Areal Surface Texture Parameter Measurement in Micro Injection Mould Cavities
Areal surface metrology in micro-cavities requires non-contact optical instruments with matched bandwidth filters to verify steel texture and polymer replication.
Electric Discharge Machining
Meaning
Subtractive thermal manufacturing processes shape conductive tool steels through controlled spark erosion across a dielectric gap. Mold making facilities utilize electric discharge machining to form deep ribs, narrow slots and intricate textures in hardened cavity blocks. High thermal energy creates a re-melted heat affected zone that alters surface metallurgy.
Datasheet steel hardness values do not reflect the localized brittleness of the white layer formed during spark discharges.
Spark Erosion
High frequency electrical discharges vaporize metal particles from the workpiece surface inside a hydrocarbon dielectric bath. Voltage potential breaks down dielectric insulation to form a plasma channel between electrode and tool steel. Continuous fluid flushing removes eroded metal debris to maintain spark gap stability.
Carbon buildup from cracked dielectric fluid causes localized short circuits and irregular cavity geometry.
Surface Recast
Thermal pulse duration determines the thickness of the un-tempered recast layer left on cavity walls. Thick recast layers develop micro-cracks that transfer unwanted surface defects onto injection moulded parts. Secondary chemical etching or hand polishing removes brittle surface layers before texturing.
Tool Integrity
Electrode wear alters dimensional tolerances on tall rib features during roughing cycles. Copper tungsten electrodes provide superior spark resistance during prolonged erosion of hardened steel inserts. Regrind resin processing amplifies release friction against unpolished spark eroded sidewalls.
Tooling specifications mandate stress relief heat treatment after heavy erosion passes.