A method of precision machining called electrical discharge machining (EDM) removes material from a workpiece using thermal energy rather than mechanical force. A thin, single-strand metal wire and deionized water used to...
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This article contains everything you need to know about sinker EDMs and their use.
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Sinker Electrical Discharge Machining (EDM) is a metal machining process used to create molds, dies, and parts using electrical sparks to erode material from a workpiece. It is preferred over other machining processes due to its ability to produce complex shapes with a high degree of accuracy and repeatability.
The sinker EDM process gets its name from how it sinks into a workpiece as it erodes the material. The process is sometimes referred to as burning as it creates micro sized craters to shape and form the workpiece. The workpiece has to be electrically conductive or a ferrous alloy to be able to be shaped by sinker EDM.
The sinker EDM process is used by manufacturers due to its ability to cut extremely tiny pieces with exceptional tolerances. It is often used to produce detailed products that are too delicate to be produced using any other process. Sinker EDM is used to produce prototypes for customers to examine and for engineers to adjust for other means of processing.
The first step in the Sinker EDM process is to design the electrode. The electrode is typically made of copper or graphite and is shaped to match the desired shape of the workpiece. The electrode is mounted on the machine's electrode holder and connected to the power supply.
A dielectric fluid is used in the EDM process to act as a coolant and an electrical insulator. During the EDM process, the dielectric fluid circulates around the electrode and workpiece to prevent arcing and to remove the eroded material. It helps control the temperature of the machining area to prevent thermal expansion.
The types of dielectric fluids are made from petroleum based liquids or synthetic oils with some water based fluids also being available. Dielectric fluids are formulated to have high electrical resistance and low viscosity with the ability to insulate the electrical discharge and flow freely around the workpiece. Some types of dielectric fluids contain additives to improve their cooling and lubricating properties.
The dielectric fluid is a highly critical part of the sinker EDM process since it flushes away the bits of burnt metal and electrode from the work area into the filtration system.
The workpiece, composed of a ferrous conductive metal, is selected as a metal that can be shaped to conform to the end product. It is placed on a worktable and secured using clamps or fixtures. The workpiece is lowered into a tank filled with the dielectric fluid with the surface to be machined exposed.
The electrode is positioned over the workpiece, using a servo control system, and lowered into the dielectric fluid until it touches the surface of the workpiece.
The power supply sends a high-voltage electrical discharge between the electrode and the workpiece. This creates a spark that erodes the workpiece material and shapes it according to the electrode's geometry. When the electrode gets close to the workpiece, an electrical sparks jumps between it and the workpiece. The spark generates temperatures as high as 8000o C up to 12000o C (14,432o F up to 21,632o F), which erodes the metal in the shape of the electrode.
The spark is controlled by adjusting the pulse duration, current, and other parameters of the power supply. The workpiece is eroded in a controlled manner, removing minute particles of material. The dielectric fluid circulates around the machining area to remove the eroded material and prevent arcing.
The progress of the process is monitored by the controller that switches on and off as needed in accordance to the electrode size, material removal rate, and the desired surface finish. The operator can adjust the machining parameters as needed to ensure that the process is proceeding smoothly and accurately.
Sinker EDM produces very smooth, even, mirror-like finishes, which may require extra processing depending on the parameters of the part being produced. Finishing enhances the appearance and durability of the part as well as meets the dictates of its design.
Sinker EDM can be used to shape the hardest and most difficult metals as long as they are conductive. The process results in very low distortion and no residual stress. The initial EDM process was discovered in 1943 when electrodes were submerged in a dielectric fluid to make controlled erosion possible. The process was developed to replace etching tools that did not have sufficient power to cut through metals.
Small hole EDM uses a small hollow diameter spinning electrode made of brass to form and shape the workpiece. The process of small hole EDMs is similar to drilling but has the advantages of EDM machining. Known as EDM drilling or EDM micro hole drilling, small hole EDM machining requires very little force and is ideal for making delicate precision parts.
As with all forms of EDM processes, small hole EDM machining can be used on any ferrous metal regardless of its hardness. The brass tube channels electricity to make different size holes. Small hole EDMs are used to place minute holes in the workpiece, even when the workpiece has inclined faces or difficult to reach positions.
Conventional Sinker EDM, known as die sinking EDM, uses an electrode made of copper or graphite shaped to the desired profile of the part being machined. Once the electrode is powered, it is lowered into dielectric fluid where sparks are discharged to erode the material from the workpiece to form the desired shape.
The process of conventional sinker EDMs allows for accurate replication of precision parts without concerns for deflection with tolerances of +/- 0.0003 inch. The exceptional level of precision provided by conventional sinker EDM has made it the go to method for the creation of prototypes and intricate small parts.
Orbital Sinker EDM is a variation of conventional Sinker EDM that uses a specially designed electrode that rotates and orbits around the workpiece during machining. It creates a larger discharge area and reduces electrode wear to allow for faster and more precision machining.
Ram EDM produces its spark along a formed electrode instead of a wire. A servo system prevents the ram electrode from touching the workpiece. The process has the same capabilities as wire sinker EDM and is able to form parts with exceptional precision and intricacy. Ram EDM allows for a wider range of machining operations, including the production of more complex shapes and features.
With wire or small hole EDM, material is removed along a simple line or at a single point. Ram EDM makes it possible to remove material to form three dimensional shapes with the electrode being a negative image of the completed workpiece. The electrodes for ram EDM are CNC machined to create the negative image. Normally made of brass, the Ram electrode is capable of machining hard metals like tungsten carbide and Inconel.
Multiple electrode sinker EDM is able to machine several areas of the workpiece at the same time. Each of the areas being machined has the same shape, accuracy, and finished surface. It is a faster time saving process that reduces the amount of set up time but can have inaccuracies and produce rough finishes.
Pulse Power Sinker EDM is a process that uses advanced pulse generators to control the discharge energy for longer periods of time and improve machining accuracy and surface finish. It is used for materials that are difficult to machine using conventional Sinker EDM processes.
The on time pulse of energy applied is extended with pulse power sinker EDM. With a longer pulse, more material is removed from the workpiece. It produces larger and broader holes than those created by short time pulses. Additionally, more heat sinks into the workpiece and spreads, which means more area of the workpiece will be affected with the affected area being deeper.
Each variation of Sinker EDM has advantages and limitations. The selection of the best process depends on the specific application and desired results. All metal working manufacturers provide guidance and expertise in regard to determining the best process.
Material selection is an important consideration in sinker EDM, since the type of material being machined has an impact on the success and outcome of the process. There are several factors that need to be considered when selecting a material for sinker EDM machining. The key factor in the process is the conductivity of the workpiece that is being shaped.
Only metals with conductivity can be used in the sinker EDM process. Other materials, such as ceramics, can have conductive metals included in their processing such that they can be shaped by sinker EDM. The process of sinker EDM includes the easy flow of electricity to create the electrical discharge. A conductive workpiece completes the electrical circuit created by the sinker EDM machine and allows current to pass through it. Untreated ceramics and plastics are unable to conduct electricity and cannot be processed by sinker EDM.
The melting point of the material being machined is an important consideration that impacts the amount of energy required to melt the material and the rate of the erosion process. Higher melting points require more energy and longer cycle times. The sinker EDM process is not affected by the hardness of a metal but its thermal properties determine its machinability.
The melting temperature of a workpiece determines how the sinker EDM machine performs and is measured by the metal removal rate (MRR), which is affected by a metal’s melting point and thermal conductivity. Of the various metals used for sinker EDM machining, tungsten carbide has an extremely high melting point.
The machinability of the material is also an important consideration as it impacts the efficiency and effectiveness of the sinker EDM process. Materials that are difficult to machine, such as hardened steels, require more time and energy to remove material and may wear down the electrode more quickly.
The surface finish of a part is reflected in its appearance and affects how it slides over another part. In sealing applications, surface finish is essential. The sinker EDM process creates micron (µ) sized holes across the workpiece, which is different from cutting tools that leave a directional lay.
One of the main reasons for using sinker EDM is the types of finishes that it produces that require very little after production processing. Sinker EDM is unaffected by the hardness of a material, which makes the selection of type of metal easier.
The rule for using sinker EDM as a method of processing is that the metal be electrically conductive, which limits the choice of metals to ferrous metals and aluminum. With this as the criteria, it would seem that copper would be the ideal metal since it is so highly conductive. Although copper is used for sinker EDM machining, it is not necessarily the first choice since the process heats copper so quickly and requires constant control.
All forms of steel are machined by the sinker EDM process. They are used for their toughness, strength, durability, and resilience. Alloy steels have elements added to improve their properties including chromium, cobalt, columbium, molybdenum, manganese, nickel, titanium, tungsten, silicon, and vanadium. The various alloys change the properties of steel and add desirable characteristics.
Copper is the perfect choice for the sinker EDM process since it has such high conductivity. The use of copper restricts the process due to copper heating quickly and passing the heat through the metal, which requires that the process be slowed and carefully controlled. Sinker EDM works with copper components that have thin walls without warping or distorting the walls.
Tungsten carbide is a difficult metal to machine since it has high hardness and melting point and is brittle, which makes sinker EDM the perfect method for machining it. The heat that is generated is conducted differentially due to the structure of tungsten carbide.
Electrodes for tungsten carbide are made of copper using negative electrode polarity, which produces very low surface roughness. When machining tungsten carbide, using sinker EDM, the removal rate is very slow due to the nature of the metal. Small intricate and complex geometries can be produced using the process.
Titanium has exceptional strength to weight ratio, corrosion resistance, and the ability to withstand high temperatures. Due to its biocompatible properties, it is widely used for medical implants. The high hardness of titanium makes it difficult to machine using conventional machining methods. As with tungsten carbide, it is machined using copper electrodes with pulse on and off time.
Inconel, Hastelloy, and Monel are nickel alloys with resistance to heat, corrosion, and oxidation. They are used for high temperature applications like gas turbines, aerospace, and chemical processing equipment.
Aluminum is an extremely abundant metal that is used in a wide assortment of applications and products. Its natural resistance to oxidation, corrosion, and rust makes it a highly durable metal. Aluminum is seldom used in its pure form and is normally alloyed with other metals to improve its properties. It is well suited for work with sinker EDM due to its ability to be shaped into intricate and complex shapes.
The list of metals above are a small sampling of the metals that are processed by sinker EDM machining. In essence, any metal that is conductive can be machined and shaped using the process. It is up to the manufacturer and customer to determine the best metal to fit an application.
The parts of the sinker EDM process includes the worktable, electrode, tank, dielectric fluid, servo control system, control panel, filtration system, and a power source. The central part of the process is the workpiece to be shaped that is made of a conductive metal and capable of completing an electrical circuit. The dielectric fluid can be deionized water or a non-conductive lubricating oil. The various components work together to form and shape the final product.
The worktable is the part of the machine where the workpiece is placed and secured during the machining process. It can be moved in the X, Y, and Z axes to allow for precise positioning of the workpiece.
The tank is filled with the dielectric fluid that is deionized water or non-conductive oil and where the workpiece will be immersed during machining. It prevents sparking and keeps the workpiece and electrodes cool.
The power supply generates a high-voltage electrical discharge between the electrode and the workpiece that creates a spark to erode material from the workpiece. It controls the pulse duration, current, and other parameters that affect the machining process.
The electrode is a specially shaped tool made of conductive material, such as copper or graphite. It creates the desired shape and is connected to the power supply. At the initiation of the process, it is lowered with the workpiece into the dielectric fluid in the tank. The electrode produces a non-contact sparking that removes material from the workpiece.
The servo control system is responsible for controlling the movement of the electrode, the worktable, and the spark discharge gap. It has a gap sensor that measures the voltage from each machining pulse. Its precision motor and feedback sensors ensure that the electrode moves in the correct direction and speed. The servo control system determines optimum spacing between the electrical discharge electrode and the workpiece.
The filtration system removes debris and particles from the dielectric fluid to ensure that the machining process is clean and efficient. During the sinker EDM process, sparks create minute holes in the workpiece that are removed as waste material that could interfere with the process. The filtration system captures the waste material.
The control panel is the interface between the operator and the machine. It allows the operator to input the machining parameters and monitor the progress of the machining process.
Each component of a Sinker EDM machine is essential to the overall performance and accuracy of the process. Manufacturers provide guidance and training regarding the use of sinker EDM machines. They design and produce equipment that perfectly fits the needs of their customers.
Aside from the simple linear cutting types of sinker EDM machines, there are multi axis machines capable of adding shapes and tapers on the bottom, top, and sides of a workpiece. These multi axis machines make the production process go faster and increase efficiency.
High-Speed Sinker EDM machines use advanced technologies such as high-frequency generators, advanced servo systems, and high-speed spindles to improve machining speed and precision. These machines are designed to handle high-speed machining operations while maintaining accuracy and surface finish quality.
Four-Axis Sinker EDM machines add a fourth axis to the standard three-axis motion control, allowing for more complex and precise machining operations. The fourth axis can be used to control the angle and position of the electrode during machining, which can be useful for producing complex shapes and features.
Five-Axis Sinker EDM machines add a fifth axis to the standard three-axis motion control, allowing for even more complex and precise machining operations. The fifth axis can be used to control the angle and position of the workpiece during machining, which can be useful for producing parts with intricate shapes or features.
Automated Sinker EDM machines use advanced robotics and automation technologies to streamline the machining process and increase efficiency. These machines can be used to produce parts in high volumes with minimal human intervention.
Micro Sinker EDM machines are designed to produce extremely small and precise parts. These machines use advanced technologies such as ultra-fine wire electrodes and high-precision servo systems to achieve very high accuracy and surface finish quality.
As with all forms of production equipment, there are regulations and standards regarding the use of sinker EDM machines. In the United States, they are subject to the oversight of the Occupational Safety and Health Administration (OSHA), the National Fire Protection Association (NFPA), the Environmental Protection Agency (EPA). Other laws covering their use are enacted by state and local authorities as well as international organizations.
OSHA has a number of regulations that apply to Sinker EDM machines and operators. For example, OSHA's General Industry Standard 1910.212 requires that machinery and equipment be guarded to protect workers from hazards such as moving parts, electrical hazards, and flying debris.
The NFPA has a set of standards that apply to the use of Sinker EDM machines in manufacturing environments. These standards include requirements for electrical safety, fire prevention, and hazardous materials handling.
The EPA regulates the disposal of waste materials generated by the Sinker EDM process. This includes regulations governing the disposal of spent electrode materials, cutting fluids, and other waste materials.
State and local governments may have their own regulations that apply to the use of Sinker EDM machines. For example, some states may require permits or licenses to operate Sinker EDM machines, or may have regulations governing the disposal of hazardous waste materials.
If you plan to export or import Sinker EDM machines or parts, you may need to comply with international regulations such as the International Traffic in Arms Regulations (ITAR) or the Export Administration Regulations (EAR).
It's important to note that regulations can vary depending on the specific application and industry. It's important to consult with relevant regulatory agencies and seek professional guidance to ensure compliance with all applicable laws and regulations.
The sinker EDM process is ideal for producing small intricate parts with exceptional tolerances. EDM machines can be programmed to produce a wide variety of shapes regardless of their complexity in any form of conductive metal. Its introduction has dramatically changed the capabilities of parts manufacturers and producers.
Sinker EDM is a highly versatile machining process that can be used to produce complex and intricate shapes with high precision. It can be used to machine a wide range of materials, including metals, alloys, ceramics, and composites.
Sinker EDM is a highly accurate process that produces consistent and repeatable results. This is because the process is highly controlled and can be programmed to produce the same part over and over again with high precision.
Sinker EDM does not use cutting tools, which means that there is no tool wear during the machining process. This results in improved tool life and reduced maintenance costs.
Sinker EDM produces parts with no residual stresses, which means that the parts are less likely to warp or distort during use. This is because there is no mechanical force applied during the machining process.
Sinker EDM produces parts with a very fine surface finish, which can eliminate the need for additional finishing operations. This is because the process uses a fine electrode that produces a very fine spark that erodes the material.
Sinker EDM allows for the production of complex shapes and intricate designs that would be difficult or impossible to produce with other machining processes. This means that engineers and designers have more flexibility to create innovative and high-performance products.
Sinker EDM can produce parts more quickly and efficiently than other machining processes, which can lead to reduced lead times and costs. Additionally, because the process does not produce tool wear, maintenance costs are reduced.
Overall, the benefits of Sinker EDM outweigh any considerations regarding its use and make it a highly attractive option for a wide range of industries and applications.
Since its introduction, sinker EDM technology has provided designers and engineers with a tool that can meet the needs of several industries. It has become exceptionally useful for the aerospace industry due to the necessity of aerospace parts being precision crafted and meticulously shaped. This is also true for the medical industry where errors and flaws in medical devices can be dangerous.
In a case study conducted by a leading aerospace component manufacturer, Sinker EDM was used to produce critical components for jet engines. By using Sinker EDM, the manufacturer was able to produce complex parts with tight tolerances and high precision, which resulted in improved performance and reliability of the final product. Additionally, the use of Sinker EDM allowed the manufacturer to reduce lead times and costs associated with traditional machining methods.
In a case study conducted by a medical implant manufacturer, Sinker EDM was used to produce orthopedic implants made of titanium. The manufacturer was able to produce intricate designs with high precision, which resulted in improved implant fit and patient outcomes. Additionally, the use of Sinker EDM allowed the manufacturer to reduce the time and cost associated with traditional machining methods.
In a case study conducted by an electronics component manufacturer, Sinker EDM was used to produce components for microelectronics. The manufacturer was able to produce small, intricate parts with high precision, which resulted in improved performance and reliability of the final product. Additionally, the use of Sinker EDM allowed the manufacturer to reduce lead times and costs associated with traditional machining methods.
In a case study conducted by a tool and die manufacturer, Sinker EDM was used to produce complex dies for stamping operations. The manufacturer was able to produce intricate designs with high precision, which resulted in improved tool life and reduced maintenance costs. Additionally, the use of Sinker EDM allowed the manufacturer to reduce the time and cost associated with traditional machining methods.
In a case study conducted by an automotive component manufacturer, Sinker EDM was used to produce gears for high-performance applications. The manufacturer was able to produce complex gears with tight tolerances and high precision, which resulted in improved performance and durability of the final product. Additionally, the use of Sinker EDM allowed the manufacturer to reduce lead times and costs associated with traditional machining methods.
Sinker EDM machining is capable of producing high precision parts from conductive materials. Since its introduction, more and more manufacturers have found the value of sinker EDM as a highly accurate manufacturing process that produces a wide assortment of complex parts.
Sinker EDM is widely used in the manufacturing of molds and dies for injection molding and stamping. The process allows for the creation of complex shapes with high precision and repeatability, which is essential for producing high-quality molded and stamped parts. Additionally, Sinker EDM can be used to create molds and dies from hard-to-machine materials, such as titanium and Inconel, which are often required for demanding applications.
Sinker EDM is also used extensively in the aerospace and defense industries for creating critical components for jet engines, missiles, and other applications. The process is ideal for producing complex, high-precision parts with tight tolerances, such as turbine blades, compressor vanes, and fuel nozzles. Additionally, Sinker EDM can be used to produce parts from exotic materials, such as nickel-based alloys, which are commonly used in the aerospace and defense industries.
Sinker EDM is used in medical device manufacturing for creating surgical tools and implants. The process allows for the creation of small, intricate parts with high precision and repeatability, which is essential for producing high-quality medical devices. Additionally, Sinker EDM can be used to create parts from biocompatible materials, such as titanium, which are often required for medical applications.
Sinker EDM is used in the automotive industry for producing gears, crankshafts, and other components. The process allows for the creation of complex, high-precision parts with tight tolerances, which is essential for producing high-performance automotive components. Additionally, Sinker EDM can be used to produce parts from hard-to-machine materials, such as hardened steel and titanium, which are often required for demanding automotive applications.
Sinker EDM is used in the electronics industry for creating components for circuit boards and other applications. The process allows for the creation of small, intricate parts with high precision and repeatability, which is essential for producing high-quality electronic components. Additionally, Sinker EDM can be used to create parts from a wide range of materials, including copper, tungsten, and molybdenum, which are commonly used in the electronics industry.
Sinker EDM is used extensively in tool and die manufacturing. The process allows for the creation of complex shapes with high precision and repeatability, which is essential for producing high-quality tools and dies. Additionally, Sinker EDM can be used to create tools and dies from a wide range of materials, including hardened steel, which is often required for demanding tool and die applications.
Sinker EDM is used in jewelry manufacturing for creating intricate designs and patterns. The process allows for the creation of small, intricate parts with high precision and repeatability, which is essential for producing high-quality jewelry. Additionally, Sinker EDM can be used to create parts from a wide range of materials, including precious metals and gemstones, which are commonly used in jewelry manufacturing.
Sinker EDM is also used in the production of consumer products, such as eyeglass frames, watches, and writing instruments. The process allows for the creation of small, intricate parts with high precision and repeatability, which is essential for producing high-quality consumer products. Additionally, Sinker EDM can be used to create parts from a wide range of materials, including stainless steel, aluminum, and plastic, which are commonly used in consumer product manufacturing.
Aside from its many advantages, sinker EDM has limitations to what it can produce. Additionally, sinker EDM machines are expensive to purchase and maintain. It is a slow process that is unable to produce high volumes of parts. With all its accuracy and precision, the use of sinker EDM has significant drawbacks that require careful consideration when choosing it as a process. 54
Sinker EDM is a slow process compared to other machining processes, which means that it may not be the best option for producing parts in large quantities or with high material removal rates.
While Sinker EDM can be used to machine a wide range of materials, some materials are more difficult to machine than others. For example, materials with high melting points or low thermal conductivity may be more difficult to machine with Sinker EDM.
Sinker EDM machines can be expensive to purchase and maintain, which may not make them a viable option for some small businesses or individuals.
The Sinker EDM process generates a significant amount of waste material and produces a lot of heat, which can have environmental impacts if not managed properly.
The Sinker EDM process uses high voltage electrical discharge, which can be hazardous if not properly managed. Additionally, the process can produce hazardous fumes and debris, which can pose a safety risk to operators.
Despite these considerations, Sinker EDM remains a popular and effective machining process for a wide range of applications. Proper training, maintenance, and safety protocols can help to mitigate these potential issues and ensure that the process is used safely and effectively.
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