Meaning
Fluid flow distribution ensures that polymer melt enters multiple mould cavities under identical velocity and pressure conditions. Achieving rheological balance requires designing the runner system so that the flow resistance and shear heating are equal along all flow paths. This balance is necessary to produce parts with uniform weight and dimensions across all cavities.
Runner Optimization
Standard runner geometries often fail to deliver balanced flow because of asymmetric shear heating. Utilizing specialized runner inserts or flow directors corrects the temperature distribution, establishing a true rheological balance in the melt stream. This adjustment prevents some cavities from filling faster than others.
Symmetric Filling
Non-uniform filling rates lead to differential shrinkage and warpage among parts from the same shot. When flow balance is maintained, every cavity reaches volumetric fill at the exact same millisecond. This simultaneous filling reduces the stress concentrations in the parts and creates a more stable process window.
Part Consistency
Quality control in high-volume moulding depends on achieving identical properties from every cavity of the tool. Proper flow balancing eliminates the need to run the process with high melt temperatures or extreme packing pressures to compensate for cool cavities. This reduction in process severity improves the lifetime of the tool and the moulding press.
By keeping the variation between cavities to a minimum, manufacturers can reliably meet tight tolerances in assembly operations that use parts from the same moulding run.
