Let down Ratio

Dosing Mechanism

Gravimetric feeders measure base resin and additive concentrate feeds to maintain accurate dosing control directly above the moulding machine feed throat. Setting a let down ratio of two percent requires adding two kilograms of masterbatch concentrate to ninety-eight kilograms of virgin polymer matrix. Deviation in feeder accuracy disrupts color consistency and alters additive concentration across the moulded part.

Lowering the ratio saves expensive concentrate costs but increases the risk of color streaking and localized UV degradation in thin wall sections.

Color Consistency

Precise dosing ensures uniform optical density and tint strength across complex multi-cavity injection moulds. When processing with a low let down ratio, back pressure setting on the injection screw must increase to ensure adequate dispersive mixing within the melt barrel. Inadequate shear mixing yields uneven pigment dispersion, causing visible color bands and mechanical stress concentration points in the final article.

Process Variation

Screw design variations and melt temperature fluctuations affect dispersive mixing efficiency without altering feed weight inputs. Process engineers adjust barrel temperature profiles to optimize masterbatch dispersion when changing resin lot viscosities.