Blowroom & Carding
Too little twist and the roving breaks in the creel. Too much and the ring frame cannot draft it.
— rpm
The speed this twist and delivery demand
The twist multiplier here is on the English cotton count basis; a multiplier quoted on the metric or tex system is a different number for the same twist, and moving a recipe between systems without converting is a standard source of hard or soft roving. Roving bulk density is not a constant - it depends on fibre, twist and how the strand is measured - so the diameter and twist angle are representative rather than precise, and they should be used for comparison rather than as absolute dimensions. Flyer speed is the twist requirement only and takes no account of the mechanical limits of the flyer, the bobbin build or the tension the roving can carry at that speed. Production assumes continuous running; doffing is excluded and is treated in the bobbin build tool, where on a speed frame it is a substantial deduction.
Roving Twist Multiplier, Flyer Speed & Production — free, with the formula and a worked example, at Textile School.