Meaning
Post-processing treatments eliminate the hard and brittle recast layer formed during electrical discharge machining. White layer removal is necessary because the intense heat of the spark alters the metallurgy of the tool surface. This layer is often highly stressed and contains microscopic cracks that can propagate under load.
It must be mechanically or chemically cleared to ensure the tool does not fail prematurely.
Fatigue Resistance
Cyclic loading in the injection press puts immense strain on the cavity walls. If white layer removal is skipped, the brittle surface can initiate cracks that lead to catastrophic tool failure. Polishing the surface with abrasive stones or diamond paste reaches the unaffected base metal.
This process extends the service life of the mould.
Surface Finish
Aesthetic requirements for moulded parts cannot be met if the recast layer is present. The white layer removal process ensures that the final texture is uniform and free from the matte appearance left by the sparks. It allows for the application of high gloss polishes or consistent chemical textures.
Process Control
Monitoring the thickness of the recast layer helps determine the depth of the finishing pass. Effective white layer removal relies on the skill of the polisher or the precision of the chemical bath.
