ISO 25178 Surface Parameters for Injection Moulding Optical Components
ISO 25178 areal parameters define 3D optical surface texture to control stray light and guide injection moulding process windows for precision lenses.
Spatial Bandpass Filtering
Meaning
An analytical surface treatment isolates a specific band of spatial frequencies to evaluate functional textures. Spatial bandpass filtering combines high-pass and low-pass filters to remove both the large-scale form errors and the small-scale electronic noise from the surface profile. In polymer metrology, this process isolates the specific roughness scale that governs paint adhesion, tactile feel, or friction.
Frequency Isolation
Application of a bandpass filter is essential when analyzing surfaces with complex, multi-scale roughness. The spatial bandpass filtering process allows researchers to target the exact scale of texture replicated from the mold cavity. This ensures that the metrology focus remains on the features produced by the molding process rather than the raw substrate geometry.
Surface Validation
Production of consistent matte finishes on molded parts requires regular surface validation. Spatial bandpass filtering is applied to the measured surface data of the molded parts to track the replication of specific feature sizes. If the filtered profile shows a loss of mid-scale features, it indicates that the molding process is failing to replicate the mold texture due to insufficient packing pressure or low melt temperature.
Corrective actions can then be taken on the molding machine before defective parts are produced.
Mold Replication
Comparing the surface of the mold to the molded part is simplified using this filtering technique. By focusing on a narrow band of spatial frequencies, the replication fidelity of the molding process can be quantified. This assists in optimizing the molding parameters.