Using a wire cutting machine, machinists can cut different types of materials. These include copper tubing, insulated cable, Kevlar, and glass optical fiber. The process relies on electric discharge (sparks) to vaporize the material, leaving small chips and precise cut lines.
Wire-cut electrical discharge machining (EDM) is used to cut hardened metal plates with thickness up to 300mm and is ideal for requiring low stress in the final product. It is often used in the development of extrusion dies, blanking punches, and tool manufacturing.
The Wire
The wire carries one side of the charge and the workpiece, which must be a conductive material, carries the other. When the two come close enough, a hot electric spark jumps across the gap and melts away tiny bits of the metal, giving the part its desired shape. Deionized water flushes away the waste particles and keeps the process controlled.
Unlike the cutting force of an end mill, which is dependent on the material hardness, wire EDM cuts with little mechanical change to the workpiece. This makes it suitable for parts with complex shapes and designs that are not easily produced by other machining methods. For example, it can create sharp internal corners that are unachievable with an end mill.
It is also useful for machining holes that would be too difficult to cut with other methods. In addition, it can cut through thick, hard materials such as tempered tool steel. It can also cut rounded or curved surfaces that would not be possible with other types of cutting tools.
The wire can be moved in several dimensions, including large angles, which allows tapers to be cut into the workpiece. The computer controls the movements of the wire and guides, and can also change the size of the hole. The tensile strength of the wire is important because it must be strong enough to resist the stress of cutting, but also soft enough to thread through the workpiece.
The Guides
The spool of wire is held between upper and lower guides that are centered in a water nozzle head. These guides can be CNC controlled to move in the X-Y plane, and some machines can also position the upper guide independently in the U and V axes. This allows the machine to cut tapers and shapes that transition from top to bottom.
A power supply unit provides pulses of electricity that interact with the workpiece and the wire electrode to cut it. These pulses must be precise to avoid causing damage or creating burrs on the part, so a good quality power supply is important.
Wire electrical discharge machining (EDM) is used to cut plates of hard metal that are too thick for other cutting methods, or in the production of punches and tools made from extremely tough materials. It can also be used to create complex parts with tight tolerances that are difficult to make with other machining methods.
A programmable system can control the exact movement of the wire and the spark gap between it and the work-piece to achieve the desired shape. This method can be used to cut a wide variety of materials, including copper tubing, Kevlar, glass optical fiber and insulated cable, and is especially useful for cutting very thin materials that would not otherwise be feasible using other precision cutting techniques.
The Computer
The machine is controlled by a computer that allows it to perform the task as specified. These machines are often used to cut a variety of materials that cannot be easily cut using other methods. These can include metals like copper, glass optical fiber, insulated wire, and Kevlar. They can also cut various types of foam.
GF Machining Solutions’ AgieCharmilles CUT series of wire EDM machines are well-recognized for their versatility and precision. These machines offer a wide range of features that can be optimized to improve productivity, including automatic wire changing and collision protection systems. These systems can help reduce cycle time and overall cost of operation.
The programmable X-Y and U-V axes allow the machine to accurately cut tapers and shapes that transition from one plane to another. This feature is particularly important when machining complex, three-dimensional workpieces. The programmable X-Y and the U-V axes can be simultaneously repositioned to allow for quick and accurate positioning of the upper guide, increasing overall cutting speed and accuracy.
The machine uses a dielectric fluid to protect the wire and the workpiece from damage caused by the sparks created during the machining process. The dielectric fluid is typically de-ionized water. The machine is also capable of using a soluble oil or a liquid detergent as a dielectric fluid, depending on the type of application.
The Electrode
In wire EDM machining, the electrode is usually made from brass or zinc-diffused copper (stratified wire). The workpiece and the electrode are submerged in a tank with a low-conductivity dielectric fluid. Each spark that forms between the wire and the workpiece erodes some of the workpiece’s material, while flushing away cutting debris from the electrode. This method is very precise, and a typical high-end machine can make cuts at 40 millionths of an inch or better.
In addition to metals, these machines can cut other conductive materials, like custom foam pieces. In a foam wire cutter, the taut wire is heated to about 200 degrees Celsius. This vaporizes the polystyrene foam, leaving a clean, precise cut.
The wire-cut EDM technique is typically used to make extrusion tools and punch/die sets for hard metals that cannot be cut with traditional methods. It is also capable of making start-free cuts, which is especially useful when working with complex shapes and geometries. Unlike traditional EDM, the electrodes used in wire-cut EDM are simple. This allows for quicker production, as the electrodes are already formed and ready to use. The shape and size of the electrodes affect the smoothness of the cuts they make. Round electrodes produce the most accurate cuts, followed by diamond, square, and triangle shapes. In contrast, sinker EDM uses highly conductive copper or graphite electrodes that are pre-machined to the required shape and then sunk into the workpiece by erosion, creating a mold that leaves behind a negative impression of that shape.
