Screen Volume, Paste Deposit & Squeegee-Shear Viscosity

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: Mesh Count, Thread Diameter, Mesh Thickness, Transfer Efficiency, Paste Density, Paste Solids, Dye in Paste, Consistency Index K, Flow Behaviour Index n, Print Speed and Film Gap at the Blade.
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 Wet Paste Pick-Up together with every supporting figure in one pass — no value is carried over from a previous entry.
4. The supporting outputs — Mesh Pitch, Clear Opening, Open Area, Theoretical Screen Volume, Dry Deposit, Dye Applied, Shear Rate at the Blade, Apparent Viscosity at that Shear and Thinning Ratio from Rest — 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 Wet Paste Pick-Up 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 — Screen, Paste and Squeegee. 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 Wet Paste Pick-Up in the dark results panel — that is the headline figure, expressed in g/m2.
4. Check the supporting rows underneath (Mesh Pitch, Clear Opening, Open Area, Theoretical Screen Volume, Dry Deposit, Dye Applied, Shear Rate at the Blade, Apparent Viscosity at that Shear and Thinning Ratio from Rest) 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 Wet Paste Pick-Up before a trial is booked, so machine time and material in Dyeing, Printing, Color Management & Chemical Control are committed against a calculated figure rather than an estimate.
• Costing and quotation — Wet Paste Pick-Up 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 Mesh Count) shows how much of the gap in Wet Paste Pick-Up each variable explains.
• Teaching and study — the accepted ranges bracket normal Dyeing, Printing, Color Management & Chemical Control practice, so moving one variable at a time shows the shape of the relationship rather than a single answer.

Assumptions and limits

• Open area is computed from a square-weave geometry, which describes a flat screen well and a rotary nickel screen only loosely - a galvanoformed rotary screen has round or hexagonal holes and its open area should be taken from the supplier specification rather than derived here. Theoretical volume is the paste the screen can hold, not the paste it delivers: transfer efficiency covers the fraction the squeegee actually pushes through and the fabric actually accepts, and it moves with squeegee pressure, blade hardness, printing speed and above all with how absorbent the ground is, so a value fitted on one construction does not transfer to another. The power-law fit describes the shear-thinning region and nothing else; it has no yield stress, so it will happily predict a finite viscosity at zero shear where a real paste has effectively infinite viscosity and does not flow at all, and that low-shear behaviour is exactly what governs whether a print bleeds after the blade has passed. Sharpness of line and bleeding are therefore not predicted here. The shear rate is a nominal blade estimate, taken as speed over film gap; the true rate varies steeply through the film and is much higher at the screen wall.
• Every input is bounded to the range normal practice occupies (Mesh Count 10 to 200 /cm, Thread Diameter 10 to 400 um and Mesh Thickness 20 to 600 um, 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