Wire EDM- The Commonly Used Auxiliary Process in CNC Machining

(STL.News) Wire EDM is a common machining process for custom metal parts, mainly used for the processing of molds, complex shapes or microstructures, and other products.  In CNC machining, we also often use this process.  Due to its limitations, CNC machining is difficult to process parts with too fine shapes, high hardness, and high precision requirements.  Then wire EDM can make up for it. For example, the parts are bent and the gap is narrow, and normal machining tools cannot be processed properly. Then wire EDM is required.  Or the material has high hardness after heat-treated.  For it is difficult to process with general CNC machining tools, wire EDM is considered as an alternative.  For ultra-precision parts processing, wire EDM is also used because of the high accuracy requirements that ordinary CNCs cannot achieve.  So, what exactly is wire EDM?

The basic principle of wire EDM

The so-called wire EDM, as its literal meaning, is the use of moving metal wire as the electrode wire, by pulse electric spark discharge between the electrode wire and the work-piece.  So as to generate a high temperature to melt or vaporize the metal, forming a slit, thereby cutting parts.  It’s one way of EDM machining, the process of cutting metal is as easy as cutting tofu with a wire.  You can turn 360 degrees to cut any shape during wire cutting. The metal wire here is generally molybdenum wire or copper wire.  Molybdenum wire has the characteristics of high strength, fast cutting speed, long service life, and good discharge performance.  It is commonly used in wire EDM processes.

Classification of wire EDM

Wire EDM can be roughly divided into three kinds according to the cutting speed of the electrode wire: high speed, medium speed, and low speed.  The main differences among these three kinds include processing efficiency, cutting accuracy, and surface quality.  Among them, the low-speed wire EDM has the highest technology content and the highest processing accuracy.  Copper wire is commonly used for low-speed Wire EDM.  The cost of low-speed wire EDM is the highest among these three types of wire EDM, and the processing time is also the longest.

The fast-speed wire EDM is named because the electrode wire runs at a high speed during the cutting process.  The biggest advantage of fast-speed wire EDM is its high-cost performance. And it has a large market in China.  Traditional fast speed wire EDM processing uses a one-time cutting process, the processing efficiency is about 40mm²/min, the surface roughness is about Ra3.0um.  The surface has obvious wire cutting marks, and the processing accuracy is about 0.02mm.

In order to improve the processing quality and control the cost at the same time, on the basis of fast-speed wire EDM, the machine manufacturer made improvements with reference to the multiple cutting process.  Then the so-called medium-speed wire EDM appeared.  At present, the efficiency of one-time cutting of medium-speed wire EDM is about 180mm²/min.  The surface roughness after multiple cuts is below Ra1.0um.  The average efficiency after multiple cuts is 50mm²/min.  The processed surface has no obvious cutting marks.  And the precision of machining is about 0.01 mm, electrode wire loss is below 0.01mm/200,000 mm².

Of course, the above data is for reference only.  And the processed quality will be different due to different processing machines, the concentration of working fluid, and electrode wire wear conditions.

The advantages and disadvantages of wire EDM

It is not difficult to see from the above that wire EDM has the following advantages:

  1. Wide range of applicable materials. Regardless of the thickness and hardness of the material, as long as it is a conductive material, wire EDM can be performed
  2. Complicated shapes can be processed.  In addition to straight cutting, wire EDM can also cut into arcs and process complex shapes, such as a combination of straight lines and arcs.  It is also possible to perform taper processing by moving the upper and lower wires separately.
  3. Has relatively high accuracy.
  4. Reduce material damage. Because wire EDM is a non-contact process, the load on the material will not be too large.  And the thermal deformation is also small.

Just as any process is not perfect, wire EDM also has the following shortcomings:

  1. Low processing efficiency. Wire EDM is to cut while gradually melting the workpiece.  So it is slower than ordinary CNC machining tools.  The speed of the wire EDM is a few millimeters per minute, and its movement is almost invisible
  2. Cannot use bottom processing
  3. Cannot handle non-conductive materials
  4. Cannot handle the workpiece horizontally

Conclusion

The above are some basic knowledge about wire EDM.  WayKen has been focusing on CNC machining for many years and has a wealth of professional knowledge.  Our professional team can use different processes to adapt to processing various parts and ensure high quality.  We always aim to help every customer succeed in his new designs.  If you have any related needs, welcome to inquiry use.