SMS Layer Balance: Barrier Against Strength

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: Total Basis Weight, Meltblown Share, Spunbond Layers, Meltblown Fibre Diameter, Head Constant, Tensile Constant, Target Hydrostatic Head, Spunbond Cost and Meltblown Cost.
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 Hydrostatic Head together with every supporting figure in one pass — no value is carried over from a previous entry.
4. The supporting outputs — Meltblown Weight, Spunbond Weight, Spunbond per Layer, Tensile Strength, Head per Gram of Laminate, Material Cost, Meltblown the Target Head Needs, Share that Represents, Spunbond Left at that Split and Tensile at that Split — 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 Hydrostatic Head 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 — Laminate and Calibration & Target. 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 Hydrostatic Head in the dark results panel — that is the headline figure, expressed in mbar.
4. Check the supporting rows underneath (Meltblown Weight, Spunbond Weight, Spunbond per Layer, Tensile Strength, Head per Gram of Laminate, Material Cost, Meltblown the Target Head Needs, Share that Represents, Spunbond Left at that Split and Tensile at that Split) 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 Hydrostatic Head 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 — Hydrostatic Head 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 Total Basis Weight) shows how much of the gap in Hydrostatic Head 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

• Both performance relations are linear fits and both have limits the linear form does not show. Hydrostatic head does not rise indefinitely with meltblown weight: below roughly two or three grams per square metre the layer has pinholes and delivers almost no head at all, so the linear model badly overstates thin barriers, and at the other end head saturates as the structure becomes effectively closed. Tensile is genuinely close to linear in spunbond weight over the ordinary range but depends on bonding calender temperature and pattern at least as much as on grams, and an over-bonded laminate loses tear while gaining tensile. Fit both constants on the actual laminate being made. The cost figure is polymer and conversion only and ignores the fact that meltblown output per line-hour is a small fraction of spunbond output, so the true marginal cost of a meltblown gram in a plant running near capacity is far above its material cost - which is usually the real reason a producer resists raising the share. Nothing here treats the alcohol repellency or the barrier-to-liquid-under-pressure that a medical specification actually calls for; hydrostatic head correlates with them but does not substitute for them.
• Every input is bounded to the range normal practice occupies (Total Basis Weight 8 to 200 g/m2, Meltblown Share 2 to 80 % and Spunbond Layers 1 to 6 nos, 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