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.
Indirect Profilometry
Meaning
Surface measurement performed on a replica provides a way to inspect features that are inaccessible to standard probes. Indirect profilometry involves creating a high precision cast of the tool or the part using a stable elastomer. This cast is then measured using contact or non-contact methods to reconstruct the original surface geometry.
The technique is limited by the resolution of the replication material.
Replica Inspection
Soft polymers like vinyl polysiloxane can flow into deep ribs or narrow grooves. Use of indirect profilometry allows these cured replicas to be removed and placed under a microscope or a stylus profiler. This allows for the inspection of internal surfaces that would otherwise require destructive testing.
Tool Geometry
Measuring the wear on a large mould is easier when using small replicas. Results from indirect profilometry can be evaluated in a metrology lab while the tool remains in the press. This approach reduces downtime and allows for frequent monitoring of critical dimensions.
Accuracy Factor
Fidelity of the replica depends on the viscosity and the shrinkage of the moulding compound. Successful indirect profilometry depends on elastomers that can reproduce details down to the nanometer scale. Analysts must account for any volumetric changes to ensure the measurements are defensible.