What Is Wire EDM?

The wire EDM machine cutting the mold parts-Yonglihao Machinery

Nowadays, the industry has developed and technology has advanced. Wire EDM is a specialized machining technology. It is now more widely used in the aerospace, automotive, medical devices, and tool and mold industries. This is because it is characterized by high precision, high productivity, low energy consumption, and low cost. It has changed the traditional machining process and greatly improved the quality of parts. To help you understand wire EDM, the next part of this article will focus on its definition, working principle, components, advantages and disadvantages, and uses. Let’s get the discussion started. This will help you solve problems in wire EDM machining. Continue below.

Table of Contents

Overview of wire EDM

Wire EDM, or WEDM, also known as wire cutting, is a type of machining that utilizes electrical energy to cut conductive materials. It is also a type of specialty machining. Electrical discharge machining can replace some older machining methods. It uses electricity rather than mechanical force to remove material. This gives it some unique features that traditional methods lack.

The history of wire EDM began in the mid-20th century. Soviet scientists discovered that electric sparks could melt, oxidize, and corrode metals. They found this phenomenon while studying the corrosion of switch contacts. This led to the invention of electrical discharge machining, and in 1960, the Soviet Union invented the wire-cutting electrical discharge machine. However, China was the first country to use wire EDM machines in industrial production. Later, the invention of this method greatly contributed to the development of the mechanical industry. It reduced the cost of manufacturing high-precision parts and expanded the ways of manufacturing high-precision parts.

Nozzle and wire guide control feeding device of CNC EDM wire cutting machine

Principle of Wire Cut Electrical Discharge Machining (WEDM)

Before wire EDM, the part blank must be drilled. If the workpiece is to be used for internal machining, it is mounted on the machine. The workpiece is then connected to the positive terminal of the pulse power supply. A molybdenum or copper wire is used as the cutting wire. It is threaded into the pre-machined hole. It is connected as a tool electrode to the negative terminal of the high-frequency pulsed power supply. Primary cutting is then performed using sparks and discharges. The pulsed power supply provides the machining energy and the special wire EDM working fluid is used to remove the debris generated during the machining process. An electric field acts on the cathode and anode. They are bombarded by a stream of electrons and ions. This creates a sudden high-temperature heat source in the electrode gap. It causes localized melting and vaporization of metals. The working fluid and workpiece material vaporizes. The vapor expands rapidly. The workpiece melts and vaporizes under the combined effect of expansion and working fluid ram. The workpiece material is thrown out of the discharge channel. This completes the spark discharge.

When the next pulse arrives, the process continues to repeat until the entire part is machined. At present, most wire-cutting machines are controlled by microcomputers. They are highly automated. The process is programmed to control the trajectory of the cutting wire.

There are various types of wires used in wire EDM. These include tungsten, molybdenum, copper, steel core, coated and annealed wires. You can choose the wire based on the material and accuracy of the part. To ensure machining accuracy, they should be scrapped after one use.

Components of wire cutting machine

The wire cutting machine has a worktable, wire walking mechanism, liquid supply system, pulse power supply, and control system.

Worktable: also known as cutting table, consists of three parts. It includes the middle pallet, the lower pallet, and the worktable. The role of the worktable is to install the fixture and the workpiece to be cut. According to the actual processing situation, to ensure the operation, you can choose manual or automatic operation to operate the worktable. The center pallet and the lower pallet are driven by stepper motors. They are driven by gears and ball screws to move the table longitudinally and transversely.

 Wire walking mechanism: It mainly consists of a wire storage cylinder, wire walking motor, and guide wheel. The wire storage cylinder is mounted on the wire storage cylinder pallet and is driven by the wire walking motor through the coupling to rotate the cylinder back and forth. The forward and backward rotating motion of the cylinder is simultaneously transmitted to the screw on the cylinder pallet through the gear, making the pallet do a reciprocating motion. The electrode wire is mounted on the guide wheel and the wire storage cylinder. When the wire walking motor starts, the electrode wire moves back and forth at a certain speed for wire walking.

 Liquid supply system: it includes a working liquid tank, hydraulic pump, and nozzle. It provides enough working fluid for the cutting process of the machine tool. The working fluid is mainly mineral oil, emulsion, and deionized water. Its main functions are cooling of electrodes, workpieces, and machining powders, discharge produced by explosion pressure, deionization of the discharge going area, and descaling of the discharge products.

 Pulse power supply: The pulse power supply is the energy equipment that generates pulse current. WEDM pulse power supply is one of the most critical equipment that affects the machining process index of WEDM. The pulse power supply needs to meet the cutting conditions and process indexes. It needs a large peak current, narrow pulse, high pulse frequency, small wire electrode loss, and convenient parameter setting.

 Control system: the control system directly determines the function of the machine tool. The system uses the graphics and parameters input by the customer to prepare the CNC program. The program controls the wire-cutting process and the path of the wire.

Applications of wire EDM

Wire EDM has a variety of uses. These include aerospace, medical, automotive industry, and mold making. EDM wire EDM is popular because of its high precision, smooth surface, lack of thermal deformation, and ability to cut hard metals.

Aerospace: Engine turbine blades and satellite components require extreme precision. The excellent machinability of WEDM is ideal for these parts.

Medical: It can be applied in the field of medical equipment and medical devices, such as artificial joints, prostheses, and other medical equipment and surgical instruments, implants, and other medical devices.

Automotive: It can cut a variety of automotive parts, such as body, injectors, gears, and other parts.

Mold manufacturing: Generally speaking, molds require high accuracy of parts, so it is widely used to cut the shape and details of parts.

Advantages of wire-cut machining

Compared with milling processing, wire EDM has many advantages. It is suitable for parts that cannot be satisfied by milling machining. These parts include:

  • The machining accuracy is very high; typically, EDM can achieve dimensional tolerances of +/- 0.0002”.
  • It can cut complex shapes, deep holes, and undercuts that milling cannot. It also leaves no burrs after machining.
  • It can machine hard metal materials. Excess material is easily cut away without tool wear similar to ordinary milling.
  • The tool never touches the workpiece during machining. Therefore, the workpiece is not deformed by heat after machining. Therefore, very thin and precise workpieces can be processed.

Disadvantages of wire EDM

Though WEDM has many advantages, it is not a panacea and hence has the following limitations:

  • It is only suitable for cutting conductive materials. It cannot process non-conductive materials such as plastics, composites, and natural materials.
  • The cutting speed is slow. Since it is electrical discharge machining, it is suitable for some small batch parts.
  • Susceptible to environmental influences. The working environment during wire EDM processing affects the cutting. It is necessary to meet the processing requirements.
  • The processing cost is high because the wire cannot be reused.

Machining tips when taper cutting by wire EDM

Taper cutting is more difficult to remove chips than normal cutting. You can minimize the occurrence of wire breakage by increasing the discharge interval.

When cutting some special workpieces, the thermal stress generated by cutting will lead to the deformation of the workpiece and affect the cutting accuracy. You can shorten the distance between the upper nozzle and the upper surface of the workpiece so that the cutting fluid can cool down the machining part more efficiently, and at the same time reserve different machining allowances according to the material of the workpiece, to minimize the machining error caused by thermal deformation.

The hardness of the electrode wire must be satisfied. Try to increase its tension. Also, reduces the energy of individual discharge pulses. These will reduce the deflection of the electrode wire.

Wire EDM Machining-Specialty Workpiece Machining Processes

Precautions to be taken during wire EDM machining

It can be used to machine small holes and complex shapes, but cannot machine blind holes in parts.

The narrow slit produced during machining and the small amount of metal etching are conducive to the reuse of materials and the improvement of the utilization rate of materials.

When the workpiece is too thick, it’s hard for the fluid to enter and fill the gap. This affects accuracy and roughness and reduces part quality.

Cracks, deformation, and other problems may appear on the workpiece’s surface during processing. You should do proper heat treatment and rough machining before processing. This will remove defects in the material and blank shape and improve machining accuracy.

The future trend of wire-cut electrical discharge machining

With the continuous development of aerospace, medical, mold manufacturing, and other industries, the future parts will become more and more complex, and the requirements for wire-cutting processing will become higher and higher, I believe that shortly, the wire-cutting technology will be in the processing accuracy, processing speed, processing efficiency, and processing costs will be further improved, and it will become a high-efficiency, high-quality processing method.

Yonglihao Machinery specializes in the processing of mechanical parts. It has rich experience and expertise in EDM wire-cutting processing. If you have wire EDM projects and needs, please contact us. We will provide you with professional services and complete solutions.

FAQ

WEDM machines can cut any conductive material such as metals and alloys. These materials include steel, aluminum, brass, tungsten, and various stainless steel, nickel, and titanium alloys. It is mainly used for cutting hard materials.

Typical high-end machines maintain line positioning accuracy of 40,000 millionths of an inch (0.000004 inches). Specialty high-precision machines are accurate to 0.000001”.

WEDM uses a lot of energy. This affects the carbon footprint. However, as technology advances, this impact will become more environmentally friendly.

The material to be processed determines the electrode wire. To ensure the quality of the workpiece, the electrode is used only once and then discarded.

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