Electrical discharge machining#Sinker EDM

The sinker EDM ( electrical discharge also sinks Senkfunkenerosion or sinking EDM ) is a process of erosion radio.

Method

Sinking EDM machines are built primarily as Badmaschine - the workpiece is thus in a bath of dielectric. As a dielectric, a non-conductive oil or deionized water is used. The machining head is mobile and carries out the movement in the Z - axis. The table states the movement in the X- and Y -axis. Sinker can be designed as a conventional machine tools or as a CNC machine. Even machines with automatic change of the electrode are available and allow automatic processing of several parts of the workpiece in a row.

The electrode ( cathode) is approximately the negative shape of the workpiece to be machined (anode ), and is often made of copper or graphite. Because the material removal not only occurs in the direct contact between the workpiece and the electrode, but at a certain proximity of the spark jumping through the dielectric, the electrode must be dimensioned smaller. This so-called spark gap usually has a size of a few hundredths to tenths of millimeters. The size of the spark gap is dependent on the discharge technology set on the machine (electrical voltage and current, discharge interval, pause interval). Technologies with a higher removal rate result in a larger spark gap and a rougher surface texture. The removal caused by thermal mechanisms, in particular by melting or evaporation of the material. The removed material is carried away by the gas bubble formed in the dielectric and the dielectric itself. The dielectric is continuously filtered in a loop.

Not only the workpiece, but also the electrode is subject to a material removal. By judicious choice of discharge technology one tries to optimize the ratio of workpiece and Elektrodenabtrag. For the finishing ( finishing) a new electrode is often needed and chosen a finer technology.

Areas of application

The sinker EDM is often used in tool and mold making. There are so molds, dies or punch made ​​.

With the machine and electrode suitable all conductive materials can be processed independently of their hardness. Also as a preparatory process for the wire EDM has the sinker EDM an important role. The starting hole in which the wire electrode is threaded later, can also be produced in already hard steel by means of die-sinking EDM. Through coordinated rotation of the electrode with simultaneous Z- feed is also threaded in hard materials can be eroded. The movements of the X - and Y-axis tracks or undercuts can be realized.

Drill EDM

A special application of the Senkerodierens is the drill EDM (also spark erosion drilling or Bohrerosion ). The machine used is called a start hole drilling machine. The machine is so called because the resulting holes are usually, but not always, used as a starting or threading hole for subsequent wire EDM.

The basic technology is constant, the discharge strategies and machine structure but are optimized for the fastest possible production of holes. As the electrode copper or graphite tubes with diameters of the 0.13 to 3 mm and a length between 300 and 800 mm were used. This be pushed automatically to compensate for the erosion of the electrode. The electrode rotates during the manufacturing process, resulting in an even burn and quicker removal on the workpiece. Through the electrode tube dielectric is constantly pumped ( pressure up to 60 bar) to wash away the removed material.