Sinker
EDM
High-Precision
Tolerances to ±0.0001″
for tooling and die components
Twin City uses Sinker EDM for machining complex cavities, sharp internal corners, and intricate geometries in metal materials. Twin City EDM & MFG has used this process since 1959 to deliver reliable, high-tolerance parts for clients in the Medical, Aerospace, Defense, Dental, and industrial sectors. Whether you’re cutting deep cavities in tool steel or producing detailed features in exotic alloys, or impossible features in production parts, our sinker EDM capabilities offer superior results with accuracy down to ±0.0002″.
What Is Sinker EDM?
Sinker EDM, also called RAM EDM, plunger EDM, or conventional EDM, uses an electrically charged electrode to erode material from a workpiece submerged in dielectric fluid. Unlike wire EDM, which slices through the part, sinker EDM forms shapes by gradually removing material with the electrode. This method excels in producing blind cavities, internal angles, or small features that traditional machining cannot reach.
Twin City EDM manufactures all graphite, copper, and brass electrodes in-house, allowing for complete control over quality, design, and lead time.
Benefits of Sinker EDM
Sinker EDM offers several key advantages over conventional machining methods:
- No Mechanical Stress: The process does not use physical force, which prevents warping or distortion in brittle, heat-treated, or stainless materials.
- Superior Surface Finish: Achieves surface finishes down to 8 RA without the need for secondary polishing.
- High Accuracy: Tolerances as tight as ±0.0002″ and repeatability of ±0.0005″.
- Works with Hardened or Exotic Metals: Easily machines tool steels, Stainless, Inconel, titanium, Kovar, and other materials that are difficult to cut with traditional tools.
- Unmatched Precision for Cavities: Ideal for tooling, die components, surgical parts and tools, aerospace, and defense.
The Sinker EDM Process: Step by Step
- Electrode Design & Build: Twin City EDM produces custom electrodes in-house from graphite, copper, or brass to match the geometry of the desired cavity.
- Workpiece Setup: The metal part is fixtured and submerged in dielectric fluid, which helps cool the part and control spark erosion.
- Machining via Electrical Discharge: The electrode delivers a series of electrical discharges to the workpiece, vaporizing the metal without physical contact.
- Flush and Clean: Debris from the erosion process is flushed away by the dielectric fluid, allowing the cut to stay clean and consistent.
- Inspection and Quality Control: All parts undergo rigorous testing and measurement, including CMM scans and visual inspections.
This process can be automated entirely using CNC controls and robotic cells to ensure speed, consistency, and reduced labor time.
Applications and Sample Projects
Twin City EDM uses sinker EDM to support a wide range of precision machining projects. Applications include:
- High-tolerance surgical components
- Aerospace housings and jet engine parts
- Defense equipment and cavity generation
- Precision Parts with high tolerance features
- Unmachinable side features
Why Choose Twin City EDM for Sinker EDM?
Over 60 Years of Experience: A trusted partner since 1959
In-House Electrode Manufacturing: Total process control from design to delivery
Advanced Automation: CNC sinker EDMs with robotic tool and part changers for lights-out production
Certified for Quality: ISO 9001:2015 and ISO 13485:2016 compliant
Fast Turnarounds: Typical lead times of 1–2 weeks
Materials Expertise: From stainless steel to Nitinol, we machine what others won’t touch
Contact us to learn how we can support your goals with our sinker EDM services.