Tooling Surface Polish Impact on First Article Inspection Accuracy
Uncalibrated optical scans on mirror-polished plastic introduce up to fifteen micrometers of false elevations, ruining First Article Inspection accuracy.
Cavity Polishing Clearance
Meaning
Physical gaps between moving tool components accommodate the removal of material during the final smoothing of mold surfaces. Engineers calculate cavity polishing clearance to ensure that the abrasive stones or diamond pastes used to achieve a mirror finish do not compromise the fit of sliding cores. This dimension prevents the tool from binding once it reaches operating temperature.
It is a specification for parts requiring high optical clarity or specific textures.
Tooling Tolerance
Precise machining of the mold base must leave enough room for the manual labor involved in finishing. Since cavity polishing clearance involves removing microns of steel, the initial build must account for this reduction in wall thickness. Failure to plan for this material loss results in parts that exceed their outer tolerance limits.
Ejection Friction
Smooth surfaces reduce the force required to remove a part from the cavity. Proper cavity polishing clearance ensures that the finish is uniform across all vertical walls. Without it, micro-scratches or uneven depths create drag that leads to stress whitening or deformation during the ejection stroke.
Friction stays low.
Maintenance Access
Tool life depends on the ability to periodically restore the surface finish. A generous cavity polishing clearance allows for multiple refurbishment cycles over the life of the mold. The absence of this space makes the tool a single-use asset that cannot be repaired after the surface sustains wear.