Sometimes referred to as spark machining, sinker electrical discharge machining (EDM) is the primary or standard method of removing metal. This type of process takes place via a series of rapidly recurring electrical discharges that occur between a workpiece in the presence of the dielectric fluid field and a cutting tool, also known as an electrode.
EDM machining services are an electro thermal production process used in the manufacturing industry to facilitate injection molding, which is the process used for producing workpieces in large volumes. Injection molding is most frequently used in mass production processes when the same part is being created in duplication over thousands, or even millions of times, in direct succession.
Most injection molding tools are easily fabricated through a standard machining process for businesses, but there are times and circumstances where a certain geometrical shape requires the use of a variety of EDM processes.
Mostly used by industries that perform mold-making and tool and die tasks for mass production, EDM is also highly useful in aviation and power generation turbine components. EDM is increasingly applied to creating prototype and production parts in the aerospace and electronics industries where production requirements remain relatively simple and low. The process is important in working with parts that are made from materials that are often difficult to maintain or that contain small or oddly shaped angles, complex cavities or intricate contours.
The two major types of EDM are wire and sinker. The sinker type of EDM is also called Ram or conventional EDM. The primary difference between the two types of EDM involves the type of electrode used.
Wire EDM uses wire as the electrode medium, as the name suggests. Wire EDM is an electro thermal production process that uses a thin wire to wear away the surface of the workpiece to create straight or tapered cuts in the desired pattern. Operators managing the process may choose different diameters of wire, depending on the complexity and precision of the cut.
In the wire EDM process, a thin single-strand metal wire, used in conjunction with deionized water, which is used to conduct electricity, allows the wire to cut through metal using the heat from electrical sparks.
Other parts can only be used by the less conventional EDM, the sinker, which, unlike wire EDM, does not completely cut through the part. It literally sinks a required shape into the workpiece.
The sinker process uses a custom machined electrode to remove material in the shape of a specifically designed and designated electrode. In the process, the electrode becomes immersed into the material to erode the material surface, from top to bottom and all the way around. The fine-tuned electrical power serves to balance surface finish and speed with higher power settings that are used to create quick rough cuts. Low power settings serve to produce a very fine surface finish toward the end of the process.
The tiny metal chips remaining are removed by vaporization and melting process, constantly washed away by the continuously flushing dielectric field fluid.
The sinker EDM process is largely used to create complex cavity shapes in tool and die applications. Such applications include metal stamping dies and plastic injection molds. The sinker process begins with machining a graphite electrode to form a “positive” of the desired cavity before the electrode is then carefully plunged or immersed into the workpiece, which causes sparking over its surface as the process closes the sparking gap, creating the distance required for sparking.
The actual process performed when using sinker types of EDMs begins with two metal parts being submerged in an insulating liquid before being connected to a current source. The source of the current is then switched on and off automatically, depending on the specifications set on the controller. Each time the current is switched on, an electric tension is created between the two metal parts.
The distance between the two metal parts comes into play as well. If the two parts are set within a fraction of an inch, the electrical tension discharges, allowing a spark to jump across. The spot where the spark strikes are where the metal is heated up so much that it melts. Multiple such sparks spray out during the process, one after another, but never simultaneously, and gradually reshape the piece of metal into the desired form, in conformity with the shape of the electrode. It takes several hundred thousand sparks to occur per second before adequate erosion takes place to create the desired form.
During the cavity type EDM or volume EDM cutting process, a cavity begins to form in the work metal, and the deeper it becomes, the tougher it is for fresh dielectric fluid to enter the cavity to remove debris, thus quenching the workpiece and electrode to continue working. At this point, the flushing of the cavity becomes an essential part of the EDM process to provide a smooth and even flow of dielectric through the gap to properly create the appropriate gap, cleared of eroded electrode particles. Further, flushing allows fresh dielectric into the gap for stable cutting and to prevent arcing.
With Hi-Tek Manufacturing, you can count on our expertise in sinker EDM services to create imprinted shapes in metal within blind cavities without cutting all the way through a part or otherwise compromising the integrity or stability of a workpiece. In our process, we focus on the most organic process associated with sinker EDMs, which starts by creating an inverse of the desired shape out of a copper or graphite electrode. We use our high-speed mill, grinder or other high-functioning methods for this task. Once we have the perfect inverse of the desired shape, we sink the electrode into the construction material to create the part. This type of EDM process is perfect for mold making, creating threads and tapping holes, and creating shapes in very hard metals before placing them under heat treatment.Request Quote