Roving Bobbin Build, Doff Interval & Changeover Loss

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: Bare Bobbin Diameter, Full Bobbin Diameter, Traverse Lift, Package Density, Roving Linear Density, Front Roller Delivery, Doff Time, Spindles on the Frame and Shift 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 Doff Interval together with every supporting figure in one pass — no value is carried over from a previous entry.
4. The supporting outputs — Roving per Bobbin, Roving Length per Bobbin, Production Lost to Doffing, Doffs per Shift, Roving per Doff, Effective Frame Production, Package Volume and Build Ratio — 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

Substituting

Nearly five per cent of the frame is spent doffing, and it does not appear in any speed or twist calculation. On a mill running three speed frames that is most of a fourth frame lost to changeover - which is the entire business case for automatic doffing.

How to use it

1. Work through the input groups in order — Bobbin Build and Frame & Doffing. 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 Doff Interval in the dark results panel — that is the headline figure, expressed in min.
4. Check the supporting rows underneath (Roving per Bobbin, Roving Length per Bobbin, Production Lost to Doffing, Doffs per Shift, Roving per Doff, Effective Frame Production, Package Volume and Build Ratio) 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 Doff Interval 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 — Doff Interval 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 Bare Bobbin Diameter) shows how much of the gap in Doff Interval 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.

Reading the result

Typical bands and what each one is telling you.

Assumptions and limits

• The package is treated as a plain annular cylinder. A real roving bobbin is built with tapered ends so that it can be doffed and handled without the coils collapsing, and that taper removes a few per cent of the nominal volume - so measured capacity runs below the geometric figure. Package density must be measured rather than assumed; it moves with twist, winding tension and build settings. The doff time entered should be the full frame-stopped time including creeling and restart, not the time to strip the bobbins - restart to full speed is a real part of it. Effective production assumes doffing is the only stoppage; ends down, cleaning and lot changes are additional and are not included here.
• Every input is bounded to the range normal practice occupies (Bare Bobbin Diameter 20 to 100 mm, Full Bobbin Diameter 60 to 250 mm and Traverse Lift 100 to 700 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.

Standards and further reading

• ISO 2060 / ASTM D1907 - linear density of the roving.
• ASTM D1425 - unevenness, which false draft during winding shows up in.
• ISO 8119 - Textile machinery, Spinning preparatory machinery dimensions.

Questions people ask