The loop from take-off to purchase order has five steps. The engineer takes off the material per zone from the approved drawing and specification. The take-off becomes a purchase request. The request is approved. The approved request becomes one purchase order to one supplier. The order is received against, line by line. The loop closes when the receipt lands as stock linked back to the request and the zone that needed it. It stays open — and material gets bought twice, or never — whenever a step re-types what the previous step already said. The discipline that holds the loop together is a catalogue: every line, from take-off to receipt, refers to the same stock item by its ID, so a description typo cannot mint a second item and fork the trail.
Per zone, from the approved drawing, against an approved material submittal. Each line is a catalogue item, a quantity and a unit. A take-off from an unapproved specification is a purchase the consultant may reject; hold it until the submittal is approved, or record who said to proceed anyway.
The take-off becomes a purchase request carrying the same item IDs and the zones that need them. Ideally the request is generated from the take-off rather than typed from it; every retyping is a chance to lose a line or change a quantity.
Someone with the right to commit the company reviews the request — quantity against the zone, item against the specification, timing against the site. Rejection is recorded with a name and a reason; a rejected request cannot become an order.
One approved request becomes one purchase order to one supplier, with a system-minted reference, the supplier as a linked record, currency and tax, and an approval ladder that reflects company policy. The order lines keep the item IDs from the request.
The store receives against the order line: ordered, previously received, receiving now. Partial deliveries leave a visible balance; over-receipt is refused; each line lands as a stock batch. The loop is closed when the receipt is a batch that knows its order, its request and its zone.
Traceability hangs on the catalogue. If "ALU PROFILE 6063 T6 50x50" and "Alu profile 6063-T6 50 x 50" are two items, the store has two stocks, the request cannot see the second, and the same profile is bought twice. One person owns the catalogue; procurement is trained to search before creating; and a request that cannot resolve to a catalogue item is treated as an exception — allowed when unavoidable, but flagged as untraceable so nobody mistakes it for a clean line.
When the store tries to cover a zone from stock and cannot, the shortfall should become a new request automatically, for exactly the missing quantity, linked to the zone. Manually noticed shortfalls arrive late and get rounded up "to be safe", which is how surplus stock is born.