Autoleveller Dead Length & Residual Variation

The formula

This is the expression the tool evaluates. Every term is named underneath, with the unit it must be supplied in.

How the result is derived

Step by step, from the values you type to the figure on screen.

1. The 6 inputs are read from the form on every keystroke: Delivery Speed, Measuring Point to Correction Point, Servo Reaction Time, Incoming Sliver CV, Correction Achieved on Long Faults and Share of Variance Below Dead Length.
2. Each value is checked against the accepted range in the input table below. A value outside its range stops the calculation rather than producing a misleading figure — the results blank out and a message appears.
3. The validated values are substituted into the expression above, which resolves Shortest Correctable Wavelength together with every supporting figure in one pass — no value is carried over from a previous entry.
4. The supporting outputs — Transport Dead Time, Total Delay Including Servo, Dead Length of Sliver, Residual Sliver CV, Variation Reduction and CV Left by Short Faults Alone — come from the same pass, so they always describe the same case as the headline figure.
5. Results are rounded for display only. The full-precision value is used throughout the chain, so reading a rounded intermediate figure back into the tool by hand can shift the last digit.

What each input means

Where to read each value on the floor, the unit it must be in, and the range the tool accepts.

What the tool returns

The headline figure and every supporting value it is built from.

Worked example

The tool loads with this case already solved — the Shortest Correctable Wavelength shown above is its answer. Change one value and the difference from this baseline is the sensitivity of the result to that variable.

How to use it

1. Work through the input groups in order — Machine Geometry and Sliver Variation. The defaults are a realistic case, so you can change one value at a time and watch what moves.
2. There is no calculate button. Every figure recalculates as you type or drag, which is what makes this usable for a what-if sweep rather than a single answer.
3. Read Shortest Correctable Wavelength in the dark results panel — that is the headline figure, expressed in m.
4. Check the supporting rows underneath (Transport Dead Time, Total Delay Including Servo, Dead Length of Sliver, Residual Sliver CV, Variation Reduction and CV Left by Short Faults Alone) before acting on the headline — they are where an implausible input usually shows itself first.
5. Reset to defaults returns every field to the reference case, which is the quickest way to check whether a surprising result came from the tool or from an input you had changed earlier.

Where this is used

• Process planning — establishing Shortest Correctable Wavelength before a trial is booked, so machine time and material in Blowroom, Carding, Drawing & Roving Control are committed against a calculated figure rather than an estimate.
• Costing and quotation — Shortest Correctable Wavelength is an input to the cost sheet, and quoting from a worked number rather than a remembered one is what keeps a margin intact.
• Troubleshooting — when the floor result drifts from plan, entering the measured values (starting with Delivery Speed) shows how much of the gap in Shortest Correctable Wavelength each variable explains.
• Teaching and study — the accepted ranges bracket normal Blowroom, Carding, Drawing & Roving Control practice, so moving one variable at a time shows the shape of the relationship rather than a single answer.

Assumptions and limits

• The shortest correctable wavelength is taken as twice the dead length, the sampling limit below which a periodic fault cannot be resolved at all — a real leveller degrades gradually as wavelength approaches it rather than failing at a step, so treat the figure as an optimistic boundary and not a specification. Note the direction of the speed term: raising delivery speed shortens the dead time but the dead length changes only through the servo component, so the machine does not become blinder in metres as fast as operators expect — but the correction quality within the band does fall, because the servo has fewer millimetres to act in. Short-wave faults are the ones an open-loop leveller cannot touch by construction, and they are exactly the drafting waves generated inside the machine itself, downstream of the measuring point. Sliver CV is also not yarn CV: levelling corrects mass per unit length, not fibre orientation, hooks or short-fibre distribution, and a perfectly levelled sliver still spins badly if the fibre inside it is wrong.
• Every input is bounded to the range normal practice occupies (Delivery Speed 10 to 1500 m/min, Measuring Point to Correction Point 10 to 5000 mm and Servo Reaction Time 0.1 to 500 ms, and so on for the rest). Those bounds are guard rails against typing errors, not a claim that the formula fails one unit outside them.
• The calculation is deterministic: the same inputs always give the same result. It carries no allowance for machine condition, operator skill, ambient conditions or lot-to-lot material variation unless an input above explicitly represents one.
• Nothing is sent anywhere. The maths runs in your browser, so the numbers you type never leave the page.

Questions people ask