Second Source Tooling Priced before the First Tool Wears Out
Pricing secondary tooling during initial contract negotiation locks steel costs and machining rates before primary tool wear destroys commercial leverage.
EDM Electrode Gap
Meaning
Physical spacing between the tool electrode and the steel workpiece determines the discharge energy and material removal rate during mould engraving. The EDM electrode gap must be precisely calculated to achieve the target cavity dimensions on the mould. Correct gap size ensures the generated spark produces the specified surface texture without eroding the electrode.
Dimensional Control
Machined dimensions of the cavity are larger than the electrode due to the sparks bridging the distance. Setting the EDM electrode gap involves balancing the overcut with the tool wear. Small gaps yield tight tolerances.
Dielectric Circulation
Flushing of the hydrocarbon fluid through the spark area removes the vaporised metal and cracked carbon. Inadequate fluid flow across the EDM electrode gap causes secondary arcing and ruins the surface finish of the steel. This problem produces micro-cracks in the mould wall that act as stress concentration points for premature fatigue failure.
Surface Finish
Roughing and finishing stages utilize different electrical settings to produce either high metal removal rates or smooth surfaces. A wider gap is used during initial roughing to clear material quickly, while a narrow gap combined with low current achieves the fine finishes required for smooth plastic demoulding. Properly managed discharges ensure the cavity walls do not hold defects that could tear the plastic during ejection.