ISM defines a "CHANGE ORDER" as being "A purchaser's written authorization to the supplier to modify or change an existing purchase order. In public sector purchasing, these changes generally must be within the scope of the contract."
You being in manufacturing won't make a difference; being in public purchasing would (due to the usual greater restrictions on what can be changed without public notification/re-bidding/reopening the process, etc).
Hope this helps.
DONALD G BARBER JR, C.P.M., A.P.P., CM, CPIM, C.A.M., CPSM
828 Sycamore Creek Road
Ripley WV 25271