Definition
Firm: All materials, production and production capacity are fixed, closest to the current period.
In detail
The Demand Time Fence is the segment closest to the present within the Time Fence; in this phase materials, production, and capacity are all fixed and fully frozen, and new demand can only be pushed to the next period, not "only demand can be adjusted." It solves the problem of how to respond to demand changes in the short term, ensuring committed orders are not disrupted. The difference from the Planning Time Fence is that the latter allows adjusting the product mix. Typical output is the rules for the demand freeze period, specifying which orders cannot be changed.
Example in practice
Within the demand time fence, a customer suddenly requests an increase in order quantity. Since materials and capacity are locked, sales can only negotiate with the customer to postpone the additional demand to the next period. By clarifying the rules, the production plan is not disrupted, and the customer understands the constraints.