Optical Profilometry Metrology Protocols for Indirect Tool Cavity Topography Verification
Calibrated silicone replicas combined with optical profilometry yield sub-micron tool cavity topography metrics without destructive sectioning.
Primary Surface Profile
Meaning
A raw measurement trace represents the total, unfiltered surface texture of a material before any spatial wave filters are applied. In quality inspection, the primary surface profile contains both the short-wavelength roughness and the long-wavelength waviness of the moulded part. This baseline scan provides the complete physical contour of the surface for subsequent analysis.
Metrology Baseline
Surface analysis starts with gathering a continuous line of height data using a contact or non-contact stylus. This primary surface profile is collected across a designated evaluation length, capturing every surface variation. By keeping the profile raw, engineers can see the cumulative impact of tooling scratches and processing inconsistencies.
Filters are subsequently applied to extract specific parameters like average roughness.
Tooling Correlation
Moulded parts inherit their surface texture directly from the tool steel surface finishing and machining marks. Milling tool paths create distinct waviness patterns, while grinding produces finer, aligned scratches. Inspecting the raw profile allows toolmakers to verify if the steel has been polished to the specified SPI standard.
It also helps diagnose tool wear by comparing new parts with baseline runs. When a tool surface degrades over thousands of cycles, the primary profile of the part changes, signaling that the mould requires maintenance.
Moulding Evaluation
Process drift, such as variations in pack pressure or cooling rate, manifests as deviations in the primary profile. Inconsistent shrink rates across the part surface cause macro-waviness, which shows up as broad waves on the scan. High melt pressure forces the polymer to conform tightly to the steel texture, reducing micro-roughness.
Monitoring this profile ensures cosmetic consistency in high-gloss consumer electronics.