Meaning
Compared to chemical etching and conventional electrical discharge machining, ultra short pulse laser processing transfers thermal energy without creating heat affected zones. Sub picosecond pulse delivery, categorized as femtosecond laser texturing, ablates tool steel substrates at the sub micron scale to produce hydrophobic or low friction mould microstructures. This process sets surface energy and directional friction properties on tool cavity walls for specialized injection moulding applications.
The technique governs deterministic surface texturing but stops at deep material removal due to low volumetric ablation rates.
Thermal Ablation
Laser pulses lasting under five hundred femtosecond duration concentrate optical energy faster than heat diffuses into the metal lattice. Cold ablation vaporizes the target steel surface without liquefying adjacent metal, preventing recast layers or microcracking. Microscopic pillar arrays and crosshatch textures produced by this technique modify molten polymer wetting behavior during injection.
Moulded parts inherit exact micro textures, altering surface contact angles without chemical coatings. Process parameters including laser wavelength and spot overlap control feature depth and spatial pitch on the mould steel. Clean ablation surfaces preserve high steel hardness, eliminating post laser heat treatment requirements.
Surface Topography
Periodic surface structures generated by laser interference patterns create functional optical or tactile effects on moulded parts. Submicron ripples modify light reflection, generating iridescent color effects on clear polycarbonate surfaces without pigments. Precision control of laser polarization produces uniform directional friction profiles across the cavity.
Replication Fidelity
High viscosity resins require elevated cavity pressure to fully penetrate laser etched micro features. Incomplete filling of submicron cavities reduces hydrophobic performance on final moulded parts. Moulders optimize melt temperature and injection speed to ensure full polymer replication of laser textured steel.
