Electric Discharge Machining (EDM), also called spark or sparking process, is a highly accurate manufacturing process for creating shapes within components and assemblies. EDM connects a metal workpiece to a power supply and uses a shaped tool or electrode to erode material in order to form the desired geometry or pattern.

Based on the different types of electrodes used and the different purposes intended for, there are two types of EDM process - wire cutting EDM and sinker EDM. Wire-cutting involves pre-drilling a hole in the workpiece and then feeding a metal wire through the hole as an electrode to cut the workpiece along desired profile. By contrast, sinker machines cut workpieces without pre-drilling holes and typically use a machined graphite or copper electrode to form the desired details.

In comparison to CNC machining, spark process provides a number of benefits both in tooling and component productions:

• High processing precision comparable to that of CNC machining
• Deep cavity (slenderness ratio>10) processing ability
• Thin wall section processing ability
• Small radius of interior corners (≤0.3mm)
• High hardness of workpieces (≥55HRC)
• Free of metal burrs, as are common in CNC machining
• Complex logos directly attainable, both immersed and raised
• Good surface smoothness

EDM process plays an important role in wrought metal forming techniques. It sometimes serves as the ultimate solution to the fabrication of highly complex and demanding part that is a challenge to other processing techniques. It has further broadened our capabilities to provide cutting-edge manufacturing solutions to our clients.

Case study: Tooling for press-fit connectors via EDM process

There has been growing interest in press-fit technology versus conventional soldering method. In comparison, press-fit technology exhibits a number of advantages enabling more reliable PCB assembly and lower costs. A press-fit connector uses either solid or compliant type of pin to insert into the PCB through hole. Compliant pin, which compresses during insertion, is considered a better solution than solid pin.

In ordre to press-in all contact pins of the connector simultaneously into respective contact holes of the PCB, such a large force has to be evenly applied to the housing with the help of a properly designed press-in tool. The photo shows such a tooling developed from D2 tool steel by Eversun. Its work surface is everywhere in contact with the plastic housing but nowhere in contact with the brass units. This way the pressure applied can be evenly distributed on the compliant pin matrix without roughing the brass components. This range of fixtures is generally produced with a ±0.05mm tolerance, heat treated to HRC 55 and chrome finished.