Optical Profilometry Replica Metrology Protocol for Mould Cavity Topography
Indirect optical profilometry on elastomeric cavity replicas yields sub-micron texture data while eliminating tool teardown and optical access limits.
Gaussian Filtering
Meaning
Mathematical algorithms applied to surface topography data remove high-frequency noise and provide a smoothed profile for roughness analysis. Gaussian filtering uses a weighted average function to separate the long wavelength waviness from the short wavelength roughness. It is the standard method defined in international protocols for characterizing the texture of moulded parts and tool surfaces.
The filtering process stops when the data is split into the desired spatial frequency bands.
Data Smoothing
Raw data from a profilometer often contains spikes from dust or electronic noise. Application of gaussian filtering suppresses these outliers without distorting the underlying shape of the surface. This creates a clean baseline for calculating parameters like ra or rz.
Metrology Accuracy
Cutoff lengths determine which features are considered part of the roughness and which are part of the waviness. Selecting the wrong parameters for gaussian filtering can lead to incorrect pass or fail decisions during quality control. Consistency in filtering is necessary for comparing results between different laboratories.
Surface Texture
Characterization of the mould finish helps in predicting the friction and the appearance of the plastic part. Proper use of gaussian filtering reveals the true nature of the machining marks or the chemical grain. This information allows for the optimization of the polishing process.