Post Consumer Recycled Content Tax Exemption Verification Procedures
Exemption from plastic packaging taxes requires EN 15343 chain-of-custody dossiers and mass balance ledgers backing physical PCR fractions above statutory thresholds.
Volumetric Dosing Drift
Meaning
Unintended variation in the volume of colorant or additive delivered per unit time can lead to inconsistent material properties in the molded product. Preventing volumetric dosing drift is crucial in injection molding and extrusion, where the ratio of masterbatch to virgin resin must be tightly controlled. This phenomenon occurs when variations in bulk density, material flow, or screw wear cause the feeder to dispense different amounts of material.
If this drift is not corrected, it can lead to parts with varying color or reduced physical properties.
Drift Mechanism
Volumetric feeders run on the assumption that a given rotation of the dosing screw always delivers the identical mass of material. Through volumetric dosing drift, changes in pellet size, moisture content, or regrind ratio alter the packing density of the resin, causing the actual mass fed into the machine to fluctuate. This issue is particularly pronounced when using a high percentage of regrind, which has an irregular shape compared to uniform virgin pellets.
Color Consistency
Inconsistent addition of color concentrates leads to unacceptable variations in the cosmetic appearance of the final part. When volumetric dosing drift occurs, the parts may fail visual inspections or exhibit uneven color distribution. This is a significant issue for automotive interior parts and consumer electronics where color matching is tightly specified.
Process Stabilization
Transitioning to gravimetric dosing feeders, which continuously weigh the material being dispensed, eliminates this source of process variation. This modification ensures that the correct percentage of additive is maintained regardless of changes in material density.