Improving surface finish in electrical discharge wire cutting (EDM)

The surface finish achieved through electrical discharge wire cutting (EDM) varies: oil cutting can reach Ra 0.2μm, water cutting Ra 0.4μm, and EDM surface finish generally falls between Ra 0.2-0.3μm, typically around Ra 0.6-0.8μm. In many instances where parts cannot undergo polishing, a high-quality surface finish from EDM or wire EDM becomes crucial.

EDM wire cutting, a precision machining method in modern manufacturing, is renowned for its high accuracy and versatility in processing various materials. However, the surface finish of the cut often serves as a critical measure of machining quality.

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Key Factors Affecting Surface Finish

1. Optimization of Discharge Current
   • By optimizing the discharge current and selecting lower current values, the discharge process can be effectively controlled to achieve a smoother cut surface.
2. Adjustment of Discharge Pulse Time
   • Adjusting the discharge pulse time allows for precise control of the energy output of the EDM. Appropriate pulse timing promotes uniform melting and evaporation of the material, thereby enhancing the surface finish of the cut.
3. Control of Gap Between Molybdenum Wire and Workpiece
   • Proper gap control ensures continuous discharge while avoiding instability caused by excessive gaps, directly impacting the surface finish.
4. Appropriate Cutting Speed
   • The selection of cutting speed significantly influences surface finish. A slower cutting speed helps improve the smoothness of the cut surface by ensuring better control over the machining process.
5. Inspection and Adjustment of Molybdenum Wire Wear
   • Regular inspection and replacement of severely worn wire are fundamental to maintaining surface finish quality.
6. Maintenance of Worktable Flatness
   • Keeping the worktable flat reduces vibrations and deformations during the machining process, thereby improving surface finish.

Impact of Surface Finish on Wire Cutting

A high-quality cut surface not only enhances the product’s appearance but also reduces the need for subsequent processing. Controlling the heat-affected zone and effectively releasing stress are crucial for preventing cracks and deformations during machining.

How to Improve Wire Cutting Surface Finish

1. Select Appropriate Cutting Conditions
   • Reasonable discharge and working fluid parameters are essential for reducing surface roughness.
2. Reduce Cutting Wire Diameter
   • Finer cutting wires result in higher surface finish quality.
3. Utilize Advanced Molybdenum Wire Technology
   • Low-oxide compound molybdenum wires help narrow the discharge gap and reduce surface roughness.
4. Post-Processing Measures
   • Techniques such as polishing, grinding, and electrochemical polishing can further enhance surface finish.