Quantifying Micro Structure Transfer Loss in Laser Textured Injection Tooling Cavities
Polymer micro-structure transfer loss in laser-textured tooling stems from melt freezing kinetics and trapped gas counter-pressure, requiring variotherm control.
Depth Transfer Ratio
Meaning
Fidelity measurements in micro-injection moulding compare the depth of a replicated plastic feature to the depth of the metal cavity that formed it. This depth transfer ratio quantifies replication accuracy for microfluidic channels and sub-millimetre structured surfaces. When the value falls below unity, polymer melt has frozen before completely filling the bottom of the cavity.
Moulders adjust melt temperature and holding pressure to drive the value closer to one.
Fidelity Metric
Complete replication of high aspect ratio features requires precise thermal control of the mould insert. The depth transfer ratio varies according to the viscosity of the polymer and the speed of the injection phase. Solidification of the flow front in narrow channels creates an incomplete feature.
Process Variable
Melt temperature stands out as a primary driver of feature reproduction in thin-wall applications. This ratio climbs when the mould temperature is held close to the glass transition point of the amorphous resin. Fast heating cycles prevent the skin layer from forming too early.
Quality Control
Inspection routines use non-contact optical profiling to determine if the replicated features meet the design specification. Low replication rates lead to functional failures in microfluidic assays due to shallow channel dimensions. Regular audit checks of the part dimensions during the run prevent the shipment of defective batches.