Lathes and milling machines are commonly associated with machining, but wire electrical discharge machining (EDM) offers specialized advantages for certain applications.
Wire EDM is an electrothermal process that employs electric discharges to shape conductive materials, allowing for the creation of intricate designs. Widely used in parts manufacturing, this technology supports a broad range of materials and has extensive applications across industries. This article will delve into wire EDM’s capabilities and its role in the manufacturing sector.
What Is Wire EDM?
Wire Electrical discharge machining (EDM) is a precision machining method that uses thermal energy to remove material from a workpiece. Professionals call it different names like spark erosion, wire erosion, spark eroding, wire cutting, wire burning, and die sinking. In this process, a thin metal wire and deionized water conduct electricity to cut metal and prevent rust. The tool electrode, typically made of brass or layered copper, moves along a predetermined path to shape the workpiece.
The history of electrical discharge machining (EDM) dates back to Joseph Preistly’s observations in 1770. He noted material removal from electrodes due to electrical discharges, also known as electro-discharge erosion. In the 1940s, Soviet researchers, the Lazarenkos, laid the groundwork for modern wire EDM and small hole EDM. Their work led to innovations in electric discharge machining, especially for hard-to-work materials like tungsten.
At the time, in the US, spark-erosion machines were being developed to remove broken bolts and taps from aluminum castings. In 1967, a successful wire EDM machine emerged from experiments with punch-card-driven mills converted into wire eroders in the Soviet Union. By the 1980s, EDM could achieve a functional machining rate of 64 mm2/min, offering a viable alternative for challenging materials.
How Does Wire EDM Work?
Wire EDM machining operates by creating an electrical discharge between the wire electrode and the workpiece. While the workpiece remains stationary, the moving wire guides the cut, producing electric sparks near the grounded workpiece. A high voltage between the tool electrode and the part generates an electric spark upon contact, melting small bits of metal in the process. This discharge removes material from the workpiece as the spark jumps across.
Wire EDM relies on the wiring system and the dielectric fluid for efficient, precise cuts and a quality surface finish. The wire is usually brass or copper, occasionally coated with zinc for better performance. Deionized water acts as a medium to regulate powerful sparks. It acts as an insulator between the wire electrode and the workpiece until a significant electric charge difference occurs. This controlled insulation leads to consistent EDM sparking, resulting in a smooth and even cut.
Main Components of Wire EDM Machine
The components of the wire EDM machine work together to shape materials effectively, each playing a crucial role in the machine’s operation.
CNC Control
CNC systems rely on high-precision stepper motors and robust programming instructions. They can oversee the wire EDM process by automating cutting and managing the wire path sequence.
Dielectric Fluid
The tank in wire-cut EDM must hold dielectric fluid. It prevents small particles from sticking to the wire electrode. Deionized water is commonly used because it cools the process and produces a smooth workpiece surface. It also removes debris and prevents thermal stress on the workpiece.
Electrodes
The wire acts as the cathode, while the workpiece serves as the anode in this process. A servo motor is responsible for controlling the wire electrode during cutting to prevent contact with the workpiece.
System for Running
This system controls the tension and speed of the electrode wire feed. It ensures the reciprocating feed of the wire electrode and manages the coiling of the wire on the drum without causing an overlap.
Wire
The wire is the electrode for creating electrical discharge. Consequently, the thickness of the workpiece and its shape directly affect the diameter of the wire. Some of the wires used include the following:
- Brass: the most popular choice, balances affordability, conductivity, and cutting speed.
- Copper: the original wire EDM material, provides good conductivity but suffers from slow cutting speeds and low durability.
- Tungsten and molybdenum: though more expensive, are available for increased cutting speeds and wear resistance.
- Coated wires: they include zinc-coated and diffusion-annealed varieties, and they enhance cutting performance or cater to specific material combinations.
- Steel-core brass wires: they offer improved straightness and stability for precision cutting tasks.
Working Table
It supports and secures the workpiece, with two separate stepper motors controlling its movement. The relative motion between the work table and the cathode wire finishes the wire EDM machining process. High-speed machines feature X- and Y-axis slides on their work tables, utilizing a linear guideway and ball screw for movement. The XY structure boasts established controllability and mechanical rigidity, which is widely accepted.
Power Supply
This unit delivers pulses ranging from 100V to 300V to the workpiece and the wire electrode. It also controls the frequency and intensity of the charges flowing through the electrode for interaction with the workpiece. A sophisticated power supply unit is necessary to provide the correct type and quality of charges during the process.
Recycling System
A pump draws deionized water (the working solution) out of the tank, passing a filter through to remove the impurities. Afterward, it is directed into different nozzles before it is returned through a filter around the tank. Changing the filter and working solution is necessary if they affect cutting quality.
Considerations in Wire EDM
Getting optimal results when working with this technology requires carefully considering some essential factors. Let’s examine them below.
Types and Dimensions of EDM Wire
EDM wire diameters range from 0.0008 to 0.013 inches. Thinner wires need lower power settings and cut more slowly. Plain brass wires with a 0.010-inch diameter are common in over 80 percent of EDM tasks. Choosing the right wire depends on the material being machined and the expected results from the wire erosion process.
Geometry of the Part
While wire EDM can cut intricate shapes, part geometry can make or break your design. The wire diameter limits how sharp your internal corners can be. So, design corners that are wider than twice the wire thickness for a clean cut. Always factor the kerf created during the process into your design to avoid parts ending up undersized. Deep, narrow slots can be tricky. The wire needs room to maneuver. Consider adding draft angles or strategically placed holes for better wire access. If you’re working with multiple flat parts, experts recommend stacking the workpieces for efficient, unattended batch processing.
Requirements for Surface Finish and Tolerances
Ultra-smooth surfaces are achievable through this technology, but rougher cuts are faster and cheaper. Always match the finish to the part’s needs. For example, a mold may need a mirror finish, while a bracket might not. Likewise, tighter tolerances require more precise cuts, increasing machining time and cost. Analyze how much tolerance variation your application can handle. High-precision parts often require multiple, progressively finer cuts. Factor in this extra machining time during the design phase.
Material Thickness and Electrical Conductivity
It excels at thin to medium materials. Thick workpieces might be better suited for traditional machining methods. Thinner materials typically require less cutting time and produce finer surface finishes. Furthermore, the process relies on electrical discharge, and only conductive metals are compatible. These highly conductive materials like copper cut faster. Consider this for production efficiency, especially for high-volume jobs.
Considerations for Time Efficiency
Wire cut EDM is fast, but smart design choices can help you save some time. For example, you want to minimize complex cuts. Simple geometries with straight lines and minimal curves reduce machining time. It’s best to start with a faster rough cut, and then follow with a slower, finer finishing pass. Working with manufacturers that have EDM machines with automatic wire threading to minimize downtime between cuts is also a great choice.
Programming and Control for EDM
As mentioned earlier, CNC control is an essential component of the EDM machine. Therefore, don’t overlook the role of wire EDM programming. Use Computer-Aided Manufacturing (CAM) software to generate efficient toolpaths that minimize travel time and maximize cutting efficiency. You can also leverage techniques like corner rounding or spark gap control in your CAM program for tricky corners and thin features. Simulating the wire path virtually before running the machine will help you catch errors and potential collisions early to save time and avoid costly mistakes.
8 Best Wire EDM Machines
Choosing the right machine depends on your production needs. Whether you prioritize efficiency and uptime or size and precision, there’s a model for you. Here’s a concise overview of the top eight wire EDM machine manufacturers.
Mitsubishi
Mitsubishi Electric is renowned for its advanced technology, reliability, and precision. They have machines that boast high-speed cutting abilities, superior accuracy, and excellent surface finish. This manufacturer is also known for user-friendly software and CNC controls, facilitating easy programming and efficient operations.
ONA
ONA offers four series: modular, compact, hole-drilling, and custom options. The compact machines have small footprints yet provide maximum precision, while the modular ones offer exceptional flexibility. This range ensures ONA has a WEDM suitable for every part size, part geometry, and application.
Makino
Makino is known for durability, stability, and incredible performance. Their machines feature high-speed machining proficiency, intelligent automation, and advanced control systems achieving tight tolerances and superior accuracy. U6 H.E.A.T is the renowned one. Extreme. It uses high-energy applied technology for superior and precise machining, especially for intricate shapes and tight tolerances.
FANUC
Fanuc focuses on user-friendly interfaces and intuitive programming. Their machines excel in accuracy, efficiency, and long-term reliability. One of Fanuc’s popular machines, the Alpha C600iA, is known for its robust construction, reliability, and stability. It offers excellent cutting performance, high precision, and user-friendly operation, integrating CNC control systems seamlessly.
Sodick
Sodick is well-known for its high-precision manufacturing equipment, which is preferred for its accuracy, cutting speed, and surface finish qualities. They utilize innovative technologies like linear motor drives for high productivity and responsiveness. Sodick’s intuitive software and advanced control systems help enhance user convenience.
Agie
GF Machining Solutions offers several machines known for reliability, versatility, and precision. They feature adaptive machining, advanced tooling options, and automatic wire threading. These machines also come with high cutting speeds and energy efficiency.
Charmilles
Charmilles offers the same machines as Agie, including the CUT X series and the more advanced CUT P series. There is an Intelligent Power Generator that increases cutting speeds, and dedicated technologies optimize efficiency in terms of wire consumption. This reduces maintenance time and maximizes profits for manufacturers.
Seibu
Seibu stands out as the sole EDM manufacturer that guarantees cutting accuracy up to +1.0 microns. They provide four EDM series: one oil-type series and three water-type series. One of the oil-type machines is the MEX15. It achieves straight lines with a tolerance of less than 0.1 microns. It also boasts pitch shape and contour accuracy of up to +0.5 microns.
Materials for Wire EDM
While this technology is extensively used in many industries, it is only compatible with a handful of materials. Let’s check out some of those materials.
Pre-hardened die steel is ideal for CNC wire EDM due to its inherent hardness achieved through controlled heat treatment. This eliminates the need for additional heat treatment after machining and maintaining shape integrity throughout the process. Its hardness minimizes wire deflection, leading to smoother surface finishes and an extended tool lifespan.
Titanium, with its excellent conductivity, is also well-suited for wire EDM, generating minimal heat during operation, crucial for maintaining dimensional accuracy.
Austenitic stainless steel, known for its corrosion resistance and high thermal conductivity, ensures sharp cutting tools and prevents thermal damage during machining.
Tungsten and molybdenum, with high melting points, withstand intense heat during EDM, ensuring minimal thermal distortion and efficient heat dissipation.
Bronze and brass offer good machinability but are less cost-effective due to lower melting points and reduced tool life.
Non-hardened steel also suffers from tool wear and higher machining costs, making it less cost-effective than hardened steel or titanium alloys for applications.
Applications of Wire EDM
The incredible efficiency and versatility of this technology make it extensively useful in various industries. Here’s a brief look at the applications.
Automotive
Wire EDM technology is vital in the automobile industry, enabling the precision manufacturing of critical components like cylinder heads, valves, and fuel injectors, which require exact tolerances and complex shapes. It handles various materials, including alloys and tool steels, and is also essential for producing molds and dies for automotive part casting, stamping, and forming.
Aerospace
Aerospace manufacturing needs complex geometries and tight tolerances. Wire machining helps craft intricate shapes in parts for landing gear, aircraft engines, and other crucial components. Furthermore, it is integral in creating molds for plastic injection parts used in aircraft interiors. These molds require high accuracy, making it a top tool for the task.
Medical Devices
Wire EDM cutting is indispensable in medical manufacturing, offering the precision needed for producing complex instruments like forceps and intricate orthopedic implants. Its ability to meet strict specifications ensures the efficacy and compatibility of medical devices within the human body.
Electronics
With the wire EDM technique, microelectrodes—used in microelectronics for circuitry and sensors—can be produced with efficiency. These microelectrodes frequently need very tight tolerances to perform properly in electronic equipment. It is a great option because it can produce these components with micron-level accuracy. It is also useful in creating connector pins and lead frames for integrated circuit (IC) packaging due to its high level of precision.
Die Tooling
With wire EDM technology, injection mold inserts can be produced quickly. Often, these mold inserts need precise forms to guarantee the exact reproduction of the intended plastic parts, and this precision technique helps achieve this. Manufacturers also use it to create stamping dies to guarantee the correct formation of the sheet metal components. It is also useful for extrusion dies, blanking dies, shaping tools, and cutting punches.
Tolerances for Wire EDM
Wire cutting is among the most precise manufacturing processes there are. So, tight tolerances are not out of the ordinary for it. The actual tolerance depends on several factors including the project’s intricacies, machining capabilities, and the operator’s skills.
However, the standard and acceptable tolerances are an industry benchmark that a lot of manufacturers follow.
Standard Tolerance and Fine Tolerance
Standard Tolerance
- Linear Tolerances: Typically range from ±0.005 to ±0.001 inches (0.127 to 0.0254 mm), indicating the permissible deviation for features like holes, slots, or profiles.
- Hole Diameter Tolerances: Usually between ±0.0005 to ±0.001 inches (0.0127 to 0.0254 mm), ensuring machined holes stay within the defined diameter.
Fine Tolerance
- Linear Tolerances: Achieves precision at the micron level, typically ranging from ±0.0002 to ±0.0001 inches (0.0051 to 0.00254 mm), vital for applications needing utmost accuracy.
- Hole Diameter Tolerances: Ranges from ±0.0001 to ±0.00005 inches (0.00254 to 0.00127 mm), highlighting exceptional precision.
Factors Affecting Tolerances in Wire EDM
It is famous for its micron-level precision, making it ideal for intricate applications. However, its precision isn’t fixed and hinges on several factors:
- Machine Stability: A stable machine ensures better precision in cutting actions.
- Wire Quality and Diameter: Its purity, diameter, and electrical traits influence the machining process. Optimal results require a balance between wire quality and diameter.
- Workpiece Material: While some materials are more accessible to machines, the material choice must align with the application’s needs.
- Flush Conditions: The flow of the dielectric medium, affects the quality of the machining process, aids in material removal, consistent electrical discharges, and effective heat dissipation.
- Machine Calibration and Maintenance: The machine’s capabilities are pivotal. Superior machines with adept operators are essential for achieving the best tolerances.
- Thermal Stability: To maintain the known precision, controlled electric arcs are crucial. Thermal instabilities can jeopardize accuracy, emphasizing the importance of consistent conditions.
Wire EDM vs Other EDM Techniques
The wire EDM technology follows the same fundamental principle as the conventional EDM. However, these processes still have some notable differences that set them apart. In this section, we will examine how it differs from other EDM processes.
Wire EDM vs Conventional EDM
Traditional EDM is slower than its wire counterpart because it requires the development and shaping of electrodes, often made from highly conductive materials like copper or graphite. In contrast, the setup for wire EDM is quicker, as it starts as soon as the wire is in place, making it ideal for rapid production needs. Additionally, it achieves greater accuracy because the wire itself acts as the electrode, capable of cutting materials as thin as 0.004 inches. This capability makes it particularly effective for machining complex parts. The wire, acting as a thin, heated electrode, allows for a smoother machining process compared to traditional methods where electrode shapes and sizes can affect the finish.
Wire EDM vs Sinker EDM
Sinker EDM, employing custom-shaped electrodes, excels in creating complex 3D shapes and blind cavities, while wire EDM is optimal for precise 2D profiles and intricate patterns, making it suitable for high-tolerance components. Wire cutting uses a thin wire and deionized water as a dielectric fluid, typically achieving finer finishes. In contrast, sinker EDM uses graphite or copper electrodes with hydrocarbon or kerosene oil, and may produce rougher surfaces but is better for thicker materials. Wire EDM machining is favored for ultra-precise applications like aerospace parts and microchips, whereas sinker EDM is widely used in mold and die-making for automotive and manufacturing industries.
Wire EDM vs Hole Drilling EDM
Hole Drilling EDM uses a dedicated thin tube electrode to drill precise, minimal-taper holes, especially in small diameters and hard-to-reach areas. This method specializes in creating holes with specific shapes or sidewall features, capable of drilling as small as 0.003 inches (0.076 mm). In contrast, CNC wire EDM achieves intricate two- and three-dimensional features, such as gears and dies, with tight corners and radii, but its minimum hole size is constrained by the wire diameter. While EDM cutting provides faster speeds for complex shapes, Hole Drilling EDM is more efficient for simple, straight holes.
Advantages of Wire EDM Cutting
EDM technology has revolutionized manufacturing solutions, and precision wire EDM plays a big role in this. Here are some of the benefits it offers:
Enables Complex Part Production
This technology is highly favored for manufacturing intricate and precise components, especially in industries like healthcare and aerospace. Its capability to produce highly detailed 2D profiles and 3D shapes with tight internal radii and fine details is unmatched. The thin single-strand wire allows for erosion of fine details, with wire sizes as small as 0.02 mm. Likewise, there are no limitations in tool access.
Delivers Accuracy and Precision
Wire machining is renowned for its exceptional accuracy, which makes it capable of creating intricate shapes with high precision. The thin wire in this process enables precise cutting through materials, ensuring parts meet exact specifications. This precision is crucial in medical devices, aerospace, and mold and die-making, where deviations can lead to significant consequences. The use of thin wire in this process allows for precise cuts and strict adherence to tolerances.
Eliminates the Need for Expensive Molds
The simple wire electrode in this process keeps the tool cost relatively low. It eliminates the need for expensive molds or equipment by directly cutting workpieces. This process enables rapid and precise cutting of hard and thin materials. It requires fewer human resources and offers quicker turnaround times than conventional methods. Moreover, the technique reduces material usage and waste generation.
Operates Without Mechanical Force
Wire EDM cutting stands out from other processing methods by effectively cutting tough, thin, and delicate materials without causing stress or bending. It eliminates physical cutting forces, ensuring that delicate or fragile parts are machined without distortion, cracks, or damage to features. Additionally, it allows parts to be cut directly in their hardened state without undergoing geometric changes.
Results in Minimal Burr Formation
CNC wire EDM excels at cutting hard and delicate materials without harming cutting tools or distorting material surfaces or edges. Its continuously moving wire ensures an accurate, burr-free finish, eliminating the need for additional deburring or cleanup. The process consistently delivers excellent edge quality due to its absence of a wheel or saw teeth, resulting in minimal burrs and a typical kerf width of 0.1 to 0.3 mm (0.004” to 0.012”).
Disadvantages of Wire EDM Cutting
While this process offers various benefits for many applications, machinists still need to be aware of certain drawbacks.
Limited to Conductive Materials
The technique is limited to materials that conduct electricity, given its process of rapidly applying controlled electrical charges along a metal wire. This limitation means that materials such as composites or those covered with a dielectric cannot be practically used with EDM.
Slower Than Conventional Methods
One notable drawback of wire EDM cutting is its labor-intensive nature. Although modern EDM machines have features of CNC abilities and automatic wire threading (AWT), allowing for “lights out” operation to compensate for slow cutting speeds, it still requires human involvement. Alternative techniques such as thin-wheel abrasive cutting is preferred for high-volume production of parts that have diameters larger than 0.5 mm (0.020′′).
Restrictions on Bottom Processing
The technology is also unable to process materials from the bottom. This is due to its operation as a wire saw, which focuses on cutting vertically rather than horizontally or from below. In situations where bottom processing is essential, sinker EDM machines are the preferred choice.
Cannot Process Horizontally
Due to its vertical orientation, wire EDM operates like a saw and cannot process materials horizontally. This limitation means that intricate designs or features that require horizontal cutting cannot be achieved with this process alone.
Choosing the Right Wire EDM Service Provider
Finding the right service provider is crucial for a business’s growth and success, especially when seeking wire EDM services. Here are key qualities to consider:
- Quality: A reliable manufacturer should consistently deliver high-quality options, products, and services. This includes the final output and the entire process, from communication and project management to post-production support.
- Technology and Capabilities: A partner with advanced technology and a diverse range of machining capabilities can offer innovative solutions, easily handle complex projects, and adapt to evolving industry demands.
- Experience: An established track record demonstrates the manufacturer’s ability to handle different types of projects, navigate challenges effectively, and deliver consistent results.
- Precision: A reputable service provider should prioritize precision in every aspect of their work, from initial planning and programming to execution and quality control.
Are you looking for specialized services that check all the boxes? RapidDirect offers tailored wire EDM solutions. Whether you’re prototyping, testing small batches, or scaling up production, we have the expertise and technology for excellent outcomes. We combine advanced technology with experienced professionals to deliver the best results. Upload your project details for an instant quote today.
Conclusion
Wire EDM machining is a precise and versatile machining process ideal for creating intricate shapes and geometries for many industries. It is also handy for prototyping or producing one-off parts. It offers several benefits over many other manufacturing processes. However, mastering Wire EDM requires expertise for consistent, high-quality outcomes.
RapidDirect excels in this area, leveraging years of experience and innovation to unlock wire EDM’s full potential. We turn complex designs into top-notch products, going beyond market expectations. Our mission is to set new standards in precision machining, ensuring our clients get exceptional solutions. Contact us today! We’re ready to collaborate with you to find the perfect solution.
