EDM (Electrical Discharge Machining)

Applications of EDM for Castings and Forgings

1. Precision Hole Drilling (EDM Drilling):

• Application: EDM drilling is used for making small, precise holes in castings and forgings, particularly in hardened materials where traditional drilling would be difficult. This is useful in aerospace components, engine parts, and molds.

• Example: Drilling cooling holes in turbine blades or oil passages in engine blocks.

• Benefit: EDM can create holes with very small diameters (down to 0.2 mm) and high aspect ratios, making it ideal for complex, hard-to-reach cavities.

2. Contour and Profile Cutting (Wire EDM):

• Application: Wire EDM is used for cutting complex contours, profiles, and geometries from castings and forgings. It can cut intricate shapes and delicate features with high precision.

• Example: Cutting intricate parts for molds, die inserts, or tooling, as well as cutting keyways or grooves in castings.

• Benefit: Wire EDM can achieve high accuracy and fine surface finishes, even on very hard materials.

3. Mold and Die Making:

• Application: EDM is widely used in the production of injection molds, die-casting molds, and stamping dies. It is capable of producing fine details and complex shapes that are difficult to achieve with conventional machining.

• Example: Creating fine detail and complex shapes in steel or carbide molds for high-precision injection molding or die-casting.

• Benefit: EDM can machine features that cannot be made with traditional tools due to material hardness or complexity.

4. Surface Finishing:

• Application: EDM can be used to improve the surface finish of castings and forgings, especially when producing hard-to-machine materials or delicate features. The process is ideal for creating smooth surfaces on metal parts.

• Example: Smoothing out the surface of forged parts used in high-precision engines or cutting tools.

• Benefit: It provides a very smooth surface with low surface roughness (Ra values of 0.1–0.3 microns), which can significantly improve part performance in applications like molds and dies.

5. Forming Complex Geometries:

• Application: EDM is ideal for producing intricate and geometrically complex shapes that are difficult or impossible to achieve with traditional cutting methods. This includes deep cavities, narrow slots, and complex 3D contours.

• Example: Creating geometric features in aerospace parts, medical implants, or automotive engine components.

• Benefit: EDM can work on materials that are tough or hard to machine using other methods, such as superalloys or titanium.

6. Hardening and Wear Resistance:

• Application: In some cases, EDM is used to improve the hardness of specific sections of a casting or forging by selectively applying heat to areas in need of enhanced wear resistance.

• Example: Creating localized hardened areas in automotive components like gears or turbine blades.

• Benefit: EDM offers high precision and local control over heat application, enabling selective hardening or material removal in specific regions.

7. Cutting Thin or Delicate Parts:

• Application: EDM can be used to machine thin or delicate parts that might be distorted or damaged by conventional machining methods. It allows for cutting very thin sections of metal without causing warping or distortion.

• Example: Cutting fine features in aerospace or medical parts that require intricate shapes with minimal material removal.

• Benefit: EDM offers high precision and minimal material distortion, even on thin or delicate components.

Recommended Machines for EDM

1. Wire EDM Machines:

• Sodick AQ Series: Sodick is a leading manufacturer of wire EDM machines known for their precision, speed, and reliability. The AQ series provides excellent surface finishes and precision for cutting complex geometries in hard materials.

• Makino U-Series: The U-Series from Makino offers high-precision wire EDM machines designed for cutting complex shapes and profiles. These machines provide fine surface finishes and are suitable for high-precision casting and forging parts.

• Mitsubishi FA Series: Mitsubishi offers a range of wire EDM machines that provide excellent cutting speeds and high precision. The FA series is widely used in the aerospace and automotive industries for cutting intricate profiles in tough materials.

2. Sinker EDM Machines:

• AgieCharmilles CUT 20P: AgieCharmilles is a recognized leader in EDM technology, and the CUT 20P is a popular choice for precision sinking and cavity creation. This machine offers high-speed, high-accuracy performance, making it ideal for machining hard materials like tool steels and carbide.

• GF Machining Solutions Sinker EDM: These machines offer high-precision sinking capabilities for producing deep cavities and complex geometries in castings and forgings. These machines are used in mold-making and aerospace parts.

• Charmilles Roboform: Charmilles' Roboform series is known for its advanced features and precision, making it suitable for intricate and detailed EDM applications, such as deep-hole drilling and precise cavity work.

3. EDM Hole Drilling Machines:

• Ona QX: Ona’s QX series EDM hole drilling machines are renowned for high-speed, high-precision drilling of deep, small-diameter holes in hard materials. These machines are often used for aerospace and medical parts.

• Makino EDM Hole Drilling Machines: Makino’s hole drilling EDM machines are ideal for precise and high-quality hole drilling in thick, hard materials like castings and forgings. They are used in industries where small holes need to be drilled with high accuracy and consistency.

4. Fast Hole Drilling EDM Machines:

• Hitachi Seiki EDM: Known for their precision in drilling small, high-quality holes in difficult-to-machine materials. These machines are ideal for applications where deep-hole drilling is needed in castings and forgings, such as cooling holes in turbine blades.

• Sodick AG Series: The AG series is designed for high-speed hole drilling with high precision, ideal for creating small, intricate holes in hard-to-machine materials.

Dimensional Inspection Measures

1. Coordinate Measuring Machines (CMM):

• Zeiss Prismo: A CMM used to measure the dimensional accuracy of EDM components. It can measure the dimensions of small or complex features like holes, cavities, and intricate geometries with high precision.

• Mitutoyo Crysta-Apex: This CMM system is suitable for measuring parts produced by EDM, checking the critical features of complex geometries such as cavities, contours, and thin sections, ensuring that all dimensions are within tolerance.

2. Micrometers and Vernier Calipers:

• Digital Micrometers (Mitutoyo or Starrett): These tools are used for measuring external diameters, thickness, and depths of small EDM features, such as keyways, profiles, and holes.

• Vernier Calipers: Common for measuring both internal and external dimensions and checking the overall dimensions of EDM parts, especially for holes and profiles.

3. Profile Projectors:

• Keyence Digital Projector: This optical device helps inspect and measure the profiles of EDM parts. It projects the part's profile and allows operators to compare it against the blueprint to ensure correct dimensions and features.

• Mitutoyo Profile Projector: Used to visually inspect the shape and dimensions of broached or machined profiles, especially for checking the precision of keyways or grooves created via EDM.

4. Surface Roughness Testers:

• Mitutoyo Surftest SJ-301: EDM typically produces high-quality surface finishes. This surface roughness tester measures the roughness of EDM-machined parts, ensuring they meet required specifications for both aesthetic and functional purposes.

• Hommel-Etamic T1000: This tester is used to ensure that EDM components meet specified roughness requirements, often in the range of 0.1–0.3 µm Ra.

Inspection Reports

1. First Article Inspection (FAI):

• The FAI report documents the first part produced from an EDM machining operation, verifying that the part meets dimensional specifications and the required tolerances. This report will include dimensional measurements, surface finish data, and tooling/part setup parameters.

2. Dimensional Inspection Report:

• The report includes a comprehensive analysis of the part’s dimensions (such as hole size, depth, width, or geometry) and any deviations from design tolerances. It may include measurements taken from CMM, micrometers, or profile projectors.

3. Surface Finish Report:

• A detailed report on the surface roughness values, such as Ra (average roughness), Rz (average peak-to-valley height), and other relevant parameters that indicate the finish quality of the EDM-ed surfaces.

4. Material and Hardness Test Reports:

• Material certificates (MTRs) ensure that the castings or forgings meet the necessary material specifications for EDM machining. Hardness test results, such as Rockwell or Vickers hardness, are used to confirm the material's suitability for EDM processing.

Quality Control Measures

1. Pre-EDM Inspection:

• Inspection of the raw casting or forging to ensure that the part is free from defects such as cracks, voids, or material inconsistencies that could interfere with the EDM process.

2. Tool and Electrode Wear Monitoring:

• EDM tooling (electrodes and wires) is subject to wear during the machining process. Regular monitoring of electrode condition and material removal rates is essential for maintaining high accuracy in EDM operations.

3. In-Process Monitoring:

• During the EDM process, various sensors and controllers monitor parameters like discharge energy, electrode wear, and flushing conditions to ensure consistent machining quality.

4. Post-EDM Inspection:

• Once the EDM process is completed, post-processing inspection ensures that the EDM part meets all required dimensional tolerances and surface finish specifications. Non-destructive testing (NDT) techniques, such as ultrasonic testing or dye penetrant testing, can be employed to detect internal cracks or defects in the machined features.

5. Statistical Process Control (SPC):

• Real-time monitoring using SPC tools ensures the EDM process remains stable and within acceptable limits, reducing the risk of producing non-conforming parts.

Advantages of EDM for Castings and Forgings

1. High Precision: EDM offers extreme precision, allowing for the creation of complex geometries and features with tight tolerances on hard metals or difficult-to-machine materials like tool steels, titanium, or carbide.

2. No Mechanical Stress: Since EDM is a non-contact process, there is no mechanical force applied to the workpiece, reducing the risk of distortion, warping, or damage to delicate or thin sections.

3. Capability to Machine Hard Materials: EDM can machine hard and heat-treated materials, which are often difficult or impossible to machine using traditional methods.

4. Complexity: EDM can produce complex, intricate shapes that would be challenging or impossible to achieve with conventional machining, such as deep holes or fine details in molds and dies.

5. Excellent Surface Finish: EDM produces high-quality surface finishes that often require minimal additional post-processing, reducing overall manufacturing time and cost.

EDM is an invaluable tool for producing high-precision, complex parts from castings and forgings, especially in industries like aerospace, automotive, and medical device manufacturing. The combination of advanced machinery, rigorous inspection procedures, and quality control practices ensures the production of high-quality EDM parts that meet strict tolerances and functional requirements.