Roll Build, Splice Count & Converting Yield

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 9 inputs are read from the form on every keystroke: Finished Roll Diameter, Core Diameter, Web Caliper, Web Width, Basis Weight, Parent Roll Length, Web Wasted per Splice, Time per Splice and Converting Line Speed.
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 Wound Length together with every supporting figure in one pass — no value is carried over from a previous entry.
4. The supporting outputs — Roll Weight, Radial Build, Wraps on the Roll, Splices in the Roll, Web Wasted, Usable Length, Yield Lost to Splices, Run Time per Roll, Splice Downtime per Roll and Availability Lost — 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 Wound Length 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 — Roll Geometry and Splicing. 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 Wound Length in the dark results panel — that is the headline figure, expressed in m.
4. Check the supporting rows underneath (Roll Weight, Radial Build, Wraps on the Roll, Splices in the Roll, Web Wasted, Usable Length, Yield Lost to Splices, Run Time per Roll, Splice Downtime per Roll and Availability Lost) 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 Wound Length before a trial is booked, so machine time and material in Nonwovens, Filtration, Hygiene & Technical Webs are committed against a calculated figure rather than an estimate.
• Costing and quotation — Wound Length 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 Finished Roll Diameter) shows how much of the gap in Wound Length each variable explains.
• Teaching and study — the accepted ranges bracket normal Nonwovens, Filtration, Hygiene & Technical Webs practice, so moving one variable at a time shows the shape of the relationship rather than a single answer.

Assumptions and limits

• Caliper is the input that decides everything and it is the one most often taken from the wrong measurement: what matters is the compressed thickness of the web as wound under tension, not the free-state caliper from a thickness gauge, and for a lofty nonwoven the two can differ by a factor of two. Back-calculate it from a roll of known length rather than measuring a sample, and the geometry becomes reliable. The model treats caliper as constant through the build, while a real roll is wound harder at the core and softer toward the outside, so the true length sits a little above this figure on a soft-wound roll and a little below on a hard one. Splice count uses a uniform parent-roll interval and assumes every splice falls inside the roll being wound; in practice a splice landing near a set change is often trimmed out at no additional cost, so the waste figure is a mild overstatement and the downtime figure is not. The availability loss is the number worth arguing with a supplier over: at these settings the stops cost several times what the wasted web does, and a converter comparing parent-roll offers on price per kilogram alone is comparing the smaller of the two effects.
• Every input is bounded to the range normal practice occupies (Finished Roll Diameter 100 to 3000 mm, Core Diameter 25 to 600 mm and Web Caliper 0.005 to 10 mm, 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