Injection Mould Cavity Surface Roughness Measurement Using Silicon Replicas
Indirect silicone replica metrology resolves deep mould cavity roughness parameters non-destructively within five percent variance of direct steel scans.
Transfer Loss
Meaning
A physical reduction in a process variable occurs as energy or material moves from one point to another in a manufacturing system. In injection moulding, transfer loss refers to the drop in hydraulic or melt pressure between the injection nozzle and the mould cavity. Minimizing this loss is critical for ensuring that sufficient packing pressure is applied to the solidifying polymer.
Pressure Drop
As the polymer melt flows through the runner system and the gate, viscous friction and restriction cause a substantial loss of pressure. Thin gates and long runner paths increase this flow resistance, resulting in high transfer loss. This means the pressure inside the cavity is significantly lower than the pressure recorded at the nozzle.
Tool designers must carefully size runners and gates to balance flow resistance against material waste.
Processing Impact
High pressure loss limits the ability of the machine to pack out the part, leading to defects like sink marks and voids. If the pressure in the cavity is too low, the polymer cannot fully conform to the tool surface, causing poor texture replication. Moulders often increase the melt temperature to reduce viscosity and mitigate this flow resistance.
However, this adjustment can extend cooling times and increase the risk of thermal degradation.
Quality Control
Monitoring pressure loss involves installing transducer sensors inside the mould cavity to measure the actual pressure achieved during the cycle. Comparing cavity pressure to nozzle pressure provides a clear measure of process efficiency. This measurement helps operators detect gate freeze-off and ensure batch-to-batch consistency.