Comparing EDM and CNC Machining: How to Choose the Optimal Precision Manufacturing Method

In precision metal machining, EDM (Electrical Discharge Machining) and CNC turning/milling (Computer Numerical Control) are two commonly used manufacturing methods. Each has distinct advantages and limitations, making the choice of machining method critical for part quality, lifespan, and production efficiency. Many clients often ask: For high-hardness materials or micro-structured components, which method is best? This article provides an in-depth analysis.

EDM Machining: The First Choice for High Hardness and Complex Geometries

The greatest advantage of EDM lies in its ability to machine materials and geometries that are challenging for traditional cutting tools：

• Extremely hard metals: Suitable for hardened steels, tungsten carbide, and other materials that would quickly wear conventional tools or are otherwise unmachinable.
• Complex geometries and deep internal corners: EDM can precisely cut deep slots, internal angles, and fine recesses.
• High dimensional accuracy: EDM achieves minimal machining errors, ideal for components requiring exceptional dimensional stability.

However, EDM surfaces often show electrical discharge marks, and cross-sections may have discontinuous, serrated edges. Components requiring high surface finish or fully continuous surfaces may need post-process polishing after EDM.

CNC Machining: Efficiency and Surface Finish Advantages

CNC machining offers significant advantages in efficiency and surface quality, particularly for 3D surfaces or coated parts：

• Superior surface finish: CNC can achieve Ra < 0.4 μm, reducing the need for post-polishing.
• Continuous cross-section: Maintains structural integrity and mechanical performance of parts.
• High production efficiency: CNC is typically faster than EDM for large volumes or complex parts.

For products that prioritize appearance, precision surfaces, and high machining efficiency, CNC is often the ideal choice.

Case Study: CMP10V Components with TiN Coating

We received a challenging request for a component made of CMP10V, with a tip only 0.5mm in size and requiring TiN coating. The client initially used EDM, but the tip’s sharp edges were discontinuous, affecting assembly and mechanical performance.

By switching to full CNC machining, we preserved the sharp tip geometry while achieving a surface roughness of Ra 0.3 μm. No post-polishing was needed, maintaining dimensional stability. As a result, component lifespan doubled, performance improved significantly, and production efficiency increased. This example highlights the importance of selecting the appropriate machining method based on part characteristics.

Conclusion: Choose the Machining Method That Fits Your Component

There is no “absolute best” machining method—only the solution best suited to your component’s properties. Before design and manufacturing, understanding the strengths and limitations of EDM and CNC is essential：

• EDM：Best for extremely hard materials, complex internal corners, and parts requiring ultra-high dimensional precision, though surfaces may require post-processing.
• CNC：Best for components needing high surface finish, continuous cross-sections, and efficient production.

With professional machining strategies and process planning, your products will achieve longer service life, more stable quality, and improved production efficiency, enhancing overall competitiveness.