EDM Magnetic Filters Cut Down EDM Machine Problems

Editor: Ahlam Rais

EDM machines offer precision accuracy, however, the process can be challenging. It is vital that the machine's systems are equally efficient, especially it's fluid management and filter efficiency. This is where magnetic filters come in as it is capable of filtering fine-particles and micron-sized particles from dielectric fluids in EDM machines which makes sure that the fluid is clean and protected from contamination.

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Contaminated or dirty dielectric fluid can negatively affect the Electrical Discharge Machining process causing problems such as slower cutting speeds, metal removal rate and lower quality and rejected parts that fail quality control.
Contaminated or dirty dielectric fluid can negatively affect the Electrical Discharge Machining process causing problems such as slower cutting speeds, metal removal rate and lower quality and rejected parts that fail quality control.
(Source: Eclipse Magnetics)

Wire Electrical Discharge Machining (EDM) is one of the most powerful and precise methods of cutting within the manufacturing industry, recently creating a buzz with its impressive capabilities that have recently benefitted from drastic improvements in the capability of the machines, as well as certain factors including machine tool construction, CNC controls, contamination removal rate and cutting speed.

With EDM machining expected to grow to be a 6-billion-dollar industry by 2027, the process is fast becoming a highly sought-after area of expertise thanks to its ability to produce intricate parts from conductive materials that would otherwise be impossible to machine. But even with its precision accuracy, and high-quality results, the process can - and often does - come with its own problems.

With advancements in machine ability, it's important to ensure that the machine's systems are equally efficient, particularly it's fluid management and filter efficiency. Until recently, such solutions have been difficult to come by. However, with the help of magnetic technology, many problems can be overcome that increase machine efficiency significantly.

Electrical Discharge Machining

Wire EDM (also known as spark machining or spark eroding) is a metal fabrication process in which a shape is obtained using electrical discharge energy to erode workpiece material. There are three types of EDM, wire discharge, conventional die sinking and EDM drilling.

The cut is created by generating a series of high-frequency sparks between a conductive workpiece and an electrode, such as copper, brass, graphite or tungsten. As the spark jumps from the electrode to the workpiece, it takes with it microscopic particles that are flushed away by a dielectric fluid (generally deionised water or a specialised non-conductive oil.)

Efficiently filtered dielectric fluid is instrumental to producing highly accurate and high-quality machined parts and is essential for transferring the charge during the process, flushing particles out of the gap between the workpiece to prevent them from forming bridges that cause a short circuit.

Hurdles in EDM Machining process

Contaminated or dirty dielectric fluid can negatively affect the Electrical Discharge Machining process causing problems such as slower cutting speeds, metal removal rate and lower quality and rejected parts that fail quality control. Without proper filtration methods, particulates can deposit over time and accumulate within imperative parts of the machine and begin to interfere with its ability.

Up to date wire Erosion or EDM machines demand high standards of surface finishing accuracy often to a 1–3-micron tolerance, improving the filtration can make a big difference in consistently meeting that standard.

Whilst poor quality parts are a significant issue, the particulate build-up in the dielectric fluid often have a more detrimental and costly impact due to their notoriety of affecting future work-pieces as well as causing long-term maintenance problems. Solenoids that power the machine's pumps and circulate the fluid can be easily damaged by this build-up. Such parts are particularly delicate and expensive to replace.

However, secondary sparking, or re-spark, is one of the main hindrances that occur during the EDM machining process, resulting in a high percentage of generated energy wastage. It occurs when metal particles that have been pushed from the workplace and continue to flow in the dielectric fluid. Fluids within EDM processes are continuously circulating and without fast and effective filtration, the particles from the metal sheet will be left within the system. Such particles can be just microns in size; however, they can cause a spark bridge between the electrode and workpiece that ultimately slow the cutting process significantly.

In the case of Wire EDM Machines these problematic particulates within the dielectric fluid can also result in increased wire breakages. Once a wire breaks, the machine needs to be re-threaded by a dielectric jet. The fluid should be clear of particles to prevent further snagging to the rethreaded wire which can in turn result in further wire breakages, making the process unstable.

However, it’s key to the process to keep wire breakage and re-threading to a minimum as the automated re-threading system is time-consuming and can be unreliable, in some cases forcing the operation to stop completely. This is particularly troublesome for 24/7 processes as many machining hours could potentially be lost due to a single break during hours that workshops staffing resources are reduced.

Magnetic Filtration

The main purpose of filters within EDM machining is to remove mechanical impurities from the dielectric fluid, maintaining the effectiveness of the machine, the quality of the part and protecting the machine from untimely wear and tear and blockage. Magnetic technology offers effective fine-particle filtration, removing even micron-sized particles from dielectric fluid ensuring a cleaner, more efficient fluid.

By using a magnetic filter in conjunction with the traditional spun or fleece polyester or pleated paper barrier filter, fluids benefit from the highest level of protection. Using a barrier or media filter alone can allow particles smaller than the pore of the filter to flow through, leaving the fluids susceptible to secondary sparking. By introducing magnetic technology, in conjunction with a barrier filter, these particles are quickly and safely removed, making sure that virtually all contamination is removed.

Maintaining the correct flow rate and capacity through the filtration process is also important to ensure efficient working of the fluid system to deliver clean fluid. If filters can't keep up with processing, it can result in the loss of fluid supply to the working area of the machine.

The Micromag magnetic EDM filter, designed and manufactured by Eclipse Magnetics, is one such innovation that provides the solution for solving many problems that occur during the EDM process and increasing the output of the machine. Its high-intensity collection capabilities coupled with its high-strength magnetic core and an optimised fluid flow orientation work effectively to remove virtually all ferrous particles from the dielectric fluid without impacting the flow rate of the fluid. The cleaner fluids help lead to marked improvements in secondary sparking, significantly less wire breakages, increased machine productivity and longer tool life.

The low-cost filter offers a rapid return on investment – often within just weeks of installation - and, with its easy-clean design, the collected swarf can be quickly and efficiently disposed of and recycled, significantly cutting down on the need for high-cost consumables.

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