Cold Pad Batch Dosing Pump Ratio Calibration Procedures
Dosing pump ratio calibration in cold pad batch dyeing prevents reactive dye hydrolysis, shade tailing, and costly bulk fabric rejections.
Dynamic Viscosity Differential
Flow Resistance
Fluid flow variation arising from shear-dependent resistance between the core and boundary layers of a moving liquid dictates the penetration rate of dye formulations into thick yarn packages. In continuous pad dyeing, the dynamic viscosity differential between high-shear zones under the squeeze rollers and low-shear zones in the bath determines the pick-up consistency. A small differential maintains uniform liquid absorption across varying fabric speeds.
This stability prevents shade variation when the production line accelerates or slows down.
Rheological Mechanism
Non-Newtonian behavior in polymeric print pastes and dye thickeners causes the viscosity to drop as the shear rate increases. The dynamic viscosity differential represents this change in fluid behavior under mechanical stress. During high-speed application, the paste flows easily through the screen mesh, but it thickens immediately upon contact with the fabric.
This thickening prevents the print from bleeding or spreading beyond the intended pattern boundaries.
Dyeing Impact
In package dyeing machines, this differential affects how easily the liquor forces its way through the dense wound package of yarn. If the liquid is too thick at low shear, the center of the package remains under-dyed.
Measurement Practice
Laboratory testing with a rotational viscometer at multiple shear speeds measures this property before the dye liquor is pumped into the production tanks.