of the tool.
Key Terms in PECM
When discussing PECM there are some key terms that are used on a routine basis:
Cathode: The cathode represents the tool in the PECM process. It can be referred to as the tool, cathode, or electrode. In most cases, it is designed and manufactured for each specific application. Typically, the cathode is the inverse of the desired shape to be machined.
Anode: Used to refer to the workpiece or the material that will be dissolved away. The anode can take on many forms including, but not limited to wrought stock, a near net shape cast piece, a conventionally machined part, a 3D printed or additively manufactured part, etc.
Electrolyte: This is the working fluid in the ECM process and it is flushed between the cathode and the anode. The electrolyte is typically a salt-based solution that serves two purposes. One, it allows electrical current to flow between the cathode and anode. Two, it flushes away the by-products of the electrochemical process including metal hydroxides of the dissolved metals.
Gap: Formally known as the interelectrode gap (IEG), the gap is the space that is maintained between the cathode and the anode during the machining process. In electrochemical machining the gap is a major contributor to the performance of the process. The introduction of PECM has allowed for gap sizes on the order of 10 to 100 μm (0.0004 to 0.004") and ultimately the ability to resolve much smaller features in the final workpiece.
Why use PECM?
Pulsed electrochemical machining possesses some key advantages over other manufacturing processes.
Hardness is irrelevant - the electrochemical removal process is unaffected by the hardness of the material. The hardness also does not determine the speed of the process. Refer to the materials section for a list of materials that Voxel has experience with, or check out this post for a full description.
Stress free - PECM is a non-contact and non thermal process; therefore, the material properties remain unchanged.
Burr free - the electrochemical process inherently favors sharp corners and is quite often used as a deburring process. Therefore, there is zero risk of burr generation during machining.
Pristine surfaces - Voxel has demonstrated surface finishes of .005-.200 μm Ra (0.2-8 μin Ra) in a variety of materials directly out of the machining process. As a result typical secondary surface finishing techniques can be eliminated.
Near-infinite tool life - The cathode or tool is not consumed during the process of machining. Therefore the same tool can be used for high volume production runs.
Parallel processing - PECM is well-suited for production applications because it can not only form entire surfaces of a part at one time, but also it can also be paralleled to manufacture multiple parts (or multiple features) side-by-side in a single operation.
Want to learn more?
If you are interested in learning more about the PECM process or how it could be of benefit to your application, please get into contact with us. We look forward to hearing from you!