Areal Surface Texture Parameter Measurement in Micro Injection Mould Cavities
Areal surface metrology in micro-cavities requires non-contact optical instruments with matched bandwidth filters to verify steel texture and polymer replication.
Elastomeric Replica Casting
Meaning
A nondestructive testing technique allows the high-resolution copying and analysis of hard-to-reach or complex surface finishes. This Elastomeric Replica Casting involves applying a liquid polymer, often a two-part silicone, to the surface of a mould cavity or a finished part, allowing it to cure, and then peeling it away. The resulting replica is analyzed using optical or stylus profilometers to measure the surface roughness.
Casting Process
The curing polymer must have extremely low shrinkage to ensure that the microscopic details of the surface are replicated with high fidelity. It must also have sufficient elasticity to be removed from undercut regions without tearing or permanently deforming. This makes it possible to inspect the surface of mould inserts without disassembling the tool or risking damage to the steel.
Metrology Technique
Once the replica is cured, it is measured in a laboratory environment where advanced instruments can analyze the surface texture. This method achieves sub-micron resolution, making it suitable for checking the quality of diamond-turned surfaces or EDM finishes. It provides a permanent physical record of the surface state at a specific point in time.
Defect Analysis
Moulders use the replicas to identify the onset of mould wear, pitting, or micro-cracking.