Meaning
Surface abrasion mechanisms occurring at the microscopic scale involve the displacement of material from a groove without immediate metal removal. During the moulding of glass-filled polymers, micro ploughing occurs as hard abrasive fibres slide against the steel surface of the mould. This action pushes the metal aside to form raised ridges along the wear track, weakening the surface before actual material loss occurs.
It happens primarily in high-shear regions such as the gate area and runner junctions.
Friction Mechanism
Hard particles traversing a softer substrate create plastic deformation that alters the surface texture of the steel. In injection moulding, micro ploughing represents the initial phase of abrasive wear caused by hard reinforcements within the polymer matrix. As the melt flows, these particles act as tiny wedges that gouge the polished cavity walls.
This continuous deformation increases the surface roughness over time, making part ejection more difficult. Over thousands of cycles, this friction alters the heat transfer coefficient of the cavity wall by introducing a micro-textured barrier between the resin and the cooling channels.
Tooling Wear
Progressive damage from abrasive polymer compounds leads to the degradation of high-finish surfaces. When micro ploughing continues unchecked, the displaced metal ridges eventually break away under the shear stress of the flowing resin. This creates loose metal particles that accelerate subsequent erosive wear within the cavity.
Correct steel selection or protective hard coatings can mitigate this wear phase.
Process Control
Moulding operations minimize surface degradation by controlling the injection velocity and melt temperature. Lowering the shear rate reduces the force with which abrasive reinforcements strike the steel surface. When the velocity is managed, the occurrence of micro ploughing decreases, extending the service life of the polished tooling inserts.
Consistent temperature profiles also prevent localized viscosity increases that worsen abrasive friction.
