Production Planning
The line does not empty, it dilutes. Each turnover clears only about 63% of what is left.
— kg
Material produced before the blend is inside tolerance
Perfect mixing is the assumption behind the exponential, and a blowroom is not perfectly mixed — dead zones in hoppers and ducts hold pockets of the old fibre that emerge later as isolated contamination rather than a smooth decay, and those stragglers are what cause barré and dyeing faults long after the blend reads clean. The reverse direction is also not symmetric: synthetic into cotton and cotton into synthetic clear at different rates, and traces of polyester in a cotton run are far more damaging than the reverse. Where changeovers are frequent, running dedicated lines usually beats optimising the transition.
Blowroom Blend Changeover Transition Waste Modeler — free, with the formula and a worked example, at Textile School.