Batch & Changeover How long a warp runs and what it costs to replace

Batch Length m

Production Rate m/h

Full Changeover h

New beam gaited through healds and reed

Tie-In Changeover h

Same construction, ends knotted to the old warp

Batches Sequenced as Tie-Ins %

Shed & Value Scale and what the recovered time is worth

Looms

Scheduled Hours h/yr

Contribution per Metre /m

Availability Recovered by Sequencing

— %

Random style order against grouped construction

Changeover Load & Value Recovered

Contribution Recovered: — /yr
Extra Metres Woven: — m/yr
Time Lost, Random Order: — %
Time Lost, Sequenced: — %
Mean Changeover After Sequencing: — h
Run Time per Batch: — h
Changeovers per Loom: — /yr
Changeover Hours per Loom: — h/yr

The model assumes the loom runs at the stated rate for the whole batch and that the changeover is the only interruption; stop-driven losses are a separate and usually much larger term, and the two should be added rather than compared. Tie-in time excludes the beam preparation, warping and sizing that happen off the loom, so the figure here is machine downtime rather than total lead time. The similar-batch fraction is a property of the order book and the planning horizon, not of the shed, and it should be measured from history rather than assumed. Where a knotting machine is shared between many looms, tie-in time also carries a queueing component that this model omits and that grows sharply once several looms run out together - which they will, because sequencing tends to synchronise them.

Loom Changeover Load & the Gain from Sequencing Similar Styles — free, with the formula and a worked example, at Textile School.