In Situ Optical Surface Profilometry for Narrow Injection Mold Cavities
In situ optical profilometry resolves sub-micron cavity wear in narrow tool ribs using fiber-coupled chromatic sensors sealed behind purged sapphire windows.
Surface Roughness Rz
Meaning
Surface texture parameters in mold manufacturing measure the average height difference between the highest peaks and lowest valleys across a sample length. Specifying surface roughness Rz is critical for defining the finish of mold cores to ensure consistent release of molded parts. This metric captures isolated surface flaws that other averaging methods might miss.
It provides a reliable benchmark for the toolmaker during polishing.
Moulding Quality
Ejection forces are highly dependent on the micro-texture of the molding steel. A high surface roughness Rz along the core increases mechanical interlocking and causes the plastic part to stick during the ejection phase. This sticking can lead to part deformation or ejector pin marks.
Maintaining a low roughness value ensures smooth part release.
Wear Resistance
Repeated scraping against abrasive polymer melts wears down the tool steel texture. When surface roughness Rz is kept within range, release agents are retained in the micro-valleys. Tool life is extended by minimizing friction.
Measurement Protocol
Accurate assessment of tool steel finishes requires standardized stylus instruments or optical profilometers. Because surface roughness Rz is sensitive to single high peaks or deep scratches, multiple measurements must be taken across the molding face to ensure uniformity. This averaging helps eliminate localized anomalies from the final report.
Consistent documentation confirms compliance with the tool specification.