Loom Allocation Matrix & Contribution per Machine Hour

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 10 inputs are read from the form on every keystroke: Picks per Inch, Fabric Width, Order Length, Fabric Contribution, Air-Jet Insertion Rate, Air-Jet Reed Width, Air-Jet Cost per Hour, Rapier Insertion Rate, Rapier Reed Width and Rapier Cost per Hour.
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 Best Contribution per Hour together with every supporting figure in one pass — no value is carried over from a previous entry.
4. The supporting outputs — Air-Jet Contribution, Rapier Contribution, Advantage of Better Option, Air-Jet Output, Rapier Output, Width Utilisation on Best Loom and Machine Hours for Order — 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 Best Contribution per Hour 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 — Order and Machine Options. 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 Best Contribution per Hour in the dark results panel — that is the headline figure, expressed in /h.
4. Check the supporting rows underneath (Air-Jet Contribution, Rapier Contribution, Advantage of Better Option, Air-Jet Output, Rapier Output, Width Utilisation on Best Loom and Machine Hours for Order) 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 Best Contribution per Hour before a trial is booked, so machine time and material in Production Planning & Sequencing are committed against a calculated figure rather than an estimate.
• Costing and quotation — Best Contribution per Hour 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 Picks per Inch) shows how much of the gap in Best Contribution per Hour each variable explains.
• Teaching and study — the accepted ranges bracket normal Production Planning & Sequencing practice, so moving one variable at a time shows the shape of the relationship rather than a single answer.

Assumptions and limits

• Output is the mechanical rate at 100% efficiency; multiply by the real running efficiency, which differs systematically between machine types and is often the factor that reverses the ranking. Width utilisation is reported because a narrow order on a wide loom wastes capacity rather than material — that cost is real but appears as under-recovery elsewhere, not in this margin. Style-dependent constraints decide most allocations in practice: not every construction runs on air-jet, weft colour changes and heavy or delicate yarns push work to rapier regardless of contribution, and warp changeover time is excluded here entirely.
• Every input is bounded to the range normal practice occupies (Picks per Inch 5 to 300 PPI, Fabric Width 30 to 400 cm and Order Length 50 to 500000 m, 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