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Die sinking: principles, basics, and function

When other processes reach their limits due to the material properties, die-sinking EDM performs with excellent dimensional accuracies and surface qualities. High-tensile alloys and all electrically conductive materials – regardless of the degree of hardness and material thickness – can be shaped with extremely small cutting widths and optimum accuracies. Even complicated 3D shapes of the highest quality are feasible.


What is die sinking?

Die-sinking EDM is a special spark erosion process and figures among the material-removing manufacturing processes. The principle is based on the eroding force of electrical charges, this enables the machining of all electroconductive materials regardless of their strength and intended shape. Die-sinking EDM has therefore become a very important technology in the manufacturing industry.


How does EDM work?

Die-sinking EDM is based on the physical removal principle: During spark-erosive machining, the material is removed by brief, locally separated electrical spark discharges. The erosion process takes place in an electrically non-conductive aka dielectric fluid. Both the electrode and the workpiece are placed in a dielectric liquid. We differentiate three phases:

Ignition phase:

A wire or a solid electrode (+) and the workpiece (-) are placed at a predefined distance (working gap). The application of an electric voltage leads to the formation of an electric field. Collision processes of the accelerated electrons and ions convert kinetic energy into thermal energy. If the dielectric liquid evaporates, new charge carriers are generated. A discharge channel in the shape of a plasma gas bubble forms: the clearly visible spark.

Discharge phase:

As the electrical current flow increases, the discharge channel expands. The surrounding dielectric is tough and creates a counterpressure constricting the discharge channel at both the electrode and the workpiece. Due to the high current density, intensive heating, melting, and vaporization of the material can be achieved.

Interval phase:

The voltage is switched off. The gas bubble implodes and the remaining smeltery is ejected. The dielectric rinses the solidified ablation particles.


What are the advantages and possible applications of die-sinking EDM?

Die-sinking EDM can be applicated in tool and mold making. Typical scopes of application are the pressure of die casting molds, complicated 3D molds, forging dies, or undercuts. The manufacturing process takes place on contour-controlled EDM machines, which offer a wide variety of shapes due to superimposed movements in all axes. EDM stands out with perfect accuracies, especially in the production of components with narrow and deep contours. Even when it comes to large material thicknesses, extremely small cutting widths can be realized – with optimum shape accuracy and linearity. Excellent surface finishes of up to Ra 0.11, highly polished surfaces, and manufacturing tolerances in the micro range are feasible.


What are the costs?

Due to long shaping times and the complex production of accurately shaped electrodes, the costs are quite high. This fact is most noticeable when it comes to individual parts and small batch sizes. Also, design, material, and manufacturing costs plus labor expenses must be taken into account.


Which electrodes are suitable?

All electrodes with good electrical conductivity, a high melting point and low electrical resistance are applicable. Also, the size of the spark gap and the wear have to be considered. The most common materials used are copper, graphite, tungsten-copper, and copper-zinc alloys.


How do you construct a die-sinking EDM machine?

Die-sinking EDM machines are CNC-controlled systems. Usually, they are designed as bath machines due to the dielectric liquid. A feed and bearing control, a generator for producing the discharge current, and a container with filter and pump for the dielectric are required.


How accurate is die-sinking EDM?

Die-sinking EDM machines shape with the maximum accuracy of all mechanical applications. Surface qualities of up to Ra 0.05 µm and manufacturing tolerances of 2 μm can smoothly be achieved. The die-sinking performance can be optimized by using oil as a dielectric as well as specially refined electrode material.


When is die-sinking EDM useful?

Die-sinking EDM is suitable for a precise production of complex molds made of materials that are difficult to shape, especially in tool making and mold making. Typical examples are injection molds, forging dies, prototypes or components for turbine construction, or automotive engineering.


Thanks to our new, high-precision die-sinking EDM machine for the micro range, we are capable of eroding the smallest and finest cavities, slots, and contours of any kind. With a smaller number of electrodes, we achieve minimum corner radii of < 0.02 mm. This reduces the manufacturing effort and increases productivity. An extremely high repeat accuracy makes the required machining perfection feasible. Due to an exceptionally high surface quality as well as the highest detail accuracy – even when utilizing micro electrodes – parts for the highest demands can be eroded. By producing 3DS surfaces, it is possible to improve the anti-scratch characteristics of the plastic parts as well as to achieve an adjustable gloss level of the finished plastic part. Furthermore, the 3DS surface process reduces the adhesion of the plastic part during the injection process in the mold. This enables us to increase the de-molding speed during spraying and to reduce the accumulation of residues during the spraying process in the mold. These facts have a positive effect on maintenance times, costs, and productivity.

Senkerodieren mikroskop Erodierstruktur
fraesen senkerodieren 1
fraesen senkerodieren 2


  • Surface roughness up to Ra 0.08
  • High detail accuracy
  • Exceptionally high surface quality
  • Diminutive corner radii – even with deep sinking < 0.02 mm
  • Shaping of special materials such as ceramics and hard metals
  • Processing of other materials such as hardened, alloyed, or stainless steels (INOX), non-ferrous metals
  • Clear advantages of 3DS surfaces:
    1. Appearance and quality – customizable gloss level of the plastic parts, improvement of anti-scratch characteristics.
    2. Reduced adhesion of plastic parts in the mould allows increased demoulding speeds
    3. Less residue accumulation in the mould reduces cleaning and maintenance times, allows longer moulding autonomy

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The accredited ISO certificates 9001 and 13485 confirm how we go without saying. With these certificates, we fulfil the strict quality management regulations for the supply of products which have to meet official requirements and for the manufacturing of medical products as well. We adhere to the strict regulations with both the stringent manufacturing processes and the terms of accompanying technical documentation.

You’ve got the issue – RETERO GmbH comes with the solution
We specialize in manufacturing of micro and small parts made of conductive materials, especially of ceramics and hard metals.

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