Nonwovens
Batt weight is a mass balance, not a setting. The layer count is just the ratio of what goes in to what comes out.
— g/m2
From the mass balance, before any drafting
The mass balance is exact and the two throughput figures are printed side by side precisely so that it can be seen to close; if they differ, an input is wrong rather than the machine. Carriage speed is taken as equal to the web infeed speed, which is what a well-set lapper does - the carriage has to consume the web at the speed it arrives or the web is either stretched or heaped at the apron. Real machines vary carriage speed through the stroke and decelerate at the reversal, which is what produces the heavier selvedges every crosslapped batt has, and profiling systems exist specifically to compensate for it; none of that is modelled here, so the batt weight computed is a mean across the width rather than a profile. Lay angle is reported from the cross-direction, so a small number means fibre laid nearly across the machine and a strongly cross-oriented batt. Drafting after the lapper reduces weight and rotates fibre toward the machine direction, trading the cross-direction strength the lapper just built for machine-direction strength; the weight after drafting is given but the reorientation is not, and a heavily drafted batt is a different fabric rather than a lighter one.
Crosslapper Mass Balance, Layer Count & Lay Angle — free, with the formula and a worked example, at Textile School.