Tool Steel Recutting Strategies versus Process Window Optimization Dynamics
Recutting tool steel establishes a stable process window that lowers long-term scrap costs and cycle times compared to forced parameter tuning.
EDM Erosion
Meaning
Thermal removal processes for hardened steels and alloys provide the necessary precision for complex mould geometries. Controlled electrical discharges known as edm erosion vaporize microscopic volumes of metal between an electrode and the workpiece. Adopting such a method allows for the creation of sharp internal corners and deep ribs that traditional milling tools cannot reach.
Material removal concludes once the desired cavity depth or finish is reached.
Dielectric Fluid
Hydrocarbon oils or deionized waters act as an insulating barrier until a specific voltage is reached. High voltage breakdown within the fluid channel focuses the energy of the edm erosion into a narrow plasma arc. Rapid cooling of the molten metal occurs as the fluid flushes the debris away from the cutting zone.
Electrode Wear
Graphite or copper shapes determine the final geometry of the cavity but lose their own mass during the discharge. Excessive edm erosion on the tool itself leads to rounded corners and dimensional drift in the finished mould. Engineers compensate for this by using multiple electrodes for roughing and finishing stages.
Surface Integrity
The recast layer formed on the steel surface consists of brittle metal that has been melted and resolidified. While edm erosion produces a uniform matte texture, this layer may contain microcracks that require manual polishing or chemical etching to prevent premature tool failure. The thickness of this heat-affected zone depends on the intensity of the discharge and the efficiency of the cooling fluid.
Secondary finishing pulses reduce the depth of the cracks and ensure the tool steel retains its fatigue resistance during high-pressure injection cycles.