What Is EDM Machining

EDM means Electrical Discharge Machining, it is a common method for spare parts production.

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Features of EDM

1.

There are no significant mechanical chip forces during machining, and materials that are conductive or semi-conductive can be machined regardless of workpiece hardness and stiffness. But it cannot process non-metallic conductive materials.

2.

Small holes and complex shape parts can be machined, but blind holes cannot be machined.

3.

The wire loss is small and the machining accuracy is high.

4.

The slits produced during processing are narrow, and the amount of metal corrosion is small, which is conducive to the reuse of materials.

5.

When the workpiece material is too thick, it is difficult for the working fluid to enter and fill the discharge gap, which will affect the machining accuracy and surface roughness.

6.

During the machining process, problems such as cracks and deformation may occur on the surface of the workpiece. Before machining, proper heat treatment and rough machining should be performed to eliminate defects in material properties and blank shape and improve machining accuracy.

7.

The workpiece is processed by numerical control programming technology, and the processing parameters can be adjusted, which is easy to realize automatic processing.

Classification of edm machining

1. Wire edm machining or named wire cutting

(1) fast speed wire edm machining

fast speed wire edm machining is generally used for fast wire cutting electrode wire, and the general processing speed can reach 6~12m/s. The machining accuracy and surface finish of the workpiece are not high. It is commonly used for mass production of parts. Because it is fast and cheap.
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(2) Middle speed wire edm machining

The middle speed wire edm machining belongs to the category of reciprocating high-speed wire EDM machine tools, which realizes multiple cutting functions on the high-speed reciprocating wire EDM machine. The middle speed wire edm machining has the advantages of fast and slow wire cutting, but it is necessary to pay attention to the deformation treatment during the cutting process. The thermal stress generated by the workpiece during cutting will cause non-directional and irregular deformation of the material, resulting in uneven cutting and falling and affecting the cutting accuracy. Therefore, during the cutting process, different machining allowances must be reserved according to different materials to fully release the internal stress and deformation. It is commonly used for the parts production, which need good surface and cheap cost.

(3) Low speed wire edm machining

The low speed wire edm machining is generally 0.2m/s, and the accuracy is up to 0.001mm. Usually, copper wire is used as the electrode wire. The electrode wire moves in one direction at a low speed, and the quality of the machined surface is close to the grinding level. The low speed wire edm machining adopts the method of continuous wire feeding of electrodes, and the electrodes can be supplemented when they are lost, so the machining accuracy can be improved. The surface roughness value of the workpiece processed by WEDM can generally reach Ra0.8μm and above, and the roundness error, linear error and dimensional error are smaller than those of WEDM. It is commonly used for moulds production.

2. Laser edm machining or named laser cutting

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The material to be cut is irradiated with a high power density laser beam, so that the material is quickly heated to the vaporization temperature and evaporated to form holes. Complete the cutting of the material.

(1) Laser vaporization cutting

A laser beam with high energy density is used to heat the workpiece, so that the temperature rises rapidly, reaching the boiling point of the material in a very short time, and the material begins to vaporize to form vapor. These vapors are ejected at a high velocity, and at the same time as the vapors are ejected, cuts are formed in the material. The vaporization heat of the material is generally large, so a large power and power density are required for laser vaporization cutting.

(2) Light melting cutting

When laser melting and cutting, the metal material is melted by laser heating, and then non-oxidizing gas (Ar, He, N, etc.) is sprayed through a nozzle coaxial with the beam, and the liquid metal is discharged by the strong pressure of the gas to form a cut. Laser melting cutting does not need to completely vaporize the metal, and the energy required is only 1/10 of the vaporized cutting. Laser melting cutting is mainly used for cutting materials that are not easily oxidized or active metals, such as stainless steel, titanium, aluminum and their alloys.

(3) Light oxygen cutting

The principle of laser oxygen cutting is similar to that of oxyacetylene cutting. It uses a laser as a preheating heat source and an active gas such as oxygen as a cutting gas. On the one hand, the blown gas acts on the cutting metal to produce an oxidation reaction, releasing a large amount of oxidation heat; on the other hand, the molten oxide and molten material are blown out from the reaction zone to form a cut in the metal. Since the oxidation reaction in the cutting process generates a lot of heat, the energy required for laser oxygen cutting is only 1/2 of that of melting cutting, and the cutting speed is much higher than that of laser vaporization cutting and melting cutting. Laser oxygen cutting is mainly used for easily oxidized metal materials such as carbon steel, titanium steel and heat-treated steel.

(4) Optical Scribing and Controlled Fracture

Laser scribing uses a high-energy-density laser to scan the surface of a brittle material, so that the material is heated and evaporated to form a small groove, and then a certain pressure is applied, and the brittle material will crack along the small groove.

Advantage of laser edm machining

Compared with other thermal cutting methods, laser edm machining generally characterized by fast cutting speed and high quality. Specifically summarized in the following aspects.

1. good cutting quality

2. High cutting efficiency

3. fast cutting

4. non-contact cutting

5. Variety of cutting materials

(1) Carbon steel

This material gives better results when cut with oxygen. When oxygen is used as the process gas, the cut edges are slightly oxidized. For sheet thicknesses up to 4mm, high pressure cutting can be performed with nitrogen as the process gas. 

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In this case, the cut edge will not be oxidized. For plates with a thickness of more than 10mm, using a special plate for the laser and applying oil to the surface of the workpiece during processing can get better results.
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(2) Stainless steel
Oxygen can be used where oxidation of the cut face is acceptable; nitrogen is used to obtain an oxide-free, burr-free edge that requires no further treatment. Coating an oil film on the surface of the sheet will result in better perforation without compromising machining quality.
(3) Aluminum
Despite high reflectivity and thermal conductivity, aluminum can be cut up to 6mm thick, depending on alloy type and laser capability. When cutting with oxygen, the cut surface is rough and hard. With nitrogen, the cut surface is smooth. Pure aluminum is very difficult to cut due to its high purity, and can only be cut when a “reflection absorption” device is installed on the system. Otherwise reflections can destroy optical components.
(4) Titanium
Titanium sheets are cut with argon and nitrogen as process gases. Other parameters can refer to nickel-chromium steel.
(5) Copper and brass
Both materials have high reflectivity and very good thermal conductivity. Brass with a thickness of less than 1mm can be cut with nitrogen gas; copper with a thickness of less than 2mm can be cut, and the processing gas must be oxygen.
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Copper and brass can only be cut if a “reflection absorber” device is installed on the system. Otherwise reflections can destroy optical components.

Application of edm machining

Both wire edm machining and laser edm machining are good for production, they can help you to speed up the production and save the cost. You can choose the better one to use in your production.

You can also contact Ningbo Sinster Machine Co., Ltd to do it for you, Sinster can provide you the perfect products in China cheap price. Sinster have good experience in combining edm machining with cnc machining, cnc milling, cnc drilling, cnc grinding to produce your spare parts. Please see more details for cnc service at: https://www.syluecncmachining.com/cnc-machining-services

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Sinster 2000W Laser Cutting Equipments

Sinster Laser Cutting Equipments Working

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The workpiece on the machine

Laser Cutting Products made from Sinster

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If you're curious about if your parts are ideal for laser cutting services, reach out to our team at once for more details with your email address.

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