Card Sliver Draft, Can Capacity & Change Interval

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: Delivery Speed, Delivered Sliver, Chute Feed, Machine Efficiency, Can Diameter, Usable Can Height, Coil Packing Density, Can Change Time 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 Can Run Time together with every supporting figure in one pass — no value is carried over from a previous entry.
4. The supporting outputs — Total Draft (Chute to Sliver), Delivery Rate, Can Capacity, Sliver Length per Can, Cans Filled per Shift, Can Changes, Production Lost to Doffing and Can Working Volume — 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

Twenty-two kilometres of sliver in one can is the figure that makes the drawframe creel make sense: a can that lasts nearly three hours on the card lasts a fraction of that at the drawframe, where eight of them feed one delivery.

How to use it

1. Work through the input groups in order — Delivery & Draft and Can & 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 Can Run Time in the dark results panel — that is the headline figure, expressed in min.
4. Check the supporting rows underneath (Total Draft (Chute to Sliver), Delivery Rate, Can Capacity, Sliver Length per Can, Cans Filled per Shift, Can Changes, Production Lost to Doffing and Can Working Volume) 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 Can Run Time 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 — Can Run Time 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 Delivery Speed) shows how much of the gap in Can Run Time 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

• Can capacity uses the full cylindrical working volume; a real can has a spring base or a fixed bottom plate and the sliver does not fill the extreme corners, so measured capacity runs a few per cent below the geometric figure. Packing density should be measured by weighing a full can rather than taken from a catalogue, since it depends on coiler setting and sliver tension as much as on the fibre. The doffing loss assumes the card stops for the change; automatic can changers overlap the change with running and reduce this to near zero, in which case the interval still matters for labour but not for output. Total draft is nominal, and it takes no account of fibre orientation or of the licker-in and flat waste that leave between feed and delivery - use the card production tool for the waste-corrected output.
• Every input is bounded to the range normal practice occupies (Delivery Speed 20 to 800 m/min, Delivered Sliver 0.5 to 20 ktex and Chute Feed 10 to 2000 ktex, 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 - determination of linear density, for the ktex figures.
• ASTM D1425 - Unevenness of Textile Strands, the companion measurement on the delivered sliver.
• ISO 8115 - Cotton bale dimensions and density, for the upstream material this feeds from.

Questions people ask