ISO 25178 Surface Parameters for Injection Moulding Optical Components
ISO 25178 areal parameters define 3D optical surface texture to control stray light and guide injection moulding process windows for precision lenses.
Nickel Phosphorus Insert
Meaning
Ultra-precision tooling components coated with an electroless alloy of nickel and phosphorus are utilized in injection moulding to produce high-quality optical components. These parts feature a highly homogeneous amorphous structure that allows for single-point diamond turning to achieve sub-nanometer surface roughness. Using a nickel phosphorus insert ensures that complex geometries, such as aspheric lenses, are replicated on plastic parts with extreme accuracy.
Tooling Manufacture
Machining the tool insert relies on diamond turning because the amorphous alloy does not have grain boundaries that would cause micro-chipping. Engineers deposit the coating onto a substrate material like steel or copper, then turn it to the desired optical profile. The resulting nickel phosphorus insert provides a durable molding surface that resists chemical wear from corrosive polymer outgassing.
Because the coating has a low coefficient of friction, it improves the release characteristics of the moulded lenses. This durability allows high-volume production runs without degradation of the optical surface finish.
Process Variable
Mould temperature must be carefully controlled when using these specialized inserts to prevent thermal shock and coating delamination. Rapid heating and cooling cycles can induce shear stresses between the alloy and the steel substrate.
Molded Defect
Wearing of the insert surface leads to a loss of optical clarity in the moulded polymer lenses. Micro-scratches on the tool appear as cosmetic defects on the plastic parts, rendering them unusable for precision cameras or sensors.