Production Schedule Capacity & Constraint Solver

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: Order Quantity, Fabric Linear Weight, Working Days to Due Date, Scheduled Hours per Machine-Day, Looms Allocated, Net Delivery per Loom-Hour, Dyeing Machines Allocated, Batch Size, Door-to-Door Cycle Time, Stenters Allocated and Net Throughput per Stenter-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 Schedule Slip together with every supporting figure in one pass — no value is carried over from a previous entry.
4. The supporting outputs — Binding Work Centre (1 weaving / 2 dyeing / 3 finishing), Load at the Binding Work Centre, Weaving Load, Dyeing Load, Finishing Load, Quantity Feasible in the Window, Machine Hours Short at the Constraint and Whole Dyeing Batches Required — 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

The dyehouse is over by nine per cent, so the obvious move is a third machine. Run it again with three: the feasible quantity rises from 82031.25 m only to 92664 m, not to the 123046.875 m the dyehouse alone would then allow, because weaving takes over as the constraint at 97.1251 per cent. A whole dyeing machine buys 13 per cent more capacity, and the three per cent of headroom left at the looms is the entire return on the next one.

How to use it

1. Work through the input groups in order — Order & Due-Date Window, Weaving, Dyeing and Finishing. 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 Schedule Slip in the dark results panel — that is the headline figure, expressed in days.
4. Check the supporting rows underneath (Binding Work Centre (1 weaving / 2 dyeing / 3 finishing), Load at the Binding Work Centre, Weaving Load, Dyeing Load, Finishing Load, Quantity Feasible in the Window, Machine Hours Short at the Constraint and Whole Dyeing Batches Required) 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 Schedule Slip before a trial is booked, so machine time and material in Quality Systems, Traceability, Utilities & Factory Decisions are committed against a calculated figure rather than an estimate.
• Costing and quotation — Schedule Slip 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 Order Quantity) shows how much of the gap in Schedule Slip each variable explains.
• Teaching and study — the accepted ranges bracket normal Quality Systems, Traceability, Utilities & Factory Decisions 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 three centres are loaded independently and the slip reported is the largest single slip, which assumes lots overlap between stages so that the constraint alone governs the finish date. Where lots cannot overlap - one dye lot must be complete before finishing starts, for instance - the true slip approaches the sum of the positive slips, so treat this figure as the optimistic bound. Rates must be net, not nameplate: the loom figure has to include loom efficiency, warp stops and beam gaiting, the dyeing cycle has to be door-to-door including load, fill, heat, fixation, drain, rinse, after-treatment and unload, and the stenter figure has to include roll and recipe changes. Scheduled hours per machine-day must exclude planned maintenance and shift handover; entering 24 flatters every load by roughly nine per cent. Nothing here models variability, queueing, sequencing rules, shade-family constraints, transport between stages or reprocess, and a right-first-time rate below 100 per cent adds dyeing batches directly to the count. Only weaving, dyeing and finishing are loaded - if warping and sizing, inspection or packing is the real constraint in your plant, put it in place of one of these three rather than assuming it has slack. The tool loads a single order, so it answers whether that order fits an empty window, not whether it fits alongside the work already committed.
• Every input is bounded to the range normal practice occupies (Order Quantity 100 to 5000000 m, Fabric Linear Weight 20 to 5000 g/m and Working Days to Due Date 1 to 365 days, 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 22400-2 - Automation systems and integration, key performance indicators for manufacturing operations management, part 2: definitions of utilisation efficiency, allocation ratio and throughput rate that underlie the load figures here.
• IEC 62264-1 (ISA-95) - Enterprise-control system integration, part 1: models and terminology, which separates production capability from production capacity and from the schedule that consumes it.
• ISO 9001:2015 clause 8.2.3.1 - review of requirements for products and services: the organisation must confirm it can meet what it commits to before accepting the order, which is exactly this calculation.
• ISO 3801 - Textiles, woven fabrics, determination of mass per unit length and mass per unit area, which fixes the grams-per-metre figure that converts running metres into dyehouse kilograms.

Questions people ask