How to improve the cutting efficiency of your wire EDM machine?

Wire EDM machine is mainly used for die mould making for its higher accuracy. Just like a coin has two sides, the wire EDM machine has its disadvantage like its lower cutting speed. How to improve its cutting efficiency while keeping its higher accuracy?

During the die mould making, the multi times cutting is adopted in order to improve its cutting surface roughness. There are two cutting steps: the main cutting (or the first time cutting) process and repairing cutting process. When the processing efficiency is low, it is necessary to distinguish between the main cutting process and the repairing cutting process.

1.     What are the reasons of that the main cutting efficiency is low?

1.1 The reason of the coolant condition

In actual production, the main reason that affects the main cutting efficiency of Wire EDM is whether the high-pressure flushing can be carried out. The high-pressure water flushing is needed to remove chips and reduce the higher temperature in the cutting path. Due to the fact that the upper and lower nozzles are not attached to the surface of the workpiece, the high-pressure water cannot effectively rush into the cutting area, resulting in a significant reduction in processing efficiency. In order to ensure the machining efficiency, the distance between the upper and lower nozzles and the workpiece surface should be controlled at about 0.1 mm. If this requirement cannot be met, the distance should be as close as possible. In order to avoid the leakage of high-pressure flushing water along the edge of the workpiece, the cut blank should be made into a shape that is conducive to the flushing requirements, such as the blank is made into a plate, and multiple parts are arranged together, and the surplus materials are used for clamping each other.

No matter the punch and die, try to cut the small threading hole. In the case of the  Wire EDM with pre machining allowance, the allowance should be as small as possible, and the electrode wire should be exposed for cutting.

1.2 The reason of EDM wire 

The diameter and material of electrode wire have great influence on the efficiency of main cutting. There are two kinds of electrode wire diameter of 0.20 mm and 0.25 mm in WEDM. When the height of the workpiece is less than 10 mm, the Φ 0.2 mm electrode wire can get a better main cutting efficiency than the Φ 0.25 mm electrode wire because of the narrow slit, thin workpiece and small total erosion amount. When the workpiece height is more than 40mm, the machining efficiency of Φ 0.25mm electrode wire is about 25% higher than that of Φ 0.2mm electrode wire. Because of the increase of thickness, the thicker electrode wire can withstand greater pulse energy, and the wider cutting path is better to chip removal. As far as the electrode wire material is concerned, the cheap brass wire is the most widely used in practical production. Brass wire is an alloy of pure copper and zinc. The lower melting point of zinc can improve the washing performance in the processing process. At the same time, in the cutting process, zinc is vaporized by high temperature, which makes heat transfer to the workpiece surface. Therefore, theoretically, the higher is the zinc ratio, the better is the processing efficiency. But in the manufacturing process of brass wire, when the proportion of zinc exceeds a certain range, the material will become too brittle to be suitable for drawing. Later, people thought of adding a layer of zinc on the outside of brass wire, that is, coated wire, its processing efficiency can be increased by about 30% compared with brass wire, and it is not easy to break the wire. In the pursuit of high efficiency processing, coated wire is preferred.

1.3 The reason of regular and standard maintenance.

It is the basis of high efficiency machining to carry out regular and standard maintenance work for WEDM machinery tool. It is necessary to make sure that the wires are in good contact with each other. When the wear groove depth of the power feed contact exceeds the radius of the electrode wire, the position of the power feed contact must be replaced. The surface of the power feed contact should be polished with sandpaper to remove the oxide layer to improve its conductivity. If the lower guide wire core seat is not cleaned for a long time, the cooling water of the lower power feed contact and even the flushing water for the processing of the lower nozzle will seriously affect the processing efficiency. Therefore, the maintenance of the lower guide wire core seat should be carried out regularly. When the reading of the water pressure gauge is greatly different from the process setting value, it is necessary to check whether the nozzle is damaged. It will affect the actual pressure of high-pressure flushing water and greatly reduce the processing efficiency. If necessary, replace it in time.

2.     What are the reasons of that the repairing cutting efficiency is low?

2.1 The reason of workpiece material deformation. 

If the workpiece deforms in the process of cutting, it will obviously affect the efficiency of finishing. If it is light, the processing efficiency will be reduced, and even the situation that it cannot be repaired will appear when the deformation is large. In order to prevent the deformation of die in Wire EDM, some suggestions must be taken. First of all, the material with small deformation should be selected and the correct heat treatment process should be adopted; secondly, the processing technology should be arranged reasonably. The large cavity or narrow and complex cavity can be pre processed to release the stress of the cutting part, and the large cavity should have multi-stage temporary allowance. The punch parts should be processed with threading holes on the material for closed contour processing; thirdly, the cutting path should be optimized, including assembly Clamp, location of temporary storage, pre-cutting path, etc.

2.2 The reason of the bigger allowance value.

In order to get reliable machining quality, the machining parameters generated by the machine process expert system are generally conservative, and the material allowance reserved between the two cutting paths is relatively large. In actual production, the efficiency of repairing cutting can be greatly improved by modifying the offset and reducing the material allowance. For example, the offset of cutting one and trimming three generated by process expert system is 0.246, 0.166, 0.146 and 0.136, which can be modified to 0.233, 0.163, 0.145 and 0.136. However, it should be noted that the material allowance should not be reduced too much; otherwise it will lead to under repair of the machined surface.

2.3 The reason of more repairing cutting times

The more times of repairing cutting, the better surface roughness can be obtained, and the more finishing, the more processing time will be multiplied. Therefore, the cutting times should be determined according to the processing requirements of die parts, and the cutting times should be reduced as far as possible on the premise of meeting the processing requirements, so as to ensure the high efficiency of mold production. For more than four times of multiple cutting, because the final finishing energy is very small, and the discharge state is affected by various factors, it is easy to have extremely low cutting efficiency. In this case, constant speed cutting can be set for the last finishing worker, which can not only ensure the processing speed, but also achieve the required surface roughness.

You can improve the cutting efficiency of your wire cut EDM machine, once the above true reasons are diagnosed.

For more information about the operation of the wire cut EDM machines or EDM wear parts, please feel free to contact us.

Tech EDM Team

www.techedm.com

sale@techedm.com