Bulk Density Variance

Feed Consistency

Gravity-fed hoppers rely on a steady flow of material to ensure even filling of the screw flights. A high bulk density variance disrupts this flow by changing the pressure exerted at the throat of the machine. Operators often observe surging when the material packing shifts suddenly.

This instability forces frequent adjustments to the process settings to maintain part quality.

Shot Weight

Inconsistent material packing directly affects the mass of resin delivered in each cycle. When bulk density variance increases, the volumetric metering of the screw no longer equates to a predictable mass of polymer. This discrepancy results in short shots or over-packed parts that flash at the parting line.

Maintaining a tight range for this property is a requirement for high-precision moulding applications where weight tolerances are narrow.

Storage Influence

Environmental conditions and handling methods contribute to the compaction of resin during transport. Long-term storage in tall silos increases the pressure on the bottom layers, which leads to a higher local density compared to the top of the vessel. Vibration during shipping also causes smaller particles to settle, which further drives bulk density variance.

Regular sampling from different levels of the container identifies these gradients before the material enters the production line. Monitoring these levels prevents unexpected changes in the melt behavior during a run. Performance improves when the material is homogenized before use.