In tool making, die-sinking and wire EDM rank among the established machining processes - and the dielectric fluid sits at the centre of each. This overview shows the role it plays in the spark erosion process, the functions it performs and why its quality decides performance and cost-efficiency directly.
As a material-removing machine tool, an EDM machine works electrically conductive materials by spark erosion. For this, the machine needs a tool (electrode) with high electrical conductivity and a dielectric fluid that fills the space between tool and workpiece. It mostly works metals such as steel, aluminium, copper and brass. Graphite and some types of ceramic also machine well by erosion.
For machining, an electrical voltage is applied between the workpiece and the electrode. The electrode is a negative of the shape to be worked into the workpiece. Pulsing direct current then creates an arc between the electrode and the workpiece. Evaporation and spalling remove the parts of the workpiece that do not belong to the final shape. The non-conductive dielectric fluid flushes away the removed and evaporated material.
To build the electrical field, the dielectric fluid must create optimal conditions as fast as possible, so that a spark bridge forms. Just as fast, it must deionise the discharge channel at the end of the pulse to allow the next discharge. In doing so, it should "constrict" the discharge channel to raise the discharge efficiency.
The electric spark strikes the workpiece at around eight to twelve thousand degrees Celsius. This shows how effectively a dielectric must cool the electrode and the workpiece. Overheating leads to significantly higher wear. Besides this function, the dielectric must also reliably condense the metal vapors that form during the electrical discharge machining process.
To effectively prevent process disruptions, the debris particles that form must be flushed out of the erosion zone.
To build the electrical field, the dielectric fluid must create optimal conditions as fast as possible, so that a spark bridge forms. Just as fast, it must deionise the discharge channel at the end of the pulse to allow the next discharge. In doing so, it should "constrict" the discharge channel to raise the discharge efficiency.
The electric spark strikes the workpiece at around eight to twelve thousand degrees Celsius. This shows how effectively a dielectric must cool the electrode and the workpiece. Overheating leads to significantly higher wear. Besides this function, the dielectric must also reliably condense the metal vapors that form during the electrical discharge machining process.
To effectively prevent process disruptions, the debris particles that form must be flushed out of the erosion zone.
EDM processes must prove their cost-efficiency and productivity again and again. The dielectric fluid in use is a key factor for performance and yield. Depending on the application, very specific requirements apply in concrete terms. High performance in dielectric fluids usually means more intensive removal alongside less wear and ageing. Dielectric fluids from esgemo meet these demands through targeted additives.
In spark-erosion metalworking, the dielectric fluid does more than provide ionisation, insulation and cooling - its most important function is reliably carrying the removed particles out of the spark gap. This overview shows how the right flushing method and the right dielectric fluid prevent arcs, short circuits and workpiece damage.
The purpose of a dielectric fluid in spark erosion is ionisation, insulation, cooling and the removal of eroded particles. Flushing particles out of the spark gap matters greatly for spark-erosion metalworking. In wire EDM as in die-sinking EDM, the optimal flushing action of the dielectric fluid prevents dirt build-up. Such build-up bridges the electrode and workpiece, which in turn can cause arcs or short circuits. These are especially counterproductive, because they would destroy the electrode and the workpiece.
So the right flushing method for the process and the right dielectric fluid are what count.
Excellent cooling and flushing properties are in demand. The quality of the dielectric fluid must stay constant during the flushing process to secure consistently good results. The goal is precise, high-quality spark erosion.
During flushing, the main functions of a dielectric fluid range from insulating the electrode and workpiece, through creating optimal conditions for building the electrical field, to ionisation for the spark discharge. Add to this the cooling of the electrode and the workpiece and, of course, the main function: flushing and carrying eroded particles out of the working gap.
Together with the flushing method suited to the process, a high-performance dielectric fluid achieves positive results in removal rate, electrode wear, workpiece surface quality and reproduction accuracy.
Open flushing is the most common flushing method in spark erosion. It comes into use whenever additional flushing holes cannot be made. With this method, take care that any poorer flow conditions can lead to particle deposits in corners.
Pressure flushing is just as well established as open flushing. Here the flushing runs through a flushing pot, either through a flushing hole from above through the electrode or from below through the workpiece. What determines the result is not the flushing pressure but the flow rate.
If the finished workpiece needs parallel walls and a fine finish, suction flushing is the right choice. Here the debris particles are drawn away from the spark gap. The technique works much like pressure flushing, except that in this case the material is not pushed out of the working gap along the electrode but drawn away through the electrode. The advantage is that it prevents unwanted discharges. With small gap widths and low flow rates, suction flushing requires close attention to ensure that enough dielectric reaches the spark gap to keep the electrical discharge machining process stable. Combined with pressure flushing, suction flushing is a popular choice for complex machining tasks.
Open flushing is the most common flushing method in spark erosion. It comes into use whenever additional flushing holes cannot be made. With this method, take care that any poorer flow conditions can lead to particle deposits in corners.
Pressure flushing is just as well established as open flushing. Here the flushing runs through a flushing pot, either through a flushing hole from above through the electrode or from below through the workpiece. What determines the result is not the flushing pressure but the flow rate.
If the finished workpiece needs parallel walls and a fine finish, suction flushing is the right choice. Here the debris particles are drawn away from the spark gap. The technique works much like pressure flushing, except that in this case the material is not pushed out of the working gap along the electrode but drawn away through the electrode. The advantage is that it prevents unwanted discharges. With small gap widths and low flow rates, suction flushing requires close attention to ensure that enough dielectric reaches the spark gap to keep the electrical discharge machining process stable. Combined with pressure flushing, suction flushing is a popular choice for complex machining tasks.
Experience and practical knowledge are the key to choosing the right dielectric fluid across the different flushing methods too. In this respect, the esgemo portfolio offers the right medium for each method, one that meets environmental and safety requirements and delivers economically optimal results with sustainable efficiency.
Wire EDM - also called wire cutting or cutting EDM - is a high-precision, shape-giving spark-erosion process. The following overview shows which dielectric fluid comes into use, which drawbacks deionised water brings and how corrosion protection or oil-based dielectric fluids deliver better results.
Wire EDM (also called wire cutting, or cutting EDM) is a shape-giving manufacturing process (cutting process) and belongs to the spark-erosion forms of machining. It stands out for high precision and is usually extremely dimensionally and geometrically accurate. Wire EDM machines all electrically conductive materials, regardless of their hardness or thickness.
The process works with a wire that serves as the electrode. This is usually a brass wire 0.02-0.33 mm thick, wound onto spools and fed via guide rollers straight to the workpiece. A power generator puts the wire under voltage and brings it so close to the workpiece that a spark jumps across. This spark develops temperatures so high that it melts or practically vaporises the material. The spark always jumps at the point where the gap to the workpiece is smallest. After the discharge, the wire is spent and is discarded.
So that the discharge can always proceed optimally and the resulting erosion debris is carried away quickly, the workpieces are cut in a liquid dielectric fluid. In wire EDM, this dielectric fluid usually consists of deionised water. Through constant flushing, the dielectric fluid carries the erosion debris out of the cutting gap quickly and cools the wire at the same time.
Wire EDM cuts through the hardest metals with ease, but it has much longer machining times than other forms of metalworking. Achieving the best possible surface roughness also usually requires several cuts. Using deionised water has its drawbacks too. The dielectric fluid is very cheap, but when the workpiece stays in the machine for longer periods it causes rust, which can also lead to pitting.
To prevent rust during machining with several cuts and the longer dwell times of the workpieces in the water, a corrosion inhibitor can be added to the water. This stops the workpiece from rusting during machining and also protects all machine components. One product developed for exactly this application is esgeCor RDE. At the correct application concentration, this product behaves completely neutrally in use. It does not affect the conductivity of the dielectric fluid and does not clog filters, deionisation resins or limit switches.
An additional way to prevent workpiece corrosion is treatment with a corrosion protection spray. This wax comes dyed red - as a better contrast agent - or colourless. A further way to prevent corrosion is the use of oil-based dielectric fluids. Some special machines - such as the QWD from the Vollmer company in Biberach, Swabia - therefore also work with EDM oil. Vollmer developed this machine specifically for machining PCD, PcBN and other hard materials. Unlike conventional machines, it guides the wire horizontally instead of the usual vertical arrangement. Besides corrosion protection, the advantage of using oil is that this kind of machining achieves particularly high cutting accuracy and much finer surfaces.
When machining with oil, the dielectric fluid needs a particularly good flushing action. The dielectric fluid should therefore be as thin as possible, but for safety reasons should not have too low a flash point. Dielectric fluids with a flash point >56 °C have proven especially reliable here. For many users of this technique with the Vollmer QWD machines, the dielectric fluid esgeSparc SE 75 is therefore recommended. Designed specifically for this application, this dielectric fluid delivers very good cutting results alongside ideal flushing performance. Thanks to a relatively high flash point, it also has a low tendency to evaporate and is therefore economical in use.
Further EDM processes are die-sinking EDM and hole-drilling EDM.
In EDM, safety and protective measures are mandatory - for the health of employees as much as for environmental protection. The following overview sums up which vapours arise in the spark erosion process, how to avoid skin damage and which regulations apply.
Spark erosion forms vapours from two sources. On the one hand, vapours arise from the use of the dielectric fluid. On the other, metal vapours form. With the various dielectric fluids from renowned suppliers such as esgemo, you can be sure that no dangerous vapours - from benzene compounds, for example - arise even in continuous use, but caution is advisable with the formation of metal vapours.
To limit the hazard from chromium, nickel, tungsten carbide or molybdenum, for example, as effectively as possible, the erosion point should sit as deep under the dielectric fluid as possible. This lets the metal vapours condense in the dielectric fluid. The VDI guideline requires 40 millimetres of coverage - but for the health of employees, aim for as great a depth as possible.
Under normal circumstances - that is, with relatively insensitive skin not prone to allergies - you can assume that the dielectric fluids in common use cause no damage at all. Skin contact with the dielectric fluid usually happens only through the hands, and any liquid still clinging there comes off easily without aggressive soaps or pastes. This general safety does not necessarily apply to employees prone to allergic skin reactions, however. Decades of practice show that problem reactions occur only very rarely even here.
In principle, use suitable skin protection in every case. From our range, CoverSkin or a corresponding skin-protection ointment is available here. The situation differs with the suspended matter in contaminated or used dielectric fluid. This consists of removed particles made up of microfine pieces of material with sometimes extremely sharp cut edges. Because of their fineness, injuries on unprotected skin are hard to avoid.
In connection with the formation of vapours mentioned above, VDI guideline 3402 requires that suitable ventilation of the EDM system ensures that no gases, vapours, mists or fumes develop that endanger the health of employees. It must also rule out the formation of an ignitable atmosphere.
Where the working media make this unavoidable, a suitable extraction device must be fitted. This also affects the EDM system itself, because the electrical installation then has to meet the special conditions for fire-hazardous operating sites.
For all questions about the use of dielectric fluids in electrical EDM systems, seeking the expert's recommendation pays off. For occupational and environmental protection as well as production efficiency, the experienced consultants at esgemo can offer you the optimal product.
