Meltblown Air-to-Polymer Ratio & Fibre Diameter

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 11 inputs are read from the form on every keystroke: Die Width, Hole Density, Throughput per Hole, Process Air Flow, Air Density at Normal Conditions, Blower Specific Energy, Reference Air-to-Polymer Ratio, Reference Fibre Diameter, Attenuation Exponent, Web Width on Collector and Collector 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 Air-to-Polymer Ratio together with every supporting figure in one pass — no value is carried over from a previous entry.
4. The supporting outputs — Capillaries in the Die, Polymer Throughput, Throughput per Metre of Die, Process Air Mass Flow, Estimated Fibre Diameter, Web Basis Weight, Web Produced, Air per kg of Polymer and Blower Duty — 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 Air-to-Polymer Ratio 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 — Die & Throughput, Process Air and Attenuation & Web. 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 Air-to-Polymer Ratio in the dark results panel — that is the headline figure, expressed in kg/kg.
4. Check the supporting rows underneath (Capillaries in the Die, Polymer Throughput, Throughput per Metre of Die, Process Air Mass Flow, Estimated Fibre Diameter, Web Basis Weight, Web Produced, Air per kg of Polymer and Blower Duty) 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 Air-to-Polymer Ratio 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 — Air-to-Polymer Ratio 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 Die Width) shows how much of the gap in Air-to-Polymer Ratio 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

• The diameter relation is a calibrated power law, not a first-principles attenuation model: real drawdown depends on air velocity and temperature at the nosepiece, polymer melt-flow index, melt temperature and die-to-collector distance, none of which appear here. Fit the reference pair on the line being modelled and the tool will track a change in ratio faithfully; take the reference from a textbook and it will not. Air-to-polymer ratio is computed on mass, which is the comparable basis across lines running different air temperatures - a volumetric ratio quoted at one temperature means something different at another, and comparing two lines on volume is a common way to reach a wrong conclusion. Basis weight assumes all extruded polymer lands on the collector inside the working width, so it ignores edge trim and any shot or fly extracted, both of which are real and both of which make the delivered web lighter than this figure. Blower duty is a first estimate from a specific-energy figure and covers the process air only; die heating, quench and the extruder are additional, but on a meltblown line they are the minority of the load, which is the point worth carrying away.
• Every input is bounded to the range normal practice occupies (Die Width 0.1 to 6 m, Hole Density 5 to 100 /inch and Throughput per Hole 0.02 to 3 g/hole/min, 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